Qatar Survey Manual

Qatar Survey Manual – Table of Contents

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Content Page

Preface

1.1 Introduction 1

1.2 Purpose 1

1.3 Scope 1

1.4 Acronyms, Definitions and Abbreviations 2

1.5 Acknowledgement 3

Chapter 1 – Control Survey

Abbreviations 5

1.1.0 Datum 6

1.1.1 Reference Ellipsoids 6

1.1.2 Geodetic Datum 7

1.1.3 Vertical Control Datum 8

1.1.4 Map Projection 8

1.1.5 Geoid Model – Qatar95 8

1.2.0 Standards 10

1.2.1 Introduction 10

1.2.2 Order – Horizontal Control 10

1.2.3 Order – Vertical Control 11

1.2.4 Instructions and Guidelines for Control Surveys 13

1.2.4.1 Control Survey 13

1.2.4.2 Control Survey Returns 14

1.2.4.3 Digital Data Structure (To be used for CGIS Data Backing up requirements)

14

1.2.5 Specification for Surveys and Reductions 15

1.2.5.1 Electronic Distance Measurement – EDM 16

1.2.5.2 Horizontal Angle Measurement 18

1.2.5.3 Spirit, Auto or Digital Leveling 19

1.2.5.4 EDM Height Traversing 22

1.2.5.5 Trigonometric Heighting 25

1.2.5.6 GNSS Heighting 25

1.2.5.7 Decimal Places for Height Values 25

1.2.5.8 Global Navigation Satellite System (GNSS) 25

1.2.5.9 Triangulation and Trilateration Surveys 37

1.2.6 Validation of GNSS Equipment 38

1.2.7 Calibration of Electronic Distance Meter 42

1.2.8 Continuously Operation Reference Stations (CORS) 44

1.2.9 Monumentation of Control Points 45

References 47

Appendix 1A – Sample Transformation Calculations 48

Appendix 1B – Monument Types 50

Appendix 1C – EDM Calibration Measurements 76

Appendix 1D – Horizontal and Vertical Angle Observations 77

Chapter 2 – Cadastral Survey

Abbreviations 81

2.1.0 Governing and Administrative Authority for Cadastral Survey 82

2.1.1 Definition and Types of Cadastral Land 82

2.1.2 Types of Cadastral Survey 82

2.1.3 Types of Boundary Limits 83

2.1.4 Power of Director (GSD) 83

2.1.5 Duties of Director (GSD) 83

2.1.6 Committee on the Admission of Engineers (CAE) 83

2.1.7 International and Local Company Registration/Accreditation Requirements 84

2.1.8 Accreditation of Surveyors 87

2.2.0 Survey Requirements for Cadastral Land 87


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2.3.0 Survey of Land Parcels 87

2.3.1 Coordinated Cadastre 88

2.3.2 Survey Datum 88

2.3.3 Parcel, Beacon & Parcel Numbers 88

2.3.3.1 Application for Parcel, Beacon & PD Numbers 88

2.3.3.2 Parcel and Beacon Numbering System 88

2.3.4 Numbering of Temporary Controls (TC) 89

2.3.5 Survey Control Monuments 89

2.3.6 Guidelines for Using GNSS in Cadastral Surveys 90

2.3.7 Boundary Limits of Cadastral Boundary 92

2.3.7.1 Area 92

2.3.7.2 Accuracy Specifications for Setting Out 92

2.3.8 Authorized Marks 92

2.3.8.1 Types of Marks 92

2.3.8.2 Feature Codes for Cadastral Marks 94

2.3.9 Authorized Plan Forms 94

2.3.10 Land Cadastral Plan 94

2.3.11 Drawing Specifications for Land Cadastral Plan 94

2.3.12 Information to be Shown on Land Cadastral Plan 95

2.3.13 Survey Report 96

2.3.14 Quality Control of Cadastral Surveys 97

2.3.14.1 Processes of Quality Control 97

2.3.14.2 Surveyors’ Check List 98

2.4.0 Strata Survey 99

2.4.1 Strata Cadastral Parcel Numbering System 99

2.4.2 Administrative Procedures 99

2.4.3 Field Survey Procedures 99

2.4.4 Strata Cadastral Plan 100

2.4.5 Drawing Specifications for Strata Cadastral Plan 101

2.4.6 Information to be Shown on Strata Cadastral Plan 101

2.4.7 Deliverable Requirements for Cadastral Strata Survey 103

2.5.0 Encroachment 103

2.5.1 Encroachments Discovered in Cadastral Surveys 103

2.5.2 Reporting Encroachments 103

Appendix 2A(a) – Sample Property Documents 104

Appendix 2A(b) – Sample Property Documents 105

Appendix 2B – Sample Property Documents (Strata) 106

Appendix 2C – Request for Parcel, Beacon and PD numbers 107

Appendix 2D – Cadastral Surveys Features Codes 108

Appendix 2E – Form to Report Encroachment 118

Chapter 3 – Topographic Survey

Abbreviations 119


3.2.0 Topographic Mapping Accuracy 120

3.3.0 Specifications 122

3.3.1 Total Station Observations for Topographic Surveys 122

3.3.2 3D Terrestrial Laser Scanners 124

3.4.0 Topographic Survey Data Flow 126

3.5.0 Basic Definitions of Geospatial Data Used in CAD or GIS Databases 127

3.6.0 Data Collection and Processing Procedure for Topographic Surveys 128

3.7.0 CAD Drawing Standard 129


3.7.2 Organization and Naming of CAD Files 129

3.7.3 Level/Layer Assignments 133

3.7.4 Standard Symbology 138

3.8.0 Specifications for Topographic Surveys of Engineering and Construction Nature 139

3.9.0 Preparation of Survey Plan 142


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3.10.0 Preparation of Survey Report 143

References 145

Appendix 3A – Template Specification for Collection of Point Cloud Data using Terrestrial Laser Scanner

146

Appendix 3B – List of Type-of-Work Codes by Discipline 153

Appendix 3C – List of Type-of-Work Codes in Alphabetical Order 156

Appendix 3D – List of Main Elements in Alphabetical Order 159

Appendix 3E – List of Recommended Sub-Elements in Alphabetical Order 162

Appendix 3F – Topographic Survey Feature 172

Appendix 3G – PWA Topographic Feature Library 177

Appendix 3H – Graphic Concepts 181

Appendix 3I – Example of Q-TEL GFCODE 184

Chapter 4 – Hydrographic Survey

Abbreviations 185


4.2.0 Standards of Competence for Hydrographic Surveyors 186

4.3.0 Classification of Surveys 186

4.3.1 Special Order Surveys 187

4.3.2 Order 1a Surveys 187

4.3.3 Order 1b Surveys 187

4.3.4 Classification Table – Qatar Standards for Hydrographic Surveys 188

4.4.0 Geodetic Parameters 190

4.5.0 Positioning 191

4.5.1 Coastline Position 191

4.5.2 Wharf, Jetty, Dolphin, Ramp & Breakwater Position 191

4.5.3 Conspicuous Object and Beacon Position 191

4.5.4 Drying Rock and Obstruction Position 191

4.5.5 Navigational & Mooring Buoys Position 192

4.5.6 Sounding Position – GNSS Positioning 192

4.6.0 Depth Acquisition 192

4.6.1 By Single Beam Echo Sounder 193

4.6.1.1 Calibration of Dual Frequency Echo Sounder 193

4.6.1.2 Coverage of surveys 193

4.6.1.3 Logging of Digital Depths 194

4.6.1.4 Shoal Soundings 194

4.6.1.5 Data Processing 194

4.6.2 By Multibeam Echo Sounding 194

4.6.2.1 Calibration 194

4.6.2.2 Coverage and Detection of Seabed Features 195

4.6.2.3 Multibeam Back Scatter Parameters 195 4.6.2.4 Tidal Reduction 195

4.6.2.5 Acquisition and Processing 196

4.6.3 By Bathymetric LIDAR 196

4.6.3.1 Calibration 197

4.6.3.2 Spot Density & Depths at Chart Datum 197

4.6.3.3 Navigational Hazards Detection 197

4.7.0 Sea Floor Classification 197

4.7.1 By Side Scan Sonar 199

4.7.2 Classification by Back Scattering Echo Return 199

4.7.3 Seabed Sampling 199

4.8.0 Tidal Levels 199

4.8.1 Calibration of Tide Gauges 199

4.8.2 Setting Up of Tide Gauge 200

4.8.3 Chart Datum 200

4.8.4 Harmonic Analysis and Tidal Prediction 201

4.8.5 Relative Tidal Heights 201

4.8.6 Accuracy Standard 201


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4.9.0 Currents (Tidal Streams) 201

4.9.1 Long Term Current Recording 201

4.9.2 Accuracy Standard 202

4.10.0 Sea Floor Search 202

4.10.1 By Multibeam Echo Sounder (MBES) 202

4.10.2 By Side Scan Sonar 202

4.10.3 By Mechanical Drag Sweep 205

4.10.4 By Magnetometer Survey 209

4.10.5 Detection of Debris and Obstructions in Navigational Channels and Anchorages 209

4.10.6 Submarine Cables and Pipelines 209

4.11.0 Data Rendering 209

4.11.1 Survey Data to be Rendered 209

4.11.2 Report of Survey 210

4.11.3 Digital Records 212

4.11.4 Analogue Records 212

Glossary 213

Chapter 5 – Construction Survey

Abbreviations 217


5.2.0 Accuracy Standards 218

5.3.0 Compliance with Contract Specifications 218

5.4.0 Method of Survey 219

5.5.0 Field Survey Record 219

5.6.0 Survey Computation 219

5.7.0 Preparation of Setting Out Plan 219

5.8.0 Submission of Plans and Survey Records 220

5.9.0 Guideline on Setting Out Survey 220

5.10.0 Permitted Deviations for Setting Out Survey 221

5.11.0 Specifications and Work Procedures for Construction Surveys 222

5.11.1 Specifications for Construction Works 222

5.11.2 Work Procedures for Construction Works 222

5.11.3 Working Practice in Construction Works 223

5.12.0 Survey Marker 223

5.13.0 Plan Flow associated with Construction Survey 223

References 224

Appendix 5A – Guidelines on Accuracy of Survey Instrument 225

Chapter 6 – Gravimetric Survey


6.1.1 Existing geoid models for Qatar 229 6.1.2 Requirements for a Gravity Field for a New Geoid Model for Qatar 230

6.2.0 Terrestrial Absolute and Relative Gravimetry 230

6.2.1 Introduction to Gravity Networks 230 6.2.1.1 The Global Network IGSN 71 230 6.2.1.2 National or Regional Networks 230 6.2.1.3 Local Surveys 231

6.2.2 Instrumentation 232 6.2.2.1 Absolute Gravimeters 232 6.2.2.2 Relative Gravimeters (measuring changes in g) 232

6.2.3 Field Procedures 233

6.2.4 Office Procedures 234 6.2.4.1 Factors which Affect the Measurement of Gravity – g 234 6.2.4.2 The Precision of ∆g 236 6.2.4.3 Gravity Data Validation 237 6.2.4.4 Gravity Data Format 238

6.3.0 Airborne Gravimetry 238

6.3.1 Airborne Gravity Systems 238


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6.3.2 Field Techniques 239

6.3.3 Office Techniques 239 6.3.3.1 Processing the GPS Data 239 6.3.3.2 Processing the Airborne Gravity Data 240

6.3.4 Final Comments 240

References 241

Chapter 7 – Digital Mapping

Abbreviations 243

7.1.0 Digital Mapping General Specifications 244

7.1.1 General 244

7.1.2 Mapping Accuracy Standards 244

7.1.3 Projection, Datum, Coordinate System 245

7.1.4 Project Extent 245

7.2.0 Manual and Specifications for Aerial Photography with Large Format Digital Camera 247

7.2.1 Background 247

7.2.1.1 Choice of Reference Scale 247

7.2.1.2 Choice of Flying Height 247

7.2.1.3 Planning for Digital Aerial Camera 247


7.2.2.1 General 249

7.2.2.2 Flight Specifications 249

7.2.2.2.1 General 249

7.2.2.2.2 Flight Logs 249

7.2.2.2.3 Weather 249

7.2.2.2.4 Coverage 250 7.2.2.2.4.1 Flight Lines 250 7.2.2.2.4.2 Flying Height 251 7.2.2.2.4.3 Overlap 251

7.2.2.3 Camera 251

7.2.2.4 ABGPS and IMU 251

7.2.2.5 Data Characteristics 252

7.2.2.6 Documentation 252

7.2.2.7 Deliverables 254

7.3.0 Specifications for Ground Control for Photogrammetric Mapping 255

7.3.1 General 255

7.3.1.1 Projection, Datum, Coordinate System 255

7.3.2 Ground Control Requirements 255

7.3.2.1 Basic Control 255

7.3.2.2 Photo Control 255

7.3.2.2.1 Characteristics 256

7.3.2.2.2 Horizontal Photo Control 256

7.3.2.2.3 Vertical Photo Control 256

7.3.2.2.4 GPS for Horizontal and Vertical Control 256

7.3.2.3 Control Point Distribution 256

7.3.3 Marking Photo Control 257

7.3.3.1 Premarking 257

7.3.3.2 Postmarking 258

7.3.3.3 Airborne Global Positioning System (ABGPS) and Inertial Measuring Unit (IMU) Control

260

7.3.4 Deliverables 260

Annex 7A – Ground Control Point Diagram for Aerial and Satellite Imagery 261

7.4.0 Specifications for Aerial Triangulation 262

7.4.1 General 262

7.4.2 Aerial Triangulation 262

7.4.2.1 Definition 262

7.4.2.2 Quality 262



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7.4.3.2 Scanning of Negative/Diapositive 263

7.4.3.3 Control Point Configuration 263

7.4.3.3.1 Without ABGPS and IMU 264

7.4.3.3.2 With ABGPS and IMU 265

7.4.3.3.3 Check Points 265

7.4.3.4 Preparation 265

7.4.3.4.1 Pass Points 265

7.4.3.4.2 Tie Points 266

7.4.3.4.3 Softcopy Point Marking and Transfer 266

7.4.3.4.4 Coding 266

7.4.3.5 Mensuration 266

7.4.3.6 Adjustment 266

7.4.3.6.1 Preliminary Strip Formation 267

7.4.3.6.2 Simultaneous Bundle Adjustment 267


7.5.0 Manual and Specifications for Satellite Mapping 269

7.5.1 Background 269

7.5.1.1 General 269

7.5.1.2 Triangulation of Satellite Images 269

7.5.1.2.1 Camera Model 269

7.5.1.2.2 Coordinate System 271

7.5.1.3 Triangulation of Single Image 271

7.5.1.4 Triangulation of Block of Satellite Imagery 271

7.5.1.5 Multisensor Triangulation 272


7.5.2.1 Data Characteristics 272


7.5.2.3 Product Levels 272

7.5.2.4 Image Acquisition Order Polygon 273

7.5.2.5 Cloud Cover 273

7.5.2.6 Sun Angle 273

7.5.2.7 Imagery Options 273

7.5.2.8 File Format 273

7.5.2.9 Bits/Pixel 274

7.5.2.10 Resampling 274

7.5.2.11 Support Data 274

7.5.2.12 Mosaic 274

7.5.2.13 Block Adjustment 274


7.6.0 Specifications for the Compilation of Digital Image Mapping 276

7.6.1 General 276

7.6.1.1 Digital Orthoimagery 276

7.6.1.1.1 Definition 276

7.6.1.1.2 Quality 276



7.6.2.2 Project Extent 277

7.6.2.3 Ground Sampling Distance (GSD) 277

7.6.2.4 Data Conversion 277

7.6.2.4.1 Scanning if Analog Aerial Photography 277

7.6.2.4.2 Digital Photography or Satellite Imagery 278

7.6.2.5 Processing Algorithms 278

7.6.2.5.1 Rectification 278

7.6.2.5.2 Resampling 278

7.6.2.6 Accuracy 278

7.6.2.6.1 Scanner Accuracy 279

7.6.2.6.2 DEM Accuracy 279


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7.6.2.6.3 Pixel Size and Selection 280

7.6.2.6.4 Summary of Errors 280

7.6.2.7 Photo Selection 281

7.6.2.8 True Ortho 281

7.6.2.9 Mosaicing 282

7.6.2.10 Radiometry 284

7.6.2.11 Data Format 284

7.6.2.12 Quality Control 284

7.6.2.12.1 Reports 284 7.6.2.12.1.1 Production Flow 284 7.6.2.12.1.2 Fiducials 285 7.6.2.12.1.3 Space Resection 285 7.6.2.12.1.4 Rectification Quality (Spatial) 285


7.7.0 Specifications for the Compilation of Digital Geospatial Data 286

7.7.1 General 286

7.7.1.1 Digital (Vector) Geospatial Data 287


7.7.1.1.2 Quality 287





7.7.2.3.1 Coordinate Resolution 288

7.7.2.4 Data Model 288

7.7.2.4.1 Compilation Rules 288

7.7.2.4.2 Control Points 288

7.7.2.4.3 Hard Copy 289

7.7.2.5 Deliveries and Production Process 289

7.7.2.5.1 Production Process 289 7.7.2.5.1.1 Photogrammetric Compilation 289 7.7.2.5.1.2 Site Verification 289 7.7.2.5.1.3 Final Edit 290 7.7.2.5.1.4 CGIS Quality Assurance 290

7.7.2.5.2 Materials to be Delivered 290

7.7.2.5.3 Quality Control 290 7.7.2.5.3.1 Reports 291 7.7.2.5.3.2 Production Flow 291 7.7.2.5.3.3 Stereo Model Set-up Sheets 291

7.8.0 Specifications for the Compilation of Digital Elevation Models 292

7.8.1 General 292

7.8.1.1 Digital Elevation Models 292


7.8.1.1.2 Quality 293





7.8.2.4 Compilation Rules 294

7.8.2.4.1 Feature Digitizing Rules 294 7.8.2.4.1.1 Transportation Breaklines 295 7.8.2.4.1.2 Physical Breaklines 295 7.8.2.4.1.3 Hydrographic Breaklines 296 7.8.2.4.1.4 Building Heights 296


7.8.2.6 DEM Report 296


7.9.0 Specifications for 3D City Model Mapping 298


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7.9.1 General 298

7.9.1.1 3D City Models 298

7.9.1.1.1 Compilation 299





7.9.2.4 Vertical Aerial Photography 300

7.9.2.5 Oblique Aerial or Terrestrial Photography 300

7.9.2.5.1 Multi-Cameras Oblique Aerial Photography System 300


7.9.2.7 3D City Model Reports 301


References 302

Chapter 8 – Geographic Information System

Abbreviations 303

8.1.0 State of Qatar Geographic Information System (GIS) 304

8.2.0 Management of GIS 305

8.2.1 Strategic Management 305

8.2.2 Tactical Management 306

8.2.3 Operation Management 307

8.2.4 Executive Management 307

8.2.5 Functional Users Management 310

8.3.0 Structural Framework for the Development of Geographic Information Systems 310

8.3.1 Initiation 311

8.3.2 Evaluation 312

8.3.3 Preliminary System Design 313

8.3.4 Implementation Management 314

8.3.5 Maintenance 317

8.3.6 Feedback 318

8.4.0 Geospatial Data Overview and Standards 318

8.4.1 Geospatial Data Components 318

8.4.2 Geospatial Data Standards 319

8.5.0 Geospatial Database Specification 319

8.5.1 Vector Data Equivalence 320

8.5.2 Tabular Data Model 323

8.5.3 Qatar National GIS Data Dictionary Specifications 323

8.5.4 Accuracy of GIS Database 338

References 341

Appendix 8A – Eligible GIS Member Agencies 342

Document Control Page 345

Qatar Survey Manual - Preface

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1.1 Introduction The objective of this Qatar Survey Manual is to provide up-to-date standards and specifications for various types of survey and mapping activities in Qatar. It will also be based on generally accepted principles and practices of surveying. The Manual is also to serve as the basis for all survey and mapping activities in Qatar in the foreseeable future. Hence, all surveys conducted in accordance to the standards and specifications as laid out in this Manual will be assured of the same level of consistency and accuracy. This will ensure the reliability of all the survey data and enhance the confidence level of all its users. With this standardized survey data, it can be uploaded onto the Qatar GIS system as seamlessly as possible. To achieve the above objectives, a series of meetings and discussions, between Surbana and representatives from UPDA and various agencies, were held. The purpose of these meetings/discussions is to have an in depth understanding of the current practices and the needs of the users.

With the above users’ needs and expectations in mind,

• researches were conducted through internet,

• other academics were consulted,

• attended seminars and conferences on various surveying disciplines, and

• studies of the most relevant reports and books to derive these best practices in various types of survey for Qatar.

1.2 Purpose The Standards and Specifications in this Qatar Survey Manual will enable users:

• to understand the survey datum adopted of the State of Qatar and to adopt modern survey instrumentation and techniques to establish appropriate survey control network of international standard

• to understand the governance, administrative authority and procedure of conducting cadastral survey within the State of Qatar

• in completing a topographic survey from the field to the plan which supports the input to CGIS database

• in deciding which standard to adopt in order to achieve the accuracy that is needed for different requirements in hydrographic survey

• in achieving a good practice standard to ensure proper setting out for construction works

• to appreciate the background to, and the various techniques for, the determination of the gravity data required for precise geoid computations

• to understand the practices for Digital Mapping photogrammetrically derived or compiled from aerial photograph and/or satellite imagery

• to appreciate the management and framework for the development and maintenance of GIS in State of Qatar

1.3 Scope

This Manual covers the standards and specifications for the following types of survey: i. Chapter 1 – Control Survey This chapter covers the establishment of horizontal and vertical control networks for land-

based surveying techniques.


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ii. Chapter 2 – Cadastral Survey This chapter covers cadastral survey of land parcels and strata units within the State of Qatar.

It serves to provide the procedures, practices and a technical guide relating to the conduct of cadastral surveys in the State of Qatar. It does not list details of established practices which accredited surveyors are fully aware of and have been practicing them.

iii. Chapter 3 – Topographic Survey This chapter covers the execution of topographic surveys using Total Stations, GNSS and 3D

Terrestrial Laser Scanner. iv. Chapter 4 – Hydrographic Survey This chapter states the level of competence of hydrographic surveyors permitted to conduct

hydrographic surveys in Qatari waters, the orders of accuracy and purposes of the hydrographic surveys.

v. Chapter 5 – Construction Survey This chapter covers both the work procedures and practices governing horizontal and vertical

setting out survey for various infrastructural construction work. vi. Chapter 6 – Gravimetric Survey This chapter concentrates upon the specifications required for gravity surveys conducted

specifically for geoid computation and not intended, or applicable, for gravity surveys conducted for geophysical exploration.

vii. Chapter 7 – Digital Mapping This chapter covers the specifications and practices for Aerial Photography, Aerial

Triangulation, Digital Image Mapping, Satellite Image Mapping, Digital Vector Mapping, Digital Elevation Model and 3D Model, to be used in support of the production of Digital Orthoimagery, Vector, DEM, 3D City Model or Photogrammetrically compiled products of National Mapping Project for CGIS.

viii. Chapter 8 – Geographic Information System This chapter concentrates on the management and initiation, evaluation, preliminary system

design, implementation management, maintenance and feedback for the development of GIS. It also covers the geospatial data overview and database specifications.

1.4 Acronyms, Definitions and Abbreviations Below is a list of acronyms, definitions and abbreviations used throughout this Preface of this Manual: i. 3D – 3 Dimension ii. CGIS – Center for Geographic Information System, Qatar iii. DEM – Digital Elevation Model iv. GIS – Geographic Information System v. GNSS – Global Navigation Satellite System vi. GSD – General Survey Department


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vii. Manual – Qatar Survey Manual viii. UPDA – Urban Planning and Development Authority, Qatar 1.5 Acknowledgement We would like to take this opportunity to thank the Qatar Survey Manual Technical Evaluation Group: i. Manaf Ahmed Al Sada, CGIS Director ii. Ali Mohd. Al Majid (CGIS) – Chairman iii. Eufrepes E. Pangapalan, Jr. (CGIS) – Member iv. K. D. Ranjith Wijekoon (CGIS) – Member v. I.M. Dayarathna (CGIS) – Member vi. Mohammed Abd-Elwahab Hamouda (CGIS) – Member vii. Vladan Jankovic (GSD) – Member viii. Joalvin C. Villaroman (GSD) – Member ix. Restituto P. Villareal (GSD) – Member and also other representatives from: i. Topographic Survey Division – CGIS, UPDA ii. General Survey Department – UPDA iii. Hydrographic Section – GSD, UPDA iv. Mapping & Archives Services Division – CGIS, UPDA v. Planning & Projects Division – CGIS, UPDA vi. Planning Department – UPDA vii. various agencies like Ministry of Interior, Ministry of Minicipal Affairs & Agriculture, Qatar

Petroleum, Public Works Authority and others for their support, cooperation, patience, and most of all, guidance provided.

Qatar Survey Manual – Chapter 1 – Control Survey

5

Abbreviations

CGIS Centre for Geographic Information System

CORS Continuously Operating Reference Stations

CRS Coordinate Reference System

DGNSS Differential Global Navigation Satellite System

E Easting

EDM Electronic Distance Meter

FBM Fundamental Bench Mark

GDOP Geometric Dilution of Precision

GNSS Global Navigation Satellite System

GPS Global Positioning System

H Ellipsoidal Height

IGS International GNSS Service

ITRF International Terrestrial Reference Framework

L or λ Geographic Longitude

n Geoid Height

N Northing

NGS National Geodetic Survey (US)

O Orthometric Height

P or Φ Geographic Latitude

QND Qatar National Datum

QND95 Qatar National Datum 1995

QNG Qatar National Grid

RINEX Receiver Independent Exchange format

RTK Real-Time Kinematic

UTM Universal Transverse Mercator

WGS84 World Geodetic System 1984


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1.1.0 Datum

Geometric spatial reference data (3D position, position and height) must be presented in standardized, geodetic spatial reference systems, the so-called coordinate reference system. According to the EN ISO 19111:2007 standard (Spatial Referencing by Coordinates), a coordinate reference system (CRS) consists of two components, the “datum” and the “coordinate system”.

The datum, often also designated as the reference system, is the physical part of a CRS which establishes the reference to the Earth by definition of the zero point, the orientation of the coordinate axes and the scale. A datum can be a geodetic datum, a vertical datum or an engineering or local datum:

The coordinate system is the mathematical part of a CRS which establishes how coordinates are assigned to a geometry, e.g. a fixed point, using rules. The coordinates of a geometry can be stated, e.g. as Cartesian coordinates (X, Y, Z), ellipsoid coordinates (width, length and, where applicable, ellipsoidal height) or projected coordinates (Qatar National Grid, Gauß-Krüger mapping, UTM mapping, etc). As well as the CRS for 2D and 3D position data, some coordinate reference systems are defined for managing height data or coordinates (e.g. mean sea level heights). Transformations are necessary for the transfer of coordinates of a datum or reference system to another datum.

Underlying any coordinate used for Surveying & Mapping, or indeed any positional information, is a Geodetic Datum. It is imperative that the datum is well defined and reproducible so that any positioning activity may be related to it.

Geodetic Datum - Prime Meridian

Most geodetic datums use Greenwich as their prime meridian. Default values for the attributes prime meridian name and Greenwich Longitude shall be “Greenwich” and 0

degree, respectively.

Geodetic Datum – Ellipsoid

An ellipsoid specification shall be provided if the datum is geodetic. An ellipsoid shall be defined either by its semi-major axis and inverse flattening, or by its semi-major axis and semi-minor axis, or as being a sphere.

Geodetic datum’s in use in the State of Qatar are World Geodetic System 1984 (WGS84) and Qatar National Datum 1995 (QND95). QND95 is the datum used for surveying, mapping and related activities while WGS84 is the datum realized through the use of surveying techniques involving the Global Navigation Satellite System (GNSS). Coordinates derived through the use of GNSS are immediately transformed to QND95 except in a few circumstances such as the Civil Aviation Authorities who use WGS84 to maintain compatibility with their world-wide counterparts.

Similar to most jurisdictions, the State of Qatar uses a map projection of the reference ellipsoid so that users

may use grid {N, E} coordinates rather than the more complex geodetic coordinates { φ, λ, H }. Two projections are used in Qatar; Qatar National Grid (QNG) and Universal Transverse Mercator (UTM). QNG is encouraged throughout the State and is the only projection supported on QND95. UTM is available on the WGS84 datum only.

1.1.1 Reference Ellipsoids The parameters of the reference ellipsoid for the World Geodetic System 1984 (WGS84) are:

Semi - major axis (a) = 6,378,137.0 m Flattening (f) = 1 / 298.257223563

Qatar National Datum 1995 (QND95) uses the International (Hayford) reference ellipsoid whose parameters are:

Semi - major axis (a) = 6,378,388.0 m Flattening (f) = 1 / 297.00


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1.1.2 Geodetic Datum The two geodetic datums, WGS84 and QND95 are defined:

WGS84

WGS84 used in Qatar is defined by the United States Defense Mapping Agency in their document “Department of Defense World Geodetic System 1984 - Its Definition and Relationship with Local Geodetic Systems”, DMA TR 8350.2, dated September 30 1987 [Second Printing].

QND95

QND95 is defined by transforming WGS84 coordinates using a 7-parameter coordinate transformation,

X

Y

Z

X

Y

Z

X

Y

Z

s r r

r s r

r r s

X

Y

ZQND WGS

z y

z x

y x WGS

=

+

+

−

−

−

95 84 84

∆

∆

∆

∆

∆

∆

where the 7 parameters are:

X - translation = ∆X = +119.42480 m

Y - translation = ∆Y = +303.65872 m

Z - translation = ∆Z = +11.00061 m X - rotation = rx = - 1.164298” } The – sign must change to + sign for the Y - rotation = ry = - 0.174458” } 3 rotations in some software, considering Z - rotation = rz = - 1.096259” } its direction of rotation.

Scale change = ∆s = -3.657065 ppm

The 7 parameters, { ∆X ∆Y ∆Z rx ry rz ∆s } are exact values, that is, QND95 is defined by taking a WGS84 coordinate and applying the above transformation. The Qatar95 geoid model is incorporated into the transformation parameters. To obtain geodetically correct transformed coordinate values, the geoid model must be used.

In some instances an approximate transformation using only 3 parameters may be used,

X

Y

Z

X

Y

Z

X

Y

ZQND WGS

=

+

95 84

∆

∆

∆

where the 3 parameters are:

X - translation = ∆X = +127.78098 m

Y - translation = ∆Y = +283.37477 m

Z - translation = ∆Z = -21.24081 m See Appendix 1A for sample transformation calculation.


8

1.1.3 Vertical Control Datum The Qatar Vertical Datum is defined as the Mean Sea Level 1970-1972 being 8.0036 meters below the Fundamental Bench Mark B (FBMB, Private Mark) located at the north end of the runway at Doha International Airport.

1.1.4 Map Projection Qatar National Grid (QNG)

QNG is a transverse Mercator map projection using the following values:

Northing origin N 24° 27’ 00” Easting origin E 51° 13’ 00” False Northing 300,000.0 m False Easting 200,000.0 m Scale factor at origin

1 0.99999(exact)

Universal Transverse Mercator (UTM)

The UTM map projection used in Qatar is the standard definition of UTM. It is only used on the WGS84 datum and not QND95. All UTM values in Qatar fall in zone 39 (Central Meridian 51° East Longitude).

1.1.5 Geoid Model – Qatar95

In order to relate the ellipsoidal height derived from GNSS surveys to the desired orthometric height (sea level height) a geoid model is required. The State of Qatar has defined its own geoid model, Qatar95. It was derived by using the OSU91a geoid model and supplementing it with “known” geoid ellipsoid separations at 71 primary geodetic stations.

For users in the State of Qatar, program QTRANS is available from the Centre for GIS that computes both coordinate transformations between WGS84 and QND95 and also the Qatar95 geoid components (Geoid - Ellipsoid separation, and deflections of the vertical).

1 QNG is defined in terms of the scale factor at the origin (central meridian) not the zone width.


9

Figure 1.1: Geoid Model of Qatar (Qatar95)


10

1.2.0 Standards 1.2.1 Introduction

This section defines the fundamental requirement for a set of technical standards and specifications for horizontal and vertical control. These standards and specifications must always directly relate to the national coordinate reference systems and to the control of geodetic, engineering, mapping, cadastral surveys and spatial elements of geographic information systems.

1.2.2 Order – Horizontal Control Stations in horizontal control surveys are assigned an ORDER commensurate with the precision of the survey and the conformity of the survey data with the existing coordinate set.

The ORDER assigned to the stations in a new survey network following constraint of that network to the existing coordinate set may be; not higher than the ORDER of existing stations constraining that network.

The allocation of ORDER to a station in a network, on the basis of the fit of that network to the existing coordinate set, may generally be achieved by assessing whether the semi-major axis of each relative standard error ellipse or ellipsoid, with respect to other stations in the fully constrained network, is less than or equal to the length of the maximum allowable semi-major axis. This technique makes use of the formula adopted from “Standards and Practices for Control Surveys Special Publication 1 (SP1) V1.6” published by The Intergovernmental Committee on Surveying and Mapping (ICSM), Australia:

r = c ( d + 0.21 )

Where

r = length of the maximum allowable semi-major axis in mm. c = an empirically derived factor represented by historically accepted precision for a

particular standard of survey. d = distance between two stations in km.

The values of “c” for various ORDERs of survey are shown in Table 1.1(a) which is taken from SP1 V1.6.

Table 1.1(a): ORDER of Horizontal Control Survey

1 Experience has shown that with most modern methods of establishing closely spaced control, the overall pattern of error propagation is

not proportional to distance but rather to: the combination of instrumental and centring errors, the effects of network configuration and a host of other contributing errors - most of which defy individual identification. The errors of measurement contributing to this pattern can be divided into two groups: (a) those proportional to distance which are dominant on lines longer than one kilometre; and (b) those non-proportional to distance which are dominant on lines shorter than one kilometre. The adoption constant “0.2” as one element of the formula in the determination of ORDER will generally provide these specifications with the flexibility necessary to accommodate survey networks containing control stations which are closely spaced, widely spaced or with variable spacing.

ORDER c value (for one sigma )

0 3

1 7.5

2 15

3 30

4 50


11

A survey network is adjusted in a constrained least squares process which satisfies the a posteriori statistical tests. In the adjustment output, standard (1 σ) line error ellipses (relative ellipses) are generated from each point to adjacent points in the network. The allowable limit, for instance of 1st Order position, is calculated for each of these lines and compared to the ellipse’s semi-major axis.

If all the line error ellipses from a point are less than or equal to their limit for 1st Order, and the constrained points in the least squares adjustment are 1st Order or better, then hypothesis is true and the position may be adopted as 1st Order.

If line ellipses from a point are greater than the limit for 1st Order, or the constraint stations in the least squares adjustment are less than 1st Order, the hypothesis is false and the position should be tested for a lower Order.

Example:

The line error ellipses and distances from point 1 to points 2, 3 & 4 are as shown:

From To Semi-major axis Distance 1st Order allowable limit

1 2 0.23 m 33 km 7.5(33+0.2) = 0.248 m

1 3 0.16 m 27 km 7.5(27+0.2) = 0.204 m

1 4 0.30 m 42 km 7.5(42+0.2) = 0.316 m

As the semi-major axes of the line error ellipses from Point 1 to Points 2,3 & 4 are all less than their respective 1st Order limit, provided all constraint stations in the constrained least squares adjustment are 1st Order or better, Point 1 may be classified as 1st Order.

With ORDER, it is recognized that assessment of the quality of a network following a constrained adjustment remains dependent upon a subjective analysis of the adjustment, the survey, and the ties to the existing coordinate system. The ultimate responsibility for the assignment of ORDER to the stations in a survey network must remain within the subjective judgment of the geodesists of the relevant authority. As a comparison, Table 1.1(b) depicts the conventional order of horizontal control survey

1 based on relative

distance accuracy.

Table 1.1(b): Conventional ORDER of Horizontal Control Survey1 in the State of Qatar

1.2.3 Order – Vertical Control The assignment of an ORDER is largely technique dependent.

ORDER assigned to the height of a mark following a constrained adjustment will be commensurate with:

• the order of the constraining heights,

1 All horizontal control coordinates values should be shown up to 3

rd decimal of meter

Order Classification

(Relative Distance Accuracy) Equivalent

ppm

0 1:1,000,000 1 ppm

1 1:100,000 10 ppm

2 1:50,000 20 ppm

3 1:25,000 40 ppm

4 1:10,000 100 ppm


12

• the precision of the transformation from one height datum to another,

• the magnitude of the discrepancy between the newly heighted and existing height differences of the survey marks at the abuttal of the new and existing leveling routes/vertical networks, and

• for GNSS heighting, the accuracy of the geoid-ellipsoid separation. ORDER of height of a mark from a survey is allocated on the basis of the fit of that survey to existing (constraining) heights. This technique makes use of the formulae adopted from (SP1) V1.6 published by The Intergovernmental Committee on Surveying and Mapping (ICSM), Australia. The formulae are shown in Table 1.2(a) for the different surveys:

Table 1.2 (a): Values of c for Various ORDERS of Heights

Differential leveling1

r = c√ d Trigonometric and GNSS heighting

2

r = c(d+0.2)

ORDER c (for 1 σ) ORDER c (for 1 σ)

0 2 - -

1 4 - -

2 8 - -

3 12 3 30

4 18 4 50

Where: r = maximum allowable error, in mm. c = an empirically derived factor for each particular ORDER of survey result. d = distance between two stations in km Example: Consider a closed spirit-leveling network with a closure of 0.007 m, around a 15 km long loop. The standard deviation of each of the heights assigned to the 5 newly established Benchmarks, after a minimally constrained network adjustment, is approximately 0.001m.

Despite the closure rate and height values of better than ORDER 1, the equipment and procedures3 used

requires that ORDER 3 or lower be assigned to the network.

The survey is connected to one ORDER 1, two ORDER 2 and three ORDER 3 existing Marks. Though the constrained adjustment of the leveling loop achieved better than ORDER 1 agreement with the existing control, the highest ORDER to be allocated for the survey is ORDER 3

With ORDER, it is recognized that assessment of the quality of heights following a constrained adjustment remains dependent on a subjective analysis of the adjustment, the survey, and ties to the existing height system. The ultimate responsibility for the assignment of ORDER to the heights in a survey network must remain within the subjective judgment of the Authority or personnel in charge of the survey or of the vertical adjustment. Table 1.2 (b) depicts the conventional criteria used in the State of Qatar for the order of vertical control survey based on elevation closure. It could be used for comparison.

1 For differential leveling - the standard deviation of each height observation is less than or equal to the maximum allowable value (r).

2 For GNSS and trigonometric heighting - the standard deviation of each height observation is less than or equal to the maximum

allowable value (r). 3 See Table 1.5 in Section 1.2.5.3


13

Table 1.2 (b): Conventional ORDER of Vertical Control Survey in the State of Qatar

Order Classification – Elevation Closure (mm)

0 1.5 √K1

1 1.5 √K1

2 3 √K1

3 12 √K1

4 24 √K1

1.2.4 Instructions and Guidelines for Control Surveys

1.2.4.1 Control Survey For maintaining accuracy levels, internal consistency of the Horizontal & Vertical control networks and CGIS data backup procedures, following guidelines to be followed in executing control surveys. (A) Horizontal Network (Using Spatial Technique)

(i) Fixed or Reference stations must be in a higher order than the intended horizontal order of the new stations.

(ii) Fixed or Reference stations to be selected to equally distribute in all quadrants. (iii) Observation schemes and observation log sheets to be properly maintained. (iv) Sufficient baselines between fixed or reference stations to be observed in an equally distributed

manner. At least three fixed/reference stations to be connected in every network. (v) Including perimeter baselines, at least three baselines with every new station to be observed with

other new stations when network has more than four stations. (vi) Few baselines to be observed connecting new stations lying at the extreme locations of the

perimeter in the network when possible (more than 5 stations) for good strength of the network. (vii) When Spatial Technique (GNSS) is used, STS (Static) and RSTS (Rapid static) modes are

accepted. A minimum observation time is ten (10) min. for dual frequency receivers and can go up depending on the length of the base line.

(viii) For better network adjustment at least three GNSS receivers to be occupied for one session observations simultaneously.

(ix) Least-squares adjustment to be done for network constraint adjustment. (x) For checking internal consistency with existing control stations, few baselines to inter-visible or

nearby stations to be observed. However, these baselines should not be included in the final adjustment & computations.

(xi) Final coordinates values must be given in QNG coordinates (QND95 Datum) showing to 3rd

decimal. GNSS heights must be showing to 2

nd decimal.

(xii) For getting correct GNSS height values, QATAR95 Geoid model to be applied in the computations.

(B) Vertical Network

(i) Fixed or Reference stations must be in a higher order than the intended vertical order of the new stations.

(ii) For Second or Higher, order leveling must be done both ways (up and down) with standard manner. Final height values must be showing to 4

th decimal.

(iii) Least-squares adjustment must be done for level network adjustment (specially 2nd

Order and above)

(iv) Field records and level line route diagrams to be maintained properly and attached to the final report.

1 √K = square root of distance in kilometres


14

(v) GNSS heights are always in 5th order classification. Values showing up to 2

nd decimal.

1.2.4.2 Control Survey Returns (A) Complete Survey Report (Hard copy) Separate sections for Horizontal network and Vertical network in same report or two different reports will be acceptable. These reports should contain following sections:

(i) Front Cover – displaying Project name and other information (ii) Project summary file in MS word, MS excel or Plain text format. It should include the following

details which are used to update tables and control database,

• Project reference number or numbers

• Area name

• Period of Survey (Start date and End date)

• Instrument used for Observation (with brand, model and serial numbers)

• Observation method or scheme briefly

• Names of Survey Software used for computation and adjustments

• Reference/Fixed station details (Name, Northing, Easting, Height, H_order, V_order, Monu_type, Fixed status)

• New stations coordinates (Name, Northing, Easting, Height, Monu_type, Remarks) (iii) Computation Files - Adjustment & Computation List files, Computation summary files, Log files,

Original manual data entry forms, GNSS log sheets, Diagrams generated from computation software ….. etc.

(iv) Field Notes – GNSS Log sheets, Original manual data entry forms ….etc (v) References – Field Diagrams, Fixed stations data…etc (vi) Description sheets for new monuments

(B) Digital Data

(i) GNSS Raw data - Leica system 1200 raw data is accepted. For other brand GNSS receivers, RINEX format digital raw data is a must.

(ii) Digital level Data – Field raw data & Edit data. (iii) Computation & adjustment listing files, summary files and output files. (iv) Survey report Project summary file in MS word, MS excel or Plain text format. (v) Digital copies of other files included in Survey report. (vi) Digital copies of Survey stations' description sheets.

1.2.4.3 Digital Data Structure (To be Used for CGIS Data Backing Up Requirements)

Following Directory structure1 is to be followed. All data files are to be in unlocked mode.

1. Level 1 qarsxx xx indicate more stations included qars number. 2. Level 2 yymm eg: 0901 - "09" indicate year, "01" indicate month of observation

started. 3. Level 3

2 (i) doc Digital copies of all attached documents to the report.

(ii) rawdata/ssssss/yydddx where, ssssss – station name yyddda – yy (year) ddd (gpsday) a (session/occupation) e.g. rawdata/560036/08366a (observed on 31-Dec-2008, 1

st occupation)

rawdata/560036/08366b (observed on 31-Dec-2008, 2nd

occupation)

1 Directory structure levels 1-3 are a must.

2 Appropriate sub directories under the level 3 depend on the requirements of the control project.


15

(iii) Adjustment - Network adjustment files (iv) leveling/rawdata - digital raw data from filed data /editdata - edit data for leveling /adjustment - digital files for leveling adjustment

(v) descriptions - digital copies of new station description sheets in MS Excel format

Sample Directory Structure as follows

1.2.5 Specifications for Surveys and Reductions Control networks are produced by making suitably accurate measurements and referring them to identifiable adjacent control points in the existing network. The combination of survey design, instrumentation, calibration procedures, observation techniques and data reduction methods comprise a control survey system.

The required ORDER of fit to the control points of the proposed survey will determine the field methods and reduction techniques to be employed to achieve them.

The purpose of this section is to provide the surveyor with a guide to the minimally acceptable practices which apply to the equipment, and to the appropriate reduction methods to meet the standards of a particular ORDER of survey.

Adherence to the Recommended Practices described in this section is NOT mandatory in order to achieve a given ORDER. However, if not used, the onus is on the user to prove that the practices used will achieve the desired level of precision. Survey Techniques

Each of the following sections deals with a specific surveying technique. The sections are not designed to be used as a text book and may not contain comprehensive lists of techniques and procedures. It is assumed the user of this document has a basic understanding of the techniques being used. If not, a suitable reference text should be consulted.


16

1.2.5.1 Electronic Distance Measurement - EDM

Table 1.3 (a): EDM Observation Requirements

ORDER

0 1 2 3 4

Number of days of observations

2 1 1 1 1

Number of sets of full measurements

1

4 4 2 1 1

Move prisms between sets2 Yes Yes Yes Optional --

Range of fine readings3 <2(5+d)mm <2(5+d)mm <2(5+d)mm 7ppm 15 ppm

Difference between two sets3 <2(5+d)mm <2.5(5+d)mm <2.5(5+d)mm -- --

Difference between means of each day's measurements

3

< 3(5+d)mm -- -- -- --

Observation between 2 hours before local noon, and 2 hours before local sunset

4

Yes Yes Yes Optional Optional

Atmospheric dial setting (where possible)

Zero Zero Zero Optional Optional

Allow minimum warm up time5


Thermometer type Mercury in glass Mercury in

glass Mercury in

glass Mercury in

glass Mercury in glass

Graduation Interval < 10 C < 1

0 C < 1

0 C < 1

0 C < 1

0 C

Estimate temperature to 0.10 C 0.1

0 C 0.1

0 C 0.1

0 C 0.1

0 C

Estimate pressure to 0.3 hPa 0.3 hPa 0.3 hPa 0.3 hPa 0.3 hPa

Wet bulb readings or relative humidity readings

Yes Yes Yes Optional --

Metrology at both ends of measured lines before and after measurements

Yes Yes Yes At time of

observations --

Reciprocal vertical angles6

Yes simultaneous

Yes simultaneous

Yes Optional Optional

National standard traceability of EDM

Yes Yes Yes Yes Yes

Calibration Requirements

All ancillary equipment should be regularly calibrated, carry unique identifiers, and (where relevant) be regularly compared against each other.

The frequency standard should be traceable to the national standard, and calibrated once per year.

The additive constant and the oscillator frequencies of the EDM unit should be determined at least annually, and after each repair or maintenance of the EDM unit.

1 A full measurement with a direct readout instrument shall consist of a number of readings (e.g. 6 to 10) over several minutes, after

which the instrument should be re-pointed and electronically realigned, for a further group of readings. This comprises a set. A full measurement with an indirect readout instrument shall consist of a series of fine readings on the relevant different frequencies. A set is defined as two full measurements, taken one after the other.

2 Not required if the coarse distance is known.

3 Where d is the length measured, in km.

4 Observations may be performed outside of the specified times (except at Sunset or Sunrise) as long as a statistically proven correction

factor is applied. 5 The minimum warm-up time to be determined during frequency determination.

6 Simultaneous reciprocal or reciprocal vertical angles are not required if the heights of both ends of the line are known accurately. A one

way vertical angle is sufficient to determine K, the coefficient of refraction accurately.


17

Table 1.3 (b): Electro-Optical EDM Reduction Procedures

ORDER 0 1 2 3 4

Additive constant correction

Yes Yes Yes Yes Yes

Reflector additive constant correction

Yes Yes Yes Yes Yes

Cyclic error correction Yes Yes Yes Yes Optional

Frequency correction Yes Yes Yes Baseline Baseline

Barometer correction Yes Yes Yes Yes Optional

Thermometer correction Yes Yes Yes Yes Optional

1st velocity correction (atmospheric correction.)

Yes Yes Yes Atmospheric

dial Atmospheric

dial

Arc to chord correction (beam curvature correction.)

Yes Yes Yes Over 5 km Optional

2nd velocity correction (dip correction)

Yes Yes Yes Over 5 km Optional

Chord to chord correction (combined slope & mean sea level)

Yes Yes Yes Combined

Scale Factor Yes

2nd chord to arc correction (geoidal chord to arc correction.)


Geoid to ellipsoid correction



18

1.2.5.2 Horizontal Angle Measurement

The observation requirements for horizontal angle measurement are shown in the table below. Adherence to these requirements should ensure that the appropriate level of precision is achieved.

Table 1.4: Horizontal Angle Observation Requirements

ORDER 01 1

1 2 3 4

1. Required Time of Day

Two hours either side of sunrise/set. Yes

Any time except 1200-1500hrs (LMT) Yes

Any time, subject to checks Yes Yes N/A

2.Instrument Least Count Category

Highest 0.5” 0.5”

High 1” 1” 1” 1”

Medium 6” 6”

3. Horizontal Zero Settings Yes Yes Yes Yes N/A

4. Set

A. Minimum number of sets 62 6

2 2 2 1

B. Number of rounds per set 6 6 6 4 4

5. Field Checks

A. Residual from mean of any direction within each set

(i) should seldom exceed 3” 3” 3” 3” 5” (ii) should never exceed 4” 4” 5” 6” 10”

B. Ranges within each set

(i) should seldom exceed 4” 6” 6” 6” 10”

(ii) should never exceed 6” 8” 10” 12” 20”

For applicable sets, an additional round should be observed when a range is exceeded, however if two rounds exceed the range the sets should be re-observed, under improved conditions:

C. Ranges between sets

(i) should seldom exceed 1.5” 2” 3” N/A N/A

(ii) should never exceed 3” 4” 4” N/A N/A

6.Observation Corrections

Instrumental Systematic Errors Yes Yes Yes Yes Yes

Signal Phase Errors Yes Yes Yes Yes Yes

Dislevelment of the Trunnion Axis Yes Yes Yes Yes

Horizontal Refraction Minimize using appropriate procedures for prevailing conditions.

Deflection of the Vertical Yes Yes

Skew Normals Yes Yes

1 Instrument and tripod should be shaded.

2 Sets should be observed in equal proportion over two days.


19

1.2.5.3 Spirit, Auto or Digital Leveling Differential leveling is the conventional method of leveling for the propagation of orthometric heights. Heights are commonly propagated using spirit, automatic and digital levels. Alternatively, heights can be propagated by EDM Height Traversing, using Total Stations.

Table 1.5: Differential Leveling Equipment Characteristics with Order

ORDER

0 1 2 3 4

Level-minimum requirements

0.2mm/km spirit level

or 0.4 mm/km

digital level1

0.4mm/km automatic non digital level with parallel plate

micrometer or

0.4mm/km digital level

1.

As for Order 1

1.0-1.5 mm/km or

better automatic or

digital level

1.

1.5mm/km or upward (ie. less

sensitive) auto-

collimating or digital

1 or

spirit level.

Staff construction minimum Requirements (Analog

2 or

bar coded3)

Rigid Invar. Rigid Invar.

Rigid Invar or folding & telescopic

staff

Folding or telescopic

staff

Folding or Telescopic

staff

Staff graduation interval (Analog staves).

5mm 5mm or 10mm

As for Order 1

10mm 10mm

Tripod construction Rigid Rigid Rigid Rigid Rigid or

telescopic

Bubble attached to staff Yes Yes Yes Yes Optional.

Solid, portable change points

No - Route is pre-

marked. Yes Yes Yes Optional.

Umbrella for level Yes Yes Yes No No

1 Digital Levels have been developed by several manufacturers in recent years to offer automated staff reading and digital recording of

leveling observations. These instruments offer protection against both staff reading errors and booking errors. 2 Analog refers to staves that have accepted metric or foot face patterns that have been developed over time for optical levels.

3 Bar coded refers to staff face patterns developed specifically for digital levels.


20

Table 1.6: Differential Leveling Equipment Testing

ORDER

0 1 2 3 4

System test prior to commencement (eg ISO, DIN or Princeton)


Maximum standard error in the slope of the line of sight as determined by the system test

Spirit level: 1”/2mm run Automatic or digital:

0.4” setting accuracy.

Spirit level: 1.5”/2mm

run. Automatic or digital:

0.4” setting accuracy.

Spirit level: 4”/2mm run. Automatic or digital: 0.8”

setting accuracy.

Spirit level: 10”/2mm

run. Automatic or digital:

1.0”setting accuracy.

--

Vertical collimation check (eg. Two-Peg Test) Frequency Maximum collimation error

Daily 2” or 0.3 mm

over 30m. (Digital

levels can “Store” the

results)

Daily 2” or 0.8 mm

over 80m.

Daily 4” or 1.5 mm over

80m.

Daily 10” or 4 mm over

80m.

As required 10” or 4 mm over 80m.

Level cross-hair verticality check

Yes Yes Yes Yes Optional

Staff calibration frequency Immediately prior to commencement of leveling, and at 3 monthly intervals whilst in continued use.

Within 6 months of use.

Optional

Staff bubble verticality to be within

5’ 1

10’ 10’ 10’ 10’

Thermometers accurate to 0.5°C 1°C 1°C 1°C Optional

1 5’ is equivalent to 4.5mm movement at the top of a 3m staff. Supporting braces are essential.


21


22

Table 1.8: Differential Leveling Reduction Procedures

ORDER

0 1 2 3 4

Orthometric correction to be applied

Yes Yes Yes Optional N/A

1.2.5.4 EDM Height Traversing

Differential leveling is the conventional method of leveling for the propagation of Orthometric Heights. A variant of the common technique of spirit leveling is EDM-Height-Traversing where the difference in height between change points is determined using observations of zenith angles and slope distances. The most convenient mode is that of Leap-Frog EDM-Height-Traversing to two reflectors of fixed height in the usual backsight / foresight mode used in leveling.

Table 1.9: EDM Height Traversing Equipment Characteristics

ORDER 0 1 2 3 4

Electronic Tacheometer (Total Station) requirements

- - - 2 mm + 2 ppm distance and

3” zenith angle

3 mm + 2 ppm distance and 5”

zenith angle

Accuracy of Level Sensor or compensator

- - - 1.5” 2.5”

Diametrical Circle Reading on Vertical Circle (or equivalent)

- - - Optional Optional

Entry of Temperature and Pressure for on-line First Velocity Correction

- - - Yes Yes

Refraction and Earth Curvature Correction enabled

- - - Yes Yes

Target / Reflector construction: Minimum requirements

- - -

1 - 2 Standard Reflector Rods with

balanced and tilting Prism

1 - 2 Standard Reflector Rods with balanced

and tilting Prism

Reflector Rod Support - - - Bipod/ Two Leg Struts

Optional

Bubble attached to Reflector Rod

- - - Yes Optional

Solid, portable change points

1

- - - Yes Yes

Umbrella for instrument - - - No No

1 All temporary (change plates) and permanently marked change points must feature a small central hole so that the reflector rod does

not slide off.


23

Table 1.10: EDM Height Traversing Equipment Testing

ORDER

0 1 2 3 4

System test prior to commencement

- - - Optional Optional

Calibration of index errors of vertical circle and level sensor

- - - Daily As required

Staff bubble verticality to be within - - - 10’ 10’

Barometers accurate to - - - 2 hPa 2 hPa

Thermometers accuracy - - - 1°C Optional

Table 1.11 (a): EDM Height Traversing Observation Procedures

ORDER 0 1 2 3 4

EDM Height Traversing Method 1 - - -

Leap-Frog or Reciprocal

2

Leap-Frog or Reciprocal

2

Number of sets to target - - - 1 1

Pointing in first set: (In second set, if applicable, first FS, then BS)

- - -

BS(FL), BS(FR), BS(FR), BS(FL), FS(FL), FS(FR), FS(FR), FS(FL)

BS(FL), BS(FR), BS(FR), BS(FL), FS(FL), FS(FR), FS(FR), FS(FL)

Max Spread per set - - - 1.5 mm 3.0 mm

Height difference recorded to nearest

- - - 1 mm per pointing 5 mm per pointing

Temperature and Pressure measured and entered into the instrument

At start, middle and finish of each ‘leveling ‘run and at pronounced changes of temperature

At start of ‘leveling’ run

Maximum length sight In Leap-Frog EDM Height Traversing

- - - 120 m 150 m

Slope distance recorded (for balancing FS and BS distances) to:

- - - 1.0 m 1.0 m

Minimum ground clearance of line of sight

- - - 0.3 m 0.2 m

1 Leap-Frog” EDM-Height-Traversing: "Leap-Frog" EDM-Height-Traversing involves the one target remaining at a particular change

point for both sightings. To avoid the possibility of the target being placed on a different point the target is not to be moved between the back-sight and foresight. Two target/reflectors are employed (on reflector rods with struts). As in spirit leveling, it is imperative that the electronic tacheometer (total station) is set up in the middle between the two reflectors. Recorded are the height differences (between the instrument’s trunnion axis and the reflector) that are computed by the electronic tacheometers. In consequence, the ambient temperature and pressure must be input into the instrument since the slope distances must be corrected for temperature and pressure (first velocity correction) online. See Rüeger & Brunner (1982) and The Canadian Surveyor, 36(1): 69-87.

2 “Non-Simultaneous Reciprocal” EDM-Height-Traversing: Normal EDM traversing equipment is employed with one electronic

tacheometer, two reflector/target assemblies and two to three tripods. To connect to bench marks, the instrument has to be set up within 20 m. The height difference between instrument and bench mark is obtained by zenith angle measurements to some marks on a leveling staff on the bench mark (or to a prism on reflector rod with struts on the bench mark). Between tripods, the zenith angles and the slope distances are measured forward and backwards. Since this provides two height differences per leg, reciprocal EDM-Height-Traversing is only done one-way. Depending on the accuracy requirements, the lengths of the legs in reciprocal EDM-Height-Traversing can be significantly longer than in Leap-Frog EDM-Height-Traversing. See Rüeger & Brunner (1982).


24

Table 1.11 (b): EDM Height Traversing Observation Procedures

ORDER 0 1 2 3 4

Back-sight and fore-sight lengths to be equal within

- - - 10 m (set out) 20 m (set out)

Observing times Sight lengths might have to be reduced to achieve “Max Spread per

Set” in poor observing conditions (e. g. heat shimmer)

Two-way leveling in Leap-Frog EDM Height Traversing

- - Yes (But NOT in reciprocal EDM-Height-

Traversing)

Even number of instrument set-ups between bench marks

Yes in Leap-Frog EDM-Height-Traversing with two reflector rods (Not applicable for Reciprocal EDM-Height-Traversing)

Optional

Minimum number of holding marks used for temporary suspension of leveling

- - - 2 1

Minimum number of holding marks used for temporary suspension of leveling > 5 days

- - - 3 overlapping

marks re-leveled within 2√d

1

Maximum misclosure (mm) of forward and reverse leveling runs

- - - 12√d 24√d

d is the distance in kilometers between benchmarks

Minimum number of bench marks used to prove datum

- - - 3 2

Maximum misclose (mm) on datum BM’s

- - - 12√d 24√d

d is the distance in kilometers between benchmarks

Table 1.12: EDM Height Traversing Reduction Procedures

ORDER

0 1 2 3 4

Orthometric correction to be applied

- - - Yes N/A


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1.2.5.5 Trigonometric Heighting Trigonometric heighting is achieved using several individual items of survey equipment. Unless directly specified to achieve a desired ORDER of trigonometrical heighting, use procedures and standards for the particular observation type (e.g. vertical angle, distance).

Table 1.13: Trigonometrical Heighting Specification

1.2.5.6 GNSS Heighting

After applying correct geoid model to the ellipsoidal height obtained using GNSS, the resulting orthometric height is classified as 5

th Order and is round up to 2

nd decimal place.

1.2.5.7 Decimal Places for Height Values

Order No of decimal place (m)

0 4

1 4

2 4

3 3

4 3

5 2

1.2.5.8 Global Navigation Satellite System (GNSS)

(i) Introduction

• Over recent years the surveying profession has witnessed the growing capability and widespread use of the Global Navigation Satellite System (GNSS) for a number of surveying operations.

ORDER

1 2 3 4

Simultaneous reciprocal - - - Optional

Non-simultaneous Reciprocal - - - Optional

One way Observations - - - Yes

Observing times (Local Mean Time) d > 16km d < 16km

- - - 1400-1600 1000-1600

Number of sets - - - 1

Number of pointing (per set) - - - 6

Maximum range per set - - - 8”

Meteorological Observations - - - Yes


26

• These guidelines indicate best practice for the use of GNSS for surveying applications. The purpose of this section is to present these principles in general terms so that they can be applied by users to achieve a quality result.

• It should be noted that these guidelines do not represent legal traceability of measurement. (ii) Geodetic Datums and Geoid Separations

• The WGS84 (World Geodetic System 1984) is the geocentric datum, used for broadcast and precise ephemerides associated with GPS satellite systems.

• All adjustments of GNSS data should be 3 dimensional on the WGS84 ellipsoid.

• Horizontal survey measurements, once completed, should form a closed figure, and where possible, be connected to a minimum of three (3) existing stations in the geodetic network with an Order appropriate to the survey being undertaken. Reference station coordinate values in the national geodetic datum should be obtained from CGIS

• The vertical datum used in Qatar is Qatar National Datum (QND)

• Where orthometric heights are to be calculated from the GNSS observations, the selected control stations should have, when possible, accurate vertical datum heights. Otherwise, additional GNSS connections should be observed to BenchMarks with good vertical datum heights. These connections, along with the geoid model, enable fitting to the vertical datum

• Qatar geoid separation values (n values) should be obtained from the Qatar95 Geoid model, available from the CGIS.

(iii) Equipment Validation

• If required, the equipment and software can be validated over existing, high quality geodetic network marks. The relevant authority can be contacted for more information.

• Another useful method is to measure a ‘zero baseline’, which is achieved by connecting a single GNSS antenna to two GNSS receivers using a special antenna cable splitter. The positions obtained from the two receivers should agree at the sub centimeter level.

(iv) Fundamental GNSS Techniques There are three fundamental GNSS techniques:

• absolute point positioning

• differential GNSS (using pseudo range measurement - DGNSS)

• relative positioning (using carrier phase observations) These guidelines generally refer only to relative GNSS positioning, which requires two or more GNSS receivers, observing carrier phase observations. The exception to this is the section on GNSS observations for global/regional processing where only one survey quality GNSS receiver is required, but the data collected is later processed with data from global and regional GNSS sites, using on-line processing services. It is the responsibility of the user to assess which GNSS technique or combination of GNSS techniques should be used to achieve the task being undertaken, having regard to the manufacturer's specifications for the equipment and survey specifications.

(v) Planning a GNSS Survey

• Network Design and Geometry (Horizontal and Vertical Networks)

– When planning a GNSS survey, the first step should be choosing the appropriate technique for the precision required. Table 1.14 provides a guide to the user as to what technique should be used in order to achieve a particular class of survey.

– The location and distribution of points in a GNSS survey do not depend significantly on factors such as network shape or inter-visibility, but rather on an optimum layout with sufficient redundancy for carrying out the intent of the survey.

– All GNSS surveys should be connected to the state control where it is available, for the purposes of survey integration, legal traceability and quality assurance. Such connection may be a regulatory requirement in some local authorities.


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– The planning of the observations should be such that the error budget is sufficiently minimized. Redundancy in the observations is the best way of dealing with most of the error sources.

– Important issues are positive mark identification, centering, height of antenna phase centre as well as antenna orientation and independent re-occupation of the same point, after a sufficient lapse of time.

– Horizontal survey measurements, once completed, should form a closed figure; reference station coordinate values in the national geodetic datum should be obtained from CGIS.

– A supplement or alternative to independent reoccupations could be the inclusion of conventional observations of appropriate accuracy (for example to create ties between unavoidably unclosed GNSS polygons in the same adjustment).

– The higher Order reference stations should be used for controlling the network accuracy with equally distributed manner.

Table 1.14: GNSS Method vs Order

ORDER 0 1 2 3 4

Technique

Classic Static � � � � �

Fast Static / Rapid Static � � �

Guide to minimum station spacing km

1

10 5 0.5 N/A N/A

Typical station spacing in km 2 10-100 5-15 0.5-5 >0.05 N/A

Independent occupations per station

3

at least 3 times (% of total stations)4

at least 2 times (% of total stations)4

40% 100%

20% 100%

10% 100%

Minimum independent baselines at each station

4 4 4 3 2

The Stop & Go and RTK GNSS methods are used only in establishing temporary controls without any classifications/Orders. Independent Baselines – An independent baseline measurement in an observing session is achieved when the data used are not

simply different combinations of the same data used in computation of other baseline vectors observed in that session.

– In the one session, observing with n receivers, the total number of baselines that can be computed is n(n-1)/2. However, only n-1 of those baselines are independent. The remainders – trivial baselines - are formed from combinations of phase data used to compute the independent baselines. The results from observations of the same baseline made in two different sessions are independent.

– Generally independent baseline processors assume that there is no correlation between independent vectors. Trivial baselines may be included in the adjustment to make up for such a deficient statistical model. If the mathematical correlation between two or more simultaneously observed vectors in a session is not carried in the variance-covariance matrix, the trivial baselines take on a bracing function simulating the effect of the proper correlation statistics, but at the same time introducing a false

1 Minimum station spacing is illustrated using a 5 mm noise level after adjustment. Below these minimum distances, special efforts are

required to reduce the error budget. For a noise level of 10 mm these values are to be approximately doubled. 2 These values relate to the using of conventional equipment and proprietary software.

3 Independent occupations per station may be back to back, but the antenna should be re-set for each occupation. The minimum

observation period should be observed with each occupation as per the manufacturers’ recommendations. 4 For example for a ORDER 1 network aim for:

(i) 20% of stations are to be occupied at least three times; (ii) 100% of stations are to be occupied at least twice.


28

redundancy in the count of the degrees of freedom. In this case the number of trivial baselines in an adjustment is to be subtracted from the number of redundancies before the variance factor (variance of unit weight) is calculated. If this approach is not followed, trivial baselines are to be excluded from the network altogether.

• Minimum GNSS Occupation Time

Table 1.15: Minimum GNSS Occupation Time

Single Frequency

Length of Baseline < 5 Km > 5 to <10Km > 10 to <15km

Static 20 minutes 20 to 50 minutes1 50 to 75 minutes

1

Fast Static @ 95% confident level 15 minutes 15 to 20 minutes N.A.

Double Frequency

Length of Baseline < 5 Km > 5km to <15Km > 15 to <50Km

Static @ 95% confident level 20 minutes 20 to 50 minutes 50-130 minutes1

Fast Static 8 to 10 minutes1

10 to 20 minutes1

N.A.

Observation times and accuracy are functions of GDOP (should be less 7), number of satellites (more than 5), ionospheric disturbances but mainly distance.

Observation times are determined avoiding both the worst “observing window” and optimum “observing window” while traditionally assuring a fixed ambiguity integer solution.

Below are some industry standard occupation times that are acceptable.

Static at 95% confident level

Single Frequency (15km max): 30 min + 2 min per km Double Frequency: 20 min + 2min per km

Fast Static at 95% confident level

Single Frequency: 15 min + 2min per km Double Frequency: 8 min + 1 min per km

Recommended epoch rate: Static -15s, Fast/Rapid Static - 5 or 10s, stop and go & RTK – 1s

(vi) Guidelines for GNSS Observations

The following guidelines refer to different types of GNSS survey techniques such as static, fast static and pseudo-kinematic.

– Users should be familiar with the procedures and recommendations contained in the GNSS equipment and software manuals and the stipulated survey standards and specification documents.

– In the event of a conflict between these guidelines and the manufacturer’s instructions, the manufacturer’s recommendations will prevail. As part of the process of keeping these guidelines current, any conflict between these guidelines and the manufacturer’s recommendations should be forwarded to the CGIS with all relevant details to allow the conflict to be resolved.

1 Indicates a range of time proportional to the vector distance.


29

– All ancillary equipment must be in good adjustment and repaired and operated competently by trained personnel. This is of particular importance with GNSS because it is a three-dimensional (3D) technique requiring accurate location of the antenna horizontally and vertically over any survey mark. All GNSS measurements relate to the exact location of the antenna. Therefore its precise relationship to the ground mark is critical to the process of obtaining quality results.

– Receivers and baseline reduction software are to be of the "geodetic" type. – Only carrier beat phase observations using two or more receivers for baseline measurements are

considered in these guidelines. – Satellite geometry during the field observation phase of any survey must be sufficient to ensure accurate

results. The maximum geometric dilution of precision (GDOP) should be no greater than 7. The user should comply with the GNSS manufacturer’s recommendation’s on GDOP values during observation periods. This can aid in resolution of integer ambiguities if required when using the GNSS manufacturers processing software.

– The elevation mask should be generally set according to the manufacturer’s recommendations, but typically should not be less than 15°.

– Inaccurate starting coordinates adversely affect the accuracy of the baseline results. Therefore, an initial geocentric coordinate within 10 m of the true position should be used for the reduction of observations. With the cessation of Selected Availability and the improvement in the receiver algorithms, the receiver-generated position is usually within this limit.

– It is not necessary to take meteorological readings. Use the GNSS reduction software defaults for tropospheric modeling.

– Antenna heights for re-occupations are to be changed by at least 0.1 m unless set up on a pillar. – The GNSS signal may be degraded or blocked by nearby buildings, trees or topography. There should be

clear visibility to the sky in all directions, down to the elevation mask being used (typically 15°) – Multipath can be a significant source of errors, particularly when short occupation times are used. A

typical high multipath environment is in the proximity of corrugated iron roofs, wet trees, high rise buildings and chain wire fences. As well as its direct effect, multipath appears as noise and can affect ambiguity resolution. Where multipath is likely, occupation time should be increased to allow the effect to be averaged away as satellite geometry changes.

(vii) Specific Observational Requirements for Various Relative GNSS Techniques Within the fundamental relative GNSS positioning technique there are several methods that have developed since the introduction of GNSS. They all employ carrier phase measurements. Whilst most of the observational requirements are comparable, there are also some specific conditions:

• Classic Static Baselines

The following guidelines apply to Classic Static baselines, in conjunction with the general guidelines:

− The observation period for shorter lines (approximately 10 km) should be at least 30 minutes. Observation periods for longer lines should increase as stated in the manufacturer's specifications or in accordance with any CGIS specifications.

− The epoch recording rate is recommended to be 15 or 30 seconds.

− The satellite geometry should change significantly during the observation period.

− At least four, but preferably as many satellites as possible should be common to all survey sites simultaneously occupied

− Dual frequency receivers are preferred but single frequency survey quality receivers may be used for short lines (less than 10 km) for non high precision applications.

− Sufficient data should be collected to resolve ambiguities. This is particularly important for lines less than 15 km.

• Fast Static Baselines (Also Known as Rapid Static or Quick Static) The following guidelines apply to Fast Static baselines, in conjunction with the general guidelines:

− Enough data should be collected to resolve ambiguities. Please refer to the manufacturer’s recommendations in relation to the length of observation periods, number and geometry of satellites and the suitability of single or dual frequency receivers.


30

− Multipath can be a significant source of errors, particularly when short occupational times are used and special attention should be paid to this issue.

− The epoch recording rate normally may vary between 5 and 15 seconds. (viii) Processing Baselines In relation to the above-described techniques, the guidelines for processing GNSS baselines are as follows:

− The quality of the results of a GNSS survey is determined by both the method of observation, including choice of equipment, and the quality of the reduction, adjustment and transformation procedures. The initial satellite datum station position for any baseline calculation should be no more than 10 meters, in error, for each part per million accuracy required and is best obtained by a transformation, or by connection to another point with its coordinates known in the satellite datum.

− Because of the effect of the ionosphere, dual frequency receivers are used on lines over a certain length. "L1-only" solutions often show less noise for vector lengths below 10-15 km. Single frequency receivers can still satisfy Order 0, 1, 2, 3 etc. requirements up to 20-odd km, but need an increasing number of hours of observation if the higher Orders of survey or longer baselines are observed. Dual frequency ambiguity fixed L1 and L2 solutions in their ion free linear combination are usually obtained for vector lengths above 10 -15 km to up to 40 or 50 km. An ambiguity fixed solution is preferred, but the longer the distance becomes the harder it is to achieve this. Ion free ambiguity float L1/L2 solutions become more common for vectors of over 40 or 50 km in lengths up to about 90 km.

− For longer baselines eventually even triple difference solutions are used, if the observation duration is sufficiently long, to enable a sufficient change in the satellite geometry during the recording session. As a guide use 30 minutes + 20 minutes per 10 km of the baseline length. Order of coordinates of new points should be based also on the distance between them Unequal baselines need to be considered in Nearby existing points should be used as Base Station. If that is not possible, Order of coordinates of a new point, unconnected to a nearby coordinated point, should be commensurate with distance between them. Some new points should be occupied from three base Stations. Additional control should be connected to check the fit of the survey to the Datum Coordinates of new base stations should be determined before commencing RTK survey Base Station with known coordinates New Point Legend.

(ix) Analysis Using Least Squares Adjustment In the case of classic static and quick static, least squares adjustments of the network, both minimally constrained and constrained by all suitable geodetic stations coordinates, should be carried out to verify that the survey meets the required standards.

Most proprietary baseline processing packages contain a suitable least square adjustment module. However, separate, specialized 3-D adjustment software should be used when adjusting a very large number of baselines, when combining GNSS and terrestrial observations or when the proprietary software does not produce relevant statistical output.

• Unconstrained Adjustment

− The processing software should be able to produce the variance/covariance statistics of the observed Cartesian vectors so that these can be input to a three-dimensional adjustment program. A least squares adjustment should be performed when deriving values for control surveys. This software should be capable of determining transformation parameters between the observed Cartesian vectors and the local geodetic system.

− Error ellipses should be calculated, after a minimally constrained least squares adjustment. They mainly prove quality of the net design rather than the quality of the observations. The error ellipses should be scaled by the a priori variance of unit weight (generally equal to one), unless the a-posteriori estimate of variance does not pass the Chi-square test. In case of the latter, the observations, the statistical model or even the mathematical model should be examined, the problem remedied and the adjustment rerun. In the case of not being able to remedy the situation, the error ellipses should be scaled by the a-posteriori variance factor.

− To confirm the quality of the observations, the standardized residuals should be checked for outliers, and these should be dealt with. The checking of the statistics often involves critical evaluation of the a priori standard deviations of the observations. If the baseline variance/covariance matrix is routinely modified


31

by a multiplier, documentation of a measurement over a test network can be required as confirmation of the multiplier used.

− In order to conform to the internal consistency requirements for a particular geometric accuracy Order the following conditions should be met: the error ellipses should confirm the capability of the network design to meet the specifications, the standardized residuals and the estimate of variance should confirm that the observations have actually met the required standard.

− All points in a survey should conform to specifications belonging to the relevant classification. This is irrespective of whether the points are connected by baseline observations or not. This is also valid when relative accuracy values are calculated to points with previously established coordinate values.

− Geoid separation values are now applied to orthometric heights of points that will be constrained in the transformation and adjustment.

• Application of Geoid Separation (n)1 Values

For users in the State of Qatar, program QTRANS is available from the Centre for GIS that computes both coordinate transformations between WGS84 and QND95 and also the Qatar95 geoid components (Geoid - Ellipsoid separation, and deflections of the vertical only on WGS84 ellipsoid).

• Constrained Adjustment

The final step is a fully constrained Least Squares adjustment. This adjustment is subjected to the same analysis as the above minimally constrained adjustment. Again error ellipses are calculated and the network is allocated an accuracy Order which enables its orderly integration with the database containing the existing data set of established coordinates.

(x) Field Notes and Data Lodgment

• Field observation recording sheets (log sheets) should be completed for each session. The receiver type, serial number and software used for reductions should be recorded on these sheets.

• An indication of independent checks on height of antenna is essential.

• Field Book (or log sheet) should contain a sketch of the relevant part of the network as well as the name and/or identifier used for each station. Each baseline measured should be clearly indicated. The reduction software may produce a printout of these details.

• The GNSS field recording sheets are available at relevant department of CGIS. (xi) Digital Data Storage

A

• Raw observational data should be archived in case an auditing process is required by the examining authority. (Note: raw data is equivalent to the surveyor’s field book and should be retained for the same length of time)

• If required by the examining authority, result files from the baseline processing and final adjustments must be supplied in digital form. The recipient may recommend the processing and/or adjustment software digital format. This enables automatic inclusion of the results in the recipient’s data base systems.

• Final adjusted coordinates are to be provided in the QND95 coordinate system. (xii) “Absolute” Positioning with GNSS

Accurate positions can be determined by GNSS observations using a single geodetic quality receiver. Although this relies on a regional or global framework of continuously operating geodetic GNSS stations, it is generally transparent to the user. The data can be processed by a variety of methods which automatically provides the results in terms of the International Terrestrial Reference Framework (ITRF) (e.g. JPL’s AutoGypsy and the Canadian CSRS-PPP). It is also possible to produce similar results from regional processing of geodetic GNSS data using specialized software (e.g. Bernese, Gamit).

1 Geoid Separation (n) values only for WGS 84 ellipsoid

A For Sample Directory structure for digital data storage, see page 16.


32

Table 1.16 gives guidelines to achieve typical Positional Uncertainty values using this type of technique. However, as this technique depends on many local & global variables the results may vary from the guidelines shown below. These guidelines do not override those which may be recommended by individual jurisdictions.

Table 1.16: GNSS Data Attributes for “Absolute” Positioning

Positional Uncertainty (m) 1

(Horiz / Vert) 0.025 / 0.05 0.05 / 0.1 0.1 / 0.2

IGS products 2 (minimum standard

accepted) IGS Final (~14

day delay) IGS Rapid (~2

Delay) IGS Ultra-rapid

(partly predicted)

GPS Receiver 3

Geodetic, dual frequency, carrier

phase & code


phase & code


phase & code

GPS Antenna 4

IGS/NGS modeled

IGS/NGS modeled

IGS/NGS modeled

GPS data format 5 RINEX RINEX RINEX

GPS data sampling 6 30 sec 30 sec 30 sec

Duration of observations 7

Multiple 24 hour sessions



Repeatability between sessions (m) (Horiz / Vert)

8 0.025 / 0.05 0.05 / 0.1 0.1 / 0.2

Transformation to QND95 9

Yes Yes Yes

Solution statistics satisfied10

Yes Yes Yes

Antenna type11 Make, model &

serial number Make, model & serial number

Make, model & serial number

Antenna height12

mm mm mm

Reference stations13 At least 3 within

1500 km At least 3 At least 3

1 Positional Uncertainty is a 95% confidence value, in metres, with respect to the datum.

2 Refer to the IGS product guidelines at http://igscb.jpl.nasa.gov/components/prods.html to see the usual delay for the various IGS

products to become available. Some services may use their own products equivalent to IGS’s (e.g. orbits, earth orientation, satellite clock corrections). The use of the IGS ultra rapid products may sometimes produce results with unacceptable uncertainty.

3 Some hand-held receivers may provide phase & code, but the quality of their data cannot be guaranteed for this type of processing

4 The processing must account for antenna phase centre variation with the azimuth & elevation of satellites. See

ftp://igscb.jpl.nasa.gov/igscb/station/general/igs_01.pcv & http://www.ngs.noaa.gov/ANTCAL/ for the latest list of antenna calibrations. The standard naming convention should be used to eliminate ambiguity, see ftp://igscb.jpl.nasa.gov/igscb/station/general/rcvr_ant.tab (see also note 11).

5 Most commercial geodetic GPS software packages will convert the proprietary observed data to the Receiver Independent EXchange

format (RINEX) (see ftp://igscb.jpl.nasa.gov/igscb/data/format/rinex210.txt for a full explanation). TEQC is a freely available quality checking package that also converts the most popular geodetic GPS receiver data types to RINEX format, see www.unavco.org/facility/software/preprocessing/preprocessing.html for details.

6 Most processes use 30 second data, but will accept any sampling rate less than 30 seconds that can be stripped back to 30 seconds

(e.g. 1, 3, 5, 6, 10, 15, 30 sec). 7 Each session should be entirely within a UT day. Although shorter duration sessions may give adequate results, they cannot be

guaranteed, particularly if local conditions are unfavourable (e.g. multi-path, interference, obscured sky view). Repeat shorter duration sessions should be observed at different times of the UT day to minimise systematic effects from the GPS system and ambient site conditions (e.g. similar satellite constellation).

8 Multiple sessions are recommended to ensure repeatability and hence confidence in the result. If two sessions do not agree within

the

required precision, a third session is required to resolve the discrepancy. Equipment should be set up again at the commencement of each session, as per normal multi observation geodetic practice, to isolate setup errors.

9 Transformation to the local datum is required. At least three fiducial positions known in both systems (ITRF and local datum)

and

include tectonic motion and transformation from ITRF to local datum. 10

To ensure that the data used is of an acceptable standard, the service provider’s solution statistics must be examined and acceptable. This may vary between systems, but typically should include: estimated coordinate precision and observation fits.

11 The calibration for an antenna can be different, even for the same brand with only slight variations in the model. Exact identification

is

essential to ensure that the correct calibration is applied (see note 4 above).

12 If the results are to be reduced to a fixed survey mark, the vertical height of the Antenna Reference Point (ARP) above this mark must be accurately measured, preferably by several independent means. Check the manufacturer’s specifications in conjunction

with the

IGS document at ftp://igscb.jpl.nasa.gov/igscb/station/general/antenna.gra and the NGS documentation at http://www.ngs.noaa.gov/ANTCAL/ to identify the ARP, as it can vary subtly even within one manufacturer.

13 Most processing services will automatically select the nearest three IGS stations as reference stations for the processing. While this can generally be relied on, for critical projects the operation of appropriate reference stations and reliability of their ITRF station coordinates (e.g. sites affected by recent earthquake movements or GPS antenna changes) should be checked before proceeding.


33

(xiii) GNSS Specifications by Survey Scope

Table 1.17: GNSS Specification by Survey Scope

Specifications Basic1

Construction2

Aerial3 Cadastral

4 Engineering

5,6

Minimum number of connections to higher order fixed known horizontal/vertical control per network

3 3 2 2 2

Minimum number of independent vectors to individual control points

2 Vectors 1 scalar

2 2 1

Max number of network traverse legs without 3 independent vectors

2 4 4 4 N/A

Dual frequency Y N N N N

Minimum satellite mask angle above horizon

13 13 13 13 13

Minimum number of satellites tracking/GDOP

5/7 5/6 5/6 5/6 5/6

Epoch recording Rate (seconds)

15 15/5 15/5/1 15/5/1 15/5/1

Field data log required Y Y Y Y N

Point description with unique name required

Y Y Y Y N

Recommended min/max station spacing(km)

0.5/15 0.3/0.6 Max 10 Max 10 Max 0.5

Survey Method

Static

Fast Static

Stop & Go

RTK(post processing)

RTK(calibration)

Conventional

Control Surveys 1 BASIC CONTROL SURVEY: The basic control survey or control densification, based directly upon zero order control, provides control

for all other project surveys and is a connected series of independent vectors, properly weighted, constrained, and adjusted least squares network.

2 CONSTRUCTION CONTROL SURVEY: This survey, based directly upon previously adjusted and fixed Basic control and being

intervisible between adjacent monuments. 3 AERIAL CONTROL SURVEY: This survey, based directly upon, as a minimum, previously adjusted and fixed higher order

Construction control, provides for the placement of survey aerial targets. Cadastral Boundary Surveys 4 CADASTRAL BOUNDARY SURVEY: This survey, based directly upon and as a minimum, previously adjusted and fixed Construction

control, providing for positions of property monuments is used to identify properties and boundary locations. Engineering Surveys 5 TOPOGRAPHIC SURVEY: This survey, based directly upon and as a minimum, previously adjusted and fixed Construction control,

provides for the location of topographic features, including utilities, surfaces, and other detail. 6 CONSTRUCTION SURVEYS: This survey, based directly upon and as a minimum, previously adjusted and fixed

Construction

control, marks the horizontal location (line) as well as the vertical location, or elevation (grade) for proposed fixed works.


34

(xiv) Vertical Control Surveys Using GNSS

Reference is made to the “Draft Guidelines for Establishing GPS-Derived Orthometric Heights (Standards: 2 cm and 5 cm) V1.4” published by National Geodetic Survey dated October 2005.

1

The following guidelines for performing GNSS surveys intended to achieve orthometric height network accuracies of 5 cm and orthometric height local accuracies of 2 cm or 5 cm, both at the 95 percent confidence level. Network accuracy - a value that represents the uncertainty in the coordinates of the point with respect to the geodetic datum. Local accuracy - a value that represents the uncertainty in the coordinates of the point relative to the coordinates of other local, directly connected, adjacent points.

Orthometric heights (O) are referenced to an equipotential reference surface, e.g., the geoid. The orthometric height of a point on the Earth's surface is the distance from the geoidal reference surface to the point, measured along the plumb line, normal to the geoid. Ellipsoid heights (H) are referenced to a reference ellipsoid. The ellipsoid height of a point is the distance from the reference ellipsoid to the point, measured along the line which is normal to the ellipsoid. At the same point on the surface of the earth, the difference between an ellipsoid height and an orthometric height is defined as the geoid height (n) (Figure 1.2).

Figure 1.2: Geoid Height

The 3-4-5 System There are three basic rules, four control requirements, and five procedures necessary for estimating GPS-derived orthometric heights. This document describes their requirements, in order to meet 2-cm or 5-cm standards, and does so in brief format. Detailed explanations can be found in the referenced reports.

Three Basic Rules

Rule 1: Follow the specific guidelines for desired orthometric heights. For example, use the guidelines for achieving 2 cm GPS-derived orthometric heights for 2 cm ellipsoid heights, and the guidelines for 5 cm GNSS-derived orthometric heights for 5 cm ellipsoid heights.

Rule 2: Use Qatar95 Geoid Model when computing GNSS-derived orthometric heights.

1 Download from http://www.ngs.noaa.gov/PUBS_LIB/DRAFTGuidelinesforEstablishingGPSderivedOrthometricHeights.pdf


35

Rule 3: Use the latest QND height values to control the project’s adjusted orthometric heights.

Four Control Requirements

Requirement 1: Occupy stations with valid QND orthometric heights. Stations should be evenly distributed throughout project. A previously determined GNSS-derived orthometric height, accurate to 2 cm, is considered a valid QND height if it is in the national spatial reference system. In these requirements, a ‘valid QND bench mark’ includes vertical control that has been leveled and/or has an orthometric height valid to 2-cm accuracy.

Requirement 2: For project areas less than 20 km on a side, surround project with valid QND bench marks, i.e., minimum number of stations is four, one in each corner of project.

Requirement 3: For project areas greater than 20 km on a side, keep distances between valid GNSS-occupied QND bench marks to less than 20 km.

Requirement 4: For projects located in mountainous regions, occupy valid bench marks that are at both the lowest elevation and the highest elevation of the area, even if the distance is less than 20 km. Consider adding additional bench marks to get a good range of elevation change.

Five Basic Procedures

Procedure 1: Perform a 3-D minimum-constraint least squares adjustment of the GNSS survey project, i.e., constrain the latitude and longitude of one control station, and one orthometric height value.

Procedure 2: Detect and remove all data outliers, i.e., high residuals, for a base line using the results from the adjustment in procedure 1 above.

The user should repeat procedures 1 and 2 until all data outliers are removed.

Procedure 3: Compute differences between the set of GNSS-derived orthometric heights from the minimum constraint adjustment using Qatar95 from procedure 2 above and published QND orthometric heights.

Procedure 4: Using the results from procedure 3 above, determine which vertical control stations have valid QND height values. This is the most important step of the process. Determining which bench marks have valid heights is critical to computing accurate GNSS-derived orthometric heights. All differences between GNSS observations on valid bench marks need to agree within 2 cm for 2-cm surveys and 5 cm for 5-cm surveys. Large areas (i.e. 50 km by 50 km) may have a systematic tilt - this tilt can be accounted for in the final constrained adjustment, with QND vertical control stations occupied with GNSS, every 20 km. However, for detecting QND height outliers, the user should estimate local systematic differences between GNSS-derived heights and leveling-derived heights, by solving and removing this systematic difference.

Procedure 5: Using the results from procedure 4 above, perform a constrained orthometric height adjustment by fixing the latitude and longitude of one control station and all valid QND heights. The user should always ensure the final set of heights is not overly distorted by the adjustment process.


36

Table 1.18: Summary of Draft Guidelines for Establishing GPS-Derived Orthometric Heights (Standards: 2 cm and 5 cm) V1.4” published by National Geodetic Survey dated October 2005

Network Requirement

Control Primary Base

Primary Base

Secondary Base

Secondary Base

Local Network

Local Network

Accuracy of Orthometric

Heights

2 and 5 cm

2 cm 5 cm 2 cm 5 cm 2 cm 5 cm

Dual Frequency Required

Yes, if base line is

greater than 10

km


greater than 10

km


greater than 10

km

Yes, if base line

is greater than 10

km

Yes, if base line

is greater than 10

km


greater than 10

km


greater than 10

km

Geodetic Quality

Antenna with Ground Plane

Yes Yes Yes Yes Yes Yes Yes

Min. Number of Stations

3 3 3 No Minimum No Minimum No Minimum No Minimum

Occupation Time

5 Hours 5 Hours 5 Hours 30

Minutes 1

30 Minutes

1

30 Minutes

1 No

Minimum 1

Number of Days Station is Occupied

3 3 3 2 2 2

2 2

2 2

2

Max. Distance Between

Same or

Higher-Order Stations

75 km 20 km 30 km 10 km 15 km 5 km 10 km

Repeat "Base Line"

YES 3 YES

3 YES

3 YES

3 YES

3 YES YES

Collect Met Data

Yes Yes Yes Yes Yes No No

Fixed Height Pole

Yes Yes No Yes No Yes No

Precise Ephemerides

Yes Yes Yes Yes Yes Yes Yes

Fix Integers Yes 4 Yes

4 Yes

4 Yes Yes Yes Yes

1 Analyses have indicated that when following all guidelines in this document, 30 minutes of observations over base lines that are

typically less than 10 kilometers will meet the standards. For base lines greater than 10 km, but less than 15 km, 1 hour sessions should meet the standards. For observing sessions greater than 30 minutes, collect data at 15-second epoch interval. For sessions less than 30 minutes, collect data at 5-second epoch interval. Track satellites down to at least 10-degree elevation cut-off.

2 Base lines must be re-observed on different days with significantly different satellite geometry.

3 The observing scheme requires that all adjacent stations have base lines observed at least twice on two different days with significantly

different geometry. 4 If base line is greater than 40 kilometers, a partially fixed or float solution, is permitted.


37

Figure 1.3: Hierarchy of Base Stations

1.2.5.9 Triangulation and Trilateration Surveys

Triangulation and trilateration methods are now rarely used for expanding or densifying horizontal control. Before GNSS, they were extensively used for this purpose. Localized triangulation and trilateration techniques using precise total station / EDM are still used sometimes for accurate structural deformation monitoring work. However, these specialized surveys are only performed around a dam or hydropower project.

(i) General - A triangulation network consists of a series of angle measurements that form joined or overlapping triangles in which an occasional baseline distance is measured. The sides of the network are calculated from angles measured at the vertices of the triangle. A trilateration network consists of a series of distance measurements that form joined or overlapped triangles where all the sides of the triangles and only enough angles and directions to establish azimuth are determined.

(ii) Networks - When practicable, all triangulation and trilateration networks should originate from and tie into existing coordinate control of equal or higher accuracy than the work to be performed. An exception to this would be when performing triangulation or trilateration across a river or some obstacle as part of a chained traverse. In this case, a local baseline should be set. Triangulation and trilateration surveys should have adequate redundancy and are usually adjusted using least squares methods.

(iii) Accuracy - Point closure standards listed in Sections 1.2.2 and 1.2.3 must be met for the appropriate accuracy classification to be achieved.

(iv) Resection -. Three-point resection is a form of triangulation. Three-point resection may be used in areas where existing control points cannot be occupied or when the work does not warrant the time and cost of occupying each station. Triangulation of this type should be considered Fourth-Order, although Third-Order


38

accuracy can be obtained if a strong triangular figure is used and the angles are accurately measured. The following minimum guidelines should be followed when performing a three-point resection:

• Location - Points for observation should be selected to give strong geometric figures, such as with angles between 60 and 120 degrees of arc.

• Redundancy - If it is possible to sight more than three control points, the extra points should be included in the figure. If possible, occupy one of the control stations as a check on the computations and to increase the positioning accuracy. Occupation of a control station is especially important if it serves as a control of the bearing or direction of a line for a traverse that originates from this same point.

• Measurements - Both the interior and exterior angles should be observed and recorded. The sum of these angles should not vary by more than three (3) arc-seconds per angle from 360 degrees. Each angle should be turned not less than 2-4 times (in direct and inverted positions).

1.2.6 Validation of GNSS Equipment A Part 2 Section 12 of the Survey Practice Handbook published by the Surveyors Registration Board of Victoria, Australia covers the Validation of GNSS equipment.

1

The GNSS validation process should test:

• equipment

• measurement techniques together with processing, and

• transformation and heighting methodologies. Successful validation will also demonstrate the competence of the surveyor in using GNSS technology to achieve the required accuracy. Ideally, GNSS validation would consist of a combination of various methodologies i.e. zero baseline test, a coordinated network, an RTK test site and a coordinated EDM calibration baseline. The combinations would be dependent on the GNSS available to a surveyor e.g. static technique only, RTK or a combination. It would be advisable for the surveyor to undertake validation once a year or as often as deemed necessary to satisfy professional due care, best practice and competence.

(i) A Zero Baseline Test (All Receivers)

This can be carried out to check the correct operation of a pair of GNSS receivers, associated antennas/cabling, and data processing software. As the name implies, a zero baseline test involves connecting two GNSS receivers to the same antenna via an antenna splitter (as recommended by the manufacturer). The computed baseline should be theoretically equal to zero and any variation will represent a vector of receiver errors (usually results should give sub millimeter results).

This is a very simple and inexpensive process which:

• verifies the precision of the GNSS receiver measurements,

• proves that the receiver is operating correctly, and also

• validates the data processing software A zero baseline test does not examine satellite ephemeris, time or atmospheric errors. However, making measurements and processing data over known baselines or a network of coordinated points can achieve this. (ii) A High Accuracy GNSS Test Network (Static Techniques)

This can be undertaken to ensure that the operation of GNSS receivers, associated antennas/ cabling, and data processing software, give high accuracy baseline/coordinate results. Satellite ephemeris errors, clock biases and atmospheric effects must be removed or minimized during baseline processing. Network validation allows GNSS equipment to be tested under realistic field conditions which includes the dynamic nature of the

1 The document can be found in the following website:

http://www.surveyorsboard.vic.gov.au/documents/surveypracticehandbook/SPH_S2_Sect12.pdf


39

satellite constellation and the atmosphere. Mission planning (finding what time of day gives acceptable GDOP for observations) is as essential for GNSS validation as it is for real survey applications. The test network should:

• consist of extremely stable ground marks with almost perfect sky visibility

• be of a very high precision e.g. first or second order

• have stations which are ALL coordinated in both the local geodetic system (φ, λ, h or x, y, z) and plane projection (E, N and QND elevations)

• have a variety of baseline lengths and directions

• consist of points with varying elevations – to check for the correct modeling of the atmosphere as well as geoid determination to obtain QND values

Network validation is suitable predominantly for static/ rapid static surveys because the baselines are generally longer than for kinematic surveys. However, RTK GNSS equipment/firmware can be checked on a network to validate the equipment and the procedures used to obtain acceptable final results. Figure 1.4 illustrates an example of a GNSS Test Network with 11 stations with the above guideline in view. The length of the baselines of the GNSS Test Networks varies from about 1 km to 8 km.

Figure 1.4: An Example of a GNSS Test Network

After observing the network, the surveyor can process the data to produce a network of vectors. These vectors can then be reviewed, adjusted and analyzed following conventional methods:

(a) Independent vectors can be used to determine loop closures and precision. (b) By holding the values of one of these sites fixed, coordinates for all other sites are derived using the

GNSS observations initially using a minimally constrained least squares adjustment. The ensuing statistics can be reviewed and assessed. Any flagged outliers can be noted and examined.

(c) A subsequent adjustment can then be undertaken holding multiple stations fixed to calculate 3D final coordinates of all stations. This ensures that the adjustment has attempted to solve the transformation


40

parameters of the local area. Final coordinates and baseline vectors can be compared to the known values.

(d) QND elevations may be required and can determined using two methods:

• During the final least squares adjustment process using Qatar95 geoid model within the software package,

OR

• Manually, after the adjustment, by calculating height differences from known benchmark QND values and comparing with corresponding ellipsoidal heights differences. A geoid model for the local area can be interpolated from this data for all other points.

(iii) A Coordinated RTK/Kinematic Test Site Kinematic surveys are generally restricted to baselines of less than 10 km and involve occupying points for a short period of time e.g. less than one minute. A test site, designed for techniques such as RTK (and possibly as a simplistic rapid static check), can be established that is an array of points to be coordinated from a fixed base station. At the end of the observation session final coordinates can be compared to a set of known values (E, N, and QND elevations).

The inclusion of obstructions such as trees could be planned into the array to test the accuracy of the re-initialization processes of the On-The-Fly (OTF) hardware and firmware. The surveyor should re-observe the array under different satellite configurations to ascertain possible precision under varying conditions i.e. for horizontal coordinates and height determination. Figure 1.5 depicts an example of a RTK Test Array.

Figure 1.5: An Example of RTK Test Array


41

(iv) An EDM Baseline Test (Static and RTK Techniques)

A pair of GNSS receivers (plus ancillary equipment) can be tested over the various pillars of a validated EDM baseline. Measurements would involve setting up one receiver on the start pillar and simultaneous observation would be made to the other one on each pillar along the baseline. Surveyors can then make a comparison the GNSS-derived distances with the known lengths of the EDM baseline.

GNSS can be used to measure the 3D geodetic vector of a baseline e.g. ∆x, ∆y, ∆z. This can then be reduced to ground distance for comparison purposes. Traditionally, EDM baselines are used to validate the distance component of a measurement and not the vector as a whole. EDM baselines are rarely longer than one kilometer (i.e. well short of the operating range of GNSS) and therefore only comparatively short distances can be checked. Finally, if the reduced GNSS measurements can verify the known distances between the markers on the pillars of the EDM baseline, it can be considered that:

• the equipment is in good working order,

• competency has been proved for the observations technique and reduction processes undertaken, and

• the GNSS receivers are capable of delivering baseline solutions that are within specification.

Figure 1.6 shows an example of a combined EDM/GNSS Coordinated Baseline.

Figure 1.6: An Example of a Combined EDM/GPS Coordinated Baseline

This method of GNSS validation would be useful for post processed and real time techniques e.g. static GNSS and RTK respectively. It is important that the surveyor is well trained in GNSS methodology and has a full understanding of the achievable accuracy of each technique so that baseline comparisons are realistic. One useful addition to an EDM calibration baseline for GNSS validation would be for the end points to be coordinated to a high accuracy i.e. via connection to first/second order marks in a surrounding observed network. Therefore, GNSS validation could include a coordinated network followed by a baseline comparison test. This combination would verify final 3D vectors and GNSS derived distances


42

(v) Additional Validation Considerations

All GNSS equipment, software and procedures should be tested before general usage. Unlike EDM equipment, GNSS receivers cannot be calibrated for scale because the definition of scale is inherent in the satellites and orbit data. However, Antennae should be checked for centering errors. These should not generally be significant if geodetic quality equipment is used for cadastral surveys.

Antenna offsets may also be present when mixing different antenna types. Measuring a line of a few meters with GNSS and comparing the results with a direct EDM or taped measurement can easily test this.

If any significant modifications or upgrades are made to the GNSS receiver or the post-processing software, then the validation must be repeated. To avoid additional fieldwork for every software upgrade, reprocess the original validation raw data with the new version and check for any changes in the results.

Another advantage of the validation process is that it allows the surveyor to train and evaluate the competency of staff employed on GNSS surveys. This is important for total quality management. 1.2.7 Calibration of Electronic Distance Meter The calibration of electronic distance measurement equipment should be taken at least once a year. Letter will be issued stating that the contractor’s instrument measures to within the manufacturer’s tolerance.

The Calibration Method

The Sprent method was chosen as the calibration method. This method allows the determination of the zero error and scale factor independently of the effects of cyclic error. The option also exists for a full least squares determination of the three errors using the same data.

Basically, the method relies on choosing a set of five base lengths that are spread over the fine measurement wavelength (unit length) of the instrument. Two instrument stations are established that are separated by half the unit length of the instrument. Thus for each of the base lengths two measurements can be made which differ by half the unit length.

Cyclic errors affecting infra-red distance measuring equipment are generally simple harmonics in nature with wavelengths equivalent to the unit length of the instrument. In addition, higher order cyclic errors also occur, but these are usually small in magnitude and are not considered here.

The cyclic error in distances that differ by half the unit length will be of the same magnitude but of opposite sign. Therefore the pairs of measurements made which differ by half the unit length will eliminate the effects of cyclic errors if subjected to linear regression. Even though the effects of cyclic errors are removed for a simple linear regression, because the ten measurements are spread over the unit length of the instrument the data is well conditioned for use in a full analysis to determine the cyclic error components as well as the zero error and scale factor.

Since the method relies on knowing the "true" length of each base length it is most important that a pillared base is used so as to eliminate centering errors. Site Description The location of the base line required several conditions to be fulfilled. The following were thought to be the most important:- 1. It should be situated on stable ground with the pillars preferably attached to the bed rock. 2. It should be free from obstructions such as overhead power lines, underground cables and vehicular

movement. 3. It should be situated in an area that is set aside specifically for the base line and will not be disturbed by

other developments. 4. The ground along the line of the base should be preferably level with a slight concavity.


43

With the above points in mind a site that fulfilled the requirements was identified in the Salwa Road Industrial Estate. A strip of land, 1000m x 75m, adjacent to the pipeline reservation running through the Industrial Estate was provided by Doha Municipality. Pillar Arrangement & Construction

It was decided to design the base line around electronic distance measurement (EDM) equipment with unit lengths of 10 m, 20 m and 30.77m (the main values used by EDM equipment, and certainly covering all types of EDM currently in use in Qatar.

The total length of the base is 920 m and has nine pillars. The first four pillars are placed 5 m, 10 m and 15.38 m apart respectively, thus giving the three half unit length separations required. The remaining five pillars are positioned evenly at 182 m spacing.

The pillars consist of a two meters length of twelve inch diameter asbestos cement pipe set into a concrete footing 1.5 m square and a minimum of 0.8 m deep. Holes were excavated to the 0.8m minimum depth or until firm bed rock was reached. Reinforcing rods were keyed into the bed rock and extend up through the pipe.

Construction of the pillars followed five distinct phases:-

1. (a) Hole excavated to bed rock. (b) Position of centre of pipe marked. (c) Three one meter reinforcing bars keyed into bed rock. 2. Concrete poured into hole to level 0.7m below ground level. 3. (a) Pipe placed in position and set vertical. (b) Concrete poured into pipe to level approximately 0.5 m above the bottom of the pipe. 4. Hole filled with concrete up to ground level. 5. (a) Pipe filled with concrete. (b) Pillar plate set central and horizontal in top of pillar. The pillar plates are of a simple vandal proof design with tribrachs screw directly onto the pillar plates. Measurement of the Base Line It is recommended to carry out measurements of each base length using a 1 mm ± 1 ppm electronic distance meter once every five (5) years or when there is a suspicion of pillar movement. Over a period of one week four sets of measurements are taken at different times of the day. Each set of measurement consists of distances measured from pillars one, two and three to each of the remaining five pillars. The measured distances are adjusted for meteorological conditions and then reduced to the horizontal. These distances were then used in a least squares adjustment to obtain values for each bay length. From the bay length values, adjusted slope distances were determined and these are used as the “true” lengths. The Calibration Procedure An instrument that is to be calibrated is first set up on pillar one and distances measured to each pillar in turn (excluding pillars two and three). The instrument is then moved to either the second or the third pillar, depending on the unit length of the instrument, and the distances to each of the pillars are measured again. Temperature and pressure are measured to determine the meteorological correction. Height of instrument and prism are measured to allow the measured distance to be reduced to the horizontal. Computation of Calibration Parameters With the distances obtained from the above procedure and the "true" distances, values for the scale factor and zero error can be obtained using the standard linear regression equations:

Scale Factor = n∑ ( xi yi ) − ∑ xi ∑ yi

n∑ x i2

− ( ∑ xi )2


44

Zero Factor = ∑ yi ∑ xi

2 − ∑ xi ∑ ( xi yi )

n∑ x i2

− ( ∑ xi )2

Where, n = number of measurements undertaken yi = "true" length of i

th section

xi = length of ith section as measured by instrument under calibration

The residuals remaining from the above linear regression can be plotted over the unit length of the instrument to obtain an indication of the presence or otherwise of cyclic error. At present the analysis of the data has been taken no further than the linear regression analysis, but it is intended also to use a least squares approach to determine values for the three error parameters. 1.2.8 Continuously Operating Reference Stations (CORS) Reference is made to “Guidelines for New and Existing Continuously Operating Reference Stations (CORS)” published by National Geodetic Survey (February 2006). General Site Requirements A CORS site is expected to have high data quality and a lifetime of at least 15 years. The latter also applies to the critical volume of space around the antenna that should remain undisturbed throughout the lifetime of the CORS site. Power and Internet outages should be infrequent and short-lived, Monument A CORS monument should be designed to maximize its stability (maintain a fixed position in three dimensions) and minimize measurement of near-surface effects. The uppermost part of the ground is subject to the greatest amount of motion e.g. soil expansion and contraction due to changes in water saturation, frost heave, soil weathering, thus increasing the depth of the monument improves its stability. A detailed discussion of benchmark stability that is equally applicable to CORS monuments is given in “NOAA Manual NOS NGS 1 Geodetic Bench Marks”. Equipment It is strongly recommends that equipment be upgraded and/or replaced as technology changes, e.g. new GNSS signals added. Equipment changes should however be minimized as they have the potential of resulting in a change in position:

• Antenna

− must be at least dual-frequency (L1 and L2)

− a calibrated phase center model for the antenna model must be available. If the user chooses to install a radome, a calibrated antenna phase center model for the antenna and radome pair must be available. The NGS database of calibrated antenna and radome combinations is available at: http://www.ngs.noaa.gov/ANTCAL. NGS strongly recommends that no antenna radome be used.

• Receiver, Settings, and Power Supply (a) Receivers must be able to:

− Track at least L1 and L2

− Track at least 10 satellites above 0 degrees

− Automatically switch between operating modes to retain full wavelength L2 when Antis-poofing (AS) is switched on


45

− Provide L1 C/A-code pseudo range or P-code pseudo range and L1 and L2 full wavelength carrier phase

− Sample at a frequency of at least 30-seconds

(b) Receivers must be programmed:

− So that no smoothing is applied to the observables

− Track with an elevation cutoff angle of 5 degrees and 0 degrees is strongly preferred

− Record at 30, 15, 10, 5 or 1-second sampling intervals

− Log hourly blocks (strongly preferred), or 24-hr blocks of GNSS time. Optimal configuration is to deliver data in real time.

− Track all satellites regardless of health status

Receivers must have an uninterrupted power supply with a minimum of 5 minutes backup power, 30+ minutes strongly preferred. Quality Control and Day-to-Day Site Operations To ensure data quality the following verifications will be made on a daily basis using TEQC (Translating, Editing, Quality Checking) to check the quality of the incoming 24-hr RINEX files decimated to 30-s epochs. TEQC is freeware available for a variety of computer platforms and operating systems from: http://www.unavco.org/facility/software/teqc/teqc.html - MP1 represents the RMS multipath in meters on the L1 pseudo range observable, averaged for a 50-

point moving window (25 minutes for 30-s epochs). - MP2 represents the RMS multipath in meters on the L2 pseudo range observable, averaged for a 50-

point moving window (25 minutes for 30-s epochs). - o/slp represents the average number of complete observations before a slip occurs simultaneously on

the derivative of the ionospheric delay observable and/or both MP1 and MP2. - IODslp represents the number of slips on the derivative of the ionospheric delay observable. The TEQC statistics will be supplemented with those obtained by forming the ionospheric free linear combination of the L1 and L2 phases by the method of double differences. This is the method used by NGS to calculate daily site coordinates. Note that double differences are dependent on data quality from two sites, unlike TEQC statistics. The combination of the aforementioned performance measures will be used to recommend equipment upgrades for prospective or existing sites whose data under-perform compared to its established peers (CORS network). In addition, these results will be used to search for systematic effects in the CORS network, such as a tendency for a model of receiver or antenna to under-perform when compared to its peers. 1.2.9 Monumentation of Control Points A modern geodetic control station should be suitable for three dimensional positioning. In addition they should be permanent and stable. Pillars used in the State of Qatar are excellent monuments for horizontal control surveys. Detailed descriptions of type of monuments used in the State of Qatar for control stations are given in Appendix 1B. Monument types proposed for each type of horizontal and vertical control survey are given in Tables 1.19(a) and (b), respectively.

Table 1.19(a): Recommended Monument Types for Horizontal Controls

ORDER OF CONTROL MONUMENT TYPES

0 A1, B1, C1, E1, J2, J4 & J5

1 Above + G1 & J1

2 Above + K1, J3, H1, H2, P1 & P2

3 Above + L1, K2, P3 & M1

4 Above + L2 & J6


46

Table 1.19(b): Recommended Monument Types for Vertical Controls

ORDER OF CONTROL MONUMENT TYPES

0 J2

1 Above + J1, J4, G1, H1 & H2

2 Above + J3

3 Above + K1, P1, P2, K2, L1 & P3

4 Above + L2, J6, A1 & M1

5 Above + B1, C1, E1 & J5


47

References 1. “Standards and Practices for Control Surveys Special Publication 1 (SP1) V1.6” published by The

Intergovernmental Committee on Surveying and Mapping (ICSM), Australia. 2. “Guidelines for New and Existing Continuously Operating Reference Stations (CORS)” published by

National Geodetic Survey (February 2006) 3. “Draft Guidelines for Establishing GPS-Derived Orthometric Heights (Standards: 2 cm and 5 cm) V1.4”

published by National Geodetic Survey dated October 2005. 4. “Survey Practice Handbook” published by the Surveyors Registration Board of Victoria, Australia.


48

Appendix 1A

Sample Transformation Calculations

The following coordinates are for the Centre for GIS’s GPS Base Station. They were computed using the QTRANS software which incorporates the Qatar95 geoid model. Results are given for both the exact 7-parameter solution and the approximate 3-parameter solutions.

7-Parameter Transformation Results

Table 1A.1: 7-Parameter Transformation Results

1 To obtain geodetically correct transformed coordinates the geoid model must be used.

CGIS Base Station

Coordinate

WGS84

QND95

Cartesian X 3,589,721.311 m 3,589,849.335 m

Cartesian Y 4,518,778.589 m 4,519,061.922 m

Cartesian Z 2,706,593.879 m 2,706,572.511 m

Latitude φ (P) N 25° 16’ 28”.07786 N 25° 16’ 25”.55474

Longitude λ (L) E 51° 32’ 10”.83490 E 51° 32’ 13”.55089

Ellipsoidal height H -11.825 m 17.258 m

Geoid Ellipsoid Separation n1 -29.083 m 0.000 m

Orthometric height O 17.258 m 17.258 m

UTM Northing NUTM 2,795,447.464 m

UTM Easting EUTM 554,001.874 m

QNG Northing NQNG 391,288.468 m

QNG Easting EQNG 232,276.613 m


49

3-Parameter Transformation Results

Table 1A.2: 3-Parameter Transformation Results

1 The signs of the Transformation Parameters are correct when using QTRANS software. For other transformation software packages

you may have to change the signs. Changing signs is not an error but may be as a result of defining the coordinate systems as right handed or left handed (QTRANS uses a left handed coordinate system) or defining which is the from coordinate” and which is the “to coordinate” in computing the transformation parameters. If you use the 7 parameters and the results are correct that is fine. Otherwise it is best to use the 3-parameter transformation to get the translations correct and then introduce the rotations and scale (parameters 4 to 7) to refine the transformation. In either case, if the signs need to be changed then all the transformation parameters should be changed or all the rotation parameters should be changed (that is, you cannot change the sign of only 1 translation or rotation - they must all be changed as a group). To obtain geodetically correct transformed coordinates the geoid model must be used. If you have any problems, or require further information, please contact the Centre for GIS.

CGIS Base Station

Coordinate

WGS84

QND95

Cartesian X 3,589,721.311 m 3,589,849.092 m

Cartesian Y 4,518,778.589 m 4,519,061.964 m

Cartesian Z 2,706,593.879 m 2,706,572.639 m

Latitude φ (P) N 25° 16’ 28”.07786 N 25° 16’ 25”.56012

Longitude λ (L) E 51° 32’ 10”.83490 E 51° 32’ 13”.55863

Ellipsoidal height H -11.825 m 17.258 m

Geoid Ellipsoid Separation n1 -29.083 m 0.000 m

Orthometric height O 17.258 m 17.258 m

UTM Northing NUTM 2,795,447.464 m

UTM Easting EUTM 554,001.874 m

QNG Northing NQNG 391,288.634 m

QNG Easting EQNG 232,276.829 m


50

Appendix 1B – Monument Types A1. Surface Concrete Monument

A surface mark of reinforced concrete separated by a layer of sand, earth or small stones from the concrete mark beneath it. The fine mark is a 2 centimeter diameter hole through the centre of both holes. The surface mark is 30 centimeters square at the top and, where possible, 80 centimeters deep. The separation between surface and buried mark is 30 centimeters. The buried mark is 20 centimeters thick. A cairn of whitewashed stone at least 150 centimeters high is constructed 200 centimeters south of the station. Station number is inscribed in the cement of the surface mark. Tripod is required.

B1. Elevated Monument, Large with Spider

An elevated pillar consisting of a 550 centimeters length of steel tube that is 30 centimeters in diameter and 0.5 centimeters thick. The steel tube is surrounded to a height of 130 centimeters below the top of the pillar by a mound of compacted desert fill. This is paved with stone and surmounted by a 15 centimeter thick concrete observing platform. A permanent stairway is incorporated in the construction. A concrete block with a brass mushroom headed bolt is constructed at the foot of the steps to serve as a benchmark. The station number is stamped on to the centre of the pillar and on the head of the mushroom bolt benchmark. There is a brass spider on top of the tube. Pillar plate is required.

C1. Elevated Monument, Small with Spider

An elevated pillar consisting of a 180 centimeter length of steel tube that is 30 centimeters in diameter. The steel tube is surrounded to a height 130 centimeter below the top of the pillar by a thick concrete foundation. A brass mushroom headed bolt is inserted in the concrete foundation on the south side of the pillar. There is a brass spider on top of the tube. The station number is stamped on to the centre of the pillar and on the head of the mushroom bolt benchmark. Pillar plate is required.

D1. Steel Vane

Used in sand dune areas only. The mark consists of a number of 120 centimeter sections of 2 centimeter diameter cast iron conduit, threaded at both ends. The sections were vibrated into the sand either to refusal or to a minimum depth of 10 meters. A 130 centimeter length of conduit was left protruding from the sand, and two triangular metal vanes were bolted to the top of the pipe, at right angles to one another. Tripod required, not possible to directly occupy.

E1. Elevated Pillar, Medium with Spider

A black mild steel pipe, 30 centimeters in diameter and 310 centimeters long, was set into a concrete foundation and keyed into bedrock where possible. Around the base an observing platform, size 150 x 150 x 100 centimeters, is available. A brass spider on top of the pillar serves as the centre mark. A step formed with building blocks was built beside the mushroom benchmark bolt. Pillar plate is required.

G1. Concrete Monument, with Bronze Plaque

A Bronze plaque embedded well into a concrete block. The block is 80 centimeters high and 50 centimeters square at the base narrowing to 30 centimeters square at the top and set 60 centimeters into the ground. There is an aluminum plaque set horizontally on top of the block. This contains the words, in Arabic and English, “State of Qatar Survey mark” & “Do not destroy”. The monument is surrounded by a 200 centimeters square guard frame of 7.5 centimeters galvanized mild steel tubing. The monument is painted white while the guard frame was painted red and white. In a few cases the guard frame is omitted where it was felt it would cause an obstruction. Tripod required.


51

H1. Buried Concrete Monument with Bronze Plaque

A bronze plaque on a cylindrical concrete block, 25 centimeters below ground surface that is covered by a cast iron surface box. The plaque is 5 centimeters in diameter and driven onto a 2.5 centimeter diameter galvanized mild steel pipe 100 centimeters long. The surface box is set with the centre of the lid vertically above the centre mark. The words “State of Qatar” and “Survey Mark” were cast into the top of the lid in Arabic and English. Where the location is in a tarmac roadway a collar of tarmac was reinstated around the lid of the box, otherwise this collar was of concrete. Tripod required.

H2. Buried Concrete Monument with Bronze Bolt (H1 modified)

A bronze mushroom bolt, marked with a cross on top, on a cylindrical concrete block, 25 centimeters below ground surface that is covered by a cast iron surface box. The head of the bolt is 2.5 centimeters in diameter and driven onto a 2.5 centimeters diameter galvanized mild steel pipe 100 centimeters long. The surface box is set with the centre of the lid vertically above the centre mark. The words "State of Qatar" and "Survey Mark" were cast into the top of the lid in Arabic and English. Where the location is in a tarmac roadway a collar of tarmac was reinstated around the lid of the box, otherwise this collar was of concrete. Tripod required.

J1. Mushroom Bolt (Benchmark)

A bronze mushroom headed bolt is set on a reinforced concrete block 80 centimeters high and 50 centimeters square at the base and 30 centimeters square at the top. The top of the concrete block is flush with ground level. Tripod required.

J2. Mushroom Bolt (Fundamental Benchmark)

This consisted of a chamber excavated to a depth of 100 centimeters or until solid rock was encountered. The inside of the chamber was lined with 15 centimeter’s wall of concrete. The private mark consists of a bronze mushroom headed bolt is set into the base of the chamber. The public mark consists of a bronze mushroom headed bolt set onto the concrete surround at ground level. The chamber was covered with a heavy duty manhole and the finished chamber has the appearance of a heavy duty manhole. The size of the manhole varies from point to point. Tripod required.

J3. Mushroom Bolt, in Buried Concrete Monument

A brass bolt, with a cross mark at top, with a head of 2.5 centimeters diameter, and 15 centimeters long is buried vertically inside a concrete block. The base of block is 30 centimeters high and 30 centimeters square, narrowing to 25 centimeters square at the top. About 0.5 centimeter of the bolt is left protruding above the concrete surface. A concrete layer of at least 10 centimeters thick should be placed beneath before the mould for the concrete block is placed. The concrete block is flush with the ground level. Point number is usually inscribed on the concrete.

J4. Mushroom Bolt, Fine Mark

On solid rock, a hole, 15 centimeters deep, was drilled and a brass mushroom headed bolt grouted into the hole. Three additional holes were drilled at varying distances around the central hole, to serve as witness marks. Tripod required.

J5. Mushroom Bolt, for Roof

A brass mushroom headed bolt grouted into position on the roof. Where possible, four reference points were established with Hilti nails. Tripod required.


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J6. Mushroom Bolt, for Kerbstone

A brass stud is fixed with a resin mix into a small hole drilled on kerbstones, concrete manhole surrounds, etc. Four hilti nails in suitable locations serve as reference points. Tripod required.

K1. Steel Pin, in Concrete

A steel pin 30 centimeters long with a diameter of 1 centimeter buried vertically inside a concrete block of 30 x 30 x 30 centimeters, with 2 centimeters protruding above the concrete surface. Point number is usually inscribed on the concrete. Tripod required.

K2. Steel Pin, in Tarmac/Bitmac/Asphalt

A steel pin 30 centimeters long with a diameter of 1 centimeter is driven to tarmac/Bitmac/Asphalt. Tripod required.

L1. Hilti Nail, Large

A hilti nail 10 centimeters long, with a head of 1.5 centimeters and diameter 0.6 centimeters is driven to tarmac/Bitmac/Asphalt with a washer. Tripod required.

L2. Hilti Nail, Small

A hilti nail 5 centimeters long and with a head of 0.5 centimeters is driven to the gap between two kerbstones, or other suitable location, with a washer. Tripod required.

M1. Steel Pipe, in Concrete

An open ended steel pipe is set in concrete. The top edge is projecting 1 to 3 centimeters above the top surface of concrete block. Point number is inscribed on concrete. Tripod required.

P1. Survey Mark in Rectangular Concrete

A survey mark, represented as M, in rectangular concrete block having variable dimensions and represented as follows: length = L, width = W and height above ground = H. The monument is usually surrounded by a square guard frame. Please refer to the remarks field for the type of the survey mark and the monument dimensions. Tripod required.

P2. Survey Mark in Circular Concrete

A survey mark, represented as M, in circular concrete block having variable dimensions and represented as follows: diameter = D and height above ground = H. The monument is usually surrounded by a square guard frame. Please refer to the remarks field for the type of the survey mark and the monument dimensions. Tripod required.

P3. Survey Mark in Concrete

A survey mark, represented as M, in concrete cast in place with no particular shape whatsoever. Please refer to the remarks field for the type of the survey mark. Tripod required.


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Appendix 1C – EDM Calibration Measurements


77

Appendix 1D – Horizontal and Vertical Angle Observations

HORIZONTAL AND VERTICAL ANGLE OBSERVATIONS Special Projects Section, General Survey Department, MMUP

Date Observer Inst.Model Serial No. Company

SET 1 Horiz. Angle Vert. Angle Horiz. Angle (D-R) Vert. Angle (D-R)

A

D 00 - 00 - 00

R

B

D

R

SET 2

A

D 30 - 00 - 00

R

B

D

R

SET 3 Horiz. Angle Vert. Angle Horiz. Angle (D-R) Vert. Angle (D-R)

A

D 60 - 00 - 00

R

B

D

R

SET 4

A

D 90 - 00 - 00

R

B

D

R

Remarks:


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Page of

Job # Place Date

Observer Recorder

Ins. Station No. Ins. Height Stn. Descr.

RO Station No. RO target Ht. Stn. Descr.

Instrument Used Make Serial No.

Beginning Time Ending Time Temp. Pres.

Object Id. No.

Object Description

Horizontal Angle Horizontal Angle Horizontal Angle Horizontal Angle

D M S D M S D M S D M S

Face L

Face R

SET 1 Mean

Ang. Diff.

Face L

Face R

SET 2 Mean

Ang. Diff.

Face L

Face R

SET 3 Mean

Ang. Diff.

Face L

Face R

SET 4 Mean

Ang. Diff.

Mean Incl. angle

Vertical Angle Vertical Angle Vertical Angle Vertical Angle

D M S D M S D M S D M S

Face L

Face R

L+R

Mean

Slope Dist. 1

Slope Dist. 2

Slope Dist. 3

Slope Dist. Mean

Horizontal Distance

Remarks


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Qatar Survey Manual – Chapter 2 – Cadastral Survey

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Abbreviations

BP Boundary Pillar

CAE Committee on the Admission of Engineers

CORS Continuously Operated Reference Station

DGNSS Differential Global Navigation Satellite System

DGPS Differential Global Positioning System



GSD General Survey Department

LAD Land Acquisition Department

LD Land Department

LIS Land Information Section

MMUP Ministry of Municipalities and Urban Planning

PD Property Document

PIN Parcel Identification Number

PRD Property Regulation Department

QARS Qatar Area Reference System

QND95 Qatar National Datum 1995


RERD Real Estate Registration Department

RINEX Receiver Independent Exchange format

RS Requisition Survey


TC Temporary Control

UPDA Urban Planning and Development Authority

WDD Working Data Disk


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2.1.0 Governing and Administrative Authority for Cadastral Survey The General Survey Department (GSD) is the governing and administrative authority for Cadastral Survey in the State of Qatar. The organization chart of GSD is depicted in Figure 2.1.

2.1.1 Definition and Types of Cadastral Land Cadastral Survey shall comprise all types of land survey executed in the State of Qatar for the purpose of demarcation and registration of land boundaries. “Land" includes:

(a) a parcel of land which is in actual possession of the owner by himself or other person holding by, through or under him;

(b) foreshore land; (c) a building or a structure erected on land or water; (d) any parcel of airspace or any subterranean space held apart from the surface of the earth; and (e) any estate or interest in land;

Types of Cadastral Land include: (a) Private Lands – any land within the State of Qatar owned by individual, group of individuals or

company. (b) Government Lands – any other land, beside Private Lands, owned by Qatar Government within

the State of Qatar.

2.1.2 Types of Cadastral Survey

(a) Demarcation Survey – survey made to define the land boundary of registered and unregistered land of private and government ownership. These include farm, beach and desert house survey.

(b) Re-demarcation Survey – survey made to re-set out previously defined land boundary.

(c) Consolidation Survey – two or more parcel of lands are consolidated and defined as one parcel.

(d) Subdivision Survey – a parcel of land is subdivided into two or more parcels.

(e) Land Adjustment Survey – survey made to define the new boundary of parcel of land determining the given area and the taken area of a parcel or (both) from the original area of the parcel. This includes: (i) personal adjustment – the owner of a private land requests for additional land area (ii) developmental adjustment – a privately owned land where a portion of the land is acquired for

development purposes by the Government

Figure 2.1: Organizational Chart of General Survey Department


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(iii) partial acquisition and total acquisition survey – privately owned land that is partially or totally acquired by Government for urban planning purposes.

(f) Strata Survey – survey made to define the boundary of a strata unit/flat of a building.

2.1.3 Types of Boundary Limits (a) Block Boundary limits

1 - defined from existing features such as roads, sikkas, etc.

(b) Property boundary limits

1 - defined by cadastral survey where beacon and parcel numbers defines the

property boundary limit.

(c) Zone Boundary limits2

(d) City Boundary limits

2

(e) Municipal Boundary limits

2

(f) District Boundary limits

2

Proper definition of such boundary limits can be obtained from planning. 2.1.4 Power of Director (GSD) The highest authority for Cadastral survey in the state of Qatar is the Ministry of Municipalities and Urban Planning. The authorized representative is the Director of General Survey Department, MMUP. 2.1.5 Duties of Director (GSD) The main duties of the Director of GSD are: (a) full responsibility of all Divisions/Sections of the GSD; (b) execution of all legal acts and regulations related to general surveying in his department; (c) decision making related to the Department; (d) approval of all Cadastre Survey works in Qatar, both Land and offshore; (e) approval of final property documents drawings, both private and government; (f) approval of employment of all surveyors, survey technicians and engineers in GSD; (g) approval for accreditation all surveyors, survey technicians and engineers in all private survey

companies registered with GSD; (h) approval of the calibration/validation of survey instruments for GSD and private survey companies

registered with GSD; and (i) approval of final plans for government acquired lands and real estate properties.

2.1.6 Committee on the Admission of Engineers (CAE) A permanent Committee to be called "the Committee for the enrollment of Engineers and Engineering Consultancy Offices" shall be formed in the Authority – defined as the General Authority for Planning and Urban Development - and constituted as follows: (a) Two Engineers from the authority one of whom shall be Chairman. (b) One Engineer from the Ministry of Energy and Industry , (c) One Engineer from the Ministry of Municipalities and Urban Planning, (d) One Engineer from Qatar General Electricity and Water Corporation, (e) One Engineer from Qatar Petroleum, (f) One Engineer from the Public Works Authority,

1 Block boundaries and property boundary limits (parcel) are defined by General Survey Department (GSD).

2 Zone, City, Municipality and District boundary limits are defined by planning.


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(g) One Engineer from Qatar Telecommunication Co., (h) Two Engineers from private Engineering Consultancy Offices, Each body shall select its representative in the Committee. A decision of the Council of Ministers, who may form the Committee, shall be issued. The membership in the Committee shall be for three (3) years renewable for another period or periods by decision of the Council of Ministers which may reform the Committee. The Committee shall make the internal regulations to organize its own works.

The Committee shall be entrusted with the acceptance and registration of Engineers and Engineering Consultancy Offices, and with determining the Engineering Professions according to their technical specializations, and the Committee shall classify the engineers and Local and International Engineering Consultancy Offices of each specialization into categories, specifying the volume and kind of engineering works to be practiced by each category.

“The Engineering Consultancy” refers “to the work of preparing architectural and construction drawings, diagrams, designs and topographic surveys; supervising over performance; giving advise; conducting feasibility studies; computation of quantities and cost estimates; and managing projects in various engineering professions”. “The Engineering Professions” refers “to the engineering activities practiced by those qualified in the division and branches of specializations of architectural, civil, electrical, mechanical, chemical, mining and other fields of engineering”. The role of GSD in the accreditation on Survey Firms is to recommend the firm to be accredited upon compliance with the accreditation criteria, specified in the following sections. 2.1.7 International and Local Company Registration/Accreditation Requirements All companies that intends to practice and deal with cadastral, topographic or any Land or Hydrographic related surveys in the State of Qatar are required to be registered and accredited with General Survey Department (GSD) of the Urban Planning and Development Authority (UPDA). The companies should meet the following requirements: (A) Company or Establishment

(i) A registered and licensed company according to Law of Qatar, to operate in the State of Qatar.

(ii) Shall have an office in the State of Qatar.

(iii) One of the major trade/services of the company or establishment should be in the field of surveying.

(iv) Shall have the resources to maintain up to date operating technology.

(v) Shall provide information with regards to its financial condition and stability. (B) Organizational Set Up of the Company or Establishment

The Company or Establishment shall present through its organizational set up that one of its major trade/services is in the field of surveying. Its authorized representative in all dealings with GSD shall represent the company in the field of Survey.

(C) Personnel

(i) It is required from the company or establishment to submit the qualifications of their personnel, educational attainment and diploma certificate, years of experience in the field of surveying.

(ii) GSD requires the company or establishment to maintain a set of regular key personnel for their offices, in the field of Survey, as follows:


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• One Senior Surveyor or Officer in Charge;

Who may qualify as the authorized representative of the company; who will sign for all survey documents and drawings submitted to GSD; and with the following qualifications;

- Holds a Bachelor degree in Civil/Geodetic Engineering/Surveying or equivalent; - Must have at least 5 years experience in office management that deals with surveying or related

engineering field. - Must have at least 5 years experience in the practice of cadastral land surveys. - Good knowledge in laws and procedures governing land surveys and property registration in the

State of Qatar. - Experienced and knowledgeable in up to date survey equipment. - Well oriented in the geography of State of Qatar. - Conversant with modern computer software in surveying and will be able to produce documents

when needed. - Must have a valid Qatar driver’s license.

• At least one Assistant Senior Surveyor or Survey supervisor; Who may act as Senior Surveyor or Officer in charge at the time the Senior Surveyor is out of the

country provided that GSD is informed beforehand of the changes (see Section (g), General Conditions), with the same qualifications as of the above with a minimum experience of 2 years in office management.

• At least three (3) Surveyors with the following qualifications;

- Must have a valid certificate in Surveying from a recognized Institute; - Must have at least three (3) years experience in land survey practices. - Good knowledge in the use of modern survey equipment. - Must have a valid Qatar driver’s license.

(D) Equipment

There should be at least two (2) sets of survey equipment complete with accessories for the purpose of carrying out survey field work operations for land surveys, in gathering data and its application.

The most modern set of survey equipment is an advantage.

The equipment shall have an annual certificate of calibration issued by an authority approved for the purpose of test and examination.

The company should submit to GSD the registration numbers of the set of equipment, where the set of equipment is thereby registered.

GSD has the right to inspect the equipment for its completeness.

In case the company will be involved in Hydrographic survey, they will be required to own or lease a set of equipment for the purpose with the approval of GSD;

In case the registered set(s) of equipment is replaced or new sets were added, the company shall report to GSD such replacement or new sets to be added which will be subjected for all necessary calibration.

All survey projects of the company shall bear the registration number of the survey equipment used. (E) Vehicle

The company or establishment should provide at least three (3) 4x4 vehicle (category “A”) either owned or leased for the purpose of transporting for the surveyors in carrying out field survey works and two (2) 4X4 vehicles for category “B”.


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GSD should be provided with the registration papers of the said vehicles. (F) Office Facilities

This covers the operating technology of the company or establishment (i.e. computer facilities).

The company should have the resources to maintain up to date operating procedures and the ability to deliver up to a certain standard.

The company may use any commercially developed software as long as it produces data compatible with the existing programs and software of GSD.

GSD shall conduct inspection of their office facilities prior to the approval of their application for registration, to make sure that they have the capability to deliver the services required and the ability to extend equitable warranty provisions. It is required from the company to submit their Method Statement in processing their data, from fieldwork operations to finalizing the data prior to submittal.

(G) General Conditions

(i) Any Applicant, whose registration is approved by GSD, will have its name added to the list of Registered Survey Companies of GSD, and this list will be made freely available to the public upon request.

(ii) Before the authorized representative of any Registered Company goes on leave or change in position, GSD should be notified in writing at least two (2) months before the scheduled leave or change in position, according to the existing policy of GSD, where the latter has the discretion to approve or reject the request.

(iii) Any Registered Company who, upon examination of their work, was found to have deliberately falsified any submitted data shall immediately be removed from the Register and neither that Company nor the approved person that represent that company is allowed to register again. The decision of GSD shall be final in this matter.

(iv) If the work delivered, upon careful verification, does not meet the standard imposed by GSD, the company will be notified with a warning letter. If the standard does not improved and was given the third warning letter, GSD may remove the company from the Register.

(v) Any Registered Company will not be allowed to sub-contract their contract with GSD to another Registered Company;

(vi) Any Applicant who fails to obtain approval for registration may apply again no sooner than three (3) Gregorian calendar months after the first attempt.

(vii) Any registered company which has been removed from the Register, for any reason other than falsifying survey data may re-apply for registration no sooner than three (3) Gregorian calendar months after the date of their removal from the Register.

(viii) GSD has the option to categorize the company based on the documents submitted on their application.

(ix) Any Registered Company shall inform GSD in writing for any changes in their operations, procedures, manpower, and equipment.

(x) In case the Company will be involved in hydrographic survey; they must have an accredited Hydrographic Surveyor who will accept responsibility for the hydrographic survey; the Hydrographic Surveyor must have successfully completed FIG/IHO/ICA accredited Category A hydrographic surveying course in a recognized institution worldwide or hold a degree in Surveying, Geodesy or Geomatics and minimum five years experience in hydrographic surveying practices.


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(H) Categorization of Registered Company

Category “A”

A company capable of mobilizing at least three (3) survey teams or more.

Category “B”

A company capable of mobilizing at least two (2) survey teams. 2.1.8 Accreditation of Surveyors Subject to the provisions of the CAE, every person who is 21 years of age and above shall be entitled to be accredited if: (a) he satisfies the CAE that he has:

(i) obtained a certificate of competency issued by the GSD after passing the prescribed examination; (ii) passed a professional examination recognized by the CAE and passed such further examination

and had such practical experience in surveying in the State of Qatar as the GSD may prescribe; or (iii) had such proper training in surveying recognized by the GSD and passed such other examination

as the GSD may require; and

(b) he has passed a professional interview conducted by the GSD or CAE to determine whether he has the aptitude and knowledge to effectively perform or engage in survey work in the State of Qatar.

2.2.0 Survey Requirements for Cadastral Land Cadastral Survey can only be executed upon the receipt of “Survey Request Form”, documents from Real Estate Registration Department (RERD), policy plan and any other related drawings. (a) A cadastral survey for any parcel of land shall not be taken to have been completed until:

(i) the boundaries of the land have been determined by straight lines; (ii) the physical boundaries of the land have been demarcated by boundary marks or defined by

approved co-ordinates or, if it is impossible or impracticable to do so, by reference to floors and walls so as to enable the boundary lines of the land to be ascertained;

(iii) the area of the land has been determined; (iv) a cadastral parcel number and point number has been assigned to the land by the GSD (see

Section 2.3.3.2); and (v) the property document showing the location of the land and its boundaries, area, cadastral parcel

number and the boundary marks placed on the land or the approved co-ordinates, has been processed, approved by, and stored on GSD Cadastral Database which is accessible to other authorized government agencies.

(b) The property document (see Appendix 2A (a) and Appendix 2A (b)) shall be prima facie evidence of the

boundaries of the parcel of land to which it refers, and of its area and PIN. (c) Any plan for a cadastral survey of a parcel of land approved by, and filed in the office of GSD may be

executed as per requested by the Land Department. 2.3.0 Survey of Land Parcels All cadastral surveys conducted shall conform to these survey procedures, format and standards as listed below.


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2.3.1 Coordinated Cadastre The GSD shall be responsible for establishing a coordinated cadastre.

(a) All boundary points are defined with unique beacon numbers as specified in Section 2.3.3. No beacon number is duplicated.

(b) Shape of the land is defined by these beacon numbers and is allocated with a unique PIN as specified in Section 2.3.3.

2.3.2 Survey Datum

1

The QND95 datum which uses the International (Hayford) reference ellipsoid on Qatar National Grid (QNG) is to be adopted for cadastral surveys in Qatar. 2.3.3 Parcel, Beacon & Parcel Numbers (a) PIN is an unique number that identifies the cadastral land; and (b) Beacon number is a unique number that identifies the boundary corner of a cadastral parcel.

Refer to Section 2.3.3.2 for the parcel and beacon numbering system. 2.3.3.1 Application for Parcel, Beacon & PD Numbers (a) Every accredited survey firm or their authorized personnel shall obtain from GSD all parcel, beacon and

PD numbers to be used in connection with the survey they will execute. (b) Application can be done on prescribed form (see Appendix 2C) or through internet. GSD will verify their

request and will allocate parcel, beacon and PD numbers to the accredited survey firm. All requests for parcel and beacon numbers should be accompanied by a drawing with an appropriate scale, showing job limits and grid coordinates. This is being undertaken to prevent duplication of beacon and parcel numbers and to initially check the Qatar Area Reference System (QARS) block location.

2.3.3.2 Parcel and Beacon Numbering System The parcel and beacon numbering system is based on the Qatar Area Reference System (QARS). Qatar is divided into registration zones which are further subdivided into a number of blocks within each zone. Within the individual blocks, a unique reference number for each individual parcel is allocated on a sequential basis and as well as the beacon numbers. The numbering of parcel numbers, which is unique for every parcel, shall be of the following formats:

(a) Land Parcel

Each parcel has a unique reference number in the form of XXYYZZZZZ where:

XX =QARS Zone YY =QARS Block ZZZZZ =Land Cadastral parcel Number allocated

(b) Beacon Number The reference number for each beacon will have the form XXYYAAAAA where:-

1 Refer to Chapter 1: Control Survey


89

XX =QARS Zone YY = QARS Block AAAAA =Unique number allocated by Survey Section.

Using the QARS zones/blocks as the initial parameter has the advantage that the vast majority of parcels surveyed within individual survey requests will have a common prefix. This will remove the necessity of full annotation on the survey plans as the individual beacons can be labeled with the suffix of the reference number only, the reference number prefix forming part of the data on the survey plan. This system of beacon referencing eliminates any chance of anomalies occurring along common boundaries. 2.3.4 Numbering of Temporary Controls (TC) (a) No TC number shall be used more than once in each survey. (b) The numbering of temporary control stations, established by traversing or GNSS, shall be as follows:

Alphabet “T” for temporary follows by JOB No : JJJJJ and alphabet “A”, “B”, “C”, ….etc…

Example : T12345A, T12345B (2nd

point), T12345C (3rd

point) and etc.. 2.3.5 Survey Control Monuments Private accredited survey firm can only make use of the existing geodetic survey control network, temporary control stations or Continuously Operated Reference Station (CORS) to commence Cadastral Survey. Method of establishing control markers should refer to Chapter 1 Section 1.2.0.

(a) Existing survey control network

Accredited surveyor shall check on the availability of control markers in the intended survey area.

(b) Establishment of control marker with CORS of Qatar.

In the event that there are insufficient control markers within the surveyed area, accredited surveyors should install and survey the new markers using static DGNSS technique.

(c) Establishment of Temporary Control Marks

(i) By Total Station

- Loop & Open Traverse (refer to accuracy in Section 2.3.7.2) - By Resection (refer to Chapter 1 Section 1.2.5.9) - By Trilateration (refer to Chapter 1 Section 1.2.5.9) - By Hanging Temporary Control Mark - Observations must be taken in 2 positions, using 3

known control stations and this hanging temporary control mark shall not be used to establish another hanging temporary control mark. The distance of this hanging temporary control mark must not be longer than the reference control mark. (See Figure 2.2 for illustration)

(ii) By Static/Rapid Static (refer to Chapter 1 Section 1.2.5.8)


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2.3.6 Guidelines for Using GNSS in Cadastral Surveys (a) GNSS equipment, software and procedures should be tested before general usage. This can be

achieved by making measurements and processing data over known baselines or a network of points. For validation of GNSS, GSD shall assign Government control stations to accredited survey firm to validate the GNSS equipment. Report on how the observations, in static or rapid static method, were taken is required to be submitted together with the raw data. Reference could be made to Chapter 1 Section 1.2.5.8 for the validation. Processing of the calibration shall be done and the certificate issued by the respective department.

(b) A survey must be connected to at least 2 existing approved Government survey marks adequate to prove its reliability, orientation, and scale. GNSS observations can be made directly between three or more appropriate existing survey marks to prove the origin in the conventional manner, eg, by comparing bearing and distances between origin marks.

Alternatively, where a base station is used outside the area of the survey, 3 or more appropriate existing surveys marks in the area of the survey need to be tied to. A transformation of the GNSS data to the local coordinate system of the origin marks may be required. The transformed data must then be used to prove the origin of the, e.g. by calculating the GNSS joins between the origin marks and comparing with the bearing and distances between origin marks.

(c) GNSS provides the ability to operate over greater distances than with conventional equipment. Often base stations outside of the area of the survey can be employed. All GNSS surveys must be undertaken in accordance with accepted good survey practice as follows:

(i) As a general rule GNSS marks should be inter-visible, particularly boundary and witness marks, to aid future surveys where conventional techniques may be used.

(ii) Where surveyors deem it helpful they may annotate lines that are not visible “NV”. (iii) GNSS observation procedures should be designed to detect and eliminate:

• ambiguity initialization errors;

• the effects of multipath;

• interference from electrical interference such as substations, microwave or other spurious radio signals;

• poor satellite geometry due to satellite configuration and/or sky coverage obstructions.

Known Control Mark

Temporary Control Mark

Radiation to Temporary Control

Observation between Known or Temporary Control Marks

Figure 2.2: Establishment of Temporary Control Marks


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(iv) All GNSS observations are to be checked by independent observations from another (independent) base station. Where re-measurement of the same vector is carried out observations are to be made at a different time (at least 30 minutes after the first observation) to enable satellite geometry to change and thus ensure that any multipath errors will be detected. Where vectors are re-measured proof that no transcription errors have occurred on the plan must be provided.

(d) Sufficient GNSS observations shall be shown on the survey plan, and annotated “GNSS”, to indicate

the general method of survey. If all observations are made using GNSS, a note in the side panel indicating that all observations are GNSS can be used in place of annotating each line. Where a line is calculated between two GNSS points it shall be annotated “calc”.

(e) Where heights are to be shown on the plan, spheroidal heights must be transformed to an orthometric height datum acceptable to the GSD, e.g. when heights are required for strata titles.

(f) Where coordinates derived from GNSS observations are being shown, they shall be provided as local circuit grid coordinates (e.g. N, E), and NOT as geocentric Cartesian coordinates (e.g. X, Y, Z) or

geographic coordinates (e.g. φ, λ, h).

(g) A report describe the GNSS survey is to include where applicable:

• a brief statement as to the purpose of the survey to enable the type of survey carried out to be put in context of the GNSS methodology used;

• what observations were made [e.g. how were ties made to permanent reference marks, witness marks and boundary marks. Were they direct GNSS

• vector measurements or were they calculated from GNSS observations;

• how check observations were made;

• a description of precautions taken to identify and minimize the effects of multipath and of gross errors.

(h) A list of the type and model of equipment used is to be provided. This should also include information

on any base station service that has been used. (i) A description of the methods used shall include as applicable:

• the method of survey used e.g. static, rapid static, stop and go, kinematic, or real time kinematic (RTK);

• the expected precision from the method of survey used. This may be provided by manufacturers, software providers, other survey literature or the surveyor’s experience;

• description of any specific parameters programmed into the receiver or used in processing that would be likely to affect the result of the survey, e.g. use of tropospheric models;

• for static observations, an indication of observation and session times;

• the mode of operation e.g. single or dual frequency observations, carrier phase, differential pseudo range, or carrier phase smooth DGNSS;

• tabulation of the observations used from any base stations;

• description of the GNSS reduction techniques used including the software used.

(j) Assessment of GNSS data quality shall be provided so that the appropriateness of the methodology used for the survey can be assessed. This may be provided by:

• the repeatability of observations e.g. the maximum difference or standard deviation of repeated observations on each line;

• a comparison of GNSS observations with underlying work;

• summary of independent checks to verify quality assessment e.g. loop closures or network analysis.


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2.3.7 Boundary Limits of Cadastral Parcel The “corners” of the cadastral land surveys are those points that determine the boundaries of the various subdivisions represented on the official plan – be it private or government lands.

The methods of determining the “corner” are as follows:

• by adopting an observed as-built feature. The allowable limit to define an as-built alignment is ±0.15 m.

• by mathematical computations using known directions or distances or both from the attached ownership drawings or as required from planning scheme

• by using a supplied coordinates from Planning

The “corner” is also defined as Beacon where a unique number is allocated (See Section 2.3.3). 2.3.7.1 Area Before the definition of the final parcel area, approval from the concerned department, ie. LD, RERD, LAD & PRD, is required. Area is shown to the nearest 1.0 m

2 on plans.

(a) Area computation (areas after demarcation)

Areas shall be computed using any appropriate mathematical formula from the coordinates of the boundary corners, in clockwise direction. The boundary corners coordinates should be correct to 3 places of decimal

The followings are the methods of determining Parcel areas: (i) by design (iv) as-built areas (ii) by required areas (v) by given dimensions (iii) as required by private owners (vi) by supplied coordinates

(b) Methods of subdivision (i) by equal areas (iii) by given dimensions (ii) by required areas (iv) by supplied coordinates If a parcel is subdivided into several parcels, the total area of each subdivided parcel shall conform to the original parcel area by applying adjustments, if necessary.

(c) Areas after re-demarcation

If a defined parcel is re-demarcated, its original area is to be adopted and all site discrepancies are to be reported. 2.3.7.2 Accuracy Specifications for Setting Out Every cadastral boundary corner position shall be determined on the ground from any of the adjusted control stations to within 0.050 meters. 2.3.8 Authorized Marks 2.3.8.1 Types of Marks All new Government Cadastral Marks shall be approved Survey Marks (see Figure 2.3). The anchor "Type A" is to be used in preference, where less hard ground conditions permit.


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Where conditions prohibit the use of either type of mark, the Technical Advisor may authorize the use of an alternative marker, being a steel pin (sp), feno mark (fm) (See Figure 2.4) or hilti nail (hn).

Existing, as built wall and building corners, concrete boundary pillars, or other physical features approved by the Technical Advisor, may be adopted as cadastral marks. Appendix 2D “Cadastral Survey Feature Codes” illustrates such cadastral marks.

It is unnecessary to renumber cadastral points where no change in coordinates has occurred. Original numbers should be used unless they are found to be incorrect or outdated as a result of QARS block errors or alterations.

Earth Anchor Type A Fluted Type B

Figure 2.3: Standard Proprietary Marker

Figure 2.4: Feno Mark

7.5 cm

9 cm

9 cm

6.5 cm


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2.3.8.2 Feature Codes for Cadastral Marks Feature codes will be required for the following: (a) All beacons included in a parcel(s) generated by the job being submitted, irrespective of whether the

beacon was computed as part of this job or a previous one. (b) All points observed as part of the current job. (c) All points computed for the current jobs which are to be shown on the PD(s) for the job. Any beacons which have been allocated a code as part of a previous job must be checked to ensure the code is still appropriate. Any problems concerning beacon descriptions from old jobs or the correct usage of codes should be resolved before submission of the job to Survey Section. It is essential that codes are allocated without variation - i.e. spaces, hyphens, slashes and commas are not to be used. If it is found that a suitable code does not exist, companies should consult Survey Section and resolve the problem before submission. 2.3.9 Authorized Plan Forms Standard plans are available for:

(i) Property Document (ii) Land Adjustment Document (iii) Total Acquisition Document (iv) Farm Land Document (v) Beach Land Document (vi) Dessert Land Document (vii) Sketches (viii) Record sheets (ix) Policy Document and (x) other plans as required by GSD

2.3.10 Land Cadastral Plan (a) Scale

(i) The scale on which the plan is drawn and the plan size shall be selected such that the coordinates of each station and the area of each cadastral parcel can be clearly seen.

(ii) On plans, if stations or boundaries are illegible or difficult to interpret, a diagram drawn on a scale larger than that of the plan, or drawn not to scale, may be added as an inset.

(iii) Built-up areas - Plans shall be drawn at scale of 1:100, 1:200 or 1:500. (iv) For other surveys – Plan shall be drawn at scales of 1:1000, 1:2000 or 1:10000.

(b) Plan form

(i) A0 (841 mm X 1189 mm) (ii) A1 (594 mm X 841 mm) (iii) A2 (420 mm X 594 mm) (iv) A3 (297 mm X 420 mm)

2.3.11 Drawing Specifications for Land Cadastral Plan (a) Line Types Boundary lines shall be represented by firm black lines, and connection lines and traverse lines in sketches shall be represented by broken black lines.


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(b) Abbreviations The abbreviations, symbols and conventional signs adopted by GSD shall be used on plans. (c) Text

2.3.12 Information to be Shown on Land Cadastral Plan (a) Title Block The title block of each land cadastral plan shall include:

(i) the QARS zone number; (ii) the scale, in the form of a representative fraction; (iii) Drawing number; (iv) RS; (v) Reference number; (vi) Location; (vii) PD number; (viii) PIN number; (ix) Job Number; (x) Date; (xi) Associated drawings; (xii) Superseded or partly superseded PDs

(b) Other Information The following information and references shall be shown on land cadastral plans:

(i) the North Point; (ii) the name of the accredited surveyor who conducted the survey and, where applicable, the name of

the assistant employed by the accredited surveyor who assisted in the conduct of the survey and the date of the completion of the survey;

(iii) the field book number and pages;

(c) Names on Plans Every land cadastral plan shall bear the names of the draftsman and the person who checked the plan and the dates of completion. (d) Certification of Plans Every land cadastral certified plan shall bear a certificate containing the accredited surveyor’s stamp with entries of his signature and date.

Description of text Size

Cadastral parcel number 3.0 mm

Area 3.0 mm

Vertex number 2.5 mm slant 750

Road name 2.5 mm slant 750

Grid value 2.5 mm

Text in Title Block 2.5 mm

PIN number 2.5 mm

Adjacent PIN number 2.5 mm slant 750

Beacon number 2.5 mm slant 750

Length 2.2 mm


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(e) Tabulated Coordinates The beacon numbers, the Eastings, the Northings and the Elevations of the beacon are to be tabulated. (f) Numerical Information on Plan The numerical data essential on land cadastral plan shall be clearly presented and shall include:

(i) station numbers; (ii) coordinates of boundaries which can be tabulated or be placed alongside the boundaries on plan

body; (iii) the area of each lot under survey be shown beneath the lot number or, for clarity, be tabulated with

the lot number; (iv) the adjacent lot numbers; (v) the lot numbers of lots under survey shall be significantly shown near the centre of the respective

lots to which they refer; (vi) the PD number; and (vii) occupational details need not be shown on PD

(g) Other Information on Plan The following information and references shall be shown on certified plans:

(i) the North Point; (ii) the name of the accredited surveyor who conducted the survey and, where applicable, the name of

every authorized assistant who assisted in the conduct of the survey, the date of the completion; (iii) the coordinate lines with their values, and cadastral map sheet lines with their respective map

numbers as may be within the area; (iv) the survey marks by means of conventional signs and abbreviations; (v) the street names and house numbers; (vi) the approved subdivision plan number; (vii) the file reference number of the Director, GSD.

(h) Plan Schedule Every PD shall contain a schedule showing the original cadastral parcel number and the number of the previous PD and, in the case of a subdivision and amalgamation, the new parcel numbers shall also be shown.

2.3.13 Survey Report (a) A survey report shall be submitted to GSD together with the completed cadastral survey and relevant

documents. This gives the Surveyor an opportunity to review the exact nature of the original request, and assess whether the final product conforms to that request. A standard form of Survey Report is filled in by the Surveyor-in-charge.

(b) The report should include, as appropriate, details of the following items:

(i) The nature of the plot/boundary description (i .e. open land with B.P.; existing house; compound wall, etc).

(ii) Method used to define/locate the boundary. (iii) Accuracies/residuals of relevant computations. (iv) Field checks used. (v) Problems encountered (i .e. restricted access to site). (vi) Any instructions given by planning which cause a deviation in the original job request. (vii) Discrepancies (i.e. areas and dimensions, encroachments, shortfalls, clashes with utilities,

planning conflicts).

(c) The report should be as brief as possible, consistent with all essential information. The data to be submitted include:


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(i) Delivered Data

• ARC cadastre drawings or their image files (pdf)

• AutoCAD Drawings (DXF File) Containing the data of all available layers surrounding the area of interest of the Job. (Polygons, Points) Supported data Layers: Live parcels, Geodetic Control Stations, Beacons, Utilities ... etc.

• ASCII File (CSV file) containing the coordinates of all DXF Points. ASCII file structure must be followed Point Name, Easting, Northing, Height in the case of strata survey.

Example CX33, 343223.221, 224587.554 T5427l7, 383283.821,234587.815 55440024,373273.121,224587:454 3280,343223.221, 681,214587.754

(ii) Accepted Data

• AutoCAD Drawings (DXF File) Containing ONLY the Final created Parcels and Beacons (Polygons, Points).

• ASCII File (CSV file) containing ONLY the Final coordinates of Beacons Points Final Beacon name must be in a defined font ("F" & NUMBER & "-" & Point Code)

Example F1-0WC, 323223.221,214587.554 F2-FM, 343223.221, 224587.554

• Raw Data File (ASCII, SDR, GSI)

(iii) GNSS Data

• GNSS raw data (RINEX File)

• GNSS Field Book (for RTK data)

(d) When the Survey meets all the requirements, the PD is issued and signed by the unit head concerned and countersigned by the Section Head concerned. A standard letter, in Arabic, is attached to the file at this point. This letter gives the following details where appropriate: (i) Area quoted on the registration documents. (ii) Actual area occupied by the plot. (iii) Additional area/areas. (iv) Taken area/areas. (v) Final allocated area.

(e) Should the case need an explanation of any sort, it will be accompanied with an English report detailing the survey work done and any specific problems. 2.3.14 Quality Control of Cadastral Surveys The function of quality control is to ensure that the final product is of a consistent format, is an accurate representation of that on the ground and meets the requirements of the UPDA. 2.3.14.1 Processes of Quality Control Quality control covers five (5) separate processes: (a) Manufacturer test/calibration certificate as per ISO standard for total stations and GNSS instruments is

verified for each instrument.


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(b) Validation/calibration of each instrument is calibrated on government baseline. (c) Field check: Government and private work is field verified under the supervision of the GSD. The

minimum check will consist of two independently observed polars, from suitable adjacent control, into each block of parcels, to ensure absence of absolute positioning error and of rotation. Additionally, all parcel perimeters will be check-taped.

(d) Office check: This is to ensure that the case file contains all relevant information, that the data is being presented in a consistent manner, that the data is unambiguous, and that the UPDA’s request has been followed.

(e) Graphic check: The location of the surveyed land parcel is checked on Arc Cadastre Database and

"charted" onto the relevant record sheet held in Archive Unit of GSD. Calibration of Total Station could be found in Section 1.2.7, Appendix 1D and 1E of Chapter 1 and all calibration for Total Station shall be performed on government baseline only. Validation of GNSS instrument for cadastral is done on government control stations and process should test for equipment, measurement techniques, processing and transformation. The specification for setting out and tape checks is as follows:

(i) Beacon coordinates: vector displacement between design and 'insitu' coordinates must not exceed 0.050 meter.

(ii) Boundary dimensions: difference between computed and field measured dimensions for any side of a cadastral parcel, not to exceed 0.050 meter.

2.3.14.2 Surveyors' Check List The following factors apply to any cadastral survey submitted for approval. (a) Completed Flow Sheet to be supplied to include the following information:

(i) UPDA Reference number (ii) Job number (iii) District, Municipality and city name (iv) QARS Reference number (v) Survey Sheet(s) No(s) (vi) Scale of Survey Sheet(s) (vii) Field Surveyor's and Company's name (viii) Summary of Parcel and Beacon numbers allocated (ix) PD number(s) (x) Number of parcels surveyed, in total.

(b) Copy of original request for survey to be supplied, accompanied by relevant Policy Plan. (Any policy

plan more than one year old must be submitted to the Planning authority, through the Section Head of GSD concerned, for updated certification).

(c) Copies of any other documents associated with the case, e.g. Design Review Committee approval,

Earthworks approval, Adjustment drawings, RERD drawings etc. (d) Original Property Documents. These must be signed (by the Company's Senior/Chief Surveyor) and

dated. A3 format PDs must include a backing sheet unless otherwise approved by the GSD. For any land owned by the Government, individual PDs are required.

(e) Submission of soft copy in magnetic medium, providing the coordinates for each cadastral beacon. This

data disk is to be of WDD format compatible with current GSD software. (f) A comprehensive job report to be supplied to include a printed coordinate list and annotated point

description (e.g. feno mark, steel pin, hilti nail in concrete, old boundary pillar, building corner, etc.). The report should include, as appropriate, details of the following items: (i) Nature of the plot/boundary description (ii) Method used to define/locate the boundary


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(iii) Accuracies/residuals of relevant computations (iv) Field checks used with results (v) Problems encountered (e.g. restricted access to site) (vi) Any instructions given by Planning/Landowner/Agent/GSD which cause a deviation from the

original job request (vii) Discrepancies (e.g. encroachments, shortfalls, clashes with utilities, planning conflicts) (viii) Cross-references to GSD Jobs/QARS file from which relevant information extracted and attached

photocopies of relevant data where computations provided on request (ix) Comprehensive listing of all parcel areas, checked against values stated on plans (x) Details of instrument(s) used, including serial number(s) for private survey firms only.

(g) Where control of a permanent nature has been established and station numbers have been allocated, all original traverse and computation sheets must be submitted, including station descriptions.

(h) Surveyor to ensure that QARS data is consistent with the most recent data held by Field Survey

Section. (i) Note that any other documentation (e.g. original field sheets) must be available, for examination by the

GSD, upon request. 2.4.0 Strata Survey A strata survey is a legal survey which describes a volume of space for a flat/unit in a condominium building; an apartment in an apartment building; a store in a shopping centre; and underground tunnel or overhead walkway. 2.4.1 Strata Cadastral Parcel Numbering System Each strata cadastral parcel has a unique reference number in the form of PINUUUNNNBBB where:

PIN as defined earlier BBB = Building number NNN = Storey number UUU = Unit number

2.4.2 Administrative Procedures (a) Final architectural drawings in hard & soft copy (3D dwg) and other related documents are to be

provided to GSD before survey;

(b) Surveyor will survey the as-constructed units with reference to the final architectural drawings.

(c) If there are any discrepancies, surveyor is to report the discrepancies to the developer and request developer to amend the architectural plan for re-submission to GSD

2.4.3 Field Survey Procedures (a) Accuracy of linear measurements

(i) Every strata cadastral parcel shall be surveyed and the linear measurements of the survey rounded off to the nearest centimeter.

(ii) The total & internal length and width of the strata cadastral parcel shall be measured. The physical height shall be measured.

(iii) At least a minimum of two (2) bench marks shall be established within or near the parcel. Easting, northing and elevation (orthometric height) shall be derived from government control station (QND 95).


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(b) Survey of buildings

(i) The building comprising the strata cadastral parcels shall be fixed directly in relation to the boundaries of the cadastral parcel.

(ii) If encroachment is detected, the amount of encroachment shall be measured, and reflected on every strata cadastral plan submitted to the Director of GSD for approval. A note stating the nature of encroachment shall be entered in the field diagram.

(d) Identical strata lots

To measure all identical strata lots on the same or different floors. .

(d) Strata cadastral parcels involving land Where the strata cadastral parcels involve land, they shall be demarcated with the approved survey marks on the ground.

(e) Strata boundaries

Unless otherwise specifically required the boundaries of a strata unit should follow features such as the inner surfaces, median plane, or outer surface of walls, floors, and ceilings.

(f) Certification

The surveyor’s report of every cadastral strata survey shall bear the accredited surveyor’s certification with entries of his signature and date.

2.4.4 Strata Cadastral Plan (a) Every Strata cadastral plan shall contain:

(i) an index building plan; (ii) a floor plan; (iii) Individual unit plan; (iv) tabulated coordinates; and (v) title block information

(b) Plan format Strata cadastral Plans shall be drawn in the Strata Title Plan format size of A3. (c) Plan scales

To fit the entire index, floor & unit plans into one A3 size plan and the scale of the unit plan shall be in 1:100 and any other regular scales.

(d) The scale on which a plan is drawn shall be so selected such that the area of each strata cadastral

parcel and all relevant details can be clearly seen. (e) If on any part of a plan, measurements or details would otherwise be illegible or difficult to interpret, a

diagram drawn on a scale larger than that of the plan, or drawn not to scale, may be added as an inset.


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2.4.5 Drawing Specifications for Strata Cadastral Plan The following shall be adhered to when drafting plans: (a) Text

(b) Line

Description Size

Strata boundary in black 0.25 mm

Cadastral boundary in black 0.25 mm

Building line in black 0.25 mm

2.4.6 Information to be Shown on Strata Cadastral Plan See Appendix 2B for Strata Property Document. (A) Title Block The title block of each strata cadastral plan shall include:

(i) the QARS zone number; (ii) the scale, in the form of a representative fraction; (iii) Drawing number; (iv) RS; (v) Reference number; (vi) District; (vii) Municipality; (viii) PD number; (ix) Job Number; (x) Date; (xi) Strata unit number; (xii) Unit area (sq.m.);

Description of text Size

Text in Building Plan - General - Adjacent PIN number - Coordinates number - Road name

3.0 mm 2.2 mm slant 75

0

2.2 mm slant 750

2.2 mm slant 750

Text in Floor Plan - Building and Floor number - Unit number

3.0 mm 2.5 mm

Text in Unit Coordinates Table 3.0 mm

Text in Strata cadastral Plan - Strata cadastral number - Area - Vertex number - Length - Scale

3.0 mm 3.0 mm

2.5 mm slant 750

2.2 mm 3.0 mm

Text in Title Block - Heading - General - Description of Unit Detail

5.0 mm 3.0 mm 2.5 mm


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(xiii) Strata Details; a.) Strata Area (sq.m) b.) Flat/Park No. c.) Electric No. d.) Flat Net Area (sq.m) e.) Service Area (sq.m) g.) Parking Area (sq.m) h.) Total Area (sq.m) i.) Share in Land Area (sq.m) (%) j.) Water no. k.) Q-tel no.

(xiv) Checked by: sign by surveyor / verifier

(B) Other Information The following information and references shall be shown on strata cadastral plans or in surveyor’s report:

(i) the North Point; (ii) the name/signature of the accredited surveyor who conducted the survey and, if applicable, the

name of the assistant employed by the accredited surveyor who assisted in the conduct of the survey and the date of the completion of the survey;

(iii) the field book number and pages, where applicable; (iv) where applicable, the number on the approved building plans from which the details on the strata

cadastral plan have been compiled; (v) where applicable, the number of the approved subdivision plan (which has been approved by the

Chief Planner under the Planning Act); (vi) where applicable, the date of the plan for the subdivision of the building which has been

authorized by a notification from the Minister under a section of the Planning Act. (C) Names on Plans Every strata cadastral plan shall bear the signature of surveyor and the person who checked the plan and the dates of completion. (D) Certification of Plans Every strata cadastral certified plan shall bear a certificate containing the accredited surveyor’s stamp with entries of his signature and date. (E) Information to be Shown on Building Plan Every building plan shall show:

(i) the PINs of the land cadastral parcel under survey and other adjacent PINs; (ii) the boundary lines of the land cadastral parcel on which the buildings is sited; (iii) the outline and number of the buildings; (iv) the building under survey with hatched interior; (iv) the street names.

(F) Information to be Shown on Floor Plan Every floor plan shall show:

(i) Building number; (ii) Floor number; (iii) details of the strata cadastral parcels on the particular floor; (iv) unit numbers with their boundaries and hatched interior.

(G) Information to be Shown on Individual Strata Unit Plan

(i) The strata cadastral number and strata area to two decimal place shall be shown near the centre of the respective strata cadastral parcel to which they refer.

(ii) The lengths of the strata cadastral boundary should be shown to two decimal place.


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(iii) The vertex of the strata cadastral boundary should be shown as 4 digit number against the vertex.

(H) Information to be Shown on Unit Coordinates Table The vertex numbers, the eastings, the northings and the elevations of the vertex are to be tabulated. 2.4.7 Deliverable Requirements for Cadastral Strata Survey

(a) Raw data derived from establishing bench mark and observation of as-built building (b) Sketch of each unit and each floor, showing observed point, final point, dimensions, area of the

unit and other related areas and services. (c) Elevation sketch showing the height of every floor derived from government control station. (d) Pictures of existing building in four (4) views in jpeg or pdf format. (e) CSV files (observed points, final points, control stations) (f) Text file to define the area of strata unit. (g) Hard copy of each Strata Property Document and Autocad dxf file.

Follow the structure provided in the autocad dxf file provided as reference. (h) Autocad dxf of building plan, floor plan and unit/flat plan. (i) And other relevant information, in digital format, as may be required.

2.5.0 Encroachment 2.5.1 Encroachments Discovered in Cadastral Surveys (a) Accredited survey firm must detect and record all encroachments in their survey sketch plans under any

situation of the encroachments. The encroachment may be on the ground, above-ground or below-ground level.

(b) Accredited survey firm shall consider the datum to be used for a survey and positional accuracy is

within ±0.050m when reporting encroachments. (c) Offsets and radiations are to be taken and recorded to determine the extent of encroachments of the

structures in relation to cadastral parcel boundaries. 2.5.2 Reporting Encroachments (a) GSD surveyors and accredited survey firms must indicate whether there are any encroachments in the

Survey Report form when submitting the job to the GSD. For any encroachment reported in the Survey Report form, the accredited surveyors are to give a brief description of the encroachment in the Remarks column of the form. See Appendix 2E for a sample form to report encroachment.

(b) Where encroachment is reported in strata survey, it is to be shown and clearly described in the Site

Plan and / or Storey Plans of the Strata cadastral plan. Accredited surveyors are to ascertain whether the common properties or strata units or both are affected. If strata units are affected, the amount of encroachment (in sq m) is to be scaled and shown in the field book and Strata cadastral plan. In such a case, the strata cadastral parcel and its area cannot include the part of the flat unit that encroaches onto adjacent land.


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105


106


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Appendix 2C – Request for Parcel, Beacon and PD numbers

M.M.U.P. GENERAL SURVEY DEPARTMENT

CADASTRAL BEACON AND PARCEL ALLOCATION REQUEST

REQUESTED ALLOCATED

JOB NO. BEACONS

QARS NO.

NUMBER OF BEACONS PARCELS

NUMBER OF PARCELS

JOB NO. BEACONS

QARS NO.


NUMBER OF PARCELS

JOB NO. BEACONS

QARS NO.


NUMBER OF PARCELS

JOB NO. BEACONS

QARS NO.


NUMBER OF PARCELS

JOB NO. BEACONS

QARS NO.


NUMBER OF PARCELS

Requested by __________________ Approved by _________________________

Date: __________________

Date: _________________

Companies are reminded that they are responsible for supplying the correct QARS data


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Appendix 2D – Cadastral Surveys Feature Codes

FEATURE : FENO MARK CODE : FM DESCRIPTION : Code to be used for all “feno type” marks currently or previously approved by Survey Section. CONVENTION : If the surveyor wishes to differentiate between an observed feno mark and a set out feno mark this should be done by way of a remark on the fieldsheet or coordinate listing. FEATURE : GOVERNMENT BOUNDARY PILLAR CODE : GBP DESCRIPTION : A concrete pillar, between 0.2m and 1.5m in height, previously used by

government survey departments to mark plot corners, road reserves and city limits. CONVENTION : Observations to be taken to the back of the pillar in the centre, and at ground level

wherever possible. FEATURE : PRIVATE BOUNDARY PILLAR CODE : PBM DESCRIPTION : Mark placed by land owner to mark plot boundaries. SKETCH : Observation points – examples only

CONVENTION : The shape of the mark will often indicate the correct points to coordinates when

observing. If this is not the case then an observation should be taken to an easily identifiable point and suitable comments, with sketch, added to the field sheets. N. B. Land owners often erect blockwork marks around established survey marks, for protection. If the original survey mark is still intact this should be the observed points and the code will be the appropriate code for the mark, NOT PBM.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : STEEL PIN IN CONCRETE CODE : SPC DESCRIPTION : A length of reinforcing steel set in concrete, approximately 0.25m cube, used as a

Government approved plot boundary marker prior to the introduction of Feno Marks. The top of the concrete was originally constructed flush with the existing ground level.

CONVENTION : The steel pin may be mark by painted rocks. A suitable annotation can be added to

field sheets and coordinate lists in such instance, if desired. FEATURE : STEEL PIN CODE : SP DESCRIPTION : A length of steel reinforcing bar driven into the ground, without concrete surround. CONVENTION : The steel pin may be marked by painted rocks. A suitable annotation can be added to

field sheets and coordinate lists in such instance, if desired. FEATURE : HILTI NAIL CODE : HN DESCRIPTION : A length galvanized or steel nail at least 12cm in length and head of at least 2cm. CONVENTION : Mark used in surfaces where other boundary marks are inappropriate e.g. in road or

pavement. FEATURE : NOT SET OUT POINT CODE : NSO DESCRIPTION : A point which has not been set out due to prevailing site condition. CONVENTION : This code is used for cases such as points inside existing properties or the nature

ground is obscured by spoil or construction is in progress. FEATURE : POINT ON CURVED WALL CODE : WC DESCRIPTION : An observed point on a curved wall. CONVENTION : The observation will usually be taken on the outside face of the wall but if another part

of the wall is observed this should recorded as a remark on the field sheets and coordinate listings. The number and spacing of observations will be such as to ensure that an acceptable representation of the curved wall-line is obtained.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : POINT ON STRAIGHT WALL CODE : WS DESCRIPTION : An observed point along a straight wall. SKETCH :

CONVENTION : The observation will usually be taken on the outside face of the wall. If another part of

the wall is observed this should be recorded as a remark on the field sheets and coordinate listings.

FEATURE : OUTER EDGE OF WALL CORNER CODE : OWC DESCRIPTION : Wall corner or bend on wall without pillars. SKETCH :

CONVENTION : Horizontal angle and distance measurements to be taken to the points of in change in

direction of the wall. Suitable corrections will be made to EDM distances if it is not possible to locate the reflector exactly on or alongside this point.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : MIDDLE OF WALL CORNER CODE : MWC DESCRIPTION : The intersection of the outer face of external and the centerline(s) of internal boundary wall(s) without pillars. SKETCH :

CONVENTION : When observed, suitable corrections will be made to EDM distances and horizontal

angles if it is not possible to locate the reflector exactly on or alongside this point. FEATURE : CENTRE OF WALL CORNER CODE : CWC DESCRIPTION : The intersection of centerlines of boundary walls without pillars. SKETCH :

CONVENTION : When observed, suitable corrections will be made to EDM distances and horizontal angles if it is not possible to locate the reflector exactly on or alongside this point.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : OUTER DEGE OF WALL PILLAR CODE : OWP DESCRIPTION : Wall corner or bend on wall with pillars. SKETCH :

CONVENTION : When observed, suitable corrections will be made to EDM distances and horizontal

angles if it is not possible to locate the reflector exactly on or alongside this point. FEATURE : MIDDLE OF WALL PILLAR CODE : MWP DESCRIPTION : The intersection of the outer face of external and the centerline(s) of internal

boundary wall(s) with pillars SKETCH :

CONVENTION : When observed, suitable corrections will be made to EDM distance and horizontal

angles if it is not possible to locate the reflector exactly on or alongside this point.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : CENTRE OF WALL PILLAR CODE : CWP DESCRIPTION : The intersection of centerlines of walls with pillars. SKETCH :

CONVENTION : When observed, suitable corrections will be made to EDM distance and horizontal

angles if it is not possible to locate the reflector exactly on or alongside this point. FEATURE : UNDEFINED WALL CORNER CODE : CW DESCRIPTION : Code to be used when using historical data for a point which is described as “wall corner” or similar. Use of this code is limited to specific circumstances and requires the appropriate

authorization. Usages :

a) When entering historical data onto the Cadastral Survey Database where the surveyed position of the wall was not defined and field checking of data is not practical or possible.

b) When the point is used in day to day cadastral work and field checks prove inconclusive.

FEATURE : FENCE CORNER CODE : F DESCRIPTION : An observed point at the turning point of a fence line or at the intersection of two

fence lines. CONVENTION : Observations to be taken at ground level.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : POINT ON CURVED FENCE CODE : FC DESCRIPTION : An observed point on a curved fence. CONVENTION : The number and spacing of observations will be such as to ensure that an acceptable representation of the curved fence is obtained. FEATURE : POINT ON STRAIGHT FENCE CODE : FS DESCRIPTION : An observed point on a straight fence. CONVENTION : Any observation of a point along a straight fence line which is not an intersection or

corner. FEATURE : CENTRELINE OF CURVED ROAD CODE : CLC DESCRIPTION : An observed point on the centerline of an existing road or road reserve. CONVENTION : The number and spacing of observations will be such as to ensure that an acceptable

representation of the curve road centerline is obtained. When a curve centerline is being coordinated each end of the curve must be identified and observe with observations along the straight at either end to establish correct alignments of each tangent.

FEATURE : CENTRELINE OF STRAIGHT ROAD CODE : CLS DESCRIPTION : An observed point on the centerline of an existing road or road reserve. CONVENTION : When observing an existing road alignment every effort must be made to locate and

coordinate the end of each straight. Additional on line observations should then between the ends as appropriate. A minimum of three observations are for any straight.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : KERB CHANNEL CURVED CODE : KCC DESCRIPTION : An observed point at the bottom of a kerb faces along a curve kerbline. SKETCH :

CONVENTION : The number and spacing of observations will be such as to ensure that an acceptable

representation of the curved kerb is obtained. FEATURE : KERB CHANNEL STRAIGHT CODE : KCS DESCRIPTION : An observed point at the bottom of a kerb faces along a straight kerbline. SKETCH :

CONVENTION : Every effort must be made to locate and coordinate the end of each straight.

Additional on line observations to be taken between the ends as appropriate. FEATURE : EDGE OF TARMAC CODE : TEC DESCRIPTION : An observed point on the edge of curved metalled road without kerb. CONVENTION : The number and spacing of observations will be such as to ensure that an acceptable

representation of the curved edge is obtained.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : CONTROL STATION CODE : C DESCRIPTION : A permanent control station. CONVENTION : All control stations designated as Geodetic Control by Survey Section or stations

based on specifications currently in use at Survey Section for the establishment of such stations.

FEATURE : TEMPORARY CONTROL STATION CODE : TC DESCRIPTION : A non-permanent control station. CONVENTION : A control station designated as Temporary by Survey Section. Any station established which fails to meet the specifications currently use for the establishment of Permanent Control Stations.

FEATURE : TREE CODE : T DESCRIPTION : An established tree. CONVENTION : Horizontal measurements will be made to the centre of the trunk with distance measurements taken at the side of the trunk level with its centre.

FEATURE : POLE CODE : P DESCRIPTION : Any pole carrying telephone or electricity supply cables. CONVENTION : Horizontal measurements will be made to the centre of the pole with distance

measurements taken at the side of the pole level with its centre. Remarks to be made to identify the type of pole.

FEATURE : LAMP POST CODE : LP DESCRIPTION : Any post carrying street lighting or floodlamp. CONVENTION : Horizontal measurements will be made to the centre of the pole with distance measurements taken at the side of the pole level with its centre.


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Appendix 2D – Cadastral Surveys Feature Codes (cont.) FEATURE : ROADSIGN CODE : RS DESCRIPTION : Any roadsign. CONVENTION : Horizontal measurements will be made to the centre of the pole with distance measurements taken at the side of the pole level with its centre.

FEATURE : TRAFFIC LIGHT CODE : TL DESCRIPTION : Any traffic signal CONVENTION : Horizontal measurements will be made to the centre of the pole with distance measurements taken at the side of the pole level with its centre.

FEATURE : PYLON CODE : PYL DESCRIPTION : Any structure supporting power cables. SKETCH :

CONVENTION : The coordinated point is to be determined as the intersection of lines connecting the

centre of each pylon base (foot).


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Appendix 2E – Form to Report Encroachment

No. Subject Accredited Surveyor’s Confirmation

1 Legal Description of Property

(i) PD. No.

(ii) QARS Zone No.

(iii) QARS Block No.

(iv) Land / Strata Cadastral parcel No.

(v) Address

(vi) Registered Easement

2 Encroachment Details

(i) Was any encroachment discovered in survey? Yes

See _______ page _______

No

(ii) Is the encroachment depicted on a Product Document?

Yes

See No

(iii) Is the encroachment resolved? Yes No

3 Land Cadastral parcels encroachment

(i) Are details of the encroachment reported in the survey report?

Yes No

(ii) Is the encroachment onto adjoining State Land?

Yes No

(iii) Is the encroachment onto adjoining private land?

Yes No

(iv) Is there any encroachment from adjoining onto parcel under survey?

Yes No

(v) Is there any encroachment from adjoining cadastral parcel onto parcel under survey?

Yes No

4 Strata Cadastral parcels Encroachment

(i) Does the strata survey encroachment cut into flat unit?

Yes No

(ii) Is the area (Sq m) of the encroached portion shown on PD & Field book?

Yes No

(iii) Is the description added on the Site Plan & Storey Plan of the Field Book and PD?

Yes No

Qatar Survey Manual – Chapter 3 – Topographic Survey

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Abbreviations

A/E/C Architecture/Engineering/Construction

AM/FM Automated Mapping/Facility Management

CAD Computer-Aided Design

CGTC CADD/GIS Technology Center (CGTC) for Facilities, Infrastructure, and Environment

COGO Coordinate Geometry

DGPS Differential Global Positioning System

DTM Digital Terrain Model


GIS Geographic Information System





TBM Temporary Bench Mark


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3.1.0 Introduction Topographic surveys are performed for the master planning, design, and construction of installations, buildings, housing complexes, roadways, airport facilities, flood control structures, navigation locks, etc. Topographic plans are developed using electronic total stations and GNSS. Some of the more common surveys are described below: (a) Reconnaissance Topographic Surveys Reconnaissance surveys are typically performed at scales from 1:5,000 to 1:10,000. They provide a basis for general studies, site suitability decisions, or preliminary site layouts. General location of existing roads and facilities are depicted, and only limited feature and rough elevation detail is shown – 2 m to 3 m contour intervals usually being adequate. (b) General/Preliminary Site Plans General or Preliminary site plans are performed at scales from 1:2,000 to 1:5,000. They depict general layout for potential construction, proposed transportation systems, training areas, and existing facilities. (c) Detailed Topographic Surveys for Construction Plans These surveys are performed at scales from 1:200 to 1:2,000 and at contour intervals of 0.2 m or 0.5 m. They are performed to prepare a base map for detailed site plans (general site layout plan, utility plan, grading plan, paving plan, airfield plan, demolition plan, etc.). The scope of mapping is confined to an existing/proposed building area. These drawings are used as a base for subsequent as-built drawings of facilities and utility layout maps, i.e., Automated Mapping/Facility Management (AM/FM) databases. (d) As-Built Surveys and AM/FM Mapping As-built drawings may require topographic surveys of constructed features, especially when field modifications are made to original designs. These surveys, along with original construction site plans, should be used as a base framework for a facility's AM/FM database. Periodic topographic surveys also may be required during maintenance and repair projects in order to update the AM/FM database. 3.2.0 Topographic Mapping Accuracy General guidance for determining project-specific mapping accuracy standards is contained in Table 3.1. This table may be used in developing specifications for map scales, feature location and elevation tolerances, and contour intervals for typical Architecture/Engineering/Construction (A/E/C) projects. (a) Target Scale and Contour Interval Specifications Table 3.1 provides commonly used map scales and contour intervals for a variety of A/E/C applications. The selected target scale for a map or construction plan should be based on the detail necessary to portray the project site. Topographic elevation density or related contour intervals are specified consistent with existing site gradients and the accuracy needed to define site layout, drainage, grading, etc., or perform quantity take offs. Accuracy of fieldwork and the density of surveyed points required of in a topographic survey are depending on the intended map scale and contour interval. In practice, design or real property features are located or laid out during construction to a far greater relative accuracy than that which can be scaled at the target (plot) scale, such as property corners, utility alignments, first-floor or invert elevations, etc. Coordinates/elevations for such items are usually directly input as feature attributes in a Computer-Aided Design (CAD) or AM/FM database. (b) Feature Location Tolerances Table 3.1, adapted from U.S. Federal Geographic Data Committee, Geospatial Positioning Accuracy Standards: Part 4, Standard for A/E/C and Facility Management, indicates recommended positional and elevation tolerances of planimetric features at the 95% confidence level. These tolerances define the primary topographic mapping effort necessary to delineate physical features on the ground. A/E/C feature tolerances


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are defined relative to adjacent points within the confines of a specific area, map sheet, or structure - not to the overall project, installation boundaries, or an external geodetic control network. These relative accuracy tolerances are determined between two points that must functionally maintain a given accuracy tolerance between themselves, such as adjacent property corners; adjacent utility lines; adjoining buildings, bridge piers, approaches, or abutments; overall building or structure site construction limits; runway ends; catch basins; levee baseline sections; etc. Feature tolerances indicated are determined from the functional requirements of a typical project/structure (e.g., field construction/ fabrication, field stakeout or layout, alignment, etc.). Few A/E/C projects require that relative accuracies be rigidly maintained beyond the range of the detailed design drawing for a project/ structure (or its equivalent CAD design file limit). In many instances, a construction feature may need to be located to an accuracy well in excess of its plotted/scaled accuracy on a construction site plan; therefore, feature location tolerances should not be used to determine the required scale of a drawing. In these instances, surveyed coordinates, internal CAD grid coordinates, or rigid relative dimensions are used.

Table 3.11: Recommended Accuracies and Tolerances:

Engineering, Construction and Facility Management Projects

Target Feature Position Tolerance Contour Project or Activity Map Scale Horizontal Vertical Interval Design, Construction, Operation & Maintenance of Facilities Maintenance and Repair (M&R)/Renovation of Existing Installation Structures, Roadways, Utilities, Etc

General Construction Site Plans & Specs: Feature & Topographic Detail Plans

1:500 100 mm 50 mm 250 mm

Surface/Subsurface Utility Detail Design Plans Elec, Mech, Sewer, Storm, etc Field construction layout

1:500 100 mm 50 mm N/A

Building or Structure Design Drawings Field construction layout

1:500 25 mm 50 mm 250 mm

Airfield Pavement Design Detail Drawings Field construction layout

1:500 25 mm 25 mm 250 mm

Grading and Excavation Plans Roads, Drainage, Curb, Gutter etc. Field construction layout

1:500 250 mm 100 mm 500 mm

Recreational Site Plans Golf courses, athletic fields, etc.

1:1,000 500 mm 100 mm 500 mm

General Location Maps for Master Planning AM/FM and GIS Features

1:5,000 1,000 mm 1,000 mm 1,000 mm

Space Management Plans Interior Design/Layout

1:200 50 mm N/A N/A

AS-Built Maps Surface/Subsurface Utilities (Fuel, Gas, or Electricity, Communications, Cable, Storm Water, Sanitary, Water Supply, Treatment Facilities, Meters, etc.)

1:1000 or 1:500

100 mm 100 mm 250 mm

Housing Management GIS (Family Housing, Schools, Boundaries, and Other Installation Community Services)

1:5,000 10,000 mm N/A N/A

Environmental Mapping and Assessment Drawings/Plan/GIS

1:5,000 10,000 mm N/A N/A

Emergency Services Map/GIS Military Police, Crime/Accident Locations, Post Security Zoning, etc

1:10,000 25,000 mm N/A N/A

Culture, Social, Historical Plans/GIS 1:5,000 10,000 mm N/A N/A

1 Table adapted from U.S. Federal Geographic Data Committee, Geospatial Positioning Accuracy Standards: Part 4, Standard for A/E/C

and Facility Management


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Design, Construction, Operations and Maintenance of Civil Transportation & Water Resource Projects Site Plans, Maps & Drawings for Design Studies, Reports, Memoranda, and Contract Plans and Specifications, Construction plans & payment

General Planning and Feasibility Studies, Reconnaissance Reports

1:2,000 1,000 mm 500 mm 1,000 mm

Soil and Geological Classification Maps 1:5,000 10,000 mm N/A N/A Land Cover Classification Maps 1:5,000 10,000 mm N/A N/A Archeological or Structure Site Plans & Details (Including Non-topographic, Close Range, Photogrammetric Mapping)

1:10 5 mm 5 mm 100 mm

Culture and Economic Resource Mapping Historic Preservation Projects

1:10,000 10,000 mm N/A N/A

Land Utilization GIS Classifications Regulatory Permit Locations

1:5,000 10,000 mm N/A N/A

Socio-Economic GIS Classifications 1:10,000 20,000 mm N/A N/A Grading & Excavation Plans 1:1,000 1,000 mm 100 mm 1,000 mm Construction in-Place Volume Measurement Granular cut/fill, dredging, etc.

1:1,000 500 mm 250 mm N/A

Beach Renourishment 1:1,000 1,000 mm 250 mm 250 mm Project Condition Survey Reports Base Mapping for Plotting Hydrographic Surveys: line maps or aerial plans

1:2,000 10,000 mm 250 mm 500 mm

Dredging & Marine Construction Surveys New Construction Plans

1:1,000 2,000 mm 250 mm 250 mm

Maintenance Dredging Drawings 1:2,000 5,000 mm 500 mm 500 mm Hydrographic Project Condition Surveys 1:2,000 5,000 mm 500 mm 500 mm Hydrographic Reconnaisse Surveys - 5,000 mm 500 mm 250 mm Offshore Geotechnical Investigations Core Borings/Probings/etc.

- 5,000 mm 50 mm N/A

Real Estate Activities: Acquisition, Disposal, Management, Audit Maps, Plans, & Drawings Associated with Military and Civil Projects

Tract Maps, Individual, Detailing Installation or Reservation Boundaries, Lots, Parcels, Adjoining Parcels, and Record Plats, Utilities, etc.

1:1000 10 mm 100 mm 1,000 mm

Guide Taking Lines/Boundary Encroachment Maps : Fee and Easement Acquisition

1:500 50 mm 50 mm 250 mm

General Location or Planning Maps 1:10,000 5,000 mm 2,500 mm 5,000 mm GIS or LIS Mapping, General Land Utilization and Management, Forestry Management, Mineral Acquisition

1:1,000 1:5,000 1:10,000

500 mm 10,000 mm 5,000 mm

200 mm N/A 2000 mm

N/A N/A N/A

Easement Areas and Easement Delineation Lines

1:1,000 50 mm 50 mm -

3.3.0 Specifications GNSS specifications for topographical survey can be found in Chapter 1 – Control Survey. 3.3.1 Total Station Observations for Topographic Surveys (a) Standard operating procedures should require that control points be measured and noted immediately

on the data collector and/or in the field book after the instrument has been set up and leveled. In making observations for an extended period of time at a particular instrument location, re-observe the control points from time to time, also before the instrument is picked up.


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(b) Precautionary guidance and recommendations on the use of Total Station.

• Never point the telescope directly at the sun as the sun’s rays may damage the diodes in an Electronic Distance Meter (EDM).

• If possible, shade the instrument from direct sunlight as excess heat may reduce the range of the sender diodes in the EDM.

• To maintain maximum signal return at longer ranges, shade prisms from direct sunlight.

• Avoid multiple unrelated prisms in the same field of view; this can cause blunders in distance observations.

• Do not transmit with a two-way radio near the total station during EDM measurements.

(c) Positioning Topographic Features with a Total Station

Topographic features are usually cut in by multiple radial sideshots from a primary project control point. This is usually a straightforward process: the remote point is occupied with the prism pole, the height of reflector and feature code recorded, and the angle and slope distance observed and recorded. If necessary, supplemental feature attributes may be added. The process is similar when using a reflectorless total station or robotic total station where the data collector is at the prism pole. Quite often objects cannot be directly occupied with a prism pole or targeted with a reflectorless total station. Off-center (or eccentric) corrections are automatically available in most data collectors to cover these situations. Offset cases include trees or circular tanks where only direction to the centre of the circular object can be sighted (Figure. 3.1(a)); a distance to the circumference and a direction to the centre of the circular object (Figure. 3.1 (b)); or high objects that are beyond the reach of a prism pole (Figure. 3.1(c), or invert elevations.

Figure 3.1(a): Horizontal Distance Offset Measurement to Circular Object (Pole, Tree)

Figure 3.1(b): Offset Distance and Angle Measurement to Circular Object (Pole, Tree)


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Figure 3.1(c): Vertical Angle Offset

The salient points surveyed for various topographic features are: (i) Point Features: Accessible center points, otherwise, a DIST & REC command procedures on Total

Stations. (ii) Polygon Features: Visible corners, otherwise, a tape measurement or ACAD Chamfer command on

lines to be connected. (iii) Line features: Feature extents, like walls, fence, kerb, roads, footpath, carpark. (iv) Elevation: On some features when required like manholes, roads, footpath, accessway, carpark. 3.3.2 3D Terrestrial Laser Scanners Laser scanners operate similarly to reflectorless total stations. However, instead of a single shot point being observed, a full field-of-view scan is performed - at a speed upwards of 500,000 points per second. Unlike a total station, the location of the scanner is not usually a required input - resulting in points that are spatially referenced to the instrument and not real-world coordinates. This is somewhat analogous to an uncontrolled photogrammetric model. Newer models allow input of the scanner coordinates from which all observed pixels may be directly georeferenced. The resultant imagery from a scan (termed a “point cloud”) provides a full 3D model of the facility, utility, or terrain that was scanned. Objects can be scanned at a high density - with output pixels smaller than 5 mm. Relative 3D accuracies approaching the millimeter level are claimed, based on redundant observations over a surface. However, 5 to 10 mm accuracy is more realistic in practice. Scans can be rapidly made - a full field-of-view scan of a site or structure can be performed in 5 to 15 minutes per setup (multiple setups generally are required to fully detail a given site or structure). Unlike a total station, however, laser scanners have no means of assigning feature codes or attributes to the measured points - this must be done in post-processing, and is often a tedious and time-consuming process. They can be used to perform traditional topographic surveys (detailed planimetry and elevations) of project sites and facilities - providing ground elevations at a high density. (a) Accuracy - The accuracy of a scanned object can be relative or absolute. Relative accuracies are

very good (5 mm or better at close ranges). Absolute accuracies depend on the accuracy of the control network developed for the site, how accurately the instrument is aligned to this network, and


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how well overlapping images (i.e., picture points or targets) are transferred and adjusted (best fit). In general, absolute accuracies can be kept within 1 or 2 cm over a small project/structure site.

(b) Density of scanned points - Laser scanners can be set to any desired scan density, e.g., from 1 mm

onwards, usually based on some short nominal distance. The higher the density, the larger is the resulting dataset and more time-consuming the data editing and processing. The purpose of the project determines the required density. For general 3D planimetry or buildings or ground elevations, a low density can be set. For detailed maps of structural members or concrete cracks, a high density is set.

(c) Field-of-View - Depending on the model and project requirements, scanners can be set to scan a full

360 degree field or zoomed (windowed) into a narrowly set field-of-view. Some laser scanners have a field-of-view of 360

o horizontal by about 300

o vertical. The reality of scanning means that even a 360º

field of view does not guarantee full area coverage; in fact, it rarely does. Laser-shadowing forces data to be collected from multiple angles for complete data coverage. A large field of view does not alleviate this requirement. Also, the angle of incidence of a measurement will have a profound impact on its accuracy and the resolution of the data in general. Keeping this fact in mind, imagine surveying a long, flat wall. If the scanner has a 180º horizontal field of view it will be able to survey the wall in a single scan. Depending on the length of the wall, measurements may be collected from angles that approach 90º, but the reliability of these measurements will be very poor.

(d) Range - In general, most detailed scans of facilities, buildings, and structures are kept at close range

- usually less than 200 m and not much beyond 300 m. The laser eye safety classification may also be a factor in longer-range scanners - a Class 3 type laser may not be desirable for surveying a populated beach but would be acceptable at a remote site. (A Class 1 laser device “denotes exempt lasers or laser systems that cannot produce a hazard under normal operating conditions” and a Class 3a laser device “denotes visible lasers or laser systems that normally would not produce a hazard if viewed for only momentary periods with the unaided eye. They may present a hazard if viewed using collecting optics.”).

(e) Scanner Operation and Data Processing - Scanners are normally mounted on a tripod, directly

onto the plate or in a standard tribrach. The scanner is set up at any arbitrary location that affords the best view of the area or object to be mapped. No absolute geospatial orientation of the scanner is required (unless the scanner model is designed to incorporate geospatial references). Most structures require multiple scans in order to develop a complete 3D model, as illustrated in Figure 3.2. In addition, multiple scans are required to cover hidden, shadowed, or obstructed areas in a single scan. These overlapping scans allow a full 3D model of the target object to be generated using imagery correlation (optical recognition) software (similar to soft-copy photogrammetry). The overlapping “point clouds” from each scan are edited for data spikes - often a lengthy process. They are then merged to form the full 3D model. This resultant 3D model is referenced only to a relative/internal coordinate system. If real-world geographic E-N-H coordinates are required, targeted points are required to be set in the scanned area/structure in order to perform a standard coordinate transformation. Once the model is generated, a variety of computer graphic enhancements can be performed. These include coloring, wire meshing, rendering, and smoothing objects. Rough point cloud images of solid objects can be smoothed using various software-fitting routines - e.g., items such as wall faces, cylindrical pipes, etc. If the resultant model is going to be exported to a CAD or GIS platform, then additional descriptor, attribute, or layer/level assignments may be required. Final data processing can represent a significant effort on some projects - a structure that is scanned in 4 hours may take as much as 40 hours or longer to process the data to a CAD compatible format. The software used for processing scanned datasets is a critical component in the overall efficiency and economy of the process.

(f) Template Specification for Collection of Point Cloud Data Refer to Appendix 3A for template specification for collection of point cloud data.


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3.4.0 Topographic Survey Data Flow Figure 3.3 outlines the various routes by which topographic data are processed into a final site plan map format. As indicated in the figure, a number of processing options exist, depending on the software.

Figure 3.3: Overview of Topographic Survey Data Flow

Figure 3.2: Typical Four Scan Locations Needed to Fully Model a Building and Cover

Obscured Areas. In Practice, Additional Scan Points May be Needed.


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3.5.0 Basic Definitions of Geospatial Data Used in CAD or GIS Databases The following subparagraphs detail some of the basic concepts and features required for field-collected topographic data that is exported to a CAD or GIS platform. These include descriptions of data dictionaries, types of feature codes and attributes, methods of feature code collection, and processing features with attributes. (a) Data Dictionary - A Data Dictionary contains the following information:

• Feature and Attribute Library

• Intelligent Feature Codes

• Data about Feature Codes

A data dictionary is created using software designed for that purpose. Features and attributes are selected, along with attribute values and expected ranges. The edited data dictionary is uploaded to the data collector. Feature symbols can also be selected for display on the field data collector. The data dictionary software should also have an ability to import a file containing existing GIS table structures or CAD layers and symbols.

(b) Feature Code - Feature Codes are descriptors identifying some unique property associated with a

topographic feature. (c) Cartographic Data - Cartographic data are observations (or shots) on spatially distributed features,

activities, or events, which are definable as:

• Points

• Lines (Arcs)

• Areas (Polygons)

(d) Attribute - Attributes are descriptive information in a database about the cartographic features located on a map. Attributes describe the characteristics of a feature - they are often referred to as non-cartographic data. Attributes can be any numeric or character value that describes the feature. Examples of attributes assigned to a tree might include:

• Height

• Diameter

• Species

• Condition

• Age

(e) Attribute Value - Attribute values are sub details given to an attribute. For example, possible values for the attributes of the above Tree feature might include:

• Height = 15 m

• Diameter = 0.75 m

• Species = Oak

• Condition = Good

• Age = 8 years

When attribute data is collected in the field, the user may be prompted on the data collector when a particular feature is shot. Attribute values can be classified as character, numeric, date, or temporal fields. This prevents the input of an incorrect value into an attribute field; for example, preventing the entry of characters into a numeric field. Attribute range limitations (or domains) are also held in the dictionary to prevent gross blunders in entering attribute data.

(f) Point Features - A point feature represents a single geographical location (such as a

latitude/longitude and altitude). A point feature type is used to represent a feature that has no length or width. Examples of point features are:

• Tree

• Sign Post

• Electric Pole

• Fire Hydrant

• Manhole


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(g) Line Features (breaklines, arcs, strings, or polylines) - A GIS line feature type is a series of geographical locations that are connected - so-called “arc-nodes.” A line feature type is also used to represent a feature which has a length but no width. Some GISs refer to line features as arcs. CAD software will mathematically define line strings as opposed to connected points in GIS. Breaklines are connected strings. Examples of line features are:

• Railways

• Wall

• Kerb

• Ditch Line features will have various attributes similar to point features, e.g., storm sewer pipe diameter, type, thickness, date set, etc.

(h) Area Features - Areas (polygons) are a series of geographic coordinates joined together to form a

boundary. An area feature type is a closed line. An area feature has a length and a width and can have attribute data. In GIS, area features are referred to as polygons. A polygon is a single arc or a series of arcs that are connected together in order to enclose an area. Examples of area features are:

• Shoreline

• Sabkha

• Wadi

• Lakes

• Parking Area

• Building 3.6.0 Data Collection and Processing Procedure for Topographic Surveys There is no standard process for moving digital field observations into a CAD platform. The steps taken vary with the type of total station used, including its internal or external data collector. Field data collection procedures can vary from simple single shot points to fully attributed polyline strings. A variety of data formats can be output from the different data collectors on the market. The field data may be imported directly into a CAD package or processed through intermediate survey software before being uploaded into the CAD package. Given the numerous variety of CAD/survey software, there are numerous methods used to process data from the field to finished CAD or GIS product. However, most data collector software is geared more towards export to AutoCAD. The following steps highlight a general process used in most systems. However, the trend today on some total station systems is to develop data on the data collector that imports directly into the CAD platform without all the intervening steps and varied format conversions described below. Step 1 - Observations. In the first step of the process, the field survey vertical and horizontal angles are measured along with slope distances using the total station. The angles and distances are stored with a point number and description in the data collector. Optionally, attribute data may also be stored with each point, including line/area string codes. COGO routines in the data collector may be employed to convert raw observed data to local grid E-N-H coordinates; optionally, these conversions may be made on a PC after the data are downloaded. If a RTK system is used, radial E-N-H coordinate data for each observed point is attached with a descriptor identifier code and saved in the data collector. Step 2 - Transfer data from data collector to PC. After completing the survey, the data are then transferred to a field or office computer via telephone, cable, or infrared modem for data processing and editing. The computer is either an in-office desktop system or a laptop model that can be used on site. A number of software systems contain modules for performing this data transfer process. One or more files may be downloaded from the data collector. Depending on the data collector software, these downloaded datasets might include:

• Raw data files in ASCII format containing all original survey, project, and attribute observations keyed or processed in the data collector.

• Native binary format of the above file

• Coordinate file containing reduced E-N-H-attribute data for each observed point

• Other types of field recorded data may also be downloaded, e.g., pen tablet field sketches and notes, digital photo images, etc.


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Step 3 - Reformatting. If a coordinate file was not directly generated in the field, then the raw data files must be processed in the computer to produce a coordinate file that contains point number, point code, E-N-H coordinate values, and a point descriptor. Survey software packages provide review and edit capabilities at this stage of the processing, checking point codes and descriptors before they are imported into the CAD platform. These software packages are also useful in generating standardized feature and attribute codes which can be uploaded to the data collector to ensure consistent observing methods. Step 4 - Convert data into a graphics design file for use in a CAD program such as MicroStation or AutoCAD. A number of software conversion programs are available to convert raw data collector files into a CAD file. Step 5 - CAD specific applications. Once data are contained in the CAD platform, the basic topographic data can be plotted for review and edit. Digital terrain models (DTM) can be generated that can be used to generate contours, quantity take-offs, etc. Final editing and addition of notes are completed, yielding topographic data in a digital format or as a plotted map. Sheet layouts are assigned and the topographic data are ready to be used for their intended engineering, design, planning, or construction function. As stated previously, many of the above steps can be skipped if field data are collected using procedures, software, and coding that is directly compatible with the final CAD platform. Thus, uniform operating procedures are needed when collecting and processing survey data. The use of proper field procedures is also essential to prevent errors or omissions in generating the final site plan or map products. Collection of survey points in a systematic and meaningful pattern aids in this process. If consistent field procedures are employed, then a minimal amount of post-processing or editing on the CAD platform will be required. 3.7.0 CAD Drawing Standard Reference is made to “A/E/C CADD Standard Release 3”, published by The CADD/GIS Technology Center (CGTC) for facilities, infrastructure, and environment, and Singapore Standard CP 83 on Code or Practice for Construction Computed-Aided Design (CAD). 3.7.1 Introduction The A/E/C CAD Standard Manual developed by the CADD/GIS Technology Center (CGTC) for Facilities, Infrastructure, and Environment is to eliminate redundant CAD standardization efforts. The manual is part of an initiative to develop a nonproprietary CAD standard that incorporates existing industry, national, and international standards and to develop data standards that address the entire life cycle of facilities development. 3.7.2 Organization and Naming of CAD Files When CAD files are transferred between different systems and organizations, their contents need to be understood to locate information, for identification of the source and to manage files. These processes will be enhanced if all parties involved in a project use a commonly understood filename convention. The concepts, formats and codes are used to name CAD files. This guideline covers three (3) filename formats and a recommended directory structure. All the filename formats and directory structure can be further sub-divided into fields. Each field describes certain attributes of the file or directory. (a) Formats of Filename

The format requires 6 mandatory fields and an optional user-defined field. The length of project identification filed may vary from 3 to 5 characters depending on the user's need. To enhance computer processing and readability, the project identification field is to be separated from the remaining fields by means of an underscore character "_".


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Table 3.2: Description of Fields in Filename Format A

Name of field Description of field Number of characters

Project identification

Represent files of the same project. 3 -5;

4 is recommended

Author Individual/company/organization responsible for creating the file.

2

Type-of-work Nature and scope of work. 2

View plane Level in a multi-storey building or orientation of an elevation view.

2

Zone Zone of the construction site 2

Version Major revisions 2

User-defined User-defined code for in-house applications. (optional field)

-

The seven fields in filename format are to be arranged in the format as shown in Figure 3.4.

Figure 3.4: Filename Format

(b) Filename Fields Project identification field represents files under the same project. The user may use between three (3) to five (5) alphanumeric characters to describe the project identification. Four characters are recommended.

Author field represents the individual/company/organization responsible for creating the CAD file. Two (2) alphanumeric characters are used for this field.

This first character indicates the discipline of the originator of the layer. It is a single alphabet in capital letter as shown in Table 3.3.

The second character provides further definition of the author whenever necessary. If the first character is sufficient to define the author of the layer, a hyphen "_" shall be used as the second character of this field. Example: A- for architect and S- for structural engineer.

This second alphanumeric character can also be used to denote different authors from the same discipline involved in the same project. Example: A1 & A2 represent two different architects working on the same project.

Type-of-work field represents the nature and scope of work in the CAD file. Two (2) alphanumeric characters are used for this field. Please refer to Appendix 3B and Appendix 3C for the list of codes.

View plane field represents the level in a multi-storey building or the orientation of the elevation view. Two (2) alphanumeric characters are used for this field. In Table 3.4, numeric variables are represented by "1". Table 3.5 illustrates some examples of the view plane field.

1 Optional field

Project I.D. Author Type-

of-work View Plane

Zone Version User-

defined1

_


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Table 3.3: Codes for the First Character of Author Field

Table 3.4: Codes for the View Plan Field

Code Author description

A Architect

C Civil Engineer

E Electrical Engineer

L Land Surveyor

M Mechanical Engineer

N Equipment Supplier

S Structural Engineer

T Telecommunication/Signal Engineer

V Other disciplines

X Contractor

Code Description

11 Numeric -Level of storey or lowest level of a typical level (11)

A- Attic

B1 Basement 1

M1 Mezzanine 1

R- Roof

-- Whole project (two "dashes")

N- North elevation view

E- East elevation view

S- South elevation view

W- West elevation view

NE Northeast elevation view

SE Southeast elevation view

SW Southwest elevation view

NW Northwest elevation view

3D 3-dimensional/isometric view

AA Duplicated alphabet -Section view (AA)

LX Longitudinal section for civil works

DT Details


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Table 3.5: Examples for the View Plane Field

When the CAD file contains only page information such as notes, legend, diagrams, or schedules instead of CAD models, the view plane is no longer relevant and the two characters can be used for description of the form of information presented. Table 3.6 depicts the forms of information and codes.

Table 3.6: Forms of Information and Codes

Zone field represents the construction zone or block number of the project. One (1) alphanumeric character is used for this field. The codes allowed in this field are A to Z, 1 to 9 and the hyphen. character (-). "-" represents all the zones in the project. If the three characters allocated for the view plan and zone fields are not relevant to the type of construction, they can be used for further description of the type-of-work with in-house codes. However, these codes are required to be documented and communicated between different parties of the project. Version field represents major revisions of the CAD file. One (1) alphanumeric character is used for this field. The sequence of codes denoting the version is A, B, C ... Z, 1, 2, 3, ..., 9. The character "X" is reserved for referenced files so that the filename does not have to be amended each time it is updated. User-defined field can be used for further identification or to provide additional information. The filename will be more than 8 characters if this field is used. Examples of Filename Format Example 1: EWOO_A2FP31B2C A file of the East Wood project in the year 2000 (EWOO in the Project Identification field), prepared by a second architect (A2 in the Author field), containing floor plans (FP in the Type-of-work field), at level 31 (31 in the View Plane field) of zone B2 (B2 in the Zone field), and is the third version of the file (C-in the Version field). Example 2: EW01_C-RDXX12B A file of the East Wood project in the year 2001 (EW01 in the Project Identification field), prepared by a civil engineer (C-in the Author field), containing road works (RD in the Type-of-work field) of section "XX" (XX in the View Plane field) in zone 12 (12 in the Zone field), and is the second version of the file (B in the Version field).

Code Description

05 Level 5

B3 Basement 3

M2 Mezzanine 2

CC Section view CC

Code Forms of information

DG Diagram

LG Legend

NT Notes

SH Schedule

SD Standard drawings


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3.7.3 Level/Layer Assignments

This guideline was prepared with reference to the following publications:

1. ISO 13567: 1998 Technical product documentation - Organization and naming of layers for CAD, Part 1: Overview and principles

2. ISO 13567: 1998 Technical product documentation - Organization and naming of layers for CAD, Part 2: Concepts, format and codes used in construction documentation

Acknowledgement is made for the use of the information from the above references.

This guideline covers the organization and allocation of layers that are used in CAD files for construction projects and is intended to be used for communication and management purposes. A list of standard CAD layer element names is provided in this code. (a) Layer Name Sub-Classification The following concepts are used in the layer name. An independent classification can be applied to each concept.

• Originator - The originator refers to the individual/company/organization responsible for preparation and creation of information on the CAD layer.

• Element - An element is a classified construction work or system. It consists of two levels of classifications, namely, main element and sub-element.

• Main element - Main element is the first level of element classification. It represents the different types of main construction works or systems.

• Sub-element - Sub-element is the second level of element classification. It represents the various sub-systems within the main element.

• Presentation - Presentation is the format or type of information presented in CAD drawings. It is related primarily to the graphic appearance on screen and paper, as against element information, which is related to construction work or system.

• Status - Status defines whether the element in addition-and-alteration works is new, for retention or demolition etc.

• User-defined - User-defined is an additional information field, which the user may wish to use for further subdivision of layers or provide a description not covered under this Singapore Standard.

All characters used in the layer names shall be both human-and machine-readable wherever possible. A layer format with fixed number of characters is used to allow selection of layers by the use of wildcard. Where reserved codes are given, they shall be used only for the purpose specified. Other project-specific codes may also be used. Layer names are divided into fields. Each field holds one concept. Fields are either mandatory or optional. Mandatory fields shall always be included in the layer names. Optional fields can be used as required in each project. The order of fields in a layer name and the number of characters for each field shall be maintained as defined in this guide unless an alternative is specifically agreed by the project partners. However, the alternative adopted shall be documented in a way that future retrieval of the layer-structured information can be ensured. To ease of application in Qatar, the Element sub-classification is to be replaced by the Feature Codes (GFCODE) of 8 characters (see Appendix I for Q-Tel GFCODEs), defined in the GIS Data Dictionaries, which covers the following geometric representation:

• Point Primitive Features

• Line Primitive Features

• Node Primitive Features

• Area Primitive Features

• Route Systems o Point Events o Linear Events o Continuous Linear Events

• Regions


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• Complex Features (not yet available, pending a later version of the GIS software platform)

For CAD drawings which are not used to update the GIS database, the stipulated naming of the Element sub-classification is applicable. If topographic or as-built surveys meant for updating the CGIS database, then the CGIS layers are to be used and not this proposed one. Please refer to Appendix F for the CGIS layers and Appendix G for the PWA Topographic Feature Library. ASHGALS produced an AutoCAD Layering Standard document, dated 5 March 2007, to provide guidelines and procedures for adopting AutoCAD layering standards in preparing design and As-built drawings, where these drawings will be automated to GIS. These standards address layer assignments, standard symbology, layers, layer names, attributes to each feature, templates, color usage associated with line widths for all mechanical, electrical, structural, architectural drawings associated with buildings, roads, drainage and city beautification drawings. The methodology in defining Layer name is mentioned below: Field 1 = Department designator Field 2 = Status / Section Designator Field 3 = Feature / Entity Designator Department designator is the primary field which identifies the department. The status or section field differentiates proposed or existing stage of the project. The Feature designator signifies the features name. For Example:

Layer Name Line

ACAD Color Usage Type Weight

D_Ex_SEW_ABD A 0 0.18 30 Abandon Sewer Line

Where,

D = Department Ex_SEW = Section/status ABD = Feature

(b) Format of Layer Name A layer name consists of the following five fields as shown in Table 3.7.

Table 3.7: Description of Fields in a Layer Name

Name of field Description of field Number of characters

Originator Individual/company/organization responsible for preparation and creation of information

2

Element Main Main element classification 4

Sub1 Sub-element classification 4

Presentation1

Forms of information presented, e.g. element, dimension, or text

2

Status1

Status of the construction work, e.g. alterations, to be removed, or existing installations (optional)

1

User-defined1 User-defined code for in-house applications (optional) -

1 Optional firld


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The above five fields of a CAD layer name are to be arranged in the format as shown in Figure 3.5.

Originator

Element

Presentation1

Status

User-defined

1

Main Sub1

─ ─ ─ ─

Figure 3.5: Layer Name Format (c) Coding Conventions The first two fields, namely originator and element shall always be used. The underscore character "_” is used between fields to enhance readability. Originator field This first character indicates the discipline of the originator of the layer. It is a single alphabet in capital letter as shown in Table 3.3. The second character provides further definition of the originator whenever necessary. Example: AL to denote Landscape Architect. If the first character is sufficient to define the originator of the layer, a hyphen "-" shall be used as the second character of this field. Example: A- for architect and S- for structural engineer. This second alphanumeric character can also be used to denote different originators from the same discipline involved in the same project. Example: A1 and A2 represent two different architects working on the same project. Element field This field indicates the type of construction work or system of the element in the layer. Classification for the construction elements or systems is in the form of eight (8) letters of the alphabet. This element field has two levels of classification, namely, the main and sub-elements. The main element consists of four (4) letters of the alphabet and is mandatory. It identifies the main construction work or system of the element. The sub-element consists of four (4) letters of the alphabet and is only used for further classification of the main element. For elements where classification using the main element is sufficient, the sub-element may be coded with four (4) hyphen characters "----".

Table 3.8 Some Examples of Classification in Element Field.

Name of element

Description of elements

Main Sub

STRC --- Staircases

STRC HANR Handrails of staircases

WALL --- Walls

WALL FIRE Fire rated walls

1 Optional field


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Standard main element names defined based on this classification are provided in the appendices of this code. Element names are arranged in alphabetical order in Appendix 3D. To achieve consistency in the construction industry, users shall make use of the main element names provided in the appendices wherever applicable. Recommended sub-element names are provided in Appendix 3E. They are grouped under their respective main element. To achieve consistency in the construction industry, users should make • use of the sub-element names provided in Appendix 3E wherever applicable. Users may generate element names that are not in the list of standard elements provided in the appendices of this code for their internal use. However, these user-defined layers shall be properly documented and communicated among the parties involved in the project. While there is no fixed rule in arriving at the 4-character abbreviation for the main and sub-elements, the general rule is to truncate the vowels and try to maintain the first and last characters. Presentation Field The Presentation field represents the format or type of information presented and is denoted by one (1) or two (2) alphanumeric characters. First character There are two levels of classification in the first character field: (1) Basic classification

• Element graphics;

• Annotation;

• Model (combination of element and annotation in model space);

• Paper/Page (paper space or page information).

(2) Further classification

• Further classification of annotations: Text, hatching, dimension and marking;

• Further classification of paper/page: Border, tabular information, notes, legends, schedules, and diagrams. The valid codes for the first character of the presentation field are given in Table 3.9.

Table 3.9: Codes for First Character of Presentation Field

1 If Text and Title need to be on separate layers, “TL” can be used for the latter.

Code Content

- Whole model and drawing page

M Model, Marking

E Element graphics

A Annotation

T Text, Title1

H Hatching, Hidden

D Dimension

P Page/Paper

B Border

I Tabular information

N Notes

L Legends

S Schedules

R Diagrams


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Second character For element graphics, the second character represents the projection/view of the element shown in the layer. The respective views are denoted by one (1) corresponding character as shown in Table 3.10.

Table 3.10: Codes for Second Character of Presentation Field

Code Description of views

- All views

1 Elevations

2 Sections

3 3D views

4 Plans

0 Details

Status The Status field is optional and it represents the status of entities used in addition and alteration (A & A) works. It is denoted by one (1) character code as shown in Table 3.11.

Table 3.11: Codes for Status Field

Code Content

N New work

E Existing to remain

R Existing to be removed

0 Existing to be moved -Original position

F Existing to be moved -Final position

T Temporary work

User-Defined Field Users may use the user-defined field for additional information or for further subdivision of layers. However, information of these user-defined fields must be properly documented and communicated among the various parties involved. (d) Examples of Layer Name Structure Example 1: A-_WALL----_E- A layer prepared by an architect (A- in the Originator field) containing element graphics (E- in the Presentation field) of walls (WALL as main element and ----as the sub-element in the Element field). Example 2: A2_AREACALC_I- A layer prepared by a second architect (A2 in the Originator field) containing tabulated information (l- in the Presentation field) of area calculation (AREA as main element and CALC as the sub-element in the Element field). Example 3: C-_ANOT----_D- A layer prepared by a civil engineer (C- in the Originator field) containing dimensions (D- in the Presentation field) for the whole CAD file (ANOT as main element and ---- as the sub-element in the Element field).


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Example 4: C-_SDRNPIPE_ED

A layer prepared by a civil engineer (C- in the Originator field) containing element graphic details (ED in the Presentation field), for a surface water drainage pipe installation (SDRN as main element and PIPE as the sub-element in the Element field). Example 5: S-_SLAB----_M- A layer prepared by a structural engineer (S- in the Originator field) containing only markings (M- in the Presentation field) of slab (SLAB as main element and ---- as the sub-element in the Element field). Example 6: M-_ACONRETN_E- A layer prepared by a mechanical engineer (M- in the Originator field) containing the element graphics (E- in the Presentation field) of air-conditioning return air system (ACON as main element and RETN as the sub-element in the Element field). Example 7: A-DOORFIRE_S- A layer prepared by an architect (A- in the Originator field) containing schedule (S- in the Presentation field) of fire-rated doors (DOOR as main element and fire as the sub-element in the Element field) for a building. Example 8: M-SANIPIPE_E3_N A layer prepared by a mechanical engineer (M- in the Originator field) containing isometric element graphics (E3 in the Presentation field) of sanitary piping (SANI as main element and PIPE as the sub-element in the Element field) for new works (N in the Status field). Example 9: C-SEWRMINR_E-_R A layer prepared by a civil engineer (C- in the Originator field) containing element graphics (E- in the Presentation field) showing the existing minor sewers (SEWR as main element and MINR as the sub-element in the Element field) to be removed (R in the status field). Example 10: E-_ELECCABL_R-_T A layer prepared by an electrical engineer (E- in the Originator field) containing electrical wiring (ELEC as main element and CABL as the sub-element in the Element field) single line diagrams (R in the Presentation field) for temporary work (T in the Status field). 3.7.4 Standard Symbology CAD drawings meant for updating CGIS database should not include any “block” as symbol. A “block” in AutoCAD is groups of graphical elements that can be manipulated as a single entity. Examples of typical blocks are windows, doors, graphic scale keys, furniture, etc. The use of such symbology enhances CAD productivity and provides an excellent opportunity for CAD standardization. As part of the A/E/C CAD Standard, the CAD/GIS Technology Center (CGTC) for Facilities, Infrastructure, and Environment published under “Appendix D: A/E/C CAD Standard Symbology” of the “A/E/C CADD Standard Release 3.0”, the standard symbology as AutoCAD blocks - each in an individual drawing (.dwg) file, patterns in a pattern library file (.pat), multilines in a multiline library file (.mln), and custom line styles in a line type library file (.lin). Graphical presentations of the entire symbology library are shown in Appendix D, “A/E/C Standard Symbology.” The symbology library contains four types of elements: Lines, Patterns, Symbols, and Objects. Lines are defined as a graphical representation of linear drawing features (e.g., utility lines, fence lines, contours). Patterns are defined as repeated drawing elements (e.g., lines, dots, circles) within a defined area. Symbols are defined as AutoCAD blocks that are representative of objects (e.g., electrical outlets, smoke


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detectors). Objects are defined as AutoCAD blocks that retain their actual size no matter the scale of the drawing. 3.8.0 Specifications for Topographic Surveys of Engineering and Construction Nature Topographic surveys are the basis for the engineering, planning, and development plans. It is critical that the information shown on the plans be correct and complete. It is also very important to understand the intended use or accuracy requirements needed by the user of the plan along with the size of the project. This information can be useful to determine whether the project should be collected by aerial mapping or ground run surveys. If the plan is to be used for engineering design then the field survey will likely include pavement sections and utility locations.

Items Included on Surveys

(a) Topography (General)

• Performed by using trigonometric techniques with the Total Station or digitized by aerial photography.

• Provide and identify the natural relief of the ground, and man-made structures.

• Topography (Location)

• Natural

• Establish the location of “top of bank”, “toe of slope,” and centerline of all streams or creeks.

• Provide cross sections at specified intervals – typically 20 m.

• Provide a “spot grade” shot +/- 10m away from “top of bank” at the cross section interval

• Provide a “top of water” shot at every 300 m interval – record date and time if tidal area or recent weather events if not tidal.

• The diameter of trees, which will be identified by common name and/or scientific name, will be measured at 1 m above ground.

• Provide location of isolated or cultivated trees

• Provide location of edge of woods at outside “drip line.”

• Locate all high points and low points along ridges and valleys.

• Note: Some circumstances may require the location of: spoil piles, sink holes, standing water, caves, and unusual rock outcrops.

• Wetlands

(b) Ditches and Drainage Features

• Establish the location of “top of bank”, “toe of slope,” and centerline of all ditches.

• Provide cross sections at specified intervals – typically 20 m.

• Provide a “spot grade” shot – typically +/- 10 m away from “top of bank” at the cross section interval.

• Locate any concrete or asphalt: flumes, V-ditches, UD – drains or channels.

• Locate all yard drop inlets and curb drop inlets.

• Measure the diameter and note the type of all pipes.

• Provide location and elevation on invert (flow line) of pipe.

(c) Storm and Gravity Sanitary Sewers

• Obtain elevations and location on the tops of manholes or drop inlets.

• Measure readings (downs) from rim of manhole to inverts

• Locate and provide elevations on inverts and manholes on the next structure out of the limits.

• Obtain location and elevations on inverts on box culverts

• Obtain location and elevations on inverts on ends of flared-end-section pipes

• Locate sanitary sewer clean outs

• Locate and describe sanitary sewer pump stations (lift stations).

• Locate approximate areas of septic fields and tanks. (d) Roads

• Locate and measure all curb and gutter features: Back of curb, flow line, and edge of gutter pan.

• Note size and type of curb and gutter.


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• Provide location of edge of pavement at specified intervals – typically 20 m.

• Note size and type of pavement.

• Provide location of centerline or “crown” of road.

• Obtain and locate all entrances.

• If concrete pavement has been overlaid with asphalt, measure approximate depth of overlay.

• Locate and note types of guardrails.

• Locate and provide elevations at the base of Jersey barrier.

(e) Railroads

• Provide location of tracks with elevations at specified intervals--typically 20 m in a curve.1

• Obtain location of all switches.

• Obtain location of all mileposts. Note: Most crossing signals provide distances to closest milepost. If a railroad milepost cannot be located, the closest railroad spur must be located and tied.

• Obtain location of all signal equipment.

• Obtain location of all Right-of-way monuments.

• Obtain location, size, and type of culverts under the railroad.

• Secure a copy of the railroad right-of-way map.

(f) Fences

• Provide location, type, and height of fence.

• Common types of fences are split rail, wood privacy, chain link, woven wire, barbed wire, etc.

(g) Cemeteries

• Location of cemetery boundary must be shown.

• Locate graves coincident with the Right-of-way and survey centerline.

• Provide an approximate count of the number of graves.

(h) Signs

• Locate and describe all overhead truss signs.

• Locate and describe all overhead cantilever signs.

• Locate and describe all breakaway I-beam traffic signs.

• Locate and describe all traffic signals.

• Locate and describe all historical markers – recording identity numbers.

• Locate, measure, and describe in detail all advertising signs or commercial billboards. It is imperative to note the owner and the license number.

(i) House & Building Location

• Locate all dwellings and buildings at the wall or footer line and note/dimension the overhang.

• Describe as dwellings, buildings, restaurants, etc.

• Identify structure address: example - house or box number.

• Describe the height of structures: example- one storey, two storeys, or split-level.

• Describe the type of construction: example - brick, wood frame.

• Locate and describe all porches, decks, carports, utility buildings, and driveways.

(j) Utility Items – Above Ground Utility Location

• Utility poles and guy wire anchors – recording number and owner.

• Light poles – recording number and owner.

• Cable TV pedestals – recording number and owner.

• Electric – cabinet, transformer, junction box, hand hole, witness post, meter, transmission tower, and Sub-Stations (note: do not enter facility).

• Water meters, valves, vaults, manholes, blow off valves, fire hydrants and witness posts.

• Gas meters, valves, test stations, and witness posts.

• Force main air vents and witness posts along line as well as valves and emergency pump connections at pump station facility (note: do not enter facility).

• Steam pipes and steam manholes.

• Petroleum pipes, witness posts, and pumping stations (note: do not enter facility).

1 Some special circumstances may also include location and elevations for the ballast rock and railroad bed.


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• Communication or telephone manholes, pedestals, hand holes, and witness posts – recording number and owner.

• Traffic control signals, manholes, cabinets, junction boxes, and hand holes. (k) Political Boundaries & Road Names

• Provide location of all monuments of city or town corporate limits.

• Obtain the location of all monuments pertaining to county or state lines.

• Locate all street name signs and route number identifiers.

(l) Government Survey Control

• Locate all government benchmarks.

• Locate all government triangulation, trilateration, and traverse stations.

• Locate all government reference marks and azimuth marks.

• Locate all state Right-of-way monuments. (m) Property Data – (if required)

• Obtain Right-of-way plans.

• Obtain pertinent data from court records such as; subdivision flats, parcel, or tract deeds and plats, and tax assessor’s cards and maps.

• Provide location of all property monuments called for in the deed as needed per scope

• Provide location of all easements. (n) Hazardous Material/Waste Sites

• Typically, all hazardous waste sites or potential waste sites will be noted.

• Obtain site plan of suspected area

• Note and record pertinent information on location of underground storage tanks, filler caps, monitoring wells and caps.

(o) Set TBMs

• Obtain and verify vertical datum as per scope.

• A minimum of two temporary benchmarks will be set on private topographic surveys.

• TBMs will be set an interval of 300 m to 500 m on typical corridor surveys. Drawing Annotation Checklist

• Advertising Signs (Billboards): Locate if needed and show license number and owner (small license plate).

• Brush, shrubbery, woods: Annotate as dense, light, mixed, etc., and type. Example: (Tree types). Description of trees: describe the type of tree, not just hardwood and pine unless it cannot be identified. Use “Shrub” instead of “Bush” in all cases.

• Buildings: Locate at the overhangs and annotate type brick, frame, etc., the height (one storey, two storey, etc.), and name if commercial. Carports, porches, steps, walks, etc., will also be shown. Example: (1 Storey frame dwelling #3098), (2 Storey brick building #4139); Building numbers need to be shown. If no number is visible note that, do not leave it blank. Sheds are structures with a roof, and four support posts; Buildings are structures enclosed by four sides, and a door; a Dwelling is a structure that someone lives in; a Commercial Building is a business; and a Restaurant is a structure that someone eats in. The occupant of a Commercial building shall also be identified.

• Bridges: Annotate type, with deck.

• Kerbs and Gutters: Annotate type and size.

• Cemeteries: Locate the extremities, the closest grave to the centerline and annotate the approximate number of graves.

• Concrete or Paved Ditches: Annotate type and width. Flow elevations and directions will be secured by a field survey.

• Concrete or Paved Flumes: Annotate type and width. Flow elevations and directions will be secured by a field survey.

• Kerbs: Annotate type and size.

• Culverts: Annotate type, size, secure invert elevations, and direction of flow.

• Dams: Annotate type.

• Entrances: Annotate type (soil, gravel, asphalt, etc.).


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• Electric Manholes and junction boxes: Annotate.

• Fences: Annotate Height and type (wood, wire, or chain link), no split rail or woven wire.

• Fire Hydrants: Annotate.

• Guardrails: Annotate type.

• Guy Wires: Need to be annotated and located (number and furthest wire if more than one).

• Government Benchmarks, Triangulation Stations, Traverse Stations, Azimuth Marks, and Reference Marks: Annotate.

• Historical Marks: Annotate identification numbers.

• High Voltage Transmission Lines: Annotate. Electric transmission lines should be shown on the survey. Show one Tower outside the limits. List the number of lines on each tower. Do not need to show the location of the overhead lines.

• Light poles: Should be described differently, based upon use. The light poles along roadways are to be called out as “Street Light”; the lights in a shopping center, at a service station, around a hotel are to be shown as “Security Light.” The light poles in someone’s yard would be shown as “Lamp Post” and ground lights illuminating signs, etc. would be shown as “Outdoor Lights.”

• Milestone: Annotate Names of all cities, towns, and villages must be annotated and all corporate limits, county and state lines located and annotated.

• Outlet Ditches: Annotate with directions of flow.

• Pavements: Annotate type and if concrete covered with asphalt, make notations.

• Pipes: Annotate type, size, invert elevations, and direction of flow.

• Property Data: Corners will be located and annotated.

• Ponds and Lakes: Annotate and collect spot level data inside the edge of water line styles.

• Roads: Annotate route numbers and street names and type.

• Right-of Way Monuments: Annotate.

• Railroads: Annotate owners, right-of-way, and distance to the nearest milepost.

• Sewage Disposal and Water Supply: Annotate for each individual developed property, well, sewer clean outs, water meters, drain fields, septic tanks, etc. See homeowner if necessary.

• Special Signs: Annotate overhead truss, signal traffic lights, railroad protective devices, etc.

• Location and description of all other signs is required. Private signs should be picked up and described, as well as the type of supports, concrete pads or bases, and heights. Street signs should be picked up and identified as “Street Sign.”

• Storm and Sanitary Sewers: Annotate type. Example: SMH=Sanitary, SSMH=Storm, DI, etc. Secure rim elevations, inverts and/or flow lines of all structures. For kerb drop inlets show elevation at low point of the throat, usually the center of actual box and measure the length of the throat.

• Trees: Annotate type and size with the diameter measured one meter above the ground. If unsure of type, hardwood will do.

• Utility Poles and Pedestals: Annotate number and owner initials. Include information if pole has light or transformer.

• Walls: Annotate type, height, and width. Witness posts: annotate type.

• Identify gas station filler caps, monitoring wells and locate concrete pads around them.

• Identifying areas of possible hazardous materials and type of possible contamination.

• Set TBM’s or BM’s approximately 500 m apart. They can be on the centerline. They should also be at all drainage crossings (canals, etc.) and bridges.

3.9.0 Preparation of Survey Plan The following information shall be included in the preparation of the various survey plans: (a) As-Built/Topographic/Planimetric Plan

(i) Boundary marks which demarcate the property boundaries and control markers with their reference number;

(ii) Lot boundary and numbers; (iii) Size and position of existing features such as trees, ponds, roads, footpaths and structures; (iv) Public service structure like gas and telecom manholes, lamp posts, hydrants, water keyboxes,

electric boxes and sewerage manholes; (v) Existing watercourse (with direction of flow indicated) including earth streams, drains, bridges

and culverts and invert levels; (vi) Spot levels and level datum adopted;


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(vii) Any other salient features exposed at site and falling within the survey corridor; (viii) Grid lines; (ix) Title boxes. (x) Legend (xi) Location plan

(b) Longitudinal Section Plan (i) Invert levels of the existing drain/earth stream; (ii) Ground levels of the centre line of proposed route; (iii) Levels of both existing copes of drains; (iv) Soffit levels and widths of bridges and culverts; (v) Invert levels at inlet and outlet of bridges and culverts including their lengths; (vi) Road levels above culverts and outlets of connecting drain; (vii) Levels of both existing earth banks; (viii) Service crossing drains and their invert levels.

(c) Cross-Section Plan (i) Cross section shall be taken at every 20 m interval unless otherwise specified; (ii) Cross section shall be done by spirit leveling; (iii) Additional cross sections shall be produced at every road culvert, bridge and existing structure

within the survey corridor; (iv) Cross sections shall be taken at right angle to the centre-lines where they are straight and

radially where they are curvilinear; (v) Cross sections shall indicate the dimensions and levels of existing earth streams, drains,

culverts, crossing tracks, posts, tree, ponds or any other features or structures within the survey corridor to show the existing surface profile.

3.10.0 Preparation of Survey Report A standardized report format should be used for all major survey projects--especially those for planned design and construction. A project report submitted in a consistent format provides essential background information to the design engineer. The following outline may be used for guidance in preparing a survey report on a topographic survey. Outline for Topographic Survey Report Section 1: General Project Description Overview of the project including location, purpose, and parties involved. Section 2: Background Reason for project (more detailed description) and more specific location description including a map. Accuracy and deliverables should be discussed in this section. Attach or include a copy of the original Scope of Work prepared by the originator. Add funding information if applicable. Section 3: Project Planning How the project was planned including but not limited to: reconnaissance results; control establishment; datums; DGNSS method(s) selected; topographic survey techniques; feature and attribute standards selected. Section 4: Data Collection Overview of how data was collected including but not limited to: Equipment used (make and model); data collection method(s) and/or techniques used; control points used; amount of data collected; number of crews and personnel per crew; how long the data collection took; data processing/error checking performed in field. Section 5: Primary Control Data Processing How the control data processing was performed including but not limited to process followed. Subsection 5-1: Total station Traversing--adjustment software, results, closures, final adjustment results and coordinate listings.


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Subsection 5.2: GNSS Control Surveys & Baseline Processing--Software used; baseline processing results (summary); reprocessed baselines and reason for; parameters for baseline processing (elevation mask, type of ephemeris used); summary results or loop closures (if applicable). Subsection 5.3: Combined GNSS, Total Station, Differential Leveling Network Adjustments---Software used; results of unconstrained adjustment, minimal constrained adjustment, and fully constrained adjustment; summary of weights used, general statistics. Section 6: Project Summary and Conclusion This section shall include overall results of the processing, products produced, listing of deliverables being submitted, list of metadata files submitted, overall accuracy of the data collection (based on results from data processing section), problems encountered during data collection and data processing, recommendations for future data collection efforts of this type or in this area (lessons learned). Section 7: Output and Reports from Software This section shall include the detailed reports and output from software packages used during the data processing. This section might have multiple subsections, e.g., one for each step in the processing that has output that is critical in evaluating results.


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References A/E/C CADD Standard Release 3 published by The CADD/GIS Technology Center (CGTC) for facilities, infrastructure, and environment

Geospatial Positioning Accuracy Standards: Part 4, Standard for A/E/C and Facility Management published by U.S. Federal Geographic Data Committee,

ISO 13567: 1998 Technical product documentation - Organization and naming of layers for CAD, Part 1: Overview and principles

ISO 13567: 1998 Technical product documentation - Organization and naming of layers for CAD, Part 2: Concepts, format and codes used in construction documentation

Singapore Standard CP 83 on Code or Practice for Construction Computed-Aided Design (CAD).


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Appendix 3A – Template Specification for Collection of Point Cloud Data Using Terrestrial Laser Scanner

3A.1.0 Introduction

The specification described here defines the standard which point clouds must meet if they are to be accepted by Client. It does not define the standard to which products derived from point clouds must attain. 3A.2.0 Provision of Point Cloud Data

3A.2.1 Pre-survey Deliverables

Prior to survey a method statement is required. In the case of terrestrial laser scanning the method statement will also include: 1. Technical specifications about the scanning system, or systems, to be used. 2. The proposed point density. 3. A description outlining the location and extent of potential data voids and a proposed method for data

collection in these areas. 3A.2.2 Certification Requirements

Laser scanning systems used must be accompanied with: 1. A certificate confirming the system is in good working order. 2. Or details of tests, performed in the last 12 months, which show the scanner to be achieving the required

precision and accuracy. Exact requirements for certification or tests should be discussed with Client and described in the method statement before work begins. 3A.2.3 Point Density and Measurement Precision

The accuracy and point density required will be stated in the project brief. This will either be defined based on a scale of survey or based a minimum feature size defined in the project brief. For example: The minimum size of feature required to be discernable in the point cloud is 10 mm in depth and 10 mm in width and height.

”

SCALE EFFECTIVE

POINT DENSITY

PRECISION OF MEASUREMENT

TYPICAL USE1

1:10 2.0 mm +/- 2.0 mm Small details/objects (up to 5 m x 5 m)

1:20 4.0 mm +/- 4.0 mm Larger details/objects (up to 10 m x 10 m)

1:50 15.0 mm +/- 15.0 mm Small structures (up to 20 m x 30 m)

1:100 25.0 mm +/- 25.0 mm Large structures (up to 40 m x 60 m)

1 Typical use is an indicator only – the project brief will specify the exact requirements for point density and precision of measurement


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The beam width of the measurement beam must not be greater than double the effective point density. All reference to point density will be provided as the average 3-D distance between points at a defined range. 3A.2.4 Overview and Detail Scans

The number and location of overview and detail scans required will be specified in the project brief were required. 3A.2.5 Overlapping Scans

Where it is acceptable to filter areas of overlapping scan data, to reduce the point density in the final registered point cloud and hence reduce file sizes and improve software performance/data handling during processing, this will be noted in the project brief. 3A.2.6 Data Voids

The number of data voids must be minimized during the survey. The project brief will outline the requirements for handling and acceptance of data voids in point cloud data. 3A.2.7 High Level Coverage

Methods used to achieve high level coverage must be described in the method statement and outlined in the final survey report. 3A.2.8 Methods Used and Required Accuracy of Control

The methods and networks used for providing survey control are required and details of the method and equipment proposed must be included in the method statement. Where a previously defined survey co-ordinate system exists: 1. The necessary information will be supplied in the project brief to allow the re-occupation of previously

installed points. This will include a full listing of 3-D coordinates and witness diagrams. Where a previous survey co-ordinate system does not exist: 1. A new system may be established. Individual survey control points are to be provided to a geometric precision/accuracy of twice the geometric precision/accuracy required by individual measurements.

3A.2.9 Registration Procedures

The residuals of the registration process must be shown to be equal to or better than the geometric precision required by the end deliverable. Where registration is done solely via a resection calculation: 1. Each scan must contain a minimum of 4 appropriately distributed XYZ control points/targets. 2. The residuals of the registration process and the geometric precision of the estimated parameters should

be noted in the survey report.


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Where registration is performed using surface matching techniques: 1. The data must include at least n + 3 appropriately distributed XYZ control points/targets, where n is the

number of scans made. 2. The residuals of the registration process and the precisions of the estimated parameters should be noted

in the survey report. 3. The geometric accuracy of the fit should be noted in the survey report. Where registration is done using a known station position and orientation: 1. The data must include at least 3 appropriately distributed XYZ control points. 2. The residuals of the registration process and the precisions of the estimated parameters should be noted

in the survey report. Irregular features in the scan data caused by cracks or features on the subject that could be misinterpreted as errors in the registration must be augmented with illustrative photography and noted in the final survey report. 3A.2.10 Targeting/Control Points

Targets must not be positioned, or be so large, that they obscure important details of the subject. In addition targets mounted on the surface of the subject must be fixed with an adhesive that will allow removal without damage to the surface. A description of the targets to be used must be given in the method statement and the location and naming of targets is to be clearly given on the site sketches that accompany the survey report. The use of natural detail points should be avoided, but where necessary the use of distinct features is acceptable providing the point density of the scan is sufficient to maintain the registration requirements in Section 2.9 of this document. The use of features at distinct corners or edges is not permitted. Where natural detail points are to be used this must be noted in the method statement. 3A.2.11 Intensity/Color

Intensity/color information will be recorded on a per point basis at each scan position where the instrumentation allows this and such information has been specified in the project brief. 3A.2.12 Supporting Imagery

Additional image data to show the location of the scanner and the subject being scanned is required for narrative purposes. This imagery will be of a high resolution and clearly portray the subject in question. 3A.2.13 Virtual Survey

The submission of deliverables must be in a format supporting the techniques of “Virtual Surveying” using Leica Cyclone or equivalent software packages 3A.2.14 Web-Based Point Cloud Format

Web-based point clouds with color-coded information must be supplied with free viewers. These viewers should have collaborative functions to share markups such as measurements, textual information, basic drawings or links to external documents, images, videos, etc.


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3A.2.15 Delivery of Survey Material

Certain standard deliverables are required for every survey performed. See Section 4.3 for a full description of the appropriate media, formats and required metadata. The standard deliverables in digital form, unless stated in the project brief, are: Project metadata

• Raw scan data

• Scan metadata

• Control information

• Registration information for all raw scans to the site coordinate system

• Registered scan data

• Web-Base Point Cloud Data (TruView or equivalent) A hard copy survey report is also required containing: 1. Witness/illustrative diagrams outlining the position of scanning stations and control points. 2. Details of the traverse/control network used, a list of the three-dimensional positions of all control points

and residuals for the computed XYZ control. 3. The precision of any parameters derived in the registration process for each scan along with the residuals

of the registration. 4. A summary outlining the completeness of the point cloud and all known data voids. 5. All site sketches/additional field notes. Two copies of all digital and hardcopy data/documentation are required on delivery. 3A.3.0 Health and Safety

Readers are referred to IEC 60825:1 (2001) for the full precautions on the user of lasers. However, explicitly: 1. Only an appropriately trained individual may operate a laser scanner on site. Signs warning visitors that

lasers are in use must also be displayed. 2. Systems that use Class 3B or Class 4 lasers are not acceptable for use on Client sites.

3A.4.0 Storage and Archive of Point Cloud Data

3A.4.1 Data Format

To assist in the future management of scan data all data is required to be delivered in a pre-specified format with emphasis on the transferability of data between software systems. The proposed delivery format of the point cloud should be discussed with Client before the survey and outlined in the method statement.

3A.4.2 File Naming Convention

Filenames should agree with the existing Client file-naming convention

CHARACTERS CODE

1-3 Three letter code for monument in question. 4-5 Two numbers representing year of data capture. 6 Code defining data type:

• L – unregistered scan data

• K – registered scan data

• J – scan metadata


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• I – scan registration information

• G – project metadata

• H – Survey control information

• C – image displaying scan data

7-8 Number of scan (leading/trailing zeros to be used).

This is not required for the project metadata file or survey control information. The following examples are given for NTU in 2008:

EXAMPLE DESCRIPTION

NTU08L01.*** The raw (un-registered) scan data, where *** is the appropriate extension.

NTU08K01.*** Registered scan data, where *** is the appropriate extension

NTU08C01 .jpg An image showing the scan data in the file NTU08L01.*** and/or NTU08K01.***.

NTU08J01 .txt An ASCII text file providing the metadata for the file NTU08L01.

***

and/or NTU08K01.***

outlined in Section 3A.4.3.

NTU08I01 .txt

An ASCII text file providing the registration parameters required to transform the data onto the defined system (normally the local site coordinate system) for the file NTU08L01.*** as outlined in Section 3A.4.5.

NTU08G.txt An ASCII text file providing the project metadata outlined in Section 3A.4.4.

NTU08H.txt An ASCII text file providing the survey control information outlined in Section 3A.4.6.

Where more than 99 scans are made during a survey it is acceptable to omit the year of data capture. Filenames must be in the 8.3 format, e.g.

“abcdefgh.ijk

”.

3A.4.3 Scan Metadata

Metadata (information relating to the captured information) is required with all raw scan data and scanning projects. Metadata should be provided in both hardcopy and digital form. It must include: 1. File name of the raw data 2. Date of capture 3. Scanning system used (with manufacturer’s serial number) 4. Company name 5. Monument name 6. Monument number (if known) 7. Survey number (if known) 8. Scan number (unique scan number for this survey) 9. Total number of points 10. Point density on the object (with reference range) 11. Weather during scanning (external scans only) 12. The file name of an image, located at the point of collection, showing the data collected – the filename

should be the same as the filename of the raw data file.

3A.4.4 Project Metadata

A single project metadata file is required with the project. This must include the following: 1. Filename(s) of the raw data used in the registration 2. Data of capture (month and year)


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3. Scanning system(s) used (with manufacturer’s serial number(s)) 4. Company name 5. Monument name 6. Monument number (if known) 7. Survey number (if known) 8. Number of individual scans 9. Scan numbers of all scans 10. Total number of points 11. Filename of the control data 12. Description of registration method (e.g. “All scans registered to local site grid using targeted points.”) 13. An index plan showing the data collected with individual scan points named 14. Weather during survey (external scans only) 15. Any scanner specific information 3A.4.5 Registration Information

The following information should be supplied as registration information: 1. Translations in the X, Y and Z axes necessary to transform the scan origin to the scan position. 2. Rotations around the X, Y and Z axes. This should be carried out in the order X, Y and Z. 3A.4.6 Control Information The following information should be supplied as control information 1. Point ID, X, Y, Z, σDX, σDY, σDZ, comment (optional) 3A.4.7 File Sizes Individual file sizes are to be limited to the capacity of a standard single CD-ROM. The compression of files is acceptable using standard compression software such as Winzip. If capacity allows, multiple scans can be placed on a single CD. 3A.4.8 Media Unless otherwise stated, all data is to be provided on CD-ROM

’s. Any text referencing is to be provided on a

suitable label applied to the top surface of the CD-ROM. On no account must any text be written directly onto the surface of the CD-ROM. 3A.4.9 Retention of Survey Documentation On request the Contractor shall make available to Client all materials used for the compilation of the required survey. This information must be retained on file by the contractors for a minimum of six years. This will include: field notes and/or diagrams generated whilst on site; the raw and processed data used for the final computation of coordinate and level values; and a working digital copy of the Metric Survey data that forms each survey (this is to include formatted 2-D and ‘raw’ 3-D data files). The precise digital format and file type of this archive is that specified in the project brief. If during this period the contractor wishes to change the format of this data archive, they are to seek Client’s permission.


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3A.5.0 Example Metadata

3A.5.1 Scan Position Metadata

3A.5.2 Project Metadata

PARAMETER EXAMPLE

File name of the raw data NTU08L02.xyz

Scanning system used (with serial number) HDS6000 (123456)

Monument name NTU_1

Survey number (if known) NA

Total number of points 857 446

The file name of an image, located at the point of collection NTU08C02.jpg

Date of capture 29/01/2008

Company name NTU

Monument number (if known) NA

Scan number (unique scan number for this survey) 2

Point spacing on the object 0.015 m (@ 30 m)

Weather during survey Sunny and calm

Filename(s) of the raw data used in the registration

NTU08L01.txt (1 – in index plan) NTU08L02.txt (2 – in index plan) NTU08L03.txt (3 – in index plan) NTU08L04.txt (4 – in index plan) NTU08L05.txt (5 – in index plan) NTU08L06.txt (6 – in index plan)

Data of capture (month and year) Jan 2008

Scanning system(s) used (with serial number(s)) HDS6000 (123456)

Company name NTU

Monument name NTU_1

Monument number (if known) NA

Survey number (if known) NA

Number of individual scans 6

Scan numbers of all scans 1- 6

Total number of points 8270541

Description of registration method All scans registered to local site grid using targeted points and resection calculation

Filename of control data NTU08H .xyz

Weather during survey Sunny and calm


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Appendix 3B1 – List of Type-of-Work Codes by Discipline

Type-of-work codes in this list are classified according to the major construction disciplines.

Drawing subject Code

Common to all disciplines

Floor plan FP

Floor plan -Elevation view FE

Floor plan -Cross section view FX

Site plan SP

Site plan -Elevation view SE

Site plan -Cross section view SX

Architectural

Access details AD

Aluminum works AL

Amenities plan AP

Area calculation AR

Bin centers BC

Buildings BD

Cabinets/wardrobes CB

Curtain walls CU

Doors DR

External works EW

Gondolas GD

Ironmongery 1M

Kitchen cabinets KC

Lifts and escalators LE

Landscape LS

Miscellaneous -Architectural MA

Parking lots PK

Railings RL

Ramps RP

Reflective ceiling plan CP

Refuse chutes RE

Roofs RF

Signage SG

Staircases SC

Substations SN

Swimming pools SM

Toilets TL

Windows WD

1 In Appendices 3B and 3C, numeric variables are represented by "1".


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Appendix 3B1 – List of Type-of-Work Codes by Discipline (cont.)



Civil

Bore holes BH

Bridges BR

Bus shelters/bays BS

Drainage DN

Demolition DM

Earth works EA

Landscape LS

Miscellaneous -Civil MC

Parking lots PK

Piling layout PL

Road works RD

Reclamation RM

Signage SG

Survey plan SV

Sewers SW

Utilities plan UP

Water works WW

Structural

Beams BM

Beam details sheet no. Bl

Columns CL

Core walls CW

Footings FT

Loading plan LP

Miscellaneous -Structural MS

Pilecaps PC

Piling layout PL

Retaining walls RW

Roofs RF

Slabs SB

Slab details sheet no. Sl

Staircases SC

Steel works SL

Stumps SU



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Appendix 3B1 – List of Type-of-Work Codes by Discipline (cont.)



Mechanical

Air-conditioning & mechanical ventilation AC

Building automation systems BA

Combined services CS

Compressed air CA

Fire services FS

Fuel oil installation FO

Gas supply GS

Mechanical handling systems MH

Miscellaneous -Mechanical MM

Plumbing services PS

Process works PW

Sanitary services SA

Scrubbers SR

Sewage treatment ST

Steam services SS

Structural coordination SO

Swimming pool SM

Electrical

Electrical power supply EL

Extra-low voltage installation EV

Lifts and escalators LE

Lighting LT

Lightning and earthing LN

Miscellaneous -Electrical ME

Telecommunication TC



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Appendix 3C1 – List of Type-of-Work Codes in Alphabetical Order

Type-of-work codes in this list are arranged in alphabetical order.

Codes Types of Work Discipline

AC Air-conditioning & mechanical ventilation mechanical

AD Access details architectural

AL Aluminum works architectural

AP Amenities plan architectural

AR Area calculation architectural

Bl Beam details sheet no. structural

BA Building automation systems mechanical

BC Bin centers architectural

BO Buildings architectural

BH Bore holes civil

BM Beams structural

BR Bridges civil

BS Bus shelters/bays civil

CA Compressed air mechanical

CB Cabinets/wardrobes architectural

CL Columns structural

CP Reflective ceiling plan architectural

CS Combined services mechanical

CU Curtain walls architectural

CW Core walls structural

OM Demolition architectural/civil

ON Drainage civil

OR Doors architectural

EA Earth works civil

EL Electrical power supply electrical

EV Extra-low voltage installation electrical

EW External works architectural

FO Fuel oil installation mechanical

FE Floor plan -Elevation view common

FP Floor Plan common

FS Fire services mechanical

FT Footings structural

FX Floor plan -Cross section view common

GO Gondolas architectural

GS Gas supply mechanical

IM Ironmongery architectural

KC Kitchen cabinets architectural



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Appendix 3C1 – List of Type-of-Work Codes in Alphabetical Order (cont.)



LE Lifts and escalators architectural/ electrical

LN Lightning and earthing electrical

LP Loading plan structural

LS Landscape architectural/civil

LT Lighting electrical

MA Miscellaneous -Architectural architectural

MC Miscellaneous -Civil civil

ME Miscellaneous -Electrical electrical

MH Mechanical handling systems mechanical

MM Miscellaneous -Mechanical mechanical

MS Miscellaneous -Structural structural

PC Pilecaps structural

PK Parking lots architectural/ civil

PL Piling layout civil/structural

PS Plumbing services mechanical

PW Process works mechanical

RD Road works civil

RE Refuse chutes architectural

RF Roofs architectural/ structural

RL Railings architectural

RM Reclamation civil

RP Ramps architectural

RW Retaining walls structural

Sl Slab details sheet no. structural

SA Sanitary services mechanical

SB Slabs structural

SC Staircases architectural/structural

SD Structural coordination mechanical

SE Site plan -Elevation view common

SG Signage architectural/civil

SL Steel works structural

SM Swimming pools architectural/mechanical

SN Substations architectural

SP Site plan common

SR Scrubbers mechanical

SS Steam services mechanical

ST Sewage treatment mechanical



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Appendix 3C1 – List of Type-of-Work Codes in Alphabetical Order (Cont.)



SU Stumps structural

SV Survey plan civil

SW Sewers civil

SX Site plan -Cross section view common

TC Telecommunication electrical

TL Toilets architectural

UP Utilities plan civil

WD Windows architectural

WW Water works civil



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Appendix 3D – List of Main Elements in Alphabetical Order The main elements in this list are arranged in alphabetical order.

Main Description

ACON Air-conditioning including heating and related ventilation systems

ANOT Annotations

AREA Areas

BAMS Building automation management systems

BEAM Beams

BLDG Buildings

BRDG Main bridges

CADI Cadastral information, lot numbers, lot boundaries

CDSH Civil defense shelters (public shelter layouts, bounds of protection)

CEIL Ceilings

CHNY Chimneys

CLAD Claddings

COLN Columns

COMA Compressed air systems

CONC Concrete structures

CPRK Car parking lots

DCON Document conveyor systems

DETA Details -offsets, walls, concrete drains, slopes, roads, fences

DOOR Doors

DPOT Railways leading to depots

DWAT Domestic hot and cold water systems

ELEC Electrical power systems

ENDO Plan endorsement by agencies

ESCR Escalators I people movers

FEAT Features -road names, rivers, reservoirs, bridges

FIRE Fire protection systems

FLOR Floors

FNSH Finishes

FOUN Foundations

FUEL Fuel systems

FURT Furniture

GASP Gas supply systems

GRID Grids

LGTN Lightning protection systems

LIFT Lifts

LIGT Lighting

LNSP Landscapes and tree planting

MEDG Medical gas systems

MEVS Mechanical exhaust I ventilation systems

MHAN Material handling systems


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Appendix 3D – List of Main Elements in Alphabetical Order (cont.) The main elements in this list are arranged in alphabetical order.

Main Description

MTAL Metal parts

OPEN Structural openings

OTHR Other installations

PAGE Paging systems

PATH Footpaths, walkways

PCAP Pile caps

PCM- Pollution control measures

PCR- Pollution control requirements

PGRD Playgrounds, park facilities

PILE Piles

POOL Swimming pools

PRCS Industrial processes

PRES Prestress elements

PUBA Public address systems

RAIL Railways

RALG Railings

RAMP Ramps

RATG Roads at-grade (kerb lines)

RCDS Refuse collection disposal systems including refuse chutes, refuse chute chambers, refuse rooms, refuse bin centers, pneumatic refuse conveyance systems

REIN Reinforcements

RETW Retaining walls

ROAD Roadways

ROOF Roofs

RSUB Roads at sub-surface (underpasses)

RSUP Flyover structures

RWTR Reclaimed water supply installations

SANI Sanitary systems

SDRN Surface water drainage

SECU Security systems

SEWR Sewers

SIGN Signage

SITE Site I external works

SLAB Floor slabs

SOIL Soil tests -field I laboratory

SPAC Space usage

SPRK Fire sprinkler systems

STEL Steel structures / trusses

STEM Steam systems

STRC Staircases

SYBL Symbols including handicap symbols


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Appendix 3D – List of Main Elements in Alphabetical Order (cont.) The main elements in this list are arranged in alphabetical order.

Main Description

TCOM Telecommunications installations

TIMB Timber parts

TOPO Topology

TRAV Traverse information, markers and coordinates

TRCK Trackwork

TVAN TV antenna systems, cable TV systems

VCUM Vacuum systems

VIAD Viaducts

WALL Walls

WATR Water supply installations

WIND Windows

XREF Reference files


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Appendix 3E – List of Recommended Sub-Elements in Alphabetical Order

Main Sub Description

ACON Air-conditioning including heating and related ventilation systems

CDDR Condensation drainage

CDWR Condenser water return

COWS Condenser water supplies

CHll Chilled water systems

CHWR Chilled water returns

CHWS Chilled water supplies

COND Condenser water systems

EQPT Air-conditioning equipment

FRDF Fresh air diffusers I grilles

FRDT Fresh air ducts

FRES Fresh air systems

FRFN Fresh air fans

MUWP Make-up water pipes

REDT Return air ducts

REFR Refrigerant systems I pipes

REGR Return air grilles I diffusers

RETN Return air systems

SUDF Supply air diffusers I grilles

SUDT Supply air ducts

SUPP Supply air systems

THEM Thermostats

ANOT Annotations

REVN Revision notes

SPNO Sketch numbers, plan numbers, cadastral map numbers, lot history schedules, legend boxes, coordinate tables

TBLK Title blocks

VPRT View-port of CAD files

AREA Areas

AREL Land lot areas

ARES Strata lot areas

BDBA Building block areas

BDBD Areas to be deducted from building coverage

CALC Area calculations

COSA Communal open space areas

COSO Areas to be deducted from communal open space areas

GFAA Areas included in Gross Floor Area (GFA) calculations

GFAB Area calculation of balconies

GFAD Areas in GFAA but excluded from GFA

GFAR Area calculation of outdoor refreshment areas

GFAQ Area calculation for quantum details

GFAS Area calculation for secondary uses or mixed use developments


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Appendix 3E – List of Recommended Sub-Elements in Alphabetical Order (cont.)


BAMS Building automation management systems

BEAM Beams

BLDG Buildings

BRDG Main bridges

CADI Cadastral information, lot numbers, lot boundaries

CADA Airspace lot boundaries and lot numbers, elevation sketches, total area tables for airspace lots

CADN Proposed new lot boundaries, house numbers, lot and marker numbers, inset diagrams

CADP Per-original lot boundaries, lot and marker numbers, per-original markers found

CADS Subterranean lot boundaries and numbers, elevation sketches, total area tables for subterranean lots

ELES Elevation sketches, including accessories, lot tables, height, lot and house numbers

MKTS Mukim I town sub-division boundaries and numbers

SHAV Share value tables

SITP Site plan diagrams

STOP Storey plan diagrams, house numbers, common properties

CDSH Civil defense shelters (public shelter layouts, bounds of protection)

AHUE Air-handling equipment, gas filters, gas-tight shut-off valves

CHIL Air-conditioning chillers, cooling towers, pump sets, pipes

DOOR CD doors, louvres, hatches, valves

ELEC

CD electrical installations, generators and related cooling systems, generator fuel systems (underground fuel tanks, fuel pipe routings), electrical switchboards and main cable support systems (ladders, trunkinqs, trays)

LGTN Lighting, switches, power outlets and circuits

MEVS Ventilation to CD shelters

MONI CD-door monitoring systems, equipment monitoring systems, control panels

OPEN Structural openings in CD shelters, openings for MCTs, pipe sleeves, puddle flanges, opening labels

PATV Telephone and bell systems, public address systems, intercom systems, MATV I cable TV systems

PRES Overpressure regime and airflow, differential pressure gauges

RETN Return air ductworks, diffusers, fans

SANI CD decontamination systems, CD drinking systems, CD 'hygiene' systems, pump sets, pipe works, tanks, shower heads, drinking points, wash basins, taps, sinks, wash troughs

SUPP Supply air ductworks, diffusers, fans

ZONE Zones of protection, CD room labels

CEIL Ceilings

CHNY Chimneys

CLAD Claddings


164

Appendix 3E – List of Recommended Sub-elements in Alphabetical Order (cont.)


COLN Columns

LOAD Loading

STIF Stiffeners

STUM Stumps

COMA Compressed air systems

CONC Concrete structures

TEND Prestress tendon profiles

CPRK Car parking lots

LEVL Car parking lot spot levels

DCON Document conveyor systems

DETA Details -offsets, walls, concrete drains, slopes, roads, fences

DOOR Doors

FIRE Fire rated doors

DPOT Railways leading to depots

DWAT Domestic hot and cold water systems

COPI Domestic cold water pipes

EQPT Domestic hot and cold water equipment

FLPI Domestic flush water pipes

HOPI Domestic hot water pipes

ELEC Electrical power systems

BUSB Electrical power bus-bar trunkings

CABL Electrical cable trays

CIRC Electrical circuits

EMER Emergency power supplies

EQPT Electrical equipment

FANS Electrical fans

SWIT Electrical switchboards

TRKG Electrical trunkings

UNDR Electrical underground conduits

ENDO Plan endorsement by regulatory authorities

BLDP Building Plan

CIDS Civil Defense Shelter

NEAP Pollution Control

NPKS National parks

PGAS Power / Gas

PUBD PUB -Drainage

PUBR PUB -Water Reclamation

PUBS PUB -Sewerage

PUBW PUB -Water

ESCR Escalators / people movers

FEAT Features -road names, rivers, reservoirs, bridges


165



FIRE Fire protection systems

ALAM Fire alarms

DAMP Fire dampers

DRYR Fire protection dry risers

ENGA Fire engine access ways

ENGH Fire engine hard-standing

EOPT Fire protection equipment

HDCO Heat detectors concealed

HDEX Heat detectors exposed

HEAT Fire protection heat detectors

HYDT Fire hydrants

REEL Fire protection hose reels

SDCO Smoke detectors concealed

SDEX Smoke detectors exposed

SMOK Fire protection smoke detectors

WETR Fire protection wet risers

FLOR Floors

LEVL Floor / platform levels

FNSH Finishes

FOUN Foundations

FUEL Fuel systems

EQPT Fuel equipment

PIPE Fuel pipes

FURT Furniture

GASP Gas supply systems

EOPT Gas supply equipment

PIPE Gas pipes

GRID Grids

LGTN Lightning protection systems

LIFT Lifts

LIGT Lighting

CIRC Lighting circuits

SWIT Lighting switches

LIGT TRKG Lighting Trunkings

LNSP Landscapes and tree planting

ARTN Aeration areas

BUFF Green buffer lines

HARD Landscaping hard surfaces

VERG Planting verges

MEDG Medical gas systems


166



MEVS Mechanical exhaust I ventilation systems

EXDT Exhaust air ducts

EXFN Exhaust air fans

EXGR Exhaust air grilles I diffusers

EXHA Exhaust air systems

FRDF Fresh air diffusers I grilles

FRDT Fresh air ducts

FRES Fresh air systems

FRFN Fresh air fans

SMKC Smoke control systems

SMKP Smoke purging systems

STPR Staircase pressurization systems

MHAN Material handling systems

MTAL Metal parts

OPEN Structural openings

OTHR Other installations

PAGE Paging systems

PATH Footpaths, walkways

OVER Pedestrian overhead bridges

UNDR Entrance and exit of pedestrian underpasses

PCAP Pile caps

PCM· Pollution control measures

APCE Air pollution control equipment

APCS Air pollution control systems

FBE- Fuel burning equipment

NPCF Noise pollution control facilities

WPCE Water pollution control equipment

PCR· Pollution control requirements

PME- Process equipment

STOR Storage facilities

UTLT Utilities

PGRD Playground, park facilities

PILE Piles

POOL Swimming pools

EQPT Swimming pool equipment

PIPE Swimming pool pipes

PRCS Industrial processes

PRES Prestress elements

CABL Prestress cables


167



PUBA Public address systems

SPKR Public address systems speakers

RAIL Railways

MALG Master alignments, chainage / labels, tangent points

PLFT Station platforms

ZONE Railway protection corridors

RALG Railings

RAMP Ramps

RATG Road at-grade (kerb lines)

RCDS Refuse collection disposal systems including refuse chutes, refuse chute chambers, refuse rooms, refuse bin centers, pneumatic refuse conveyances stems

REIN Reinforcements

BOTM Bottom reinforcements

LINK Reinforcement links

TOP- Top reinforcement

WELD Welded steel fabrics

RETW Retaining walls

PONT Survey points

ROAD Roadways

BUS- Bus stop posts or shelters

ELEM Road furniture, traffic signs, bus shelters, bus stop posts, sign boards, surveillance camera associated with roads

HUMP Road humps

INNR Inner edges and centre lines of carriage ways

KERB Road kerbs

LEVL Road spot levels

MALG Master alignments, chainage / labels, tangent points

MARK Traffic markings on roads

OUTR Outer edge of carriage ways

PONT Survey point of road lines

RESV Road reserves

SIGN Road signage

TLGT Traffic lights

WIDL Road widening lines

ROOF Roofs

RSUB Roads at sub-surfaces (underpasses)

RSUP Flyover structures

RWTR Reclaimed water supply installations

INDW Industrial water supply installations

NEWR NEWater supply installations


168



SANI Sanitary systems

DRAN Sanitary drainage

EQPT Sanitary equipment

FIXR Plumbing fixtures

PIPE Sanitary pipes

PITS Pits, sumps, hatch-boxes

VENT Sanitary vent pipes

SDRN Surface water drainage

COMD Outlines of common drains

CONN Connection of drain to roadside drains

CREL Crest protection levels for openings, stairways to basements

CRRC Collection of rain water for recycling purposes

DELE Deleted I obsolete drain lines

DRDC Computation for peak runoff and discharge capacities

FBIL False bottoms invert levels of drains

FLOW Flow directions in drains

GRAT Drain gratings

GTIR Gutter channels

INTO Outlines of internal drains

LEVL Invert levels of surface drainage

OUTD Outlines of outlet I roadside drains

MAJR Drainage, pumping mains and ducting, cable troughs

MINR Scupper drains, sump pits and pump sumps, gratings, chequer plates, steel frames, weld connections

MPLL Minimum platform levels

PIPE Surface water drainage pipes, culverts

PUMP Pump capacities, areas of source catchment

RECL Reclamation levels

RESV Drainage reserves

STDR Structures within drainage reserves

SVDR Services within drainage reserves

UGDS Drainage for basements, tunnels and underground facilities

SECU Security systems

SEWR Sewers

DEEP Deep tunnel sewers and drop shafts

LEVL Main invert levels of sewers I pumping

MAJR Major I main sewers and manholes for diameter 300 mm -900 mm

MINR Minor sewers and manholes for diameter < 300 mm

PIPE Sewer pipes

PRSS Sewage pumping mains and related pipe works

TREF Effluent outfall pipes

TRNK Trunk sewers and manholes for diameter> 900 mm


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SIGN Signage

SITE Site, external works

BASE Basement outlines

BLDG Building outlines

BNRY Site boundaries

ELEM Facilities, secondary important sub-elements put in the same layers

ISTM Instruments

KPLN Key plans

LINK Linkways, bollards

NRTH North point

PATH Footpaths

RAIL Guardrails I railings

SCVS Services manholes (TAS, SEW, WATER), electric boxes, fire hydrants, electric poles, traffic lights, telephone booths and other openings I manholes associated with utilities

STBK Building setbacks

WALL Boundary walls, site fences

SLAB Floor slabs

LOAD Loading

PLNH Concrete plinths for equipment

PLNK Precast planks

STEP Slab rises I drops

SOIL Soil tests -field I laboratory

BORE Bore hole logs

CLAY Clay

FILL Fills

ROCK Rocks

SAND Sand

TUNL Tunnels

SPAC Space usage

BLDG Building plot boundaries, building plot numbers

COSS Plot boundaries and plot numbers for communal uses I open spaces

FOOD Food outlets and food factories

MRKT Markets

SPAC POOL Layouts of swimming pools

STRA Strata unit boundaries on floor plans for strata subdivisions

TOIL Public toilets

SPRK Fire sprinkler systems

PICO Sprinkler range pipes concealed

PIEX Sprinkler range pipes exposed


170



SPRK PIPE Sprinkler pipes

STEL Steel structures I trusses

BOLT Bolts

CAGE Cages

PLTE Plates

PURL Purlins

MAJR Major members

MINR Minor members

WELD Weldings

STEM Steam systems

STRC Staircases

HANR Staircases handrails

LNDG Staircases landings

STEP Staircases steps

WLIN Staircases walk-lines

SYBL Symbols including handicap symbols

TCOM Telecommunication installations

CABL Telecommunication cables

TIMB Timber parts

TOPO Topology

CONT Site contour lines and elevations

CROS Cross sections

GRAD Site gradients

LONG Longitudinal sections

PLVL Platform levels

PONT Spot level points for earthworks computation

SLOP embankments

TRAV Traverse information, markers and coordinates

ISNM Integrated survey networks marker information

TRCK Trackwork

3R--

3R conductor rails, 3R insulators, 3R protective covers, 3R claws, 3R supports, expansion rail joints, midpoint anchors, 3R ramps, overhead catenary systems, automatic train operations (ATO), electrified tracks, Non-ATO electrified tracks

BRTL Bored tunnels / 1st stage concrete

BUFF Slidings / fixed buffer stops

TRCK CCTL Cut and cover tunnels / viaducts

CONC Construction joints / 2nd

stage concrete, sleepers

FORM Trackform types, switches / crossings

FTNR

Base plates, resilient pads, elastomer materials, bolts / nuts, springs I nylon bush, rail clips, insulating materials and miscellaneous fixings

GAUG Kinematics envelopes, structure gauges, construction gauges, wagon mounted structure gauges


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TRCK IRJT Insulted rail joints, sealing compounds, joint filers, fish plates, bolts and nuts

LINE

Rails, ballasted tracks, stabling tracks, staging tracks and test tracks, reception tracks and non-electrified tracks

MARK Chainage markers, electrical section markers and fouling point signs

PATH Walkways, cross passages, precast step units

SCCC Circuit diagrams, traction substations, drainage panels, impedance / bridging, DC supplies, wire meshes

SVCS Services, cables, brackets, pipes, jumper boxes and wave guides

TRUN Turnout geometry, turnout crossings, point machines, switches I crossings, turnout switch rails, check rails

TVAN TV antenna systems, cable TV systems

VCUM Vacuum systems

VIAD Viaducts

WALL Walls

FIRE Fire rated walls

PARP Parapet walls

PRTN Partition walls

STRU Structural walls

WATR Water supply installations

FIRE Water supply installation for fire protection systems

WIND Windows

SKYL Skylights

XREF Reference files


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177

Appendix 3G: PWA Topographic Feature Library

LAYER DESCRIPTION

1 BLD_PRML Permanent building; residential/commercial structures; covered car parks; etc. (LINES)

2 BLD_PRMP Permanent building; residential/commercial structures; covered car parks; etc. (POINTS)

3 BLD_SEML Semi-permanent building: residential/commercial structures; e.g., portable cabins, make-shift car parks; etc. (LINES)

4 BLD_SEMP Semi-permanent building: residential/commercial structures; e.g., portable cabins, make-shift car parks; etc. (POINTS)

5 BLD_STPL Building steps (LINES)

6 BLD_STPP Building steps (POINTS)

7 BLD_TEXT Building text/label

8 BRK_LNEL (Hidden) Breaklines for contouring (LINES)

9 BRK_LNEP (Hidden) Breaklines for contouring (POINTS)

10 CAD_PNTS Cadastral markers: Points (e.g., feno markers, etc.)

11 CAD_TEXT Cadastral markers: Annotation

12 CSB_SYMB Survey control point, line (Symbol)

13 CSB_TEXT Survey control point, line (Text)

14 CTR_MJOR Major contour line

15 CTR_MNOR Minor contour line

16 CTR_TEXT Contour height label

17 DWG_GRID Drawing information: Grid markings and coordinates

18 DWG_LWKS Drawing information: Limit of works

19 DWG_MTCH Drawing information: Adjoining sheet details

20 DWG_NRTH Drawing information: North arrow

21 FTM_SYML Man-made features not covered by specific layer (LINES)

22 FTM_SYMP Man-made features not covered by specific layer (POINTS)

23 FTM_TEXT Man-made features not covered by specific layer (Text)

24 FTN_SYML Naturally occurring features other than trees, shrubs (LINES)

25 FTN_SYMP Naturally occurring features other than trees, shrubs (POINTS)

26 FTN_TEXT Naturally occurring features other than trees, shrubs (Text)

27 GIS_CADS CGIS cadastral data

28 GIS_OTHR Other data imported from CGIS

29 GIS_SERV CGIS services data

30 GIS_TOPO CGIS topographical data

31 GTE_SYMB Gate symbol: Point or line feature

32 GTE_TEXT Gate: Height and descriptive text

33 LVB_SYMB Level/Spot Height: Bitmac (Symbol)

34 LVB_TEXT Level/Spot Height: Bitmac (Text)

35 LVF_SYMB Level/Spot Height: Flooring (Symbol)

36 LVF_TEXT Level/Spot Height: Flooring (Text)

37 LVG_SYMB Level/Spot Height: Ground (Symbol)

38 LVG_TEXT Level/Spot Height: Ground (Text)

39 LVO_SYMB Level/Spot Height: Other (Symbol)

40 LVO_TEXT Level/Spot Height: Other (Text)

41 LVP_SYMB Level/Spot Height: Paving other than bitmac (Symbol)

42 LVP_TEXT Level/Spot Height: Paving other than bitmac (Text)

43 MSC_LYRL Features not included in any other named layer (LINES)

44 MSC_LYRP Features not included in any other named layer (POINTS)

45 MSC_TEXT Other Annotation/Text not tied to specific feature

46 PIT_SYMB Test pits and bore holes, etc. (Symbol)

47 PIT_TEXT Test pits and bore holes, etc. (Text)

48 PLN_BRDR Plan Information: Map/Drawing main border lines


178

49 PLN_INDX Plan Information: Location and sheet index map

50 PLN_LGND Plan Information: Map/Drawing legend listing

51 PLN_NOTE Plan Information: Notes about drawing

52 PLN_TBOX Plan Information: Title box details: project name, number; consultant's, contractor's details; sheet/drawing numbers; dates; checking/approval notes, etc.

53 RDD_CLNL Design centerline (LINES)

54 RDD_CLNP Design centerline (POINTS)

55 RDD_OTHR Road design data: Other information

56 RDD_PNTS Road design data: IPs, curve points, etc

57 RDD_RSRV Road design data: Reservation

58 RDD_TEXT Road design data: Parameters and descriptive text

59 RDF_BNCH Road/Street Furniture: Bench/Seat

60 RDF_DCWL Road/Street Furniture: Decorative Wall

61 RDF_GRDN Road/Street Furniture: Garden, landscaping

62 RDF_LGHT Road/Street Furniture: Lighting

63 RDF_OTHL Road/Street Furniture: Others (LINES)

64 RDF_OTHP Road/Street Furniture: Others (POINTS)

65 RDF_PBXL Road/Street Furniture: Planter box (LINES)

66 RDF_PBXP Road/Street Furniture: Planter box (POINTS)

67 RDF_POLE Road/Street Furniture: Pole

68 RDF_TEXT Road/Street Furniture: Annotation/Text

69 RDX_BDGL Existing road feature: Bridge, flyover (LINES)

70 RDX_BDGP Existing road feature: Bridge, flyover (POINTS)

71 RDX_BTML Existing road feature: Bitmac (LINES)

72 RDX_BTMP Existing road feature: Bitmac (POINTS)

73 RDX_FPTL Existing road feature: Footpath (LINES)

74 RDX_FPTP Existing road feature: Footpath (POINTS)

75 RDX_KBFL Existing road feature: Flush kerb (LINES)

76 RDX_KBFP Existing road feature: Flush kerb (POINTS)

77 RDX_KBSL Existing road feature: Standing kerb (LINES)

78 RDX_KBSP Existing road feature: Standing kerb (LINES)

79 RDX_MBKL Existing road feature: Embankment (LINES)

80 RDX_MBKP Existing road feature: Embankment (POINTS)

81 RDX_MEDL Existing road feature: Median (LINES)

82 RDX_MEDP Existing road feature: Median (POINTS)

83 RDX_OTHR Existing road feature: Other features

84 RDX_PKGL Existing road feature: Parking (LINES)

85 RDX_PKGP Existing road feature: Parking (POINTS)

86 RDX_RNDL Existing road feature: Round about (LINES)

87 RDX_RNDP Existing road feature: Round about (POINTS)

88 RDX_TEXT Existing road feature: Annotation/Descriptive text

89 RDX_TRKL Existing road feature: Track (LINES)

90 RDX_TRKP Existing road feature: Track (POINTS)

91 RDX_UPSL Existing road feature: Underpass, tunnel (LINES)

92 RDX_UPSP Existing road feature: Underpass, tunnel (POINTS)

93 SVC_BANK Services fixtures (Commercial): ATM and similar features

94 SVC_OTHR Services fixtures (Commercial): Other

95 SVC_POLE Services fixtures (Commercial): Post/Pole

96 SVC_SBDL Services fixtures (Commercial): Sign/Billboard (LINES)

97 SVC_SBDP Services fixtures (Commercial): Sign/Billboard (POINTS)

98 SVC_TEXT Services fixtures (Commercial): Annotation/Text

99 SVD_CVTL Services fixtures (Drainage): Culvert (LINES)

100 SVD_CVTP Services fixtures (Drainage): Culvert (POINTS)

101 SVD_GLNL Services fixtures (Drainage): Drainage line, (LINES)

102 SVD_GLNP Services fixtures (Drainage): Drainage line, (POINTS)


179

103 SVD_GULY Services fixtures (Drainage): Gully/Catch basin

104 SVD_MHLL Services fixtures (Drainage): Utility/Manhole (LINES)

105 SVD_MHLP Services fixtures (Drainage): Utility/Manhole (POINTS)

106 SVD_MRKR Services fixtures (Drainage): Marker

107 SVD_OTHR Services fixtures (Drainage): Other

108 SVD_PLNE Services fixtures (Drainage): Drainage pipe line

109 SVD_PSTA Services fixtures (Drainage): Pumping Station

110 SVD_SBOX Services fixtures (Drainage): Service box

111 SVD_TEXT Services fixtures (Drainage): Annotation/Text

112 SVE_MHLL Services fixtures (Electricity): Utility/Manhole (LINES)

113 SVE_MHLP Services fixtures (Electricity): Utility/Manhole (POINTS)

114 SVE_MRKR Services fixtures (Electricity): Marker

115 SVE_OHLL Services fixtures (Electricity): Overhead line (LINES)

116 SVE_OHLP Services fixtures (Electricity): Overhead line (POINTS)

117 SVE_OTHR Services fixtures (Electricity): Other

118 SVE_POLE Services fixtures (Electricity): Post/Pole

119 SVE_SBOX Services fixtures (Electricity): Service box

120 SVE_SSTL Services fixtures (Electricity): Sub-station (LINES)

121 SVE_SSTL Services fixtures (Electricity): Sub-station (POINTS)

122 SVE_TEXT Services fixtures (Electricity): Annotation/Text

123 SVE_TOWR Services fixtures (Electricity): Tower

124 SVE_UGLL Services fixtures (Electricity): Underground line (LINES)

125 SVE_UGLP Services fixtures (Electricity): Underground line (POINTS)

126 SVF_HYDR Services fixtures (Fire Control): Hydrant

127 SVF_OTHR Services fixtures (Fire Control): Other

128 SVF_SBOX Services fixtures (Fire Control): Service box

129 SVF_TEXT Services fixtures (Fire Control): Annotation/Text

130 SVO_BNDL Services fixtures (Oil and Gas): Bund (LINES)

131 SVO_BNDP Services fixtures (Oil and Gas): Bund (POINTS)

132 SVO_GLNL Services fixtures (Oil and Gas): Oil/Gas line, (LINES)

133 SVO_GLNP Services fixtures (Oil and Gas): Oil/Gas line, (POINTS)

134 SVO_MNHL Services fixtures (Oil and Gas): Utility/Manhole

135 SVO_MRKR Services fixtures (Oil and Gas): Marker

136 SVO_OTHR Services fixtures (Oil and Gas): Other

137 SVO_PLNL Services fixtures (Oil and Gas): Pipe line (LINES)

138 SVO_PLNP Services fixtures (Oil and Gas): Pipe line (POINTS)

139 SVO_POLE Services fixtures (Oil and Gas): Post/Pole

140 SVO_SBOX Services fixtures (Oil and Gas): Service box

141 SVO_TANK Services fixtures (Oil and Gas): Tank

142 SVO_TEXT Services fixtures (Oil and Gas): Annotation/Text

143 SVP_OTHR Services fixtures (Postal): Other

144 SVP_PBOX Services fixtures (Postal): Post box

145 SVP_TEXT Services fixtures (Postal): Annotation/Text

146 SVQ_BOOT Services fixtures (Q-Tel/Telecoms): Telephone booth

147 SVQ_MNHL Services fixtures (Q-Tel/Telecoms): Utility/Manhole

148 SVQ_MRKR Services fixtures (Q-Tel/Telecoms): Service marker

149 SVQ_OHLN Services fixtures (Q-Tel/Telecoms): Overhead line

150 SVQ_OTHR Services fixtures (Q-Tel/Telecoms): Other

151 SVQ_POLE Services fixtures (Q-Tel/Telecoms): Post/Pole

152 SVQ_SBOX Services fixtures (Q-Tel/Telecoms): Service box

153 SVQ_SSTA Services fixtures (Q-Tel/Telecoms): Sub-station

154 SVQ_TEXT Services fixtures (Q-Tel/Telecoms): Annotation/Text

155 SVQ_TOWR Services fixtures (Q-Tel/Telecoms): Tower

156 SVQ_UGLN Services fixtures (Q-Tel/Telecoms): Underground line

157 SVT_BARL Services fixtures (Traffic): Barriers, rails, bollards (LINES)


180

158 SVT_BARP Services fixtures (Traffic): Barriers, rails, bollards (POINTS)

159 SVT_HMPL Services fixtures (Traffic): Speed hump (LINES)

160 SVT_HMPP Services fixtures (Traffic): Speed hump (POINTS)

161 SVT_MNHL Services fixtures (Traffic): Utility/Manholes

162 SVT_MRKR Services fixtures (Traffic): Road markings

163 SVT_OHLL Services fixtures (Traffic): Overhead cable/line (LINES)

164 SVT_OHLP Services fixtures (Traffic): Overhead cable/line (POINTS)

165 SVT_OTHR Services fixtures (Traffic): Other

166 SVT_POLE Services fixtures (Traffic): Post/Pole

167 SVT_RSNL Services fixtures (Traffic): Road signs (e.g., directions, speed limits) - LINES

168 SVT_RSNP Services fixtures (Traffic): Road signs (e.g., directions, speed limits) - POINTS

169 SVT_SBOX Services fixtures (Traffic): Service box

170 SVT_STNM Services fixtures (Traffic): Streetname post/sign

171 SVT_TEXT Services fixtures (Traffic): Annotations/Descriptive text

172 SVT_UGLL Services fixtures (Traffic): Underground cable/line (LINES)

173 SVT_UGLP Services fixtures (Traffic): Underground cable/line (POINTS)

174 SVW_BNDL Services fixtures (Water): Bund (LINES)

175 SVW_BNDP Services fixtures (Water): Bund (POINTS)

176 SVW_DRKL Services fixtures (Water): Drinking area (LINES)

177 SVW_DRKP Services fixtures (Water): Drinking area (POINTS)

178 SVW_MHLL Services fixtures (Water): Utility/Manhole (LINES)

179 SVW_MHLP Services fixtures (Water): Utility/Manhole (POINTS)

180 SVW_MRKR Services fixtures (Water): Marker

181 SVW_OTHR Services fixtures (Water): Other

182 SVW_PLNL Services fixtures (Water): Pipeline (LINES)

183 SVW_PLNP Services fixtures (Water): Pipeline (POINTS)

184 SVW_SBOX Services fixtures (Water): Service box

185 SVW_TANK Services fixtures (Water): Tank

186 SVW_TEXT Services fixtures (Water): Annotation/Text

187 SVX_MHLL Services fixtures whose types are not known or which are not included in specific layer - Manhole (LINES)

188 SVX_MHLP Services fixtures whose types are not known or which are not included in specific layer - Manhole (POINTS)

189 SVX_OTHR Services fixtures whose types are not known or which are not included in specific layer (OTHER)

190 SVX_SYML Services fixtures whose types are not known or which are not included in specific layer - LINES

191 SVX_SYMP Services fixtures whose types are not known or which are not included in specific layer - POINTS

192 SVX_TEXT Services fixtures whose types are not known or which are not included in specific layer (Text)

193 VEG_SYML Trees, shrubs; point or line feature (Symbol) (LINES)

194 VEG_SYMP Trees, shrubs; point or line feature (Symbol) (POINTS)

195 VEG_TEXT Trees, shrubs; point or line feature (Text)

196 WAL_SYML Boundary/Perimeter walls and fence lines (LINES)

197 WAL_SYMP Boundary/Perimeter walls and fence lines (POINTS)

198 WAL_TEXT Boundary/Perimeter walls and fence lines (Text)

199 WRK_CONL On-going construction works (LINES)

200 WRK_CONP On-going construction works (POINTS)

201 WRK_EXVL Excavation works (LINES)

202 WRK_EXVP Excavation works (POINTS)

203 WRK_FILL Filling material limits (LINES)

204 WRK_FILP Filling material limits (POINTS)

205 WRK_TEXT On-going works: text


181

Appendix 3H – Graphic Concepts The first step in establishing an effective CAD standard is the development of a uniform approach to presentation graphics. Presentation graphics typically consist of drawing elements such as lines, arcs, shapes, text, and their attributes (line color, line width, and line style). This chapter presents brief overviews of the characteristics of presentation graphics and the philosophy used to standardize them. (a) Line Widths Varied line widths substantially improve readability. Most commercial CAD systems provide an extensive variety of line widths. However, for the majority of A/E/C drawings, the eight line widths defined in Table 3H.1 are considered sufficient and should not be expanded unless an appreciable improvement in drawing clarity or contrast can be realized. Table 3H.1 shows information about the various allowed line widths.

• Fine (0.18 mm). Fine lines should be used sparingly, mostly for hatching/patterning (this line thickness typically does not reproduce well in blue-line format and/or in photocopies).

• Thin (0.25 mm). Thin lines should be used for depicting dimension lines, dimension leader/witness lines, note leader lines, line terminators (arrowheads, dots and slashes), phantom lines, hidden lines, center lines, long break lines, schedule grid lines, and object lines seen at a distance.

• Medium (0.35 mm). Medium lines should be used for depicting most object lines, text (dimensions, notes/callouts, and schedule), and schedule grid accent lines.

• Wide (0.50 mm). Wide lines should be used for major object lines, cut lines, section cutting plane lines, and titles.

• Extra wide (0.70 mm). Extra-wide lines should be used for minor title underlining, schedule outlines, large titles, and object lines requiring special emphasis. For very large scale details, the extra-wide width should be used for the object lines. Extra-wide widths are also appropriate for use as an elevation grade line, building footprint, or top of grade lines on section/foundation details.

• XX Wide (1.00 mm). This line weight should be used for major title underlining and separating portions of drawings.

• XXX Wide (1.40 mm). This line weight should be used for border sheet outlines and cover sheet line work.

• XXXX Wide (2.00 mm). This line weight should be used for border sheet outlines and cover sheet line work.

Table 3H.1: Comparison of Line Widths

Line Thickness

mm Typical Use

Fine 0.18 Patterning

Thin 0.25 Dimension lines, dimension leader/witness lines, note leader lines, long

break lines, schedule grid lines, and objects seen at a distance

Medium 0.35 Minor object lines

Wide 0.50 Major object lines, cut lines, section cutting plane lines, and titles

Extra Wide 0.70 Minor title underlining, match lines, schedule outlines, large titles, and

object lines requiring special emphasis

XX Wide 1.00 Major title underlining and separating portions of drawings

XXX Wide 1.40 Border sheet outlines and cover sheet line work XXXX Wide 2.00 Border sheet outlines and cover sheet line work


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(b) Line Types/Styles The predominant line types/styles used in this manual are listed in Table 3H.2. The CGTC (CAD/GIS Technology Center) has created line style files for MicroStation and AutoCAD (called tsaec.rsc and tsaec.lin, respectively), which include the line styles in Table 3.8, as well as additional discipline custom line styles. These files are available on the CGTC’s Internet site at https://tsc.wes.army.mil.

Table 3H.2: Standard Line Types/Styles

ID Description AutoCAD Designator

Example

0 Continuous Continuous

1 Dotted Dot

2 Dashed Hidden

3 Dashed spaced Dashed

4 Dashed dotted Dashdot

6 Dashed double-dotted

Divide2

7 Chain Center

(c) Line Color1

The primary reason to use color in CAD drawings is to improve the clarity of the drawing on a computer monitor. The variety of colors available in a CAD application depends on the capabilities of the computer monitor and its video card. Today, most systems are capable of displaying up to 16.8 million colors. For consistency, this manual recommends that all A/E/C drawings be created using the basic colors presented in Table 3H.3 whenever possible.

Table 3H.3: Screen Color Comparison

Color Color Number Ratios of RGB

AutoCAD MicroStation Red Green Blue

Blue 5 1 0 0 255

Gray 8 9 128 128 128

Green 3 2 0 255 0

Red 1 3 255 0 0

Yellow 2 4 255 255 0

Magenta 6 5 255 0 255

Cyan 4 7 0 255 255

White 7 0 255 255 255

Note: Color numbers for AutoCAD and MicroStation were taken from default color tables.

(d) Text Styles/Fonts Since projects designed in CAD are planned for use many years into the future and files will be used by many different individuals, use of any nonstandard font is not recommended. This includes fonts for symbology, logos, business titles, etc.

If a project is to be exchanged between CAD platforms, a general guideline would be to use True Type fonts. This would allow direct translations between the applications. If a project is to be designed in a single CAD application and there is no likelihood that there will be a need to translate it to a different CAD platform, then the native CAD application fonts could be used.

1 The recommended colours are best viewed on a monitor with a black background.


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Contrasting text styles (or fonts) are used within a drawing to delineate types of information. In most A/E/C drawings, the fonts listed below should be sufficient:

• Monotext font. This font creates text characters that are evenly spaced. Monotext font should be used where text fields need to be aligned such as in schedules or, in some cases, title blocks.

• Proportional font. This font creates text where the characters are proportionally spaced. It is appropriate for general notes, labels, or title blocks.

• Slanted font. A slanted font is used where text needs to be easily distinguished from other text.

• Filled font. Filled fonts are used primarily for titles and on cover sheets.

• Outline font. When a pen plotter is used for final output, the outline font is used as a substitute for filled fonts for major titles such as cover sheet information to save plotting time.

• Symbology font. This font should be used in cases where Greek symbols are representations for technical information.


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Appendix 3I – Example of Q-TEL GFCODE

Feature Name GFCODE

Underground Corridor TLLNUGCR

Parallel Underground Corridor TLLNUGCR

Aerial Cable Corridor TLLNACCR

Buried Cable Corridor TLLNBCCR

Surface Cable Corridor TLLNSCCR

D-SIDE Cable RATTLRTCBLS

D-SIDE Cable RATTLRTMCBL

Qatar Survey Manual – Chapter 4 – Hydrographic Survey

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Abbreviations DGPS Differential Global Position System FIG International Federation of Surveyors GIS Geographic Information System GSD General Survey Department, Qatar ICA International Cartographic Association IHO International Hydrographic Organisation MBES Multibeam Echo Sounder QC Quality Control QND95 Qatar National Datum 1995 QNG Qatar National Grid RTK GPS Real Time Kinematic Global Position System THU Total Horizontal Uncertainty TPU Total Propagated Uncertainty TVU Total Vertical Uncertainty WAD GPS Wide Area Differential Global Positioning System WGS84 World Geodetic System 1984


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4.1.0 Introduction The survey manual for Hydrographic Survey is prepared based on adaptation for the local needs with reference to IHO Standards for Hydrographic Surveys Special Publication (S44) 5

th Edition February 2008 for

Hydrographic Surveys. The IHO Standards for Hydrographic Surveys – Special Publication S44 provide the guidelines in which member states can produce their own National Standards for the acquisition of hydrographic data for the production of International recognized navigational charts with consistent standards and quality. Three classes of hydrographic surveys are described to cover the various applications for the purpose of safe navigation, coastal zone management, offshore oil and gas and offshore constructions. Each class stipulated shall in general be equal to IHO Standards in its respective orders. These are the minimum standards. More stringent standards may be defined and used in hydrographic surveys for different applications. 4.2.0 Standards of Competence for Hydrographic Surveyors Hydrographic Surveys for nautical charting shall be directly supervised by Hydrographic Surveyors who have successfully completed FIG/IHO/ICA accredited Category A (Cat A) hydrographic surveying courses in any institutions worldwide or hold a degree in Surveying, Geodesy or Geomatics. They should have a minimum of five years experience in hydrographic surveying where a minimum level of competence and active participation in precise positioning, tidal measurements, bathymetric and sonar measurements, land surveys and data management. Hydrographic Surveys for nautical charting shall be conducted by Hydrographic Surveyors who have successfully completed Cat A or Cat B courses or hold a degree in Surveying, Geodesy or Geomatics. Hydrographic Surveys other than for nautical charting shall be directly supervised by Hydrographic Surveyors who have successfully completed Cat A or Cat B courses, or hold a degree in Surveying, Geodesy or Geomatics, and have a minimum of two years experience in hydrographic surveying. Hydrographic Surveys other than for nautical charting shall be conducted by Hydrographic Surveyors who have successfully completed Cat A or Cat B courses, or hold a degree in Surveying, Geodesy or Geomatics. These surveys may be also conducted by surveyors without formal qualifications, but should demonstrate possession of the appropriate knowledge of hydrography and should have at least two years relevant experience in hydrographic surveying. The General Survey Department (GSD) will review and approve personnel, and issue accreditation before they are permitted to conduct hydrographic surveys in the waters of Qatar. Hydrographic Surveyors intending to practice shall submit their qualifications and experience to the Director of the GSD for accreditation. 4.3.0 Classification of Surveys The manual addresses the class of surveys and the minimum standards for the conduct of the hydrographic surveys and the personnel’s competence to conduct the surveys. All acquired hydrographic data have some degree of uncertainty which is related to numerous factors such as equipment accuracy and limitation, environmental conditions and sea state at the time of survey, type of vessels as platforms for the survey, weather conditions and the dynamic transient of the seabed. The standards shall ensure that the charted depths are accurate for the safe navigation of vessels and for other applications. In Port areas and approach channels minimum under-keel clearance are in force. Consequently in areas where siltation are expected to occur, regular monitoring surveys shall be conducted to ascertain the declared depths are still valid and remain safe for the maximum draft of vessels permitted.


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4.3.1 Special Order Surveys This is the most rigorous of the orders and its use is intended only for those areas where under-keel clearance is critical. Because under-keel clearance is critical a full sea floor search is required and the size of the features to be detected by this search is deliberately kept small. Since under-keel clearance is critical it is considered unlikely that Special Order surveys will be conducted in waters deeper than 40 meters.

The following surveys shall conform to Special Order Surveys:

• To determine a proposed new channel, berth, turning basin and anchorage of a Port and its Approaches.

• To declare a dredged channel and berth and the minimum depths.

• To determine the under-keel clearance and the maximum draft of vessel permitted to transit the area.

• To investigate a grounding or shoaling reported

• To determine new recommended leading lines and navigational tracks.

• High precision engineering surveys. 4.3.2 Order 1a Surveys This order is intended for those areas where the sea is sufficiently shallow to allow natural or man-made features on the seabed to be a concern to the type of surface shipping expected to transit the area but where the under-keel clearance is less critical than for Special Order above. Because man-made or natural features may exist that are of concern to surface shipping, a full sea floor search is required, and however the size of the feature to be detected is larger than for Special Order. Under-keel clearance becomes less critical as depth increases so the size of the feature to be detected by the full sea floor search is increased in areas where the water depth is greater than 40 meters.

The following surveys shall conform to Order 1a Surveys:

• To survey general navigational areas where a full sea floor search is required.

• Periodic Monitoring Surveys of channels, berths, turning basins and anchorages.

• Initial checks of abnormal changes to seabed. To be followed by Special Order Surveys if considered necessary.

4.3.3 Order 1b Surveys This order is intended for areas where a general depiction of the seabed is considered adequate for the type of surface shipping expected to transit the area. A full sea floor search is not required which means some features may be missed although the maximum permissible line spacing will limit the size of the features that are likely to remain undetected. This order of survey is only recommended where under-keel clearance is not considered to be an issue.

The following surveys shall conform to Order 1b Surveys:

• Surveys of general navigational transit areas where a full sea floor search is not required.

• To determine small craft harbors and channels where under-keel clearances are not applicable.

• For managing Navigational Aids.

• To support various maritime works, sea floor exploration, construction, and others.


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189


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4.4.0 Geodetic Parameters Hydrographic Surveys for the purpose of safe navigation shall be conducted on WGS84 Datum Universal Transverse Mercator Projection Zone 39 North. Hydrographic Surveys for purposes other than safe navigation may be conducted on WGS84 or Qatar National Datum 95 (QND 95). The Geodetic Parameters of WGS84 are as follows: Projection : Universal Transverse Mercator Zone : 39 North Spheroid : WGS84 Semi-Major Axis (a) 6378137.0m Semi-Minor Axis (b) 6356752.3142m Compression (f) 1/298.257223563 Central Meridian : Longitude 51° East of Greenwich Latitude of Origin : 0° (Equator) Longitude of Origin : 51° East False Co-ordinates of Origin : 0m North

500,000m East

Scale Factor at Central Meridian : 0.9996 The transformation from WGS84 co-ordinates to QND95 the 7 parameters are as follows:

Shift x : + 119.42480m Shift y : + 303.65872m Shift z : + 11.00061m Rotation x : - 1.164298 arc seconds Rotation y : - 0.174458 arc seconds Rotation z : - 1.096259 arc seconds Scaling : - 3.657065 ppm The 7 parameters are exact values. For a QND95 to WGS84 transformation, the signs are reversed. The signs of the Transformation Parameters are correct when using QTRANS software available at the Centre for GIS of the Urban Planning. For other transformation software packages you may have to change the signs. Changing signs is not an error but may be as a result of defining the coordinate systems as right handed or left handed (QTRANS uses a left handed coordinate system) or defining which is the ‘from coordinate’ and which is the ‘to coordinate’ in computing the transformation parameters. If you use the 7 parameters and the results are correct that is fine. Otherwise it is best to use the 3-parameter transformation to get the translations correct and then introduce the rotations and scale (parameters 4 to 7) to refine the transformation. In either case, if the signs need to be changed then all the transformation parameters should be changed or all the rotation parameters should be changed (that is, you cannot change the sign of only 1 translation of rotation – they must all be changed as a group). To obtain geodetically correct transformed coordinates the geoid model must be used. If you have any problems, or require further information, please contact the Centre for GIS. For Sample Transformation Calculation see Appendix 1A, Chapter 1 – Control Survey.


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The geodetic parameters of QNG on Qatar National Datum 1995 (QND95) are as follows: Projection : Transverse Mercator Spheroid : International (Hayford) Semi-Major Axis (a) = 6,378,388.0 Compression (f) = 1/297.0 Origin : Latitude 24° 27’ 00” N

Longitude 51° 13’ 00” E False Co-ordinates of Origin : 300,000m N 200,000m E Scale Factor : 0.99999 QNG is defined in terms of the scale factor at the origin (Central Meridian) not the zone width. 4.5.0 Positioning Horizontal control ashore shall be surveyed in accordance with Qatar Survey Manual, Chapter 1 – Control Survey. The DGPS reference beacon position shall be fixed by Land Survey method from Order 1 stations (see Chapter 1). The accuracy shall be better than 1:100,000. 4.5.1 Coastline Position The coastlines are to be delineated by Land Survey Method or RTK GPS or DGPS Positioning. The accuracy of the coastline delineated shall be in accordance with Classification Table. The coastline including the islands adjacent to the hydrographic survey area shall be surveyed. 4.5.2 Wharf, Jetty, Dolphin, Ramp & Breakwater Position Details of all wharfs, jetties, ramps and breakwaters adjacent to the Hydrographic Survey Area are to be surveyed by Land Survey Method or RTK GPS Survey. The accuracy of these features shall be in accordance with Classification Table. 4.5.3 Conspicuous Object and Beacon Position Conspicuous Objects from seawards useful for navigation should be surveyed by Land Survey Method or RTK GPS Positioning. Navigational beacons shall also be surveyed by Land Survey Method or RTK GPS Positioning. The accuracy shall be in accordance with Classification Table. Trigonometrical height of conspicuous objects and beacons shall be surveyed by Land Survey Method. The heights shall also be measured from Mean Higher High Water or Qatar National Vertical Datum to an accuracy of 0.3m. 4.5.4 Drying Rock and Obstruction Position All rocks and obstructions below Mean Higher High Water and above Mean Lower Low Water shall be surveyed by Land Survey Method or by sounding. The heights shall be measured from Chart Datum to an accuracy of 0.3m.


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4.5.5 Navigational & Mooring Buoys Positions Navigational buoys and mooring buoys positions shall be fixed by DGPS at or near maximum ebb and at or near maximum flood tide. The mean positions shall be recorded. The accuracy shall be in accordance with the Classification Table. 4.5.6 Sounding Position – GNSS Positioning All sources of horizontal errors shall be determined prior to the commencement of sounding. The total error budget shall be assessed and confirmed that the horizontal error are within the class of surveys specified. Evidence of the DGPS position accuracy shall be presented. Quality factors such as DOP values, satellite configuration, RMS values, etc shall be independently monitored. The position accuracy for single beam echo sounder shall be the position of the echo sounder transducer. For Multibeam echo sounder and Bathymetric LIDAR the position accuracy shall be the position of the sounding on the seabed. The sounding position uncertainty shall be at 95 percent confidence level and shall be recorded with the survey data. The source of differential corrections to the GPS shall be proven by placing the receiver at a known mark with higher accuracy than DGPS. It should be configured to output with quality tags in WGS84 on Zone 39 Universal Transverse Mercator Projection during comparison. Regular monitoring of position quality during sounding on the number of track satellites, PDOP and/or real time comparison with a second positioning system is recommended. For GPS quality control the following minimum criteria shall be maintained.

• The semi major axis of the positional error ellipse shall not exceed 3.5m at 95% confidence level.

• The differential correction age is not to exceed 5 seconds.

• PDOP is not to exceed 6 for sounding to continue.

• The minimum number of satellites to be tracked shall be 4.

• The minimum elevation of the satellites shall not be less than 15°. 4.6.0 Depth Acquisition The depth accuracy is the accuracy of the reduced depths at Chart Datum. All sources of individual uncertainty need to be quantified. A statistical model for Total Propagated Uncertainty shall be derived. Sources of uncertainties to be considered are as follows: Uncertainties associated with the development of the position of an individual beam must include the following: a) Positioning system errors; b) Range and beam errors; c) The error associated with the ray path model (including the sound speed profile), and the beam

pointing angle; d) The error in vessel heading; e) System pointing errors resulting from transducer misalignment; f) Sensor location; g) Vessel motion sensor errors i.e. roll and pitch; h) Sensor position offset errors; and i) Time synchronization / latency


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Contributing factors to the vertical uncertainty include a) Vertical datum errors; b) Vertical position system errors; c) Tidal measurement errors, including co-tidal errors where appropriate; d) Instrument errors; e) Sound speed errors; f) Ellipsoidal / vertical datum separation model errors; g) Vessel motion errors, i.e. roll, pitch and heave; h) Vessel draught; i) Vessel settlement and squat; j) Seabed slope; and k) Time synchronization / latency 4.6.1 By Single Beam Echo Sounder 4.6.1.1 Calibration of Dual Frequency Echo Sounder The echo sounder shall be calibrated by bar check for sounding in depths of 25m or less. For sounding up to 40m a Sound Velocity Profiler shall also be used. The draft of the transducer shall be calibrated with a shallow bar or plate suspended approximately at 1.0m to 2.0m below the transducer. The velocity of sound shall be determined by a bar or plate suspended to the maximum depth expected in the area or between 20m to 25m. After setting the sound velocity the bar or plate shall be raised at intervals of 2.0m until 2.0m below the transducer. Both the digital readings and the analogue readings of the bar or plate shall be within 0.05m of the bar wire suspended vertically below the surface of the water. The calibration shall be repeated if the accuracy is not met. Each frequency shall be calibrated separately. On the echo trace the low frequency draft shall be adjusted to 1.0m below the high frequency such that the trace shows the separation of 1.0m between the two seabed profiles. A heave compensator shall be installed next to the transducer and interfaced to the echo sounder. The effects of heave on the echo sounder shall be removed during sounding. It is important that after a major course alteration of the survey vessel, the heave compensator must be permitted to settle before recommencing sounding. Tide Readings for the reduction of soundings to Chart Datum shall be obtained from the nearest tide gauge. Accuracy of tide gauge shall be better than 0.03m. Co-tidal correction shall be applied when survey area is sufficiently far from the tide gauge station which has a tidal range and time differences from those at the survey area. Co-tidal charts shall be constructed to determine the correction to be applied. Accuracy of the co-tidal correction shall be better than 0.1m. The seabed depths to be charted shall be the sounding acquired by the high frequency (200 kHz) of the Echo Sounder. The low frequency (20kHz to 35kHz) of the echo sounder shall be used to check for false echo caused by suspended sediment and for checking of bed rocks / and or rock outcrops. 4.6.1.2 Coverage of surveys Survey lines shall be spaced at interval in accordance with Classification Table running approximately perpendicular to the seabed contours. Cross lines normal to the run lines shall be spaced at 10-15 times of main sounding lines to check the seabed depths obtained. The ping rate of echo sounder should be set between 10Hz to 20Hz depending on the speed of the survey vessel. The ping rate should be such that 0.5m of the seabed along the profile line should be ensonified. The extra depths logged can be filtered out by the software during post processing.


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4.6.1.3 Logging of Digital Depths The software used should be capable of logging all the return pings set; time and co-ordinates both derived from DGPS and dead reckoning between DGPS measurements. The latency of the DGPS and the echo ping shall be set and applied by the software in real time. 4.6.1.4 Shoal Soundings During the survey detail examination shall be conducted on shoal soundings or hazards found or previously charted to determined for least depths. Inter lines at half the line interval shall be run in two perpendicular directions covering a distance of 100m surrounding the shoal sounding patch or hazards. As an alternative the examinations may be conducted by Side Scan Sonar Sweep or Multibeam Echo Sounding or wire drag sweep. Where shoal depths are reported by other agencies or authorities and if no systematic survey is planned in the area the reported position shall be searched by Side Scan Sonar Sweep or Multibeam Echo Sounding or wire drag sweep covering an area of 1 kilometer square centering on the reported position. In the case of Side Scan Sonar Sweep or wire drag sweep close sounding (at the line interval shown in Classification Table of Order 1b) or by drift sweep over the high spot found shall be conducted to determine the least depth. 4.6.1.5 Data Processing The track plots shall be prepared and edited for spurious positions. The digital depths shall be compared with the analogue echo trace and spurious depths removed before the digital depths are imported for tidal reductions to Chart Datum. The digital depths at Chart Datum shall be selected with shoal bias at interval of 3m with x-y co-ordinates and depths. Depths shall be round up to the decimeter. For plotting to the scale of the drawing further selection and thinning of the soundings to avoid over plotting based on shoal bias shall be conducted. The principle to be strictly adhered to is that depths are never to be shown greater than they actually are relative to Chart Datum. Other corrections to be applied are as follows:

• Correction for changes of vessels draft

• Correction for squat and settlement for the speed of the vessel during sounding

• Correction for sound velocity changes 4.6.2 By Multibeam Echo Sounding 4.6.2.1 Calibration The relative positions and heights of the Multibeam Sonar Transducer, Gyro Compass, Heave, Roll & Pitch Sensors and GPS Antenna are to be measured and the offsets from the survey vessel’s axes are to be integrated in the software. In addition the draft of the vessel fore and aft shall be measured for vessel with LOA 100m or larger. The vessel’s squat and settlement at different survey speed shall be determined. Field calibration shall be based on the principle of repeatability in that the seafloor or objects ensonified shall appear the same in whatever the azimuth, at whatever the speed and whatever the motion history of the survey vessel. These field calibrations known as the patch tests shall be conducted prior to the commencement of the survey and at any significant component changed and at weekly interval. Sound Velocity profile shall be conducted prior to the patch tests.


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The patch tests shall be conducted to resolve the following biases:

• Latency - Attitude Sensor and Depth

• Latency - Positioning System and Multibeam Echo Sounder

• Roll Offset - Swath Sounder

• Pitch Offset - Swath Sounder

• Yaw Offset - Swath Sounder When all calibrations are done the various offsets can be calculated. There is a need for accurate alignment of the sensors offset results and a number of iterations have to be conducted to cancel out the influences of the different parameters. 4.6.2.2 Coverage and Detection of Seabed Features For Special Order Survey the swath to swath overlap shall be 200%. See figure 4.1. For Order 1a Surveys the swath to swath overlap shall be such that 100% coverage is attained. See figure 4.2. The full swath shall be logged. However, only the section of the swath that complied with the depth accuracy of the respective orders shall be utilized. The sounding track lines are to be run parallel and preferably parallel to the bathymetric contours. Cross lines at approximate 90° from the main lines shall be run at 10cm apart on the scale of the charts to be prepared. The cross lines shall be used to assess the quality of the bathymetric data acquired. The ping rate shall be set such that on the survey speed of vessel at least the seabed is ensonified at every 0.5m interval. 4.6.2.3 Multibeam Back Scatter Parameters The multibeam back scatter parameters shall be logged in the course of a Multibeam Echo Sounding Survey. See seabed classification survey using Multibeam Echo Sounding. 4.6.2.4 Tidal Reduction All depths acquired shall be reduced to Chart Datum from the nearest tide gauge station. If the area to be surveyed is at a distance such that the tidal characteristics differ from the tide gauge by 0.1m tidal height (due to range and time difference) co-tidal chart shall be prepared and co-tidal corrections to be applied.

Figure 4.1


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Figure 4.2

4.6.2.5 Acquisition and Processing The number of spikes shall be minimized in the Multibeam Echo Sounder data acquisition by setting parameters affecting power, gain and filter of the received data. Generally the following parameters need to be set:

• Power Level

• Transmit Pulse

• Fixed Gain and Time Varied Gain

• Speed of Sound

• Range

• Ping Rate

• Depth Filter

• Range Filter During the turning of the vessel the data acquired is to be logged but shall not be incorporated in the final processed data. The outer beams of the MBES which are not within the accuracy standard shall only be used for reconnaissance and shall be logged but not incorporated in the final processed data. During processing all parameters shall be viewed and validated by removal of spurious raw data and the integration of position and depth. The position track shall be checked before editing/filtering the depth measurements. Using the processed data a sun illuminated images with suitable vertical exaggeration and depth coded for color shall be rendered as TIFF files. Gridded depth image shall be a mean surface selection rather than shoal biased selection at grid spacing of 1m or 2m respectively for Special Order Survey or 1a Survey standard. 4.6.3 By Bathymetric LIDAR For Bathymetric LIDAR survey it is compulsory that an IHO/FIG Category ‘A’ qualified Hydrographic Surveyor with a minimum of 5 years offshore experience including surveying for nautical charting be at site and in attendance at the data processing location at all times during survey operations. The qualified Hydrographic


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Surveyor shall have the authority and experience to make and implement operational decisions and modify the survey plan if necessary. Bathymetric LIDAR survey shall comply with Order 1a & Order 1b. 4.6.3.1 Calibration A primary positioning system shall be a Wide Area Differential GPS or RTK GPS and a secondary positioning system shall be an entirely independent WAD GPS or RTK GPS. A static positioning check of both the primary and secondary positioning systems shall be carried out on a known trigonometrical station prior to the start of the survey and on each occasion when a component of the positioning system is repaired or replaced and at regular intervals throughout the survey to provide statistical analysis. A dynamic navigational calibration shall be performed on each survey flight against fixed aids to navigation or known coordinated features as a gross error check. The primary and secondary positioning systems shall be compared and the differences shown during survey. Calibration of Bathymetric LIDAR depths corrected for tide against a strip of known Bathymetric depths obtained by Multibeam Echo Sounding corrected for tide before the start of the survey and on completion of the survey shall be carried out. The depth differences shall be compared and rendered. It would be advantages to have the known bathymetric strip to include underwater obstructions with least depths accurately charted. A fully developed Total Propagated Uncertainty (TPU) showing compliance to Order 1a or 1b shall be presented with the report of survey. 4.6.3.2 Spot Density & Depths at Chart Datum Maximum line spacing shall ensure contiguous swath coverage with laser spot density of not more than 5m grid interval shown on Classification Table. All survey areas shall be flown at 200% coverage (i.e. 100% overlap). See figure 4.3. Overlapping swaths shall be flown at significant differences in tide. Depths shall be recorded to two decimal places of a meter. Cross lines shall be flown at right angles to the main line at 5000m intervals to check the depths obtained. For surveys other than for nautical charting, the 200% coverage may be reduced to 100% coverage. Depths shall be corrected for tide from co-tidal data with continuous recordings from at least two tide gauges. 4.6.3.3 Navigational Hazards Detection Navigational hazards detected by Bathymetric LIDAR shall be examined by other sea floor search methods and bathymetric systems to determine for least depths. 4.7.0 Sea Floor Classification During a hydrographic survey it is necessary that the area surveyed shall have the nature of the seabed classified for manmade debris, bedrock, gravel, sand, silty sand and clay using Multibeam Echo Sounder, Side Scan Sonar, Divers, Remote Operate Vehicle, Grab Sampler and Gravity Corer. The requirement for sea floor classification arose from the needs of vessel: (a) To determine where to anchor (b) To determine the holding ground of its anchor and the amount of cable to be veered. (c) To ascertain the safety of the anchorage (d) As an additional checks for safety of navigation.


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Figure 4.3


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4.7.1 By Side Scan Sonar For more detail requirement see Section 4.10.2. Based on Side Scan Sonar mosaics rectified true to scale the following seabed features are to be identified: (a) Area of sand waves where the sand wave heights and the wave length can be determined (b) Rock outcrops and rocky seabed (c) Clayey seabed material (d) Manmade objects and debris such as wrecks, submarine pipelines, submarine cables and other

debris. 4.7.2 Classification by Back Scattering Echo Return The back scattering data of the Side Scan Sonar, bathymetric LIDAR and Multibeam Echo Sounders can be recorded to provide for automatic classification of the seabed using suitable commercial Seabed Classification software. The first seabed echo return provides a measure of the acoustic roughness and the second seabed echo return, a measure of the acoustic hardness. A library of seabed material from the acoustic back scatter intensity can be developed by grab sampling of the seabed and samples tested in a laboratory for grain size distribution. The ground truth obtained by grab samples shall be correlated to the back scatter intensity for automatic sea floor classification. It must be noted that each instrument with different frequency will have different acoustic impedance characteristics. Consequently, the library developed for each instrument from the ‘ground truth’ shall be confined only to that instrument and shall not be used for other instrument. 4.7.3 Seabed Sampling Seabed samples can be obtained by grab sampler, gravity corer or divers. In the course of the hydrographic survey seabed samples shall be collected in a systematic pattern throughout the whole survey area. In addition the nature of the seabed of all banks, shoals and seamounts shall be classified, particularly where these features a likely to be unstable. 4.8.0 Tidal Levels Tidal observations are part of the process for hydrographic surveys for the reduction of soundings to Chart Datum and for harmonic analysis and the prediction of tide. Automatic tide gauges using the principle of acoustic pulses pinging from a fixed height to the water surface within a tide well are preferred. These tide gauges are extremely accurate and can obtain the average of a number of readings before being logged against the mean time. These tide gauges have no moving parts and at each single measurement calibration of the velocity sound against a fixed distance reflector from the transducer is also made. Minimum maintenance is needed with long term reliability. 4.8.1 Calibration of Tide Gauges a. Acoustic Tide Gauge Calibration

A calibration certificate is usually issued by the manufacturer stating the reference to the zero of the tide gauge. Notwithstanding the calibration certificate issued, it shall be calibrated by placing the acoustic transducer against a measuring tape and reference to the zero of the gauge to ping against a vertical solid structure at various distances through the full range of the tide expected in the survey area with the transducer placed horizontally. The gauge shall be set to ping at 1 Hz for a period of 30 seconds and the mean values output in tidal height and time into a data logger. All acoustic tide gauges have a fixed distance reflector to calibrate the velocity of sound in air during each measurement.


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b. Pressure Tide Gauge Calibration

Pressure tide gauges use the hydrostatic pressure for the measurement of tide. The hydrostatic pressure exerted by seawater is dependent on the density of seawater, temperature and the atmospheric pressure. The pressure tide gauge would have been calibrated in the country of manufacture. The density of seawater, temperature and atmospheric pressure may differ from where the gauge is being installed.

Prior to setting up the pressure tide gauge, the instrument shall be calibrated by securing the pressure sensor to a weight on a marked steel wire rope. The instrument shall be set to measure 30 readings at 1 Hz. The readings are averaged and displayed as the sensor is lowered at just before entering the water and at 0.5m interval below the surface level and the averaged readings noted. The sensor shall be lowered to a depth exceeding the tidal height to be measured. The sensor shall then be raised at 0.5m interval until it is out of the water. The two sets of readings at each depth shall be averaged and compared against the sensor depth measured by the marked wire. This calibration shall be conducted in sheltered waters where the water level is fairly smooth. Corrections or adjustment shall be applied to the readings as appropriate. Generally most pressure tide gauges are temperature compensated. It is recommended that this calibration be conducted at least twice per year i.e. once in summer and once in winter as the atmospheric pressure varies up to 20 mbs at Qatar between January and July.

The zero of the tide gauge shall be referenced to 2 known benchmarks and set to Chart Datum by leveling. 4.8.2 Setting Up of Tide Gauge A tide board with graduation shall be erected in sheltered water and the zero of the tide board leveled to the two known benchmarks. The Chart Datum of the tide board shall then be established. Visual readings at 5 minute interval shall be taken over a 25 hour period for comparison against the tide gauge reading during the initial period. Thereafter a single tidal height and time shall be observed at the tide board on a daily basis throughout the full duration of the survey to check against the tide gauge recordings. The zero of the tide gauge shall be leveled to one of the benchmarks at weekly interval to check for vertical displacement. Tide recordings shall at 5 minute interval with an average of 30 readings as a minimum over a 30 second period. The time for the averaged tidal height shall be logged at the middle of the measuring period. For long term tide gauge recordings comparison of visual tidal heights and time against the tide gauge shall be conducted regularly not exceeding one per week. Tide shall be recorded to two decimal of a meter with date and time to the nearest second. Tidal height shall be accurate to 1cm. The time check shall be accurate to 5 seconds against BBC six pips time check transmitted at hourly interval. 4.8.3 Chart Datum Chart Datum at various ports has been established after the Qatar Tidal Study in 1977. The Chart Datum at each Port is related to Qatar National Vertical Datum which is Mean Sea Level at Doha. Chart Datum at various Ports is close to Lowest Astronomical Tide and the values below Qatar National Vertical Datum are as follows: Tidal Stations Chart Datum below Qatar National Vertical Datum Doha Port 0.88 meters Mesaieed Port 1.30 meters Ras Laffan 0.88 meters


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Al Ruwais 1.10 meters Ras Ushayriq 0.80 meters Dukhan 0.30 meters 4.8.4 Harmonic Analysis and Tidal Prediction From long term tide recording with a minimum of one year preferably five years data shall be analyzed harmonically and the harmonic constants derived for tidal predictions. Tidal Predictions shall be compared against actual recordings to check for accuracy of the predictions. 4.8.5 Relative Tidal Heights From the harmonic constants derived at each tidal station the following relative tidal levels shall be computed: Highest Astronomical Tide - H.A.T. Mean Higher High Water - MHHW Mean Lower High Water - MLHW Mean Sea Level - M.S.L. Mean Higher Low Water - MHLW Mean Lower Low Water - MLLW Chart Datum - C.D. Lowest Astronomical Tide - L.A.T. 4.8.6 Accuracy Standard Tide Gauge shall maintain accuracy for: Time - ± 5 second

Tidal Height - ± 0.01m Tidal Prediction - ± 0.10m

4.9.0 Currents (Tidal Streams) Current are significant components to the safety of navigation. These need to be observed at entrance to harbors, channels, navigable straits, anchorages and in the vicinity of wharfs. Acoustic Doppler Current Profilers (ADCP) shall be the standard instrument for the recording of current direction and speed against time and depth. Current shall be recorded at 10 minute interval over a 32 days period. A 2 to 3 meter bins throughout the vertical depth profile shall be recorded. The recorded current shall be vector averaged at 10 minute interval and at each bin. The recording period shall be at least a full lunar cycle to permit harmonic analysis. It will be necessary that the ADCP be mounted on the seabed pointing vertically upwards preferably fitted on a gimbal and on a non magnetic structure. The ADCP can generally apply a correction for non verticality for up to 20° from the vertical. The instrument fitted on a gimbal will reduce the necessary correction to a minimum. Corrections for non verticality shall not exceed 15°. 4.9.1 Long Term Current Recording Within the Persian Gulf off Qatar the water movement is due mainly to tidal streams. In this region the North West winds predominate, although 50 percent of the time the winds are less than 10 knots. During the stronger North Westerly a South East going current is induced.


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Current shall be recorded for a minimum period of 32 days during the Winter Period when the North Westerly is stronger and for another minimum period of 32 days during the summer period when the North Westerly are weaker. Recordings should be increased to three months during each period in critical locations. The current recorded shall be analyzed harmonically for the predictions of Tidal Streams. 4.9.2 Accuracy Standard ADCP are manufactured with 3 or 4 transducers. Instrument with 3 transducers can measure the current direction, speed and vertical profile bins. However, instrument with 4 transducers with one redundant transducer are preferred as the 4

th transducer provide a measure of the accuracy of the measurement.

Instrument accuracy shall be as follows: Direction : ± 2°

Speed : ± 0.5cm/s Depth Cell Size : minimum 1m Ping Rate : 2 Hz Maximum Tilt Corrections : ± 15°

4.10.0 Sea Floor Search For Special Order and Order 1a surveys a full sea floor search are compulsory. The detection of cubic features for Special Order is 1m and for Order 1a is 2m. Instrument or technique used shall need to comply with the detection capability stated. 4.10.1 By Multibeam Echo Sounder (MBES) To achieve the Order specified for sea floor target detection, the centre to centre distance of each ping should be no more than half the required target dimension apart. A minimum of 3 pings on both along the track and across the track shall strike the target size features specified in order to ensure sufficient ensonification. A Sun illuminated 3D images of the seabed with suitable vertical exaggeration shall be prepared to assist in the interpretation of shoal seabed features. The least depth for each seabed feature shall be charted. 4.10.2 By Side Scan Sonar Sea floor search for contacts 1m cube or 2m cube using side scan sonar dual channel shall have a frequency of 300kHz or higher. The search shall be planned such that the specific target size can be detected. The limiting case requires that the contacts near the tow fish shall receive 5 sonar pulses. Outside this near field the sonar beam expansion ensures that the target will receive at least 5 pulses. Near field is taken as 25m from the tow fish. The range scale shall be set at 100m and not exceeding 150m to ensure that the specific targets can be detected. The line spacing must not be more than 125m. a. Survey Coverage The survey lines shall be run such that ensonification of the seabed shall be 200% coverage (i.e. 100% overlap). See figure 4.4. Adjacent lines where practical are to be run in opposite directions.


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The speed of the vessel shall be maintained at 6 knots or less during side scanning operation. b. Ultra Short Base Line To minimize the uncertainty of the position of the side scan tow fish astern of the vessel due to cable length paid out, depth of tow fish and vertical catenary of the cable (the last two vary with vessel speed) and cross current, a transponder shall be fitted at a short stay (about 1 – 2m) behind or ahead of the tow fish. The transponder shall be fixed by an Ultra Short Base Line interfaced to the DGPS via the navigation software. c. Safety of Tow Sensor When a tow sensor is streamed astern of the survey vessel caution must be exercised when a major course alteration is made. The length of the tow shall be shortened to ensure that the tow fish will not strike the seabed. d. Confidence Check The sonar confidence check is an important feature of the operations. Confidence check must be carried out:

a) On first streaming of the Side Scan Sonar b) At least once per day in a featureless seabed c) After repair to any part of the sonar system d) After changing tow fish or fins

Confidence check shall be carried out using a known seabed feature such as structure, buoy, wreck or natural rock outcrop or sand waves near the survey area. The position of the known seabed feature shall be detected on the near field e.g. within 25m or the outer limits of the range scale i.e. 90m. e. Height of Tow Fish The optimum height of the tow fish shall be 10% above the seabed of the range scale set i.e. 12.5m above the seabed for 125m range scale. In shallow water it may not be possible to fly the tow fish as high off the seabed as desirable. Under this condition the range scale and the survey line spacing shall be reduced. f. Position & Depth Accuracy of Seabed Features The horizontal accuracy of the seabed features hazardous to navigation detected shall be:

For Special Order Survey 2m For Order 1a & 1b Survey 5m The least depth of the seabed feature shall be determined by close soundings in the case of single beam echo sounding. The depth accuracy is as per the Order of Survey specified (see Classification Table).


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4.10.3 By Mechanical Drag Sweep Mechanical sweeps have been in existence for many decades. These clearance sweeps have been adapted from sweeping of the channel for the clearance of mines such as the Oropesa Sweep. To operate such sweep the survey vessel has to be purposely designed to handle the Oropesa Sweep. For survey requirement only the drift sweep and the Drag Sweep will be specified as modem Survey Vessels are not outfitted to handle these sweeps. The mechanical sweep shall be deployed to clear the area surveyed by Single Beam Echo Sounder or Bathymetric LIDAR. This method may be used as an alternative to Side Scan Sonar Survey or Multibeam Echo Sounder bottom search. a. Drift Sweep Drift Sweep is deployed to check the least depth over pinnacle rocks, wrecks, shoal of small extent and man-made obstructions on the seabed. The sweep wire suspended by weights supported by marked wire ropes at both ends of the vessel and at regular intervals is allowed to drift with the current or wind over the known obstruction. See Figure 4.5. At each support the marked wire rope is weighted with hand lead. As the sweep wire clears the obstruction, it is lowered until it fouls the obstruction. The vessel’s position shall be fixed by DGPS and the longitudinal axis of the vessel noted from the vessel’s gyro compass. The time of each fix shall be logged for extracting the tide from a tide gauge to reduce the sweep wire depth to Chart Datum. The sweep wire depth shall be adjusted for vertical movement caused by tide during sweeping using predicted tide. Visual watch shall be kept to see which section of the wire foul the obstructions. b. Wire Drag Sweep Wire Drag Sweep is used extensively in the past to clear a channel to certain depth. This method is still useful to clear a large navigational channel. The wire sweep with a spread of 350m to 400m shall be towed at a speed of about 1.5 knots by two vessels. The sweep wire shall be supported by weights at both ends and with the intermediate weights at about 50m intervals. The weights are secured to adjusted marked depth wires supported by inflatable floats. (See Figure 4.6 for Sweep Layout) An additional launch shall be used to calibrate the depth of the sweep wire at each section of the sweep wire spread using a drag tester (see Figure 4.7). The drag tester is lowered ahead by a launch for the section of the sweep wire to be calibrated and allowed the sweep wire to strike the drag tester. The crew manning the launch will record and call by walkie talkie to inform the Surveyor in charge the depth of the sweep wire calibrated. The crew in the launch shall also adjust the depth wires caused by tide on instructions from the Surveyor in charge. Dynamometers measuring the tension of the towed wires will indicate if the sweep wire fouls an obstruction combining with visual look out to watch for the particular float submerging. Positioning of parent vessel and consort vessel shall be fixed regularly by DGPS and time logged. The floats shall be fixed by the vessel’s radar. A radar reflector shall be secured to the top of each float. Light weight dielectric lens radar reflectors with a radar cross section 2m² are readily available for these purposes. During the sweeping operation predicted tide is used to control the depth of the sweep. Upon completion the area swept to clear to certain depth below Chart Datum shall use recorded tide for reduction during post processing.


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Figure 4.5


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Figure 4.6


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Figure 4.7


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4.10.4 By Magnetometer Survey Ferromagnetic debris, wrecks and obstructions, submarine cables and submarine pipelines lying on the seabed or buried can be detected by magnetometer survey. Ferromagnetic objects are permanent or induced dipole or a combination of both. The magnetic anomalies can be detected by an Overhauser Magnetometer or a Proton Magnetometer. The magnetic anomaly of a ferromagnetic object would vary inversely as the cube of the distance between the magnetometer sensor and the object and directly with the weight of the ferromagnetic object. Distance of the sensor and the ferromagnetic object is a major component to be considered when planning a search. To detect small ferromagnetic objects the line spacing are in general spaced at 10m apart running systematically over the area to be searched. The magnetometer sensor shall be towed at 5m above the seabed. This shall ensure that the magnetic anomalies can be detected above the earth’s magnetic intensity for small objects. The magnetometer shall be towed sufficiently astern of the vessel to reduce the effect of the magnetic influence created by the survey vessel. The instrument shall be sensitive 0.2nT with sampling rate of 4Hz with an absolute accuracy of 0.5nT. The tow sensor shall be fitted with a transponder and fixed by an Ultra Short Base Line interfaced to the navigation software. The magnetic intensity shall also be logged digitally concurrently with the DGPS x-y co-ordinates. A magnetic intensity contour map together with the individual anomalies shall be plotted for ease of detection of the ferromagnetic objects. Horizontal position accuracy shall be ±5m. 4.10.5 Detection of Debris and Obstructions in Navigational Channels and Anchorages The detection of man-made debris and obstructions hazardous to navigation shall be conducted using Side Scan Sonar technique and magnetometers. Side Scan Sonar technique may be replaced by Multibeam Echo Sounding. Upon detection of this debris in critical areas they should be examined by divers or Remote Operated Vehicles to identify the debris or obstructions. 4.10.6 Submarine Cables and Pipelines These features if lying on the seabed are to be detected by Side Scan Sonar and or Multibeam Echo Sounding. If the submarine cables or pipelines are buried, these shall be supplemented by survey with magnetometers. 4.11.0 Data Rendering The principle in compiling records of a survey is that they must be entirely intelligible to an Accredited Hydrographic Surveyor who may be required to check and reprocess the original field data if necessary. The record shall be prepared neatly, concisely and accurately. The Hydrographic Surveyor in charge shall be responsible that the records prepared by his assistants shall be in accordance with the standards specified. He will ensure that the records are independently checked and endorsed by him. All records and data shall be prepared and thoroughly documented and QC. 4.11.1 Survey Data to be Rendered The following survey data must be rendered upon completion of the survey:

a. Report of Survey (2 copies) b. Hydrographic Survey Sheets (2 copies – 1 on stable polyester and 1 paper copy) c. Tide Data (2 copies)


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d. Geodetic Data (2 copies) e. Quality Assurance (2 copies) f. Raw Original Digital Records g. Processed Digital Records h. AutoCAD Drawings of Hydrographic Survey Sheets

4.11.2 Report of Survey The report of survey shall comply but not limited with the following guidelines:

a. Introduction

• State the start and finish dates of the survey.

• List of survey personnel.

• State the Scope of Survey and Order of Survey required.

• Events of difficulty encountered that affect the progress of the survey.

• State the weather condition that affects the accuracy of the minimum depths found.

• State the accuracy of reduced depths required and achieved.

• Give an overall opinion and completeness of the survey.

b. Geodetic Parameters

• State the horizontal datum, spheroid, projection and scale used.

• State the horizontal control used for the survey, the establishment of the shore GPS reference beacon or for Wide Area Differential Corrections, the stations used for calibrations of the DGPS receiver.

• Full description of geodetic observations by GPS shall be included in the submission.

c. Survey Software Used for Acquisition

• State the hydrographic software and version used for data acquisition and QC.

d. Horizontal Position Fixing

• Describe the mode and type of positioning system used and give an opinion of the quality and reliability of equipment.

• For DGPS describe the system and the parameters set.

• Describe the calibration procedures and results.

e. Bathymetry

Single Beam Echo Sounder

• State the echo sounders and the frequencies used.

• State the squat and settlement tests conducted and how the corrections are applied.

• State the type of heave compensator used and its performance.

• State the sounding line spacing, cross lines directions and speed of sounding.

• Give a statement of the accuracy standard maintained and achieved.

• Where accuracy is not achieved over certain areas state the reasons.

• For shoal sounding investigation state the density of the sounding lines.

• Describe the calibration procedures and results. Multibeam Echo Sounder For Multibeam Echo Sounding state and prepare a sketch showing the relative positions of both horizontal & vertical for the transducer, DGPS Position, Motion Sensors and survey gyro compass along vessel’s longitudinal and lateral axes.

• Describe the field calibration procedures.

• State the offsets found in the patch tests and set in the swath sounder for � Latency between DGPS and Swath Sounder � Roll � Pitch


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� Yaw

• State the sound velocity profile found.

• State the setting applied for MBES as follows: � Power Level � Width of Transmitted Pulse � Gain Type (fixed gain, time varied gain) � Speed of Sound � Range � Update Rate � Depth Filter � Range Filter

• State swath overlaps and state areas where beam shading occurs.

• State swath angle set for acquisition and swath angle used during post processing.

• Give a statement of the accuracy standard maintained and achieved.

f. Side Scan Sonar

• State sonar used and transmission frequency.

• State confidence checks and give an opinion of quality and reliability of the sonar.

• State sonar line spacing, slant range set and speed of survey vessel.

• State tow fish layback and allowed for.

• Give a definitive statement of the sea floor coverage attained.

g. Seabed Sampling

• Describe the equipment used for sampling, sampling interval and any laboratory tests of the sample.

h. Seabed Feature, Texture and Topography

• State the distribution of seabed topography, texture and features found.

• State shoals depths and obstructions found and comparison from existing charts or previous surveys and recommendation as to the retaining of previous charted depths or to update.

i. Chart Datum and Tides

• State how the Chart Datum is established.

• State the benchmarks used to level to the tide gauge.

• State the types of tide gauge and tide pole set up, the tide calibration details and periodic checks.

• State and submit co-tidal charts and corrections applied.

j. Current (Tidal Stream)

• State the locations and the dates when current is recorded. Give a brief description of the details of the instrument installation and an opinion on the accuracy of the observations.

k. Wrecks, Obstructions & Shoal Depths Previously Reported

• Describe details of wrecks, obstructions and shoal depths investigated and give an opinion

whether the least depths have been ascertained. l. Navigational Buoys, Lights and Moorings

• Give a list of buoys, lights and moorings positions fixed, shape and color and the light characteristics. For light sectors state whether this has been checked.

m. Coastline, Topography and Conspicuous Objects

• State the methods used to survey the coastline and topography and how the conspicuous objects are fixed.

• Comment on new jetties and marinas found during the survey.


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4.11.3 Digital Records

• All raw digital recordings shall be submitted. Digital records after applying all corrections in ASCII format and AutoCAD drawings of surveys shall be submitted.

4.11.4 Analogue Records

• All original analogue traces such as echo traces and side scan sonar traces shall be annotated with Date, Area of Survey, Survey Vessel’s name, Surveyor’s Name, Roll No. and the 1

st fix No.

& last fix No. of the roll shall be submitted.


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Glossary This glossary is relevant to Chapter 4 Hydrographic Survey of the Qatar Survey Manual. A substantial part of the glossary is extracted from IHO Standards for Hydrographic Surveys S44 5

th Edition February 2008. The

terms defined provide enhancement to the clarity of terms used in the manual. Accuracy: The extent to which a measured or enumerated value agrees with the assumed or accepted value (see: uncertainty, error). ADCP: An Acoustic Doppler Current Profiler is a current meter on the seabed with four transducers pinging vertically up the water column to measure the current vectors at preset depth intervals (or cell depth) using the Doppler shift measurement from the reflected frequency of the sound. Bathymetric LIDAR: The acronym LIDAR stands for Light Detection And Ranging. Bathymetric LIDAR is an airborne Laser bathymetric system for surveying shallow water and coastal regions. The system relies on the differential timing of laser pulses reflected from the water surface and the underwater feature to determine the water depth at the point where the laser pulses strike the water surface. Bathymetric Model: A digital representation of the topography (bathymetry) of the sea floor by coordinates and depths. Confidence Interval: See uncertainty Confidence Level: The probability that the true value of a measurement will lie within the specified uncertainty from the measured value. It must be noted that confidence levels (e.g. 95%) depend on the assumed statistical distribution of the data and are calculated differently for 1 Dimensional (ID) and 2 Dimensional (2D) quantities. In the context of this standard, which assumes Normal distribution of error, the 95% confidence level for 1D quantities (e.g. depth) is defined as 1.96 x standard deviation and the 95% confidence level for 2D quantities (e.g. position) is defined as 2.45 x standard deviation. Correction: A quantity which is applied to an observation or function thereof, to diminish or minimize the effects of errors and obtain an improved value of the observation or function. It is also applied to reduce an observation to some arbitrary standard. The correction corresponding to a given computed error is of the same magnitude but of opposite sign. Drift Sweep: This sweep is used to ascertain the least depth over pinnacle rocks, wrecks, obstructions and shoal patches, etc. The drift sweeping is conducted by allowing a vessel carrying a sweep at a set depth below the water surface to drift with the current or wind over the targeted position. Drag Sweep: This sweep is used to locate wrecks, obstructions, rocks, etc in a survey channel. The sweep wire is towed by two vessels at a set depth. The sweep wire is weighted down and supported by floats at pre-determined interval. The two vessels maintain a fixed distance apart during the tow. The corridor swept is the distance between the extremities of the sweep wire. Each swept corridor is generally aligned to the channel to be swept with sufficient overlap. Error: The difference between an observed or computed value of a quantity and the true value of that quantity. (NB the true value can never be known, therefore the true error can never be known. It is legitimate to talk about error sources, but the values obtained from what has become known as an error budget, and from an analysis of residuals, are uncertainty estimates, not errors. See uncertainty) Feature: In the context of this standard, any object, whether manmade or not, projecting above the sea floor, which may be a danger for surface navigation. Feature Detection: The ability of a system to detect features of a defined size. These Standards specify the size of features which, for safety of navigation, should be detected during the survey. Full Sea Floor Search: A systematic method of exploring the sea floor undertaken to detect most of the features specified in Classification Table; utilizing adequate detection systems, procedures and trained personnel. In practice, it is impossible to achieve 100% ensonification / 100% bathymetric coverage (the use of such terms should be discouraged).


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Integrity Monitor: Equipment consisting of a GNSS receiver and radio transmitter set up over a known survey point that is used to monitor the quality of a Differential GNSS (DGNSS) signal. Positional discrepancies are continuously monitored and timely warnings are transmitted to users indicating when the system should not be used Integrity Monitoring: This is the ability of a system to provide timely warnings to users when the system should not be used. Metadata: Information describing characteristics of data, e.g. the uncertainty of survey data. ISO definition: Data (describing) about the data set and usage aspect of it. Metadata is data implicitly attached to a collection of data. Examples of metadata include overall quality, data set title, source, positional uncertainty and copyright. Oropesa Sweep: This sweep was originally designed for clearing of moored mines and has been adapted for locating wrecks and shoal patches. The sweep consists of three Kite Otter Multiplanes; two to pull the sweep wires to the port and starboard quarter of the vessel and the third to deep the two wires down at the stern of the vessel. The two Kite Otter Multiplanes are connected to two floats by float wires to maintain the sweep wire at pre-determined depths. The Oropesa sweep is managed by a single vessel with speed of up to 12 knots. Overhauser Magnetometer: This magnetometer makes use of the overhauser effect which has a free radical added to the proton rich liquid. This free radical ensures the presence of free, unbound electrons that couple with protons producing a two spin system. The overhauser effect produces a powerful method of proton polarization. The overhauser sensor measures the magnetic flux density. Proton Magnetometer: This magnetometer used proton precession frequency to measure the intensity of the earth’s magnetic field. Quality Assurance: All those planned and systematic actions necessary to provide adequate confidence that a product or a service will satisfy given requirements for quality. Quality Control: All procedures which ensure that the product meets certain standards and specifications. Reduced Depths: Observed depths including all corrections related to the survey and post processing and reduction to the used vertical datum. Sea Floor Search: A systematic method of exploring the sea floor in order to detect features such as wrecks, rocks and other obstructions on the sea floor. Sounding Datum: The vertical datum to which the soundings on a hydrographic survey are reduced. It is also called ‘datum’ for sounding reduction. Total Horizontal Uncertainty (THU): The component of total propagated uncertainty (TPU) calculated in the horizontal plane. Although THU is quoted as a single figure, THU is a 2 Dimensional quantity. The assumption has been made that the uncertainty is isotropic (i.e. there is negligible correlation between errors in latitude and longitude). This makes a Normal distribution circularly symmetric allowing a single number to describe the radial distribution of errors about the true value. Total Propagated Uncertainty (TPU): the result of uncertainty propagation, when all contributing measurement uncertainties, both random and systematic, have been included in the propagation. Uncertainty propagation combines the effects of measurement uncertainties from several sources upon the uncertainties of derived or calculated parameters. Total Vertical Uncertainty (TVU): The component of total propagated uncertainty (TPU) calculated in the vertical dimension. TVU is a 1 Dimensional quantity. Uncertainty: The interval (about a given value) that will contain the true value of the measurement at a specific confidence level. The confidence level of the interval and the assumed statistical distribution of errors must also be quoted. In the context of this standard the terms uncertainty and confidence interval are equivalent.


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Uncertainty Surface: A model, typically grid based, which describes the depth uncertainty of the product of a survey over a contiguous area of the skin of the earth. The uncertainty surface should retain sufficient metadata to describe unambiguously the nature of the uncertainty being described. Under-Keel Clearance: The minimum clearance available between the lowest point of a vessel’s keel and the seabed in which it is safe for a vessel to navigate without the risk of grounding.

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Abbreviations

BC Beginning of Curve

BS British Standard

CGIS Centre for GIS

DIN Deutsches Institut für Normung

EC End of Curve


GCSM Geodetic Control Survey Monument



IP Intersection of tangent

PD Permitted Deviation

PWA Public Works Authority

R.O.W. Right of Way


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5.1.0 Introduction No attempt is made in this guideline to detail how construction surveys should be carried out. It covers the standard and essential specifications of survey practices demanded of a Registered Surveyor. Registered Surveyors have to determine the appropriate equipment and methodology to satisfy their client’s specifications. It is also not intended to substitute technical specifications stipulated by the clients of Registered Surveyors. Contractual agreements and specifications entered into between the Registered Surveyor and his client shall take precedence over this guideline in the event of disputes. Such contractual agreements shall also preside where the directives do not cover the types of survey being undertaken.

The guideline is also by no means exhaustive. As new technologies and methods evolve, the directives will be adapted to embrace and to leverage on these developments as well as to respond to changing business needs. 5.2.0 Accuracy Standards Coordinated control points are established at the early stages of a construction project in the preparation of topographic and engineering survey. These control points should be established at an order of accuracy adequate for setting out. They should be observed and adjusted to the required accuracy. The observation scheme should form a self-checking network which can be linked to the national grid without the national grid control points introducing errors. Generally, it is recognized that the low-order control points of national mapping agencies do not have the internal relative accuracy required for construction works.

Height control is extremely important in any construction project and the most accurate results are still only attainable with traditional leveling techniques, using either digital or optical level. The control should form a self-checking network, which is linked to the precise national leveling datum.

The accuracy attainable is a function of the instrument, including the accessories, used and its operator. The overall performance relies heavily on the capabilities of both components.

The DIN (Deutsches Institut für Normung) 18723, a German industry accuracy standard for theodolites has been widely adopted worldwide by surveying instrument manufacturers. The standard deviations for angles measured in the tests are often quoted in the instrument brochures without stating the confidence level, i.e. whether it is at 68%, 95% or 99%. Users should consult the manufacturers to ascertain exactly what is quoted. The procedures stipulated in DIN 18723 are similar to those recommended in BS 7334 1990.

It is particularly important that Land Surveyors involved in setting out have an understanding of instrumental accuracies and the theory of errors. Appendix 5A provides a guideline on accuracy of survey instrument.

The following calibration procedures are the minimum requirements before executing a surveying task:-

(a) Electronic Distance Meter or Electronic Total Station used in the survey shall be properly calibrated at the EDM Calibration;

(b) Leveling instrument shall be calibrated by 2-peg method before they are used each day and after service. The Registered Surveyor shall maintain the calibration records.

(c) The accuracy of the survey equipment used must be compatible with the stipulated accuracy of the survey.

5.3.0 Compliance with Contract Specifications Clients have the prerogative to stipulate specifications other than those specified in this manual. In these circumstances, the contract specifications shall prevail over the specifications stipulated in these directives.


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5.4.0 Method of Survey Where no survey specifications are stipulated by a client, the Accredited Surveyor shall adopt or derive a method of survey that produces results complying with the required accuracy as stipulated in this manual. 5.5.0 Field Survey Record (a) Registered surveyor shall maintain proper field records for inspection whenever required;

(b) All entries in survey record are to be made in ink. Inking over entries and transcribing from other records are expressly forbidden;

(c) Every incorrect entry shall be cancelled by one horizontal stroke through all figures which shall remain legible after the cancellation;

(d) The corrected entry shall be written in full above the cancelled entry; no figure shall be altered, erased or obliterated;

(e) Electronic data logger may be used in the survey. Registered Surveyor shall ensure that all electronic data are properly documented and archived.

5.6.0 Survey Computation (a) Areas of lots and plots shall be computed using any method to the nearest tenth of a square meter (0.1

sq.m.);

(b) Scaled areas shall be entered to the nearest square meter and distinguished by the abbreviation “Sc.” after the areas.

(c) For provisional areas and boundaries, a note “Areas, boundaries and dimensions shown hereon are provisional and subject to alteration on final survey.” shall be entered on all the survey plans, sketches and computation sheets;

(d) Pre-computation for setting-out purpose shall follow the design layout plans or other approved drawings;

(e) Salient locations shall be coordinated and pre-computed dimensions of clearance shall be reflected on pre-computation plans.

5.7.0 Preparation of Setting Out Plan The following information shall be included in the preparation of setting out plans:

(a) Property Development and Building Construction

(i) Boundary stones, nails, spikes, cut-marks, etc., which demarcates the property boundaries and their reference number.

(ii) Lot boundary and lot numbers. (iii) Field traverse and control stations with coordinates shall be indicated. (iv) Bench marks and their reduced levels. (v) Pegs or reference points established on site. (vi) Grid lines.

(b) Road construction

(i) Field traverse and control stations with coordinates shall be indicated. (ii) Bench marks and their reduced levels. (iii) IP (Intersection of tangent), BC (Beginning of Curve) and EC (End of Curve) with horizontal

curve properties and coordinates shall be indicated.


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(iv) Vertical lay-out plan indicating Station distances, elevations and vertical curve properties. (c) Setting Out

(i) IP, BC and EC in a permanent like steel peg in concrete. (ii) Centerline of the road in station distances using the IPs as occupied and reference stations

when accessible and visible to each other, otherwise, an intermediary point(s) in between is necessary.

(iii) Side stakes can be done using optical square and meter method from the centerline during base preparations, otherwise, final stake out shall be done using a theodolite or a total station at highest tolerance as possible.

(iv) Long curve staking shall depend on the degree of the curve that will produce a smooth curving. Where kerb stones will be used, the degree of the curve is equivalent to a tangent distance of length of the kerb stones plus the spacing distance.

(v) Small curve staking shall originate from its center of radius as set-out. (vi) Building stake-out shall originate from the established grid reference points. A +1.0m elevation

mark of finish floor elevation in every floor shall be transferred at walls and columns. Building plumb line shall be checked as the building rises in floor by floor basis.

(vii) Levels shall be of spirit leveling method using the established bench marks as reference points whose tolerance will depend on the nature of work.

5.8.0 Submission of Plans and Survey Records All plans, field records, reports, data sheet, equipment calibration records, etc., shall be certified by the Accredited Surveyor/Surveying Company. 5.9.0 Guideline on Setting Out Survey (a) Angle and bearing measurements shall be observed, checked and recorded to the specified accuracy

of the instrument.

(b) An independent observation from another station shall be included for checks on accuracy.

(c) Always practice check horizontal angle at IPs or geodetic control stations whose distance should not be more than the distance by substance from the back sight station.

(d) Non-invar leveling staves are to be read and booked to 0.001m.

(e) Digital levels should be configured so as to allow repeat observations, with the standard deviation after five observations to be maintained at 0.001m or less.

(f) For GNSS setting out, a repeat observation at the set-out point is to be taken later after a minimum of 30 minutes and/or counter check distance measurements among each points.

(g) For setting of curves, the crown distance – the maximum separation between an arc and the corresponding chord – should be not more than 0.2 m (see Figure 5.1)


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5.10.0 Permitted Deviations for Setting Out Survey The principle of accuracy acceptance criteria for control points and setting out points has been established in BS 5964 “Building setting out and measurement” which is accepted internationally. The criteria specified are in terms of relative rather than absolute accuracies and are given as Permitted Deviation (PD) for distances, bearings, angles and levels, as shown in Tables 5.1 & 5.2 (a) Horizontal and Vertical Setting Out There are many setting out tasks in construction activities and it is not possible to classify them all. Broadly, setting out surveys are classified into four categories:-

(i) Category 1 – structure (ii) Category 2 – roadworks (iii) Category 3 – sub-structure works (iv) Category 4 – earthworks

The acceptance criteria quoted relate to distances, angles and levels and apply whether they are measured from a higher-order point or between two points in the same category. The differences between the calculated and observed distances, angles and levels should not exceed the following PDs:

Table 5.1: Permitted Deviations for Horizontal and Vertical Setting Out Survey

where L1 is the distance, in meters, between the points concerned and L2 is the shorter of the two distances defining the angle.

(b) Verticality

(i) The accuracy criteria here relate to all plumbing operation whether column and shutter alignment or the vertical transfer of second-stage setting out between floors of high-rise building;

Permitted Deviation (PD)

Structure Roadworks Drainage Earthworks

Distance (mm) ± ( 1.5 √L1) ± ( 5.0 √L1) ± ( 7.5 √L1) ± ( 10.0 √L1)

Angle (degree) ± (0.09 ÷ √L2) ± (0.15 ÷ √L2) ± (0.20 ÷ √L2) ± (0.30 ÷ √L2)

Height Difference (mm) ± 3 ± 5 ± 20 ± 30

Figure 5.1: Crown Distance of a Chord AB

Crown Distance

= R(1-cos δ)

δ

δ

R

R A

B

O


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(ii) When comparing measured plumb points with the true plumb the differences shall not exceed the following PDs:

Table 5.2: Permitted Deviations for Verticality

PD (mm)

Heights up to 4m ± 3

Heights greater than 4m ± (1.5√H)

where H is the vertical distance in meters from the bottom reference point to the upper reference point. 5.11.0 Specifications and Work Procedures for Construction Surveys Survey equipment used and control points established for construction survey must conform to the criteria of the relevant survey control specification as stipulated in Chapter 1 on Control Survey. 5.11.1 Specifications for Construction Works (a) Grid leveling Level grids are normally observed at between 20 m and 50 m intervals, and levels observed to the nearest centimeter. Each one hundred meter point to be set out by measurement, but intermediate points can be paced as long as the terrain is flat. Schemes are normally plotted at a scale ranging from 1:200 to 1:1000.

(b) Right of Way (R.O.W.) Centerline Levels

R.O.W. centerline levels are to be observed to the nearest centimeter and normally taken at an interval of 20 m plus any abrupt changes of slope. If IP coordinates are available the IP's are to be set out by bearing and distance.

(c) Cross Sections

Cross sections are normally observed at between 20 m and 50 m intervals whilst levels are to be observed to the nearest centimeter. The points that require leveling will be stipulated with each job.

(d) Earthwork Profiles

Profiles will normally be spaced at between 20 m and 50 m intervals, and for roads will be placed on the edge of the R.O.W. Normally profile crosspieces will be set at 1 m above the level of the proposed earthworks. On occasions this dimension will be reduced to allow for thickness of the road wearing course. 5.11.2 Work Procedures for Construction Works Engineering Information System Section, PWA has two main areas of responsibility which are enumerated below. (a) Engineering Survey Work The primary responsibility of this section is to execute requests for survey work emanating from the various departments in the Ministry of Public Works, and any other Government departments. The majority of the work originates from PWA (Ashghal). Jobs are varied and range from site surveys to profiling for earthworks (b) Road Opening Requests These are presented to the section to assess if any survey control will be affected by proposed road schemes.


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5.11.3 Working Practice in Construction Works All contractors must consult the Public Works Authority, or similar authority, prior to any construction works to determine if the work is likely to disturb Geodetic Control Survey Monuments. If CGIS require a Geodetic Control Survey Monument (GCSM) to be moved the Contractor will be responsible for recreating the survey mark to an approved design and specification as stated in Volume 1 on Control survey.

The Contractor shall be responsible for the protection of the GCSM, within the boundaries of the site, for the duration of the contract period, and shall be liable for all costs of any remedial work required by the CGIS.

On the practical completion of works the CGIS will issue a certificate stating that all GCSM, whether disturbed or otherwise, by the contractor have been reinstated or protected to the satisfaction of the CGIS.

In the event of failure to comply with the requirements of this Clause, the Government, without prejudice to any other method of recovery, may deduct the costs of any remedial work after the practical completion date, carried out by CGIS from any monies in its hands due or which may become due to the Contractor. 5.12.0 Survey Marker (a) Geodetic Control Survey Monuments (GCSM) of durable quality is depicted in Chapter 1 of the Survey

Manual on Control Survey;

(b) Wooden pegs of suitable length and cross-section shall be used to mark setting out points;

(c) Reference pegs shall be established for the baseline and all intersection points;

(d) Survey stakes, batter boards and other devices shall be of such configuration and dimensions as to completely fulfill their function with respect to precision requirements and period of use

5.13.0 Plan Flow Associated with Construction Survey Before any form of construction can begin, a preliminary survey is required and a contoured plan of the area at a suitable scale (usually 1:500 or larger) showing all the existing detail is produced. This plan is known as site plan.

The engineer takes this site plan and uses it for design of the project. The proposed scheme is drawn on the site plan and this becomes the layout or working drawings. All relevant dimensions are shown on these and a set of documents giving technical details about the project is included. These form part of the scheme when it is put out to tender. The contractor who is awarded the project will be given these drawings.

The contractor uses these layout drawings to decide on the location of the horizontal and vertical control points in the area from which the project is to be set out. A setting out plan will be computed and drafted to facilitate the subsequent setting out work.

As work proceeds, it may be necessary to make amendments to the original design to overcome unforeseen site problems. Any such alterations are recorded on a copy of the working drawings. This copy becomes the latest amended drawing and should be carefully filed for easy access. It is essential that the latest version of any drawing is always used, particularly if setting out operations are undertaken. It is also important to keep the drawings which show the earlier amendments; they may be needed to resolve a dispute or for costing purpose.

Upon the completion of the project, a detail survey is carried out to document the built structure to produce the as-built drawing.


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References

1. BS 5606: Guide to accuracy in Building, British Standard Institution, London.

2. BS 5964: Part 1 (ISO 4463-1), Building setting out and measurement, British Standard Institution, London.

3. BS 5964: Part 2 (ISO 4463-2), Building setting out and measurement, British Standard Institution, London.

4. BS 7334-1 (ISO 8322-1), Measuring instruments for building construction – Methods for determining accuracy in use: theory, British Standard Institution, London.

5. BS 7334-2 (ISO 8322-2), Measuring instruments for building construction – Methods for determining accuracy in use: measuring tapes, British Standard Institution, London.

6. BS 7334-3 (ISO 8322-3), Measuring instruments for building construction – Methods for determining accuracy in use: optical leveling instruments, British Standard Institution, London.

7. BS 7334-4 (ISO 8322-4), Measuring instruments for building construction – Methods for determining accuracy in use of theodolites, British Standard Institution, London.

8. BS 7334-5 (ISO 8322-5), Measuring instruments for building construction – Methods for determining accuracy in use of optical plumbing instruments, British Standard Institution, London.

9. BS 7334-6 (ISO 8322-6), Measuring instruments for building construction – Methods for determining accuracy in use of laser instruments, British Standard Institution, London.

10. BS 7334-7 (ISO 8322-7), Measuring instruments for building construction – Methods for determining accuracy in use of instruments when used for setting out, British Standard Institution, London.

11. BS 7334-8 (ISO 8322-8), Measuring instruments for building construction - Methods for determining accuracy in use of electronic distance-measuring instruments up to 150 m, British Standard Institution, London.

12. ICE design and practice guides – The management of setting out in construction, Institution of Civil Engineers and Institution of Civil Engineering Surveyors, London.

13. U.S. Federal Geographic Data Committee, Geospatial Positioning Accuracy Standards: Part 4, Standard for A/E/C and Facility Management (Public Review Draft).


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Appendix 5A

Guidelines on Accuracy of Survey Instrument

The range of instrumentation available to the surveyor today is far greater than it used to be. Choosing the right survey equipment and knowing their accuracy is often not an easy task if the job is to be done at the most economical cost and to satisfy specification. Electronic total station, level (optical or digital) will always be used in setting out. But laser and GPS now give a new dimension in approaching non-cadastral task. BS 7334, 1992 Part 1 to 8 provide test procedures in determining and assessing the accuracy in the use of measuring instruments in building construction industry, viz. measuring tape, optical leveling instrument, theodolite, optical plumbing instrument, laser instrument, instrument used for setting out and electronic distance-measuring instrument. In almost all instrument brochures, a DIN (Deutsches Institut für Normung) standard 18723 is used. DIN is equivalent to the British Standard Institution (BSI). Following DIN 18723, the test procedures lead to standard deviations for the measurements of the instruments. These are then quoted

in the instrument brochure, but often without stating whether they are ±1, ±2, ±2.5 or ±3 standard deviations. The procedure in DIN is similar to those recommended in BS 7334: 1990. For GPS equipment, there is no standard for calibration. All GPS manufacturers use the Federal Geodetic Control Sub-committee (FGCC) network in Washington, DC, USA. This is currently the only one of its type in the world and the tests are fully supervised. Another common method of testing GPS is the zero baseline test in which two receivers are connected to a single antenna using a splitter cable. Users who have no experience of accuracy determination may have difficulty in appreciating exactly what accuracy can be expected from various surveying instruments when used in different activities. BS 5606: 1990 provides suitable accuracy in use figures for a number of these (see Table 5A.1). The figures given are unlikely to be exceeded assuming that good practice is followed. The “Range of deviation” is based on 2.5 standard deviation, equivalent to 98.75% probability. The comment column in Table 5A.1 gives guidance on good practice.


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Table 5A.1: Accuracy in Use of Measuring Instrument (based on BS 5606: 1990)

Instrument Range of deviation Comment

Linear EDM for general use EDM for precise work

± 10 mm for distances over 30 m and up to 50 m

± (10 mm + 10 ppm) for distances greater than 50 m

± (5 mm + 5 ppm)

Accuracies of EDM vary, depending on make of instruments Distances measured by EDM should normally be greater than 30 m and measured from both ends

Angular Opto-mechanical reading directly to 20” Opto-mechanical reading directly to 1” 1” opto-electronic theodolite/total station

± 20” (± 5 mm in 50 m)

± 5” (± 2 mm in 80 m)

± 3” (± 1 mm in 50 m)

Scale two-face readings estimated to 5”. Two-face readings Two-face readings

Level Spirit level Water level Optical level – ‘builder’ class Optical level – ‘engineer’ class Optical level – ‘precise’ class

± 5 mm in 5 m

± 5 mm in 15 m

± 5 mm per single site of up to 60 m


/ ± 10 mm per km


/ ± 8 mm per km

Instrument not less than 750 mm long Sensitive to temperature variation where possible sight length should be equal If staff reading of less than 1 mm is required, the use of a precise level incorporating a parallel plate micrometer is essential but the range per sight preferably should be about 15 m and should be not more than 20 m

Verticality Spirit level Plumb-bob (3 kg) freely suspended Plumb-bob (3 kg) immersed in oil to restrict movement theodolite (with optical plummet or centering rod) and with diagonal eyepiece Optical plumbing device Laser upwards or downwards alignment

± 10 mm in 3 m

± 5 mm in 5 m

± 5 mm in 10 m

± 5 mm in 30 m

± 5 mm in 100 m

± 7 mm in 100 m

For an instrument not less than 750 mm long Should only be used in still condition Should only be used in still condition Mean of at least four projected points, each one established at 90

o interval

Automatic plumbing device incorporating a pendulous prism instead of a leveling bubble Four readings should be taken in each quadrant of the horizontal circle and the mean of values of readings in opposite quadrants accepted.


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BS 5606: 1990 provides no accuracy figures for GPS system. Table 5A.2 defines precision currently ascribed

to various GPS techniques. It is based on ± 2 SD, which is equivalent to 95.45% probability (1 chance in 22).

Table 5A.2: Survey Precision for GPS Techniques (95% Probability Level)

Precision

Technique Occupation Time Range Horizontal Vertical

Static L1 > 45 minutes 15 km ±(0.5 cm + 1 ppm) ±(1 cm + 1 ppm)

Static L1/L2 > 45 minutes – 24 hr Hundreds of km

±(0.5 cm + 1 ppm) ±(1 cm + 1 ppm)

Fast static L1 10 – 20 minutes 5 km ±(1 cm + 1 ppm) ±(2 cm + 1 ppm)

Fast static L1/L2 5 – 20 minutes 40 km ±(1 cm + 1 ppm) ±(2 cm + 1 ppm)

Stop/go kinematics < 10s 10 km ±(2 cm + 1 ppm) ±(4 cm + 1 ppm)

Continuous Instantaneous 10 km ±(2 cm + 1 ppm) ±(5 cm + 1 ppm)

Qatar Survey Manual – Chapter 6 – Gravimetric Survey

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6.1.0 Introduction The aim of the gravity survey of Qatar is (in the context of the specifications) to produce a geoid whose heights will enable the transformation of GPS-derived geometric heights (h) into orthometric heights (H). These H are then used for engineering and surveying design. It is thus NOT intended for these gravity data to be of such high resolution and precision that they will be useful for geophysical prospecting, or whose interpretation would enable the detection of small-scale sub-surface features. The gravity field resulting from these survey methods will, nevertheless, provide information on the medium (about 5-10km) to long wavelength features of the gravity field and the larger sub-surface structures which produced them, as well as a geoid model to the required precision. 6.1.1 Existing Geoid Models for Qatar

a) Qatar95 Geoid Model. The model OSU91a (Rapp, 1991) was fitted to geometrically determined geoid-

ellipsoid separations N where N = hGPS - Hlevel. These separations were computed at 72 network stations (7 stations were eliminated from the computations due to poor or unavailable spirit leveled heights) and introduced as constraints into the final computation of the Qatar95 geoid model. Subsequent analysis showed that the absolute accuracy of the geoid model is about 7 cm (95% confidence level) and the relative accuracy of the geoid is about 2 ppm (see Chamberlain, 1995).

b) Bahrain-Qatar Causeway Project. In 2002 Forsberg and Schmidt (2002) performed a geoid analysis for

the Bahrain-Qatar Causeway project. In this study they identified the benign nature of the gravity field, and hence the geoid, in the subject region. To quote from their report;

“Gravity values were tied to NIMA (DoD) reference gravity points in Bahrain, with reference gravity values given in IGSN71. Raw gravity readings were processed and tares isolated using the KMS adjustment programme GRADJ, giving a set of absolute gravity values with an estimated accuracy of ±0.13 mGal (where 1 mGal = 10

-5

m/s2 is the conventional unit for gravity).

Gravity measurements were done using KMS LaCoste and Romberg gravimeter G-867. The survey covered Bahrain and north-western Qatar at a relatively modest spacing. The survey took place November 13-20, 2001, with a total of 75 observations in 58 stations. Heights and positions of all points were determined by static GPS (Forsberg and Schmidt, 2002, p.3).”

Further, their analysis revealed the nature of the geoid in the northern region of Qatar.

“The gravimetric geoid model was computed by spherical FFT and EGM96 in the region 24.5-27 N, 50-52.5 E. The gravity field in the region was found to be extraordinarily smooth: for the 870 gravity points available the mean and standard deviation was –40.5 and 7.8 mGal, respectively, dropping to –0.8 and 6.0 mGal after reduction for EGM96” (ibid, p. 7). They also estimate that their geoid evaluation fitted the available GPS-Leveling control to the order of +/- 20 mm. “

It is useful to have this understanding of the area before embarking upon the work of the gravity survey, as this will influence the approach taken in both the field work and the reductions and computations. Apart from the gravity survey mentioned in 6.1.1 (b) above, there appears to be little gravity publicly acknowledged, let alone available, in Qatar. It therefore appears that the gravity survey has to be done from scratch, although it is important to access such gravity data as is available and incorporate this into the planning for any future gravity coverage. However, given the benign nature of the gravity field and geoid, and the low relief of the topography, the problems introduced by topographic effects are minimized, and the need for a high density of gravity observations is reduced. Because of the problems associated with lack of gravity both off-shore (but see Section 6.3) and in the country of Kuwait, it will be important for the purposes of the geoid solution for Qatar, to establish geometric control where possible, both around the coast and along the Kuwaiti border. Mention should also be made of the new very high resolution global model of the Earth’s geoid and gravity field, EGM08 (expected release date April-May 2008), superseding EGM96 (Lemoine et al, 1998). It has a resolution of about 5 arc minutes or 9 km, and is based upon the most recent gravity satellite missions and terrestrially observed gravity. Only tests in the region will prove how well it models the gravity field in the


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region of Qatar, but it certainly should prove to be very valuable as the basis for any geoid computations in Qatar. 6.1.2 Requirements for a Gravity Field for a New Geoid Model for Qatar

Given the nature of the topography of Qatar, the resolution of observed gravity stations to determine the gravity field can probably be reduced from (say) 5 - 10km to 10 - 15km. However, this is predicated upon the need to (i) Establish the field off-shore, most likely by airborne techniques (see Section 6.3), and (ii) Provide geometric control at the limits of the country. This can be done by GPS heighting at leveled

Bench Marks both along the Qatar-Kuwait border, and along the coast line. (Ideally the gravity field of the neighboring country of Kuwait should also be used in the gravimetric geoid evaluation. However there may be some difficulty either obtaining these data from Kuwait (if it exists), or obtaining permission to fly into this country to measure it by airborne techniques. Hence, there is a need in (ii) above to provide geoid control along the common border).

Once the gravity field of Qatar has been defined to the required resolution and precision, the geoid can be computed gravimetrically by Stokes or some other acceptable technique. It can then be “fitted” to the geometric control from (ii) above, which will help control the bias and tilt of the Qatar gravimetric geoid which will occur because of deficiencies in the gravity field beyond its borders. In the sections below, the methods and specifications for establishing the gravity field over Qatar are described. In Section 6.2 Terrestrial techniques are summarized, while Section 3 concentrates upon airborne techniques. 6.2.0 Terrestrial Absolute and Relative Gravimetry

6.2.1 Introduction to Gravity Networks (Torge, 1980, Sec. 6.3; 1989, Sec 9.1)

In an approach very familiar to surveyors, gravity is propagated across the globe and into the local regions “from the whole to the part”. We can classify these levels of gravity surveys as follows. 6.2.1.1 The Global Network IGSN 71; (Morelli et al (1971))

In this fundamental world-wide network of stations, relative gravity (“g”) is measured by 'batteries' of gravimeters along lines across the globe connecting national gravity base stations to 10 absolute stations (see, e.g., Torge, 1989, Fig., 9.1, pp 315 ff). These base stations then form the basis for all other gravity networks around the regions of the globe. They are usually measured to better than ±0.03 mGal or ±30 microGal or µGal. They are akin to the First-Order Geodetic Stations of classical geodesy. 6.2.1.2 National or Regional Networks

g is propagated through the regional network by observing gravity with two or three meters (to provide independence), and these values are tied onto the IGSN'71 above by occupying at least one of the IGSN71 stations. This survey is to provide more stations of sufficient precision in accessible areas (usually airports) to provide a datum for local surveys. An example of this would be the ISOGAL network in Australia. There is

one station in Qatar (020201, DUKHAN, N25.°39000 W50.°1667, 0.00 m above sea level, 978938100 microgal, ± 400 microgal (0.4 mGal) which could act as the gravity datum for gravity surveys in that country. Access to surrounding countries may also be required for gravimeter calibration purposes – at least until a national network is established. It is therefore recommended that, before any detailed survey is commenced, a national network be established using a battery of two to three relative gravimeters read to the highest precision, The stations of this network (and their associated eccentric stations for recovery purposes) should be established, most


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practically, at the major airports or other centers at a spacing which will allow easy access for the more detailed surveys which follow. 6.2.1.3 Local Surveys

The detailed, local gravity survey is based upon the regional stations in (6.2.1.2). Their specifications vary depending upon the purpose of the survey. For detailed geophysical work, the precision may be very high (0.05 mGal) and the spacing small (10-50m). However, as noted in Section 6.1.2 above, for the purposes of the Qatar geoid these specifications can be relaxed. Formal analyses show that, if we wish to match the precision of GPS heighting (and thus recover orthometric heights from GPS without significant loss of precision), the gravity field used in the geoid computation should be represented by mean values of 10x10 km blocks with random errors of less than ± 0.3 mGal (Kearsley, 1986). While this specification may seem rather generous, it is difficult to achieve in mountainous areas; in the region of Qatar however, given the benign nature of the topography, it should be quite easy to achieve given sufficient density of point observations. A spacing of observed points of 10 to 15 km should be sufficient to achieve the desired precision. The meter should be read to the least count of the dial or readout to allow highest precision, and heights of gravity stations established to 0.2 m (≡ 0.06 mGal). Taking as an example the Australian National Gravity Network (ANGN), the first generation network had an average spacing of 1 point every 11 km; and point observations had σg = ±0.3 mGal; σH = ±4-6 m

(Barometric) σΦ,λ = ±200 m. This network was observed well before the advent of GPS.

By using kinematic/rapid-static GPS to locate the gravity station in three dimensions, σH, σΦ and σλ are

easily recoverable to ±0.2 m, σH providing the geoid-ellipsoid separation N is known to that precision or

better. (A first approximation of N is needed to transform the h from GPS to the H at the observation point, to enable the reduction of the observed gravity to a common equipotential reference surface).

The gravity survey performed in support of the Bahrain-Qatar Causeway project (Forsberg and Schmidt, 2002) used this approach, and the results are available in that publication. Currently this appears to be the main source of gravity data on public record.

Note that the International Gravity Bureau (IGB), which operates under the auspices of the International Association of Geodesy, acts as a repository for gravity data from many different sources for the whole world. It collects data from (for example) national geodetic and geophysical authorities, validates this data (see Section 6.2.4.3), and then distributes this data to authorized users. However there is very little data for Qatar held by this bureau in their data base, so clearly the field has to be established from scratch (see Figure 6.1). Another major and valuable source of data worth investigating is the US National Geospatial Intelligence Agency or NGA (formerly National Imagery and Mapping Agency - NIMA) http://earth-info.nga.mil/GandG/ or http://164.214.2.59/GandG/.


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Figure 6.1: Gravity Data in the Region of Qatar Held at IGB 6.2.2 Instrumentation 6.2.2.1 Absolute Gravimeters (see e.g., Torge, 1989, pp. 128-179) The instruments to measure absolute values of gravity are rather bulky and very sensitive. Their operation is usually restricted to stable environments, such as laboratories, and as such is generally unsuitable for field observations. Even so, some models have become smaller over the last decade or so, making them more portable (see for example, the LaCoste Microgal-G A10 meter). Absolute gravimeters are critically important in setting up the global network however, and in many other geophysical and global geodetic studies requiring the highest accuracy. They provide scale for the network, as the calibration of the relative gravimeters depends upon the values of changes in g between stations for calibration.

Historically, different models have used springs, pendulums and falling bodies (the most common used

technique currently); a precision of o{10-9} of "g" or 1 microGal is attainable with the latter.

6.2.2.2 Relative Gravimeters (measuring changes in g) (Torge 1989, pp. 184-254) As for any field equipment, we want the gravimeter to be sensitive, rugged, reliable and, for the gravimeter, precise to better than 0.05 mGal or 50 microGal, day after day. The measurement technique is obviously instrument dependent, and the manuals supplied with the instruments comprehensively describe their use. For web sites detailing the observing techniques see also http://cires.colorado.edu/people/sheehan.anne/gravhowto.html. For elements of the Lacoste & Romberg, Scintrex and the older Worden gravimeters, see Nettleton (1976, p. 37), Dobrin, (1960, pp. 214-215), and Torge (1989, pp. 232-234; 237-241), as well as the relevant web sites, e.g., for LaCoste & Romberg (http://www.microglacoste.com/relativemeters.htm), and for the Scintrex (http://www.scintrexltd.com/gravity.html). Some general comments relating to field procedures follow. Non gravitational effects upon the gravimeter

We need to compensate for changes during measurement in ambient temperature, atmospheric pressure and the magnetic field to ensure that any variations we measure are solely as a result of changes in the gravitational attraction, and not these other possible sources which may influence the reading of the meter.


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* Ambient temperature: This can be minimized, if not eliminated, by enclosing the element in small temperature-controlled oven; by designing temperature compensation into the element; and by placing the element in a vacuum-sealed chamber.

* Air or atmospheric pressure: Again variations in pressure are controlled by enclosing the element in sealed chamber or cell; and by varying the buoyancy of cell as the air density varies.

* Magnetic field: Variations in the magnetic field are minimized by using non-magnetic alloys or materials for the springs used in the element.

Calibration Procedures The (relative) gravimeter senses the changes in gravity between successive points, and registers these changes with dial readings. The dial units then have to be calibrated so that they can be converted into units

of gravity, usually expressed in Gravimetric Geodesy as milliGal (mGal, where 1 mGal = 10-5 ms-2). The gravimeter is usually supplied with a calibration factor quoted by the manufacturer, but it is always good practice to check (and to keep checking) this factor. To calibrate the gravimeter, dial readings are taken between (at least) two known and well established gravity stations (e.g. in the National or Regional network, see 2.1.2 above). Knowing the difference in gravity between these points, and the difference in dial readings, it is possible to compute the relationship between the two by simple division. Typically, the calibration of the meter is about 0.1 mGal per dial division. In Qatar there will be some difficulty finding two well established gravity stations of sufficient precision, and these will have to be established before proceeding with the man survey. See also http://www.gravitymeter-repair.com/images/gdmanual.pdf 6.2.3 Field Procedures Before commencing the field operation, the meter must be carefully checked, as specified by the Manual specific to the instrument. The general description of the approach to the field survey follows, and is based upon Dobrin (1960, pp. 218-227); Torge (1989, Sec. 9.2). The gravity survey requires the care and precision which comes from long experience and in the first instance should only be entrusted to a party with a proven track record. They can then train technicians in the field techniques required, and achieve the transfer of technology by this mentoring process. Planning: An important consideration is the location and spacing of stations alluded to above (Section 6.2.1.3). For example, the reconnaissance surveys for oil-bearing structures with station spacing of about 10 km (e.g. the ANGN) have been invaluable in providing data for gravimetric geoid computations.

If possible, all GPS and Leveled bench marks in the control survey of Qatar are included in the gravity survey, some, where possible, as the base or pivotal stations for the gravity survey. Presumably these stations are well and permanently marked and are easily accessible, and they will be used as geometric control for the gravimetric geoid which will result from the gravity survey. (i) Position Fixing Positioning is a major item in the budget of most gravity parties. A precision of at least 0.3 m (equivalent to 0.1 mGal in the reduced gravity) is wanted in final station elevation. Rapid-static GPS, spirit leveling, or an EDM leveling traverse (if distances are short) are options. Barometric leveling is not likely to produce the

desired precision. Absolute location only needed to nearest 30 m (≡ 0.03 mGal) for the computation of normal gravity to the required precision.)

If conventional survey techniques are adopted for the position fixing, the field survey party operates about 2-3 days ahead of gravity party, but in a GPS/GNSS environment, it is possible (and usual) for geopositioning and gravimetry to proceed simultaneously.


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(ii) Gravity Measurement The gravimeter is transported by helicopter, vehicle or even by back-pack. For the calibration of the meter and to control its drift it is important to start and finish a gravity traverse on stations of known gravity (cf. Section 6.2.1.2).

To control the drift of the element of the gravimeter, it is common to revisit stations, i.e. to take repeat readings at different times, to track the behaviour of the meter’s element with time.

A number of different patterns can be used to carry out the repeat readings. a) The Grid pattern. For the grid below the measurement routine may be to measure in turn the stations

∆1, a1; ∆1, a1, a2; a1, a2, a3; a2, a3, a4; a3, a4, a5, a4, a5, b5; b5, b4, b3; ...

... d2, d3, d4; d4, d5, ∆2; d5, ∆2.

1 2 3 4 5 a + + + + +

b + + + + + ∆∆∆∆2

∆∆∆∆1 c + + + + + d + + + + +

where ∆1, ∆2 are the known stations. b) The Star pattern. In this approach four stations are located roughly on the corners of a square, about 15

km by 15 km. A station approximately central to this square is defined, and it becomes the pivotal point for the survey. Taking the above grid as the example, the point b2 is first observed, then, in turn, a1, b2, c3, b2, a3, b2, c1, b2, In this routine we have constant check upon the drift of the meter (and the tidal signal) at the repeat observations at b2. We then move onto the next block of points, and observe (e.g.) b4, a3, b4, c3, b4, a5, b4, c5. Again, b4 is the pivot, and enables drift to be controlled, while points a3 and c3 are now re-observed to provide a check against error.

The region is covered by this pattern and the whole set adjusted by least squares analysis to obtain the optimum values for all observations.

c) For many geodetic and geoid purposes it will not be necessary to achieve such a high level of

redundancy. Check stations may only be needed every third or fourth station, providing a significant saving to the field costs. Clearly the gravity survey for the Bahrain Qatar Causeway project was performed along these lines, as 58 stations were established from 75 observations. It is very important to start and finish the survey on established gravity stations.

At each field station we need to determine

GRAVITY and TIME - for the gravity component of the survey, and POSITION and HEIGHT - for the positional component of the survey. The field note recording (whether manual or digital) must be constructed to reflect these requirements – to the specifications mentioned above.

6.2.4 Office Procedures Before detailing the reduction procedure, it is necessary to appreciate the phenomena which will influence our gravity readings.

6.2.4.1 Factors Which Affect the Measurement of Gravity – g

(i) Change of Gravity ‘g’ with Latitude - ϕ

’g’ is modeled by normal or model gravity ‘γ' using an ellipsoid of given mass - M, semi-major axis - a,

flattening - f, and rotational velocity - ω to produce 'normal' gravity γ (Torge, 1980, pp. 60-62).


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On Geodetic Reference System 1980, (Torge, 1989, p. 61) where

a = 6 378 137m , f-1 = 298.2572..., we find

γ = 978032.7 (1 + 0.005 3024 sin2 φ- 5.8E-6 sin2 2φ) ...(1)

where γ is in mGal

To get γγγγ to ± 0.1 mGal we need ϕ to 100 m (≅ 3");

To get γγγγ to ± 0.01 mGal we need ϕ to 10 m. Such precisions are easily achieved with GPS positioning.

(ii) Time-Dependent Variations (a) Tidal effect: This is well modeled by conventional Earth Tide Models, and the effect is removed from the observed value (b) Gravimeter element ‘drift’: We adopt an observational procedure to determine drift so that this can also be removed (see Section 6.2.3). The tidal effect also registered in our measurements, and can be modeled out of the observations, so drift is only established once the tidal effect is removed (iii) Change of Gravity with Height (Torge, 1980, pp. 160-161) Gravity decreases with increase in height. We aim to compare g at a common elevation (say, at mean sea level. For this we need the "free air gradient" of g, to get the free air correction - cFA

... (2)

The "gravity anomaly" used in Physical Geodesy is the difference between the gravity on the geoid (g0) and

the normal gravity (γγγγ) at the equivalent point on the ellipsoidal model. Obviously gravity is not measured on

the geoid but at ground level, so g0 is approximated by finding the amount by which the gravity signal on the geoid has been weakened by moving the distance "H" above to geoid to the ground surface. The gravity on the geoid (g0) is approximated by

where g is the observed gravity, dg/dH the gradient of the gravity, and H the height above the geoid. Thus, the “gravity anomaly” we are trying to establish is approximated by the free air anomaly

... (3) where, to the first order (and, given the elevation limits in Qatar, this is sufficient

… (4)

The “free-air correction” CFA is 0.3086 H


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(iv) The Bouguer Correction This correction attempts to eliminate the attraction of matter between the observed point and the reference elevation (which is usually mean sea level, approximating the geoid). Assuming a thickness (height) 'H' and

density ρ the effect for an infinite slab of matter above the geoid is

... (5)

for H in m, ρ = 2.67 gm/cm3

CFA and CB can be combined to give a combined correction to account for both the height of the

observed point above the reference surface, and the attraction of matter between this reference surface and the observation point.

The simple Bouguer anomaly is therefore defined as

… (6)

(v) Topographic Correction - Ct

This applies a correction for departures of the terrain from the parallel-sided, infinite slab assumed in (iv). However, because of the very benign nature of the topography in Qatar, this correction is not relevant.

As mentioned above, the free-air anomaly is most important and useful to the geodesist as it better approximates the gravity signal at the geoid after the normal gravity has been removed, but assumes that matter is still present between the geoid and the surface (Torge, 1980, pp. 161-2). The Bouguer anomaly (simple or complete) can be useful in the interpolation of the gravity signal from discrete, sparsely observed points to furnish a more continuous field, as it is (at least theoretically) less dependent upon changes in topography than is the free air anomaly.

6.2.4.2 The Precision of ∆∆∆∆g

g is computed from the gravimeter display or dial readings and stored, with its position, height and other relevant data, in computer-readable form. This information will now be used to produce gravity maps. The geodesist will derive free air anomalies for geoid evaluations, and the geophysicist will compute Bouguer anomalies to 'interpret' the field and thus see if there are any geological features worthy of further investigation. (i) Impact of Errors in Measurement There are a number of possible sources of error in the free air anomaly - as one would expect from the measurement and reduction process. These include errors in: reading the gravimeter's dial (if not automatically recorded), establishing the height of the gravimeter, establishing the location of the gravimeter, and, of course, simple blunders in the observations or data processing.

Error in Height With GPS, it should be possible to establish an orthometric height to better than ± 1m, with the main component of error coming from the geoid height (assuming the N is computed from the global geopotential

model). This 1 m error introduces an error of about ± 0.3 mGal into ∆gFA. Pre-GPS the fastest way to

measure a point height value was barometrically; this may have had a precision of only ± 5 m. Such an error

would introduce an error of about ± 1.5 mGal into the point value of ∆gFA.


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Error in Position

An error in the latitude (φ) of 3" (≅100m) at a gravity station produces an error of 0.1 mGal in the normal

gravity γ. Obviously, the error in position is not critical, and φ can be established to sufficient precision by scaling from a medium scale map. If GPS is used, care must be taken to ensure that the positions derived are transformed into the geodetic datum used for the gravity data base. However, it is now common practice to transform all data bases into the geocentric WGS'84 datum, so that all data resides on a common global geodetic datum. This precision of the latitude from GPS eliminates any error.

Dial Reading Errors The calibration constant of a (Worden-type) gravimeter is typically 0.1 mGal per dial unit. An error of 1 dial unit will therefore produce an error of 0.1 mGal, which is small, compared with the error coming from the height. With the advent of automatic reading and recording of gravimeters, errors in reading the dial have been eliminated. Blunders By far the biggest problem with the data is a blunder, and it is sometimes the hardest to detect. The three sources of error listed above, if small and random, will not adversely affect the general representation of the gravity field, or map as significant errors into the resulting geoid height. However, blunders can introduce large errors into the geoid evaluation. The types of errors which can be classified as blunders include

gross errors in booking a measurement; quoting the height in the wrong units

gross errors in location (φ, λ or H).

6.2.4.3 Gravity Data Validation

To detect blunders before they are accepted into the data base and used in the computation of the geoid, the data must be validated. The main purpose of data validation is to produce a "clean" data base - that is one free from any gross errors or blunders. The most effective way to check for gross errors in the gravity data base is to map (contour) the gravity field. In theory the smoothest field is produced by the Bouguer anomaly (Section 6.2.4.1, Eq. 6). If the Bouguer anomaly field displays any unexpected features, such as spikes or sinks of data, the point(s) producing this feature must be identified, checked and, if necessary, deleted from the data base. The edited file is now replotted, and the new contour map again analyzed for departures from the expected smooth field. The process continues until you are satisfied that no gross errors remain in the data set. There are a few software packages that are capable of contouring from random data. Experience shows that SURFER, Vs. 4, is useful in the editing process (Pearse, 1995). The Bureau Gravimetrique Internationale (Toulouse) has a very powerful package that allows interactive editing, but requires much more computer power that does SURFER. Steps for Checking against Blunders (i) Reduce gravity to a 'smooth' field, for example - Bouguer anomalies (theoretically the smoothest field, so preferred) - Free air anomalies (correlated with height of gravity observation) - Residual anomalies (long/medium wavelength features from a global geopotential model removed

from the free air field) (ii) Contour plot the reduced anomaly field from (i) (iii) Identify 'unusual' features in (ii), e. g. abrupt changes in slope -> spikes & sinks (iv) 'Zoom in' on the area of this feature. This may require windowing the original data


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(v) Identify data producing the feature(s) and check observed gravity and height against (a) adjacent data (for gravity); (b) map (for height)

(vi) If data is suspect, remove it from the gravity data file. (vii) Repeat steps (i) to (vi) until all suspect points are eliminated.

6.2.4.4 Gravity Data Format The object of the gravity survey is to establish the gravity field in order to compute a gravimetric geoid for Qatar. There are various geoid computation packages available for this purpose, and they are based either upon a deterministic solution via Stokes’ integral using fast Fourier transforms or Ring Integration (Higgins et al., 1998), or a stochastic approach using least squares collocation. In either case the fundamental data required will be:

ID number, latitude, longitude, (usually in decimal degrees) gravity (in mGal) and height (m).

The format of each record is software dependent, and some approaches may also allow extra information (such as the precision of the gravity and height values). 6.3.0 Airborne Gravimetry Airborne gravimetry, that is measuring the Earth’s gravity field by placing a gravimeter on a moving platform at altitude, is a fast and efficient way to survey certain areas. This is especially so for areas with difficult access due to rugged terrain or lack of roads, or off-shore coastal zones where it is neither possible nor feasible to measure by terrestrial or marine methods. A specially modified gravimeter is placed on board an aircraft and the total gravitational accelerations are sensed by this meter. By tracking the motion of the aircraft with precise navigation the non-gravitational forces are modeled out of this signal, and the gravity recovered – to the order of ±1 to 3 mGal at a resolution of 6 to 8 km. (±1 to 2 mGal should be easily achieved in an area with benign terrain or in the offshore coastal zone, assuming the flights take place under good weather conditions. ±2 to 3 mGal would apply in mountainous areas and or if flying under non-optimal weather conditions). In the country of Qatar, Airborne Gravimetry has great potential for determining the gravity field both (i) in those land areas which have poor access, and (ii) in the off-shore coastal fringe where marine and satellite techniques are not feasible. As a first

approximation this coverage may extend to 50 km off-shore. The optimum approach will be to combine the on- and off-shore airborne campaigns into a single data set, and decrease the density of the terrestrial observations specified in Section 6.2.1.3, and use the terrestrial data to provide ground truth control for the on-shore airborne data. 6.3.1 Airborne Gravity Systems Aircraft: The aircraft is typically a single or twin engine craft with a cabin profile suited to geophysical surveys, i.e. one which enables the mounting of the equipment and has the capacity to supply the power to operate all the necessary instruments without interfering with the aircraft’s flight systems. It should also be equipped with an Autopilot and an altimeter. Single engine craft like Cessna Grand Caravan are widely used with good results for airborne gravimetry. It operates at a lower cost than twin engine aircraft. However, twin engine planes provide better safety, which could be crucial for flying over cold oceans, but this will not be a factor over the region of Qatar. Gravimeter: Typically the gravimeter is a marine gravimeter LaCoste & Romberg air/sea gravimeter; see http://www.scintrexltd.com/gravity.html, modified for airborne use (Forsberg (1999). The meter sensors are


239

mounted on pressurized vibration dampers and placed inside a floor-mounted aluminium box near the center of gravity of the aircraft. Today the Russian GT1-A gravimeter is also widely used; it has a 3-axis Schuler tuned platform and logs data at 18 Hz, (see http://www.canadianmicrogravity.com/).

Inertial Navigation System: Roll, pitch and heading can be determined by a strap down inertial sensor unit (INS), and the data digitized internally at up to 256 Hz, with records averaged measurements at 18 Hz. (NB. INS is not strictly needed in smaller aircraft where the horizontal offset between GPS antenna and gravimeter is modest). This time-tagged data is then logged.

GPS: The GPS antenna for determining the aircraft and gravimeter’s position and velocity is located on top of fuselage, preferable close to the gravimeter.

The all-important Data Logger is normally a reliable laptop with large capacity, suitably connected to the various sensors. The GPS and INS signals are recorded at a similar frequency, with all signals synchronized by GPS time.

Ground Support GPS Base Stations: There should be at least one GPS reference receiver operating at or near the airport. Redundancy is recommended; for example, for baselines longer than a few hundred kilometers it is advisable to operate additional base stations in or near the survey area. 6.3.2 Field Techniques Airfield: A gravity base station is established at the airfield, on the tarmac directly below the gravimeter’s position in the aircraft where the aircraft is normally parked. Gravity at the airborne sensor is then established by upward continuation from the base station, so the height difference between the base station and the airborne sensor must be determined; a precision of about 0.3 m (0.1 mGal) is sufficient. Airborne gravity observations are based upon the ground gravity by measuring the “airborne” meter while the aircraft is parked near the base station. Importantly, this is done both before and after the flight. Aircraft: The plane is flown at either a constant flying height of about 1000 feet or more above ground at a speed of around 120 to 130 knots, or as a very gentle draped flight (depending upon the ground topography) in order to minimize motion induced accelerations. In deciding the optimal altitude it is important to realize that the gravity variations, as mapped by airborne gravity, changes very little with altitude due to the heavy low-pass filtering applied to the final data. It is therefore often preferable to choose an altitude higher than 1000 ft in order to avoid turbulence. By this means the gravimeter senses basically the same signal but less noise. The gravimeter meter is recorded on the data logger at 1 Hz. 6.3.3 Office Techniques

6.3.3.1 Processing the GPS Data The GPS data is processed via the proprietary software relevant to the receivers and the GPS techniques used. The data are validated using a few objective criteria, for example: 1) Number of satellites above 10 degrees elevation: should be 6 or more, and 2) The PDOP or Percent Dilution of Position – a measure of the geometrical strength of the GPS satellite

configuration should be below 4, while 4 to 8 should give acceptable accuracy. A PDOP greater than 8 gives poor accuracy, and this data output should be used with caution.


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6.3.3.2 Processing the Airborne Gravity Data Filtering: A standard filter is applied to the raw data. One such filter comprises a six-fold cascaded second order Butterworth filter implemented sequential in the time domain, and is applied both forward and backward to avoid phase lag. The half-transmission point is 0.005 Hz which corresponds to a spatial resolution of around 6 km, for a ground speed of 120 knots or 60 m/s for the aircraft. For greater speeds and altitudes the resolution is adjusted as required. Validation: As for the terrestrial gravity, the quickest means of validation is to draw up a contour plot of the free air anomalies derived from the airborne solution, and this is inspected for unusual features. The values at the cross over points enable at least two independent checks of gravity at these locations. Where marine or terrestrial gravity exists it is possible to compare this data, upward continued, with the airborne values at the same locations, although this often shows up problems with the so-called “control” data than gives any real indication of errors in the airborne solution. When validated the flight level gravity is downward continued to the geoid, and merged with the terrestrially observed data to form the full gravity data set for the region. This is now ready for processing through geoid computation software. 6.3.4 Final Comments Airborne gravimetry is a highly technical and sophisticated technique, and it strongly advised for this survey to engage the services of an operator experienced in this field, preferably one which has also had experience in geoid evaluation, and thus has a good appreciation of its unique requirements.


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References Chamberlain, Charles A. (1996), GPS Basics & Status of GPS in Qatar, www.gisqatar.org.qa/conf97/links/b1.html; also see Chamberlain, Charles A. QND 1995 Final Report, April 1996 Dobrin, Milton B., 1976, Introduction to Geophysical Prospecting, (2nd Ed.), Mc-Graw-Hill, New York Forsberg, René and Schmidt, K., 2002, Geoid and Height Datum for the Qatar-Bahrain Causeway Project, Report prepared for COWI, 2

nd revision.

Forsberg, René, Olesen, A. and Keller, K., 1999, Airborne Gravity Survey of the North Greenland Shelf 1998, Technical Report # 10, Kort and Matrikelstyrelesen, Copenhagen. GT1-A airborne gravimeter, http://www.canadianmicrogravity.com/ Heiskanen, W. and Moritz, H., (1967) Physical Geodesy, W.H. Freeman and Co., San Francisco. Higgins, M. B., Forsberg, R., and Kearsley, A. H. W., (1998), The effect of varying cap sizes on geoid computations - experiences with FFT’s and ring integration, in “Geodesy on the move”, (IAG Symposia, Vol. 119), ed Forsberg, R., Feissel, M, and Dietrich, R., Springer, Hannover Kearsley, A.H.W., (1986) Data requirements for determining precise relative geoid heights from gravimetry, Journal of Geophysical Research, Vol. 91, No. B9, pp 9193-9201. Kearsley, A.H.W., (1988b) Tests on the recovery of precise geoid height differences from gravimetry, Journal of Geophysical Research, Vol. 93, No. B6, June 10, pp 6559-6570. Kearsley

, A. H. W., Forsberg,

Rene, Olesen, Arne, Bastos, L., Hehl, K., Meyer, U., Gidskehaug, A., 1998,

Airborne gravimetry used in precise geoid computations by ring integration, j Geod., Vol. 72, No. 10, Oct., 1998, pp. 600 – 605.

LaCoste and Romberg land gravimeter (http://www.microglacoste.com/relativemeters.htm) LaCoste and Romberg modified marine Gravimeter http://www.scintrexltd.com/gravity.html Lemoine, F. G., S. C. Kenyon, J. K. Factor, R. G. Trimmer, N. K. Pavlis, D. S. Chinn, C. M. Cox, S. M. Klosko, S. B. Luthcke, M. H. Torrence, Y. M. Wang, R. G. Williamson, E. C. Pavlis, R. H. Rapp, and T. R. Olson, The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM96, National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland 20771, 1998. Morelli, C., Gantar, C., Honkaslo, T., McConnel, R.K., Tanner, T.G., Szabo B., Uotila, U., and Whalen, C.T. (1971) The International Gravity Standardisation Network (IGSN71), International Association of Geodesy, publication speciale no.4 du Bulletin Geodesique. National Geospatial Intelligence Agency – http://earth-info.nga.mil/GandG/ or http://164.214.2.59/GandG/ Nettleton, L. L., 1940, Geophysical Prospecting for Oil”, 1940, McGraw Hill, New York Nettleton, L. L., 1976, Gravity and Magnetics in Oil Prospecting”, 1976, McGraw Hill, New York Rapp, R.H., Wang, Y.M. and Pavlis, N.K. (1991) The Ohio State 1991 geopotential and sea surface topography harmonic coefficient models, Report No. 410, Department of Geodetic Science and Surveying, Ohio State University, Columbus, Ohio, USA. Scintrex (http://www.scintrexltd.com/gravity.html) Torge, W., (1980) Geodesy, Walter de Gruyter & Co., Berlin.


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Torge, W., (1989) Gravimetry, Walter de Gruyter & Co., Berlin. Vanicek, P. and Krakiwsky, E., (1986) Geodesy, The Concepts. 2nd ed., Elsevier Science Publishers.

Qatar Survey Manual – Chapter 7 – Digital Mapping

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Abbreviations

3D 3 Dimension

ABGPS Airborne Global Positioning System

ASPRS American Society for Photogrammetry and Remote Sensing

CGIS The Centre for Geographic Information System

DEM Digital Elevation Model

DPW Digital Photogrammetric Workstation

DTM Digital Terrain Model

DVD Digital Versatile Disc" or "Digital Video Disc

DXF AutoCAD Drawing Exchange Format

GCP Ground Control Point

GeoTIFF Georeferenced TIFF


GSD Ground Sampling Distance

HCP Horizontal Control Point

IMU Inertial Measurement Unit

LoD Level of Details

MSL Mean Sea Level



RMSE Root Mean Square Error

RPC Rational Polynomial Coefficient

TIFF Tagged Imaged File Format

VCP Vertical Control Point

WGS World Geodetic System


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7.1.0 Digital Mapping General Specifications 7.1.1 General These specifications supersede all previous documentation pertaining to Aerial Photography, Aerial Triangulation, Digital Image Mapping, Satellite Image Mapping, Digital Vector Mapping, Digital Elevation Model & 3D Model, to be used in support of the production of Digital Orthoimagery, Vector, DEM, 3D City Model or Photogrammetrically compiled products of National Mapping Project for the CGIS. The CGIS shall be the final authority on the acceptance or rejection of photographic imagery acquired under these specifications. 7.1.2 Mapping Accuracy Standards The Mapping Accuracy Standards adopted is based on the ASPRS Accuracy Standards for Large-Scale Maps. Table 7.1 below shows some typical reference scale and its related accuracy and resolution:

Table 7.1

Reference Scale

Contour Interval

Elevation Acc. RMSE-Z

Positional acc. RMSE X-Y

Pixel Size

1:1000 0.5m 0.17m 0.25m 10~20cm

1:2000 1m 0.33m 0.5m 20~40cm

1:5000 2m 0.67m 1.0m 50cm~1m

1:10000 5m 1.7m 2.5m 1~2m

1:20000 10m 3.3m 5.0m 2.5~5m The positional accuracy is based on ASPRS Accuracy Standard for Large Scale Mapping. The contour interval is based on normal values widely adopted. RMS elevation is 1/3 contour interval as defined in ASPRS accuracy standard. Pixel size is computed based on 100 dots/cm (254 dots/in) to 50 dots/cm (127 dots/in).

In the above Table 7.1, one may find a discrepancy in that elevation accuracy is less than positional accuracy. This is due to the normal choice of the contour in the industry. CGIS may elect to lower the elevation accuracy to match the positional accuracy, in which case, the contour interval should also be relaxed; e.g. 0.75m for 1:1000 mapping. The best available specifications should be followed at the time of execution and production of any scale of aerial photography and mapping; unless and otherwise discussed and approved by the CGIS, if needed. Compilation will be specified under one of the following classifications. Unless otherwise specified, the nominal photo GSD will be employed.

Table 7.2

Project Classification

Nominal Photo Ground

Sampling Dist (GSD)

Estimated Flying Height

Digital Map GSD

Reference Map Scale

Urban Mapping 10 cm or smaller 1,000m 10 cm 1:1,000

Whole Country Mapping

50 cm or smaller 5,000m 0.5m 1:10,000

The CGIS may elect to modify these specifications to suit circumstances specific to individual projects.


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7.1.3 Projection, Datum, Coordinate System The mapping shall be cast on the Qatar National Grid (QNG), which is a Transverse Mercator Projection with the following parameters:

Table 7.3

Central Meridian 51° 13’ 00” E

Scale Factor at the Central Meridian 0.99999

Location of the Origin 51° 13’ 00” E 24° 27’ 00” N

False Easting of the Origin 200,000m

False Northing of the Origin 300,000m

Reference Spheroid International 1924 (Hayford)

Coordinates are metric. The vertical datum is the Qatar National Datum (QND) which is defined by mean sea level at Doha as measured during the period 1970-1972. This datum is referenced to two fundamental benchmarks at Doha Port and at Doha International Airport. 7.1.4 Project Extent For vector mapping, the whole county or city shall be managed as one seamless continuous map. For raster mapping (e.g. orthophotomap), the project area will be defined by tiles, also referred to as map “sheets”. Tiles are rectangular, with dimensions identified by the following Table 7.4:

Table 7.4

Project Classification East – West Dimension North - South

Dimension

Large Scale 1,000m 500m

Small Scale 10,000m 5,000m

A specific tile is uniquely identifiable by using the east-west dimension of the tile, in combination with the tile’s south west corner QNG coordinate. For large scale mapping, the east-west dimension (in meters) is divided by 1,000 and is expressed as 3 digit character string (padded by zeros on the left). The easting and northing of the south west corner are both expressed in hundreds of meters (i.e. the first 4 digits of the easting, followed by the first 4 digits of the northing).

Figure 7.1

Example of large scale map:

Tile Nomenclature 00122503985 500m

1000m

SW Tile Corner Coordinates 225000mE 398500mN


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Figure 7.2 If file size is too large for the file format or disk, the image data for the tile may be sub-divided into eight as shown below:

N1

N2

N3

N4

S1

S2

S3

S4

Figure 7.3

Each of the sub-tiles carries the tile name plus the additional sub-tile designation as shown in the diagram – N1, N2, S1, S2, etc. For the image data delivery, the tile name forms a directory, and the sub-tile designation forms the filename. E.g. For bottom first 250m by 250m subtitle, the identifier shall be 01023003900S1.

Example of small scale map:


10000m


01023003900


10000m


01023003900


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7.2.0 Manual and Specifications for Aerial Photography with Large Format Digital Camera 7.2.1 Background In recent years, there have been major changes to mapping technologies. Softcopy digital photogrammetric workstation (DPW) has totally replaced analog and analytical photogrammetric stereoplotters. In the data acquisition front end, digital cameras are fast emerging to replace analog film cameras. In this document, the emphasis will be on digital aerial photography.

7.2.1.1 Choice of Reference Scale The first consideration when planning for aerial photography is the final map reference scale. Although in digital mapping, the data can be displayed at varying scales, one should still use a reference scale determines the accuracy and resolution of the data. Refer to Section 7.1.2. 7.2.1.2 Choice of Flying Height

There flying height typically depends on two considerations. One is the contour interval which depends on reference scale, and the other is accuracy of aerial triangulation control required. The capability of stereo measurement limits the flying height through a widely acceptable value called the C-factor

For softcopy photogrammetric workstation with wide angle camera, C-factor is about 2000. Thus for 1:1000 reference scale (where contour interval is 0.5m), the flying height from C-factor consideration is 1,000m.

The accuracy of aerotriangulation controls achievable is widely estimated from the following:

Thus if rmse accuracy required is 15cm, the flying height from aerotriangulation requirement is 1,500m.

The choice of flying height is the lower of the two considerations. In the above example, it will be 1,000m. The photograph scale at 1,000m flying height is about 1:6,500. Lower flying height and larger photograph scale can be used. 7.2.1.3 Planning for Digital Aerial Camera Digital aerial camera is slowly replacing traditional analog film based camera. Table 7.5 shows the three most popular digital aerial cameras:

Table 7.5

Camera Acquisition Technique

Pixels Pixel size Focal Length

Leica ADS40 Push Broom line

scanner 12,000 (line) 6.5µm 62mm

Z/I DMC 2D Frame 8,000 x 14,000 12µm 120mm

Vexcel Ultracam 2D Frame 7,500 x 11,500 9µm 100mm


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Because of the small size of sensor, the concept of photograph (or sensor) scale is rather confusing. A new concept of GSD (ground sampling distance) has been proposed. For example, in conventional wide angle photography, using the same example figures as above (i.e. flying height = 1000m),

It may be convenient to introduce another term called scale-number such that:

Thus

If the photo is scanned with pixel size of 15 µm, the GSD of the scanned photograph is

For digital camera, the GSD for flying height of 1000m is:

It can be seen from above example, the GSD for digital camera has been designed to be almost equivalent to aerial photography scanned at 15 µm. Research has also shown that digital camera (because it reduces errors from analog to digital conversion) is about 1.5 to 2x as accurate in x-y accuracy compared to analog photography. However, as it b/h ratio is normally lower, its height accuracy is about the same as that for analog photography, for the same flying height. Thus, for planning purposes, the same C-factor (2000) and aerial triangulation factor (10,000) as that for analog camera, may be used. 7.2.2 Specifications With the above theoretical background, the following specifications were developed.


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7.2.2.1 General These specifications supersede all previous documentation pertaining to aerial photography to be used in support of the production of digital orthoimagery, or photogrammetrically compiled products for the Centre for GIS, State of Qatar. The Centre for GIS, State of Qatar (CGIS) shall be the final authority on the acceptance or rejection of photographic imagery acquired under these specifications.

These specifications detail the production of any scale of aerial photography. Compilation will be specified as being under one of the following classifications. Refer to Table 7.2.

7.2.2.2 Flight Specifications 7.2.2.2.1 General Aircraft used in the acquisition of aerial photography shall be maintained and operated in accordance with all regulations and instructions issued by the Department of Civil Aviation, State of Qatar. The air-crew shall have current licenses and medical certificates as required by their country of origin, to operate an aircraft engaged in aerial survey operations. These licenses and certificates shall be subject to the approval of the Department of Civil Aviation, State of Qatar. The aircraft and crew shall carry all applicable permits to perform aerial surveys in the State of Qatar. Appropriate clearances for each aerial photography mission must also be obtained in writing. The aircraft shall carry a current Certificate of Airworthiness issued by the relevant authority in the country of registration. The Certificate of Airworthiness shall include modifications made to the aircraft to accommodate the aerial camera and related ancillary systems. The aircraft shall be specifically modified and equipped to perform aerial photography. The camera lens system shall not be in the path of any exhaust gases or effluents from the engines. No glass camera port shall be interposed between the camera lens system and the terrain unless it is properly designed and calibrated as set out herein. The flight crew and camera operator shall have a minimum of 500 hours experience in the performance of precise aerial photography missions. 7.2.2.2.2 Flight Logs For each flight the air-crew shall prepare a flight log documenting all aspects of the flight germane to the aerial photography. The flight log shall contain the date, project name, the aircraft registration and air-crew names. For each flight line the following information shall be recorded: camera, magazine and lens serial numbers, altitude, nominal scale, aperture setting, shutter speed, compass heading, beginning and ending exposure numbers and times. Comments relative to weather conditions, equipment performance, unusual events etc. shall likewise be recorded. 7.2.2.2.3 Weather Aerial photography shall be exposed only under clear weather conditions that allow the acquisition of well-defined images. Photography shall be free of the effects of haze, smoke, dust and blowing sand. Cloud or cloud shadow shall not exceed 5 per-cent of the area of any one photograph without the written consent of the CGIS. Photography shall be exposed during times when the sun angle above the horizon is 30 degrees or greater.


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Photographic operations shall be limited to the period of time set out in the contract unless otherwise authorized by the CGIS and all other authorities governing the operation of the aircraft. 7.2.2.2.4 Coverage 7.2.2.2.4.1 Flight Lines The CGIS shall provide the aerial photography consultant with maps delineating the minimum areas to be photographed, as well as any existing data pertaining to relief within this area (such as a Digital Elevation Model). The consultant shall design the flight lines to obtain the designated sidelap and to assure full stereoscopic coverage. Each flight line shall begin and end outside the minimum area to be photographed such that a minimum of two principal points fall outside the area. The consultant shall submit a flight line plan, covering the entire area to be photographed and drawn to scale, for approval by the CGIS. No photography shall be flown in advance of the approval of the flight line plan. The flight line plan shall be drawn to scale, shall include major topographic and planimetric features in the area, and shall be referenced to the Qatar National Grid. The plan shall be at a scale such that the flight lines are depicted a minimum of 2 cm apart. Flight lines running parallel to the shoreline may be repositioned to increase the pro-portion of land in each frame. Flight lines running parallel to the mapping area boundary shall extend over the boundary by a minimum of 15 percent of the strip width. Where a flight line joins the end of another line there shall be an overlap of three principal points of acceptable photography on each of the two strips. Appropriate number, minimum 2 (two), of cross flights shall be introduced to provide additional strength and accuracy to the block.

Figure 7.4


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7.2.2.2.4.2 Flying Height A photographic mission may be comprised of any number of flying heights above datum, depending on the degree of relief, and permitted tolerance to scale variation of any terrain point throughout an individual exposure. Any terrain point within an individual exposure must be within 10 percent of the nominal ground sampling distance (GSD). For example, in a large-scale project the default nominal photo GSD is 10cm. The scale of any terrain point within any exposure must be at an actual scale ranging from 9 cm to 11 cm. Once a flying height above datum is selected, that height shall be maintained to within 10%. The following table identifies the Default Flying Height Above Terrain Median, and the Maximum Allowable Terrain Deviation for each of the project classifications. Refer to Table 7.2. The flying height is to be established above a median elevation. This median elevation is half way between the highest and lowest point for any contiguous region within the project area where the photography will be flown at the same altitude (flying height above datum). If the terrain deviation exceeds the allowable terrain deviation, then the project would have to be flown using two altitudes. In order to optimize cost, the total number of flight lines should be minimized. This is normally achieved by orientating the flight lines parallel to the larger dimension of the mapping area. 7.2.2.2.4.3 Overlap Unless otherwise specified, the forward overlap shall be 60 percent ±2 percent (i.e. 58 to 62 percent overlap). This requirement is not applicable to ADS 40 type camera which utilizes line scanning ‘push broom’ imaging technique. Unless otherwise specified, the side overlap (or sidelap) shall be 30 percent ±3 percent (i.e. 27 to 33 percent side overlap). The CGIS may elect to modify the photo configuration to suit specific circumstances. In urban areas for example, the CGIS may specify that flight lines coincide with specific features (e.g. street canyons). Similarly, different line spacing and side lap may be specified in some circumstances. Where a flight line crosses a shoreline, the forward overlap shall be increased to a nominal 90 percent, subject to the constraints imposed by the camera cycle time. The increase in overlap shall extend at least three principal points inland. 7.2.2.3 Camera The photography shall be exposed using a fully calibrated large format precision digital camera with high-resolution, low-distortion lens. The number of pixels across the flight direction should be at least 11,500. The number of pixels along the flight direction (not application to Push Broom imaging system) should be at least 7,500. The camera must carry a certificate detailing calibration by an approved agency that has been carried out within three years of the date of photography. The camera together with relevant pre-processing software, shall be capable of producing the digital photography with distortion of less than 1 pixel. 7.2.2.4 ABGPS and IMU The camera system should incorporate Airborne GPS (ABGPS) and Inertial Measurement Unit (IMU) technology which will significantly reduces the ground control points required for aerotriangulation. ABGPS work with one or more ground reference GPS base station, to provide precise location of the photo centre locations (X, Y and Z). The aircraft/camera should typically be within 30km of the ground GPS base station. The IMU utilize inertial technology to provide the roll, pitch and yaw (ω, φ and κ) of the camera system.


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Figure 7.5

7.2.2.5 Data Characteristics The camera should provide 4 bands multispectral images in the spectral bands of blue (about 450nm), green (about 550nm), red (about 750nm) and near infrared (about 850nm) Each pixel should provide at least 12 bits radiometric resolution (4096 grey levels) for all bands. The band to band registration shall be within 1/4 pixel. The camera may use its proprietary or any image file format to store the image data during acquisition and pre-processing. However, software tools must be provided to convert the image file to 16 bit TIFF (Tagged Imaged File Format) files together with relevant image support information that provides the following information:

- location and orientation of the camera centre, - the date and time of exposure of the photograph. - Focal length, aperture, shutter speed and (optional) equivalent ISO

Suitable naming convention should be proposed for identification of the photograph and image support information. The photograph (data) shall be delivered in removable harddisks which is accessible by Microsoft Windows operating system. Two sets of data shall be delivered. 7.2.2.6 Documentation Variations to the documentations and reports are subjected to the approval of CGIS. a) Camera Calibration Report b) Flight Logs c) Data Report

• A report shall be included with set of data • Project designation • Camera type and serial number, lens type and serial number, calibrated focal length


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• Range of Aperture, shutter speed and (optionally) equivalent ISO. • Date of exposure • Flight line number

o Beginning and ending file number for each flight line o Beginning and ending times for each flight line o Compass heading for each flight line

• Nominal Ground Sampling Distance (GSD) • Altitude • Consultant’s identification • Aircraft type and registration • Crew names • Comments - weather, events, equipment performance etc. • Date of pre-processing • Pre-processing software (for photograph/image and ABGPS and IMU data) • Technician’s name

d) Photograph Annotation (Support File) The following information shall be provided in an ASCII format support file:

• Project Designation o Sub area (if applicable)

• Nominal GSD • Date of exposure • Camera type • Calibrated focal length • Exposure, shutter speed and (optionally) equivalent ISO • Spectral range • Photograph compass heading • Sun azimuth and elevation angle

e) Photo Index Maps An index shall be prepared which depicts all of the flight lines. The photo index shall be drawn to scale and

provided in softcopy. The file shall be formatted for use within either an AutoCAD®

or ARCGIS/ARCSDE®

environment. A hardcopy index map (if requested) shall be printed at a scale such that the flight lines are depicted a minimum of 2 cms apart. The flight line maps shall show every photo centre. Each flight line and photo centre shall be labeled accordingly. Other information to be shown on the index shall include: title block, north arrow, scale bar and sheet index. The Title block shall contain the project designation, sub area (if applicable), consultant’s designation, date of photography, scale, and the calibrated focal length. A digital file of the flight index shall also be supplied. The file shall be formatted for use within either an

AutoCAD®

or ARCGIS/ARCSDE®

environment.


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7.2.2.7. Deliverables The following materials shall be delivered for each project:

Table 7.6

Camera Calibration Report One report shall be provided for each camera utilized on the project.

Flight Logs The original flight log for each flight shall be supplied.

Data Reports A separate data report shall be delivered for each harddisk.

Photograph annotation (Support file) To accompany each digital photograph on the same harddisk and directory.

Photo Index Maps Reproducible photo index maps and associated digital files depicting all flight lines shall be delivered.

The CGIS may elect to order additional sets of data in harddisk or hardcopy prints from the aerial photography consultant.


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7.3.0 Specifications for Ground Control for Photogrammetric Mapping 7.3.1 General This document covers ground control requirements for photogrammetric mapping projects. The fundamental requirements for control network configuration, point location, and characteristics are discussed in this document. However, the overview presented is not intended to be used for field survey design. The photogrammetric engineer should refer to appropriate survey standards and specifications for guidance in designing the project control surveys. Current standards should be employed and outdated standards and practices should be revised from time to time. 7.3.1.1 Projection, Datum, Coordinate System Refer to Section 7.1.3. 7.3.2 Ground Control Requirements Field surveying for photogrammetric control is generally a two-step process. The first step consists of establishing a network of basic control in the project area. This basic control consists of horizontal control monuments and benchmarks of vertical control that will serve as a reference framework for subsequent surveys. The second step involves establishing photo control by means of surveys originating from the basic control network. Photo control points are the actual points appearing in the photos (photo identifiable points that are used to control photogrammetric operations. The accuracy of basic control surveys is generally of higher order than subsequent photo control surveys. GPS technology is now an integral part of almost any field survey project. It is also the most cost effective method for photogrammetric control surveys. 7.3.2.1 Basic Control

A basic control survey provides a fundamental framework of control for all project-related surveys, such as property surveys, photo control surveys, location and design surveys, and construction layout. The accuracy, location, and density of the basic control must be designed to satisfy all the project tasks that will be referenced to the control. GPS technology appears to provide reference points with more consistent and more accurate locations than those established by more conventional methods. GPS survey should be tied to the Qatar National Datum. Horizontal basic control points should be angle points in traverses or vertices of network triangles. Vertical basic control points should be turning points in level routes. Vertical control obtained by GPS should be checked by conventional level loops for selected points to check accuracy of the geoid model in the project area. Conventional survey side shots or open traverses should not be used to locate basic control. Second or Third-Order plane surveys will generally be of sufficient accuracy to establish basic control for most photogrammetric mapping projects. In planning the basic control survey, maximum advantage should be taken of existing control established in the area by the CGIS. Care should be exercised before using any existing control points to verify that they are adequately interconnected or are adequately connected to the national Geodetic network in Qatar National Datum 7.3.2.2 Photo Control

Photo control points are photo identifiable or panel points that can be measured on the photograph and stereomodel. Photo control points are connected to the basic control framework by short spur traverses, intersections, and short level loops. Lengthy side shots and open traverses should be avoided.


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Photo control surveys are local surveys of limited extent. Photo control points are surveyed to the accuracy required to control the photogrammetric solution. The accuracy requirement for photo control points should generally be an order better (at least 5 times) than the accuracies of the control points computed by aerial triangulation.

7.3.2.2.1 Characteristics.

Photo control points should be designed by considering the following characteristics: location of the control point on the photograph; positive identification of the image point; and measurement characteristics of the image point. GPS derived photo control points require special consideration. The locations of GPS points must be in a location that will allow for the required GPS horizon parameters to be met.

(a) Location. Of the characteristics listed above, location is always the overriding factor. Photo control points must be in the proper geometric location to accurately reference the photogrammetric solution to the ground coordinate system. Horizontal photo control points should define a long line across the photographic coverage. The horizontal control accurately fixes the scale and azimuth of the solution. Vertical photo control should define a geometrically strong horizontal triangle spanning the photographic coverage. The vertical control accurately fixes the elevation datum of the solution. The location should be established in accordance with current photogrammetric practice considering the project area and the map accuracy requirements.

(b) Identification. The identification of the photo control points on the aerial photographs is critical. Extreme care should be exercised to make this identification accurate. The surveyor should examine the photo control point in the field with the aerial photographs. Once a photo control point is identified, its position on the photograph should be recorded and a brief description and sketch and/or cutout of aerial photo, of each point should be made. Each photo control point should be given a unique name or number. (c) Measurement. Subject to the constraints imposed by location considerations, photo control points should be designed to provide accurate pointing characteristics during photogrammetric measurements. Furthermore, control points should not be located at the edge of the image format. Photo control points falling in the outside 10 to 15 percent of the image format should be rejected. 7.3.2.2.2 Horizontal Photo Control Images for horizontal control have slightly different requirements from images for vertical control. Because their horizontal positions on the photographs must be precisely measured, images of horizontal control points must be very sharp and well-defined horizontally.

7.3.2.2.3 Vertical Photo Control

Images for vertical control need not be so sharp and well-defined horizontally. Points selected should, however, be well-defined vertically. Good vertical control points should have characteristics that make it easy for the operator to accurately put the floating mark at the correct elevation. Vertical control points are best located in small, flat, or slightly crowned areas with some natural features nearby that assist with stereoscopic depth perception. 7.3.2.2.4 GPS for Horizontal and Vertical Control GPS survey is now popular method for surveying both horizontal and vertical control since it provides precise spatial (X, Y and Z) coordinates.

7.3.2.3 Control Point Distribution If the project is small, requiring just a few models, the control can be established on the ground by conventional field or GPS surveys. The absolute geometric minimum amount of photo control needed in each stereomodel is four points.


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For larger projects requiring aerial triangulation, the distribution of ground control is discussed in the document for Aerial Triangulation. If airborne GPS procedures are integrated into the photographic flight the amount of primary ground control points required may be further reduced. Its distribution is also discussed in the document for Aerial Triangulation.

7.3.3 Marking Photo Control Photo identifiable control points can be established by marking points with targets before the flight or by selecting identifiable image points after the flight. 7.3.3.1 Premarking Premarking photo control points is recommended. Marking control points with targets before the flight is the most reliable and accurate way to establish photo control points. Survey points in the basic control network can also be targeted to make them photo identifiable. When the terrain is relatively featureless, targeting will always produce a well-defined image in the proper location. However, premarking is also a significant expense in the project because target materials must be purchased, and targets must be placed in the field and maintained until flying is completed. The target itself should be designed to produce the best possible photo control image point. The main elements in target design are good color contrast, a symmetrical target that can be centered over the control point, and a target size that yields a satisfactory image on the resulting photographs. (a) Location. Target location should be designed according to the ground control distribution for aerial triangulation. However it is difficult to ensure that the target will fall in the planned location in the photograph when the photography is flown. Care should be taken that targets are not located too near the edge of the strip coverage so that the target does not fall outside of the model. (b) Shape. Targets should be symmetrical in design to aid the operator in pointing on the control point. Typical shapes that may be used are “+”, “T” or “Y” shape. (c) Size. Target sizes should be designed on the basis of intended photo scale so that the target images are the optimum size for pointing on the photos. Target size is related to the size of the measuring mark in the stereoplotter instruments used. An image size of about 0.050 mm square (or 2 pixels) for the central panel is a typical design value. Each leg can have width same as the central panel, i.e. 0.050 mm or 2 pixels, and length 5 times the width.


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Figure 7.6 7.3.3.2 Postmarking

The postmarking method consists of examining the photography after it is flown and choosing natural image features that most closely meet the characteristics for horizontal or vertical photo control points. The selected features are then located in the field and surveyed from the basic control monuments. One advantage of postmarking photo control points is that the control point can be chosen in the optimum location (the corners of neat models and in the triple overlap area). The principal disadvantage of postmarking is that the natural feature is not as well defined as a targeted survey monument either in the field or on the image. Typical feature that may be used for postmarking photo control points include:

i. Traffic lines ii. Sidewalk intersection (must be perpendicular) iii. Tennis Court, Basketball Court, Football field lines intersection

T

5T 5T

5T

5T

T

T

“+” configuration

“T” configuration “Y” configuration


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Figure 7.7

Figure 7.8

Figure 7.8

Tennis Court Lines

Traffic Lines


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7.3.3.3 Airborne Global Positioning System (ABGPS) and Inertial Measurement Unit (IMU) Control.

ABGPS and IMU technologies are now recommended for photo control. This procedure involves establishing the horizontal and vertical location, and attitude of the principal point of every photo at the instant of exposure. If all conditions are ideal for ABGPS and IMU (i.e., satellite configuration and signal, geoid model consistency), then no additional ground control would be required. In practice, this is not an acceptable risk considering the cost of deploying equipment and personnel to revisit the project site if problems surface after the flight. Therefore, minimal ground control should be planned. Flights plan may also incorporate a few cross flights to increase strength and accuracy to the block.

7.3.4 Deliverables

Unless otherwise modified by the contract specifications, the following materials will be delivered to the CGIS upon completion of the control surveys: a. General report describing the project and survey procedures used including description of the project

area, location, and existing control found; description of the basic and photo control survey network geometry; description of the survey instruments and field methods used; description of the survey adjustment method and results such as closures and precision of adjusted positions; justification for any survey points omitted from the final adjusted network and any problems incurred and how they were resolved.

b. Details of each control points, showing X, Y and Z coordinates and sketch or cutout photograph with

control point clearly marked. Date and time, surveyor name, organization, as well as comments if any. c. A list of the adjusted coordinates of all horizontal and vertical basic and photo control points.


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Annex 7A

Ground Control Point Diagram For Aerial and Satellite Imagery

Project Name: GCP Number: Date:

(Sketch or Cut-out Aerial Photograph/Satellite Image)

GPS Antenna Height:

Comments: ______________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

Longitude: _______________ Latitude: _______________ Height: _______________

Easting: _______________ Northing: _______________ Height: _______________

Disk / Framber Number Sketch __ of ___

Collected by: Checked by:


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7.4.0 Specifications for Aerial Triangulation 7.4.1 General These specifications supersede all previous documentation pertaining to the application of aerial triangulation to aerial photography for the Centre for GIS, State of Qatar. The Centre for GIS, State of Qatar (CGIS) shall be the final authority on the acceptance or rejection of aerial triangulation products, produced under these specifications. These specifications pertain to the aerial triangulation of standard, wide-angle aerial digital or analog photography exposed with average of 60 percent forward overlap and 30 percent side overlap. The specifications apply to both strips and blocks of photography. The specifications apply to fully analytical methods based on softcopy digital photogrammetric workstation (DPW). Airborne GPS control (AGPS) and inertial measuring unit (IMU) are relatively new technologies though are now operationally available. These specifications will cover both aerial triangulation with and without ABGPS and IMU.

7.4.2 Aerial Triangulation 7.4.2.1 Definition Aerial triangulation is the process of densifying and extending ground control through computational means. The process “bridges” or carries ground control to contiguous stereo models, which falls between models, which contain ground control. Aerial triangulation is the simultaneous space resection and space intersection of image rays recorded by an aerial mapping camera. Conjugate image rays projected from two or more overlapping photographs intersect at common points on the ground to define the three dimensional coordinates of each point. The entire assemblage of image rays is fit to known ground control points in a least-squares adjustment process. When complete, ground coordinates of previously unknown points are determined by the intersection of adjusted rays. Besides the ground coordinates, the location of the camera centre (principal centre) as well as the orientation of the camera will also be determined. The ground coordinates of fixed photogrammetric points on each stereo model are utilized to scale and level the model during the process of absolute orientation. In DPW, the computed camera location and orientation can also be utilized in absolute orientation. Aerial triangulation is essentially an interpolation tool, capable of extending control points to areas between ground survey control points using several contiguous uncontrolled stereomodels. An aerial triangulation solution should never be extended or cantilevered beyond the ground control. Ground control should be located at the ends of single strips and along the perimeter of block configurations. Within a strip or block, ground control is added at intervals of several stereomodels to limit error propagation in the adjusted pass point coordinates. The principal inputs to the aerial triangulation process are:

1. Aerial Photography; 2. Camera Calibration Data; 3. Ground Control Point Coordinates.

7.4.2.2 Quality Each of the above inputs will have a profound effect on the quality of the aerial triangulation adjustment. For example, the accuracy (for a given photo scale) is influenced by the following factors:

• Quality of the original photograph/image (exposure, aircraft movement, image blur, handling)


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• Quality of scanning to convert negative/diapositive into digital file • Quality of the camera (the interior orientation of the camera) • Quality and density of ground control • Configuration of the ground control • Shape of the block • Quality of the point marking, transfer and mensuration • Block adjustment procedures and algorithms • Adjustments for earth curvature, atmospheric refraction and map projection • Analysis of adjustment results and the application of weights to photogrammetric control points

The CGIS philosophy is based upon achieving excellent quality and consistency in all products. Accordingly, the aerial triangulation shall be produced in strict accordance with these specifications. Where the product or associated process is not fully defined by these specifications, internationally accepted professional practice shall govern. 7.4.3 Specifications 7.4.3.1 Projection, Datum, Coordinate System Refer to Section 7.1.3. 7.4.3.2 Scanning of Negative/Diapositive With present technology, analog and analytical stereoplotters are already obsolete. Softcopy digital photogrammetric workstation (DPW) methods should be employed. Aerial triangulation with DPW is also much easier and more accurate than earlier analog and analytical methods. There is no longer any need to ‘drill’ points for measuration. If aerial photograph is not digitally acquired, the negative or diapositive should be scanned with appropriate quality scanner with typical resolution of 15~25 µm (typically 20 µm). The scanning should cover the whole image and should include the 8 fiducial marks. The affine fitting of the scanned image with camera frame templates will correct for scanner scaling error. The rms residuals after affine transformation should be less than 1 pixel. 7.4.3.3 Control Point Configuration Control point configuration, monumentation, targeting and measurement are all prescribed in Specifications for Ground Control Surveys. The salient points describing configuration are summarized hereunder. The ground cover in Qatar is such that horizontal control points should be targeted. Target configurations should be a “+”, “T” or “Y”. The minimum target sizes should be such that its resultant image on the photograph is no smaller than 15 pixel (or 15 x GSD in meters on ground). This results in the following based on the default photo scales for each of the project classifications:

Table 7.7

Project Classification Nominal (analog)Photo Scale

GSD if Digital Photo Min Target Size

Urban Mapping 1:5,000 10 cm 1.5 m

Whole Country 1:30,000 50 cm 7.5 m

Ground control points (GCPs) can either be horizontal control points (HCP) which carry measured X and Y values, vertical control points (VCP) which carry measured Z values only and full ground controls points (GCP) carry measured X, Y and Z values.


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With the popularity of GPS surveying for ground control point acquisition, there is virtually no cost difference in measuring full GCPs with X, Y and Z values against HCP or VCP. It is actually better to use full GCP in place of HCP or VCP for aerial triangulation. 7.4.3.3.1 Without ABGPS and IMU For aerial photography acquired without ABGPS and IMU, the control point requirements are as follows: For single strip of photography horizontal control points (HCP) should be placed in pairs (opposite each other on either side of the flight line) within the first and last models in the strip and at intervals of not more than four model base lengths along the strip. Vertical control points (VCP) shall also be placed in pairs (opposite each other on either side of the flight line) within the first and last models in the strip and at intervals of not more than two model base lengths along the strip.

Figure 7.9

For blocks of photography, horizontal and vertical control (full GCP) should be relatively evenly spaced and located around the periphery of the block. The spacing of horizontal control points (HCP) around the periphery should be 3 to 5 model base lengths along lines and every second line across lines. Vertical control points (VCP) should be placed at intervals of 3 to 5 models along lines and on every line. The vertical control points (VCPs) should be established in the sidelap portions of the photographs. The vertical control points (VCPs) should also be placed on every line around the perimeter of the block. Photographic blocks should be designed so as to minimize irregularities: holes, projecting lines, indentations etc. Where these irregularities are unavoidable, Horizontal control points (HCP) must be placed at all extremities and most inflection points in the block. Additional horizontal control points (HCP) and vertical control points (VCP) should be located at the centre of the block, and in the case of large blocks, relatively evenly distributed throughout the block on a grid of approximately eight to ten base lengths.

Figure 7.10

Horizontal Control

Pt (HCP) Vertical Control Pt (VCP)

Horizontal Control Pt (HCP)

Vertical Control Pt (VCP)


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7.4.3.3.2 With ABGPS and IMU Advancement in ABGPS and IMU technology incorporated in aerial camera system has allowed the camera coordinates and orientation during exposure to be precisely measured. With a base station within 30km, accuracy of 3 to 10 cms is possible. With GPS and IMU, it becomes possible to aerial triangulate the whole block without horizontal and vertical control points to acceptable accuracy. Additional cross flights can be introduced to provide additional strength and accuracy to the block.

It is still advisable to provide some horizontal and vertical at the corners and the centre of the block to ensure residual bias errors are eliminated and also provide quality checks on the aerial triangulated results.

Figure 7.11

7.4.3.3.3 Check Points The CGIS may elect to establish checkpoints within the aerial triangulation scheme. In such case the CGIS will establish the points on the ground. The consultant shall provide adjusted coordinates for these points for approval prior to finalizing the block adjustment. 7.4.3.4 Preparation 7.4.3.4.1 Pass Points Forward pass points are artificially marked points used to locate the same point in successive models along the flight line. A minimum of five (5) pass points will be located in the overlap between adjacent stereo models on the same flight line. One pass point will lie near the principal point, the other pass points will be evenly distributed in the direction perpendicular to the flight line. The outer two pass points will be in the area of sidelap between flight lines. Where possible the outer points will also serve as tie points. Pass point locations will be selected by examining the photographic prints in stereo. Pass points must be located in areas of good stereo fusion of the image and on unobscured, level ground.

Horizontal Control Pt (HCP)

Vertical Control Pt (VCP)


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7.4.3.4.2 Tie Points Tie points are artificially marked points used to locate the same point in adjacent models within different flight lines. A minimum of two tie points will be located in the sidelap area on each edge of each stereo model. Tie points should as far as possible be used as forward pass points. No tie or pass points shall fall within 5% of the edge of the photograph. Tie points should be staggered to the extent possible to minimize “hinge” effects during adjustment. 7.4.3.4.3 Softcopy Point Marking and Transfer Aerial triangulation with softcopy simplifies the procedure of pass points processing. The process involved displaying two successive photo images on the monitor screen. The operator then selects arbitrary pass points in the images/photos, and the workstation will automatically assign appropriate image/photo coordinates of that point on each photo/image. If image matching option is enabled, the operator need only select the pass point in one photo and the computer will automatically select the matching point in the other image. Images of adjacent flight line photos can also be displayed for simultaneous tie point marking. The image/photo coordinates of these pass/tie points in the overlap/sidelap area are stored in the computer's database. The marking is only a graphic overlay and does not disturb the original image/photo pixels. This operation thus eliminates the necessity of manual pugging, plate reading, and transferring required with analog and analytical plotters. 7.4.3.4.4 Coding

A systematic coding scheme shall be employed which facilitates the identification of points according to: 1. Location in the Model 2. Flight Line 3. Exposure 4. Point Type

University of Stuttgart PAT-M/PAT-B coding, currently in use by CGIS, is recommended. 7.4.3.5 Mensuration Mensuration may be carried out with softcopy digital photogrammetric workstation (DPW). The workstation must be capable of measuring down to 0.01 pixels. The workstation shall support the following corrections (not required for digital camera):

i. Affine transformation inner orientation with fiducial marks coordinates ii. Lens distortion iii. Earth curvature iv. Atmospheric refraction

If measurements are made in stereo, residual Y-parallaxes during model formation shall not exceed 3 pixels and the RMSE for the model shall not exceed 1 pixel. 7.4.3.6 Adjustment The adjustment shall be fully analytical and performed in two stages:

1. Preliminary Strip Formation 2. Bundle Adjustment


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Prior to adjustment, inner orientation of the photographs is performed to provide each photograph with photograph coordinates that match the geometry of the image focal plane and perspective centre. Affine transformation that matches the fiducial marks with camera focal plane template should be applied to remove scanner errors and lens distortion errors should also be corrected (from camera calibration information). Photographs acquired by digital camera are already inner oriented and will not need this step. 7.4.3.6.1 Preliminary Strip Formation

This step refers to the sequential assembly of independent stereomodels to form a strip unit. The sequential strip formation is a preliminary adjustment that develops initial approximations for the final simultaneous bundle adjustment. The strip formation also serves as a quality control check of the photo and in some cases also ground coordinate data. (1) Relative orientation of each stereo pair is performed by a least squares adjustment using the collinearity equations and template matching at the selection part of the stereomodel. DPW usually can do this relative orientation step fairly automatically. The stereomodel is created in an arbitrary coordinate system. The photo coordinate residuals should be representative of the point transfer and measuring precision. The photo coordinate residuals should be examined to detect misidentified or poorly measured points. (2) When stereomodels are joined to form a strip, the pass points shared between models will have two coordinate values, one value in the strip coordinate system and one value in the transformed model coordinate system which is close to the ground coordinates. The coordinate differences or discrepancies between the two values can be examined to evaluate how well the models fit to one another. Outliers can be detected at this stage and corrected.

7.4.3.6.2 Simultaneous Bundle Adjustment

(1) The strips are then joined (in virtual sense) into a block and simultaneous block bundle aerial triangulation must be adjusted by a weighted least squares adjustment method. Adjustment software will form the collinearity condition equations for all the photo coordinate observations in the block and solve for all photo orientation and ground point coordinates in each iteration until the solution converges. The adjustment shall also compensate for earth curvature and atmospheric refraction effects. (2) Least squares adjustment results should be examined to check the consistency of the photo coordinate measurements and the ground control fit. Residuals on the photo coordinates should be examined to see that they are representative of the random error expected from the instrument used to measure them. Residuals should be randomly plus or minus and have a uniform magnitude. Residuals should be checked carefully for outliers and systematic trends. Standard deviation of unit weight computed from the weighted adjusted residuals should be between 0.5 to 2 times the reference standard deviation used to compute the weights for the adjustment (0.5<σ0 < 2). (3) Accuracy of aerial analytical triangulation should be measured by the RMSE of the error in each coordinate (X, Y, and Z) direction for the checkpoints if available. The RMSE should be less than flying_height/10,000. The maximum residuals of photo coordinates and ground coordinates shall be less than 3 times the respective RMSEs.

Table 7.8

Important Statistical Measure

Standard Deviation of Unit Weight (σ0)

Between 0.5 to 2.0

RMSE of X,Y,Z coordinates < flying_height/10,000

Maximum Residuals of Coordinates

< 3 x respective RMSEs

The evaluation of the aerial triangulation and adjustment results will not be based solely on the statistical results of the adjustment. The following elements must also be evident in the adjustment:

a) Proper aerial triangulation technique with respect to control point location and tie point location.


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b) There must be no evidence of a systematic nature to the residuals on either control points or photogrammetric points.

c) The block must remain structurally sound while meeting a one percent rejection criterion. 7.4.4 Deliverables

A final report shall be delivered to the CGIS detailing:

Table 7.9

Photography And Control Used The photograph files, duly annotated shall be delivered following CGIS approval of the aerial triangulation results.

Hardware And Software Employed This must include all details that pertain to meeting these specifications.

Methodology

Preliminary Results

Final Results The final results, including an accuracy summary

Problems Encountered And Remedial Actions Taken

Technical Concerns e.g. weak areas in the block

Summary Of Ties To Other Blocks

List Of Control Problems points rejected and adjustments to standard weights

All source materials provided by CGIS are to be returned. A final, reproducible computer generated index map in DXF format will be prepared which identifies all points included in the aerial triangulation and the limits of the photos. The index will also show line and photo numbers. A listing of all adjusted coordinates for all ground control, pass points and tie points. A listing of calculated camera location at time of exposure and orientation parameters. A listing of differences at ground scale between surveyed and adjusted coordinate values for all control points. A listing of differences at ground scale between measured and adjusted tie photogrammetric points. All deliverables shall be submitted in digital form and hard copy equivalent, in appropriate media and agreed format to CGIS.


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7.5.0 Manual and Specifications for Satellite Mapping 7.5.1 Background 7.5.1.1 General In recent years, satellite imagery with GSD (ground sampling distance) of a few meters (SPOT 5, 2.5m) to less than 1m (IKONOS at 0.82m QuickBird at 0.61m and Worldview 1 at 0.50m) are commercially available. It becomes possible to use satellite imagery instead of aerial photography for certain mapping projects. Whereas airborne mission planning is done largely on a project specific basis, with parameters such as scale, attitude, light path etc., chosen to meet the needs of the project, satellite mission parameters, are fixed for the life of the mission. Some of the very high resolution satellites are shown in Table 7.10 below:

Table 7.10

Satellite Altitude (km) GSD at Nadir Swath Width Accuracy without GCPs (*)

IKONOS 681 0.82 11.3 15m

QuickBird 450 0.61 16.5 15m

EROS A 480 1.8 13.5 -

SPOT 5 832 2.5 60 25m

Worldview 1 450 0.5 16.5 5

GeoEye 1 681 0.5 15 5

(*) Excluding terrain effects Many authors have demonstrated that less 0.5 pixel accuracy is possible for IKONOS, QuickBird and SPOT 5 imagery with a number of ground control points. However from a practical point of view, where one uses a little as one control point per image strip and using block bundle triangulation of satellite imagery, the practical RMSE accuracy is about 2 pixels, or 2m in the case of IKONOS or QuickBird. With 2m X-Y RMSE and 1m GSD, this make IKONOS and QuickBird imagery directly suitable for 1:5000 scale (or smaller) mapping. IKONOS and QuickBird data are capable of DTM or Z measurement. With a few GCP to remove residual height bias, it is possible to achieve LE90 accuracy of 3m in Z. This made them suitable for 1:1000 or smaller scale mapping. . 7.5.1.2 Triangulation of Satellite Images Before discussing triangulation of satellite image, it is important to have reasonable understanding of “camera model”. 7.5.1.2.1 Camera Model The “camera model” is the mathematic model that model the ray of light connecting the ground point object coordinates (X,Y,Z) to the image plane image coordinates (x, y), factoring in the translation, orientation and perturbation of the imaging system. For standard frame aerial photography, the standard camera model is the collinearity equations:


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Where m11, m21, …, m32, m33 are the elements of the rotation matrix for the camera which is

functions of (ω,φ,κ) rotational angles f is the effective focal length. X, Y, Z is the terrestrial Cartesian coordinates Xs, Ys, Zs is the coordinates of the camera perspective centre

The collinearity equations would probably be valid if one take the standard frame camera and image the earth from a satellite. However, this is not the case. Satellite imagery (including SPOT, IKONOS and QuickBird) camera typically takes only one image line at any instant. The image is formed by the forward motion of the satellite, and each line is sampled at a split second in time from the previous. This way of imaging is usually referred to as line scanning “push broom” imaging. Research into satellite mode of this type is still progressing. Typically there are two major categories:

i. physical camera model ii. replacement camera model

In physical camera model, the absolute orientation (translation and rotation) and altitude of the camera is rigorously modeled. The satellite is already designed to provide numerous a-priori measured parameters and with them, one can compute the coordinate of any pixel within certain specified accuracy (e.g. 50m for SPOT 5 and 15m for IKONOS and QuickBird). The physical model can further be divided into two:

i. direct camera model ii. reverse camera model

For the direct camera model, one starts from the image pixel and traces the light through the imaging system and orientation and altitude of the camera. The model ray of light is then made to intersect the earth ellipsoid, with or without DEM. The reverse camera model is similar to the collinearity equations. Except that since one line is image at a time, the y (or x depending on convention) image coordinate is zero. i.e. image coordinate is [x, 0]

t. To

provide the two dimension image, the y is derived from the orbit model, as a function of time. Since IKONOS, the replacement camera model, more specifically the cubic Rational Polynomial Coefficient (RPC) model, is now becoming a popular satellite camera model. The format of RPC camera model is as follows:


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Where ρ1,ρ2,ρ3,ρ4 are cubic polynomials defined as follows:

And (φ, λ, h) is normalized coordinate of latitude, longitude and height in ground space (range from –1 to +1), (x, y) is normalized sample and line coordinate in image space The replacement camera model has two main advantages. Firstly is that it allows satellite operators to hide propriety parameters from public. Secondly, since it is application to almost all satellite imagery, users of imagery need not invest in specific satellite models. 7.5.1.2.2 Coordinate System In aerial triangulation, the local national grid coordinate system is usually used. However, for satellite imagery, it is usual to triangulate in the WGS 84 geographical system with ellipsoid height (rather than MSL height). 7.5.1.3 Triangulation of Single Image

The a-priori measured physical parameters of the satellite images are already very accurate. For SPOT 5, the accuracy is 50m. For IKONOS and QuickBird, the accuracy is about 15m. These accuracies can be improved using GCP to refine the camera model.

For the physical model, the refinement of the camera model is achieved by introducing 3 translation (∆X, ∆Y,

∆Z) and 3 rotational (pitch, roll, yaw) bias terms. The initial value of which are zero. However, due to the

small field of view and high flying height, the ∆Y and pitch parameters are highly correlated. Similarly the ∆X and roll parameters are also highly correlated. One is left with no more than 4 parameters to refine the camera model. With 4 control points per image, the accuracy of the measured coordinates can be reduced to less than 1 pixel. For replacement camera model, it is not possible to introduce the six physical bias. However, researchers have found two methods to refine the camera model:

i. affine or polynomials in image coordinate (x, y) space ii. low order polynomial of the object coordinate (X,Y,Z) space

Though not fully rigorous, sub pixel accuracy is also possible with 4 or 5 GCP used in the image. 7.5.1.4 Triangulation of Block of Satellite Imagery Whether physical or replacement camera model, it is possible to tie many strip of imagery into a block similar to aerial triangulation in aerial photography. With IKONOS imagery, research has shown that 2m RMSE (two pixels) is possible with average of one GCP per image strip, distributed in similar manner as aerial triangulation with Airborne GPS, i.e. at the corners and in the middle of the block. In the event that mono images are triangulated, one will have to provide Z coordinates to the pass points. These Z coordinates may be read off existing DTM database in CGIS.


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7.5.1.5 Multisensor Triangulation Mathematically, the possibility of multisensory triangulation is now a possibility. E.g. combining IKONOS and/or SPOT 5 and/or aerial photograph in block adjustments. Several software have such capability. However, due to the varying strength of the imaging geometry, one has really to be an expert to analyze the results of the triangulation. Multisensor triangulation is thus not recommended for operational mapping. 7.5.2 Specifications The following specifications are more relevant to IKONOS and QuickBird imagery. It is likely to be also applicable to next generation GeoEye and Worldview imagery. CGIS requirement of 0.6m GSD for its smallest scale rural mapping automatically ruled out SPOT 5 imagery.

7.5.2.1 Data Characteristics The general characteristics of imager data is as follows:

i. Spatial resolution: a. At nadir: <0.82m panchromatic, <3.2m multispectral b. 26 degrees off nadir: <1m panchromatic, <4m multispectral

ii. Spectral bands: a. 1 panchromatic band b. 4 multispectral band – blue, green, red and near-infrared

iii. Image swath (scene width) > 11 km iv. Dynamic range : >= 11 bits per pixel

7.5.2.2 Projection, Datum, Coordinate System Unless otherwise stated and if applicable, the satellite imagery shall be casted on the Qatar National Grid (QNG). Refer to Table 7.3. 7.5.2.3 Product Levels To suite CGIS requirements (based ASPRS standard for large scale mapping and US National Map standards for small scale mapping):

Table 7.11

Reference Scale Positional Accuracy Required

Ground Control Point

Ortho Correction

Image acquisition

Elevation angle (degrees)

1:50,000 25m (CE90) No yes 60° to 90° 1:10,000 (whole

country) 2.5m RMSE Yes yes 72° to 90°

DTM (whole country)

1.7m Vert RMSE

No (IKONOS & QuickBird)

Yes (GeoEye-1, Worldview-1 & Worldview 2)

-

Satellite image such as IKONOS, QuickBird, GeoEye-1 and Worldview-1 can acquire two images of the same area with different elevation to form stereo image pair. The time interval between the two images is typically less than one minute. To meet the 3m vertical rmse, the GSD must be about 0.5m (GeoEye-1 and

Worldview-1 only) and the stereo pair shall contain an image collected at low elevation angle (above 60°) and

the other at high elevation angle (above 72°) with 30° to 45° convergence. GCPs are also required to refine the camera model (or RPCs).


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CGIS has the option to: i. provide the GCP outside the scope of the project ii. include the acquisition of required GCP as part of the project.

7.5.2.4 Image Acquisition Order Polygon Image should cover the area defined by the user’s order polygon. An order polygon may be defined using one of the following methods:

• Upper left and lower right corner coordinates if the area is rectangular. • A center point and a height and width to define the area. • Shapefile format – .shp, .shx, and .dbf files.

Order polygons that fit within a swath shall be collected as one image strip. If more than one image strip is required to cover the order polygon, the overlaps between adjacent strips will be more than 1km. 7.5.2.5 Cloud Cover The very high resolution satellite imagery delivered usually has cloud cover criteria at 20%. Due to nature of weather in Qatar, it is recommended to reduce this cloud cover criteria to less than 5%. 7.5.2.6 Sun Angle The specified elevation angle of the sun is greater than 15 degrees. This is because the few satellites providing such data are in a sun synchronous orbit, collecting image at approximately 10:30 am local solar time. If in future, imagery from certain non-sun synchronous orbit is ordered, then the sun elevation angle must be specified. 7.5.2.7 Imagery Options Four possible imagery options may be selected:

i. Panchromatic – highest resolution data derived from the panchromatic (black and white) band ii. Multispectral – Blue, Green, Red and Near-Infrared lower resolution bands iii. Bundle – both the panchromatic and multispectral images, over the same geographic area are

delivered with appropriate name to show their relationship iv. Pan-Sharpened – combing the high resolution panchromatic and low resolution multispectral

image to produce a high resolution multispectral (color) image in three or 4 bands. Usually either option iii or iv is exercised. 7.5.2.8 File Format All monoscopic imagery product shall be delivered in electronic format as a GeoTIFF file. Stereo imagery should be provided in TIFF format for epi-polar projected imagery and GeoTIFF for map oriented imagery. The media for imagery products shall be DVD or other media as specified by CGIS.


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7.5.2.9 Bits/Pixel To retain the full dynamic range of the imagery which was acquired with 11 bit or more radiometric resolution, the delivered TIFF or GeoTIFF product shall be with 16 bits/pixel. 7.5.2.10 Resampling Production of the image product shall use Cubic Convolution (or Bi-Cubic) method in resampling the imagery. The GSD of the source data shall be within +/- 50% of the resample image pixel size. 7.5.2.11 Support Data All satellite imagery products must contain a metadata file. The metadata file shall contain, but not limited to, the following information:

i. image acquisition data and time ii. spectral bands iii. coordinate systems iv. sun angles v. viewing geometry vi. GSD and resolution

The metadata file shall be provided in an ASCII text file. Date of Acquisition and RMSE shall be embedded into the imagery. In addition, the imagery shall be accompanied by file(s) with information relating to the attitude, ephemeris, and camera model, suitable for advanced photogrammetric processing (i.e., orthorectification). Alternatively, equivalent information can be provided in the form of Rational Polynomial Coefficient (RPC). 7.5.2.12 Mosaic In the event that image mosaic is ordered (applicable to ortho products only), the imageries shall be radiometrically balanced against each other so as to provide a smooth and consistent look across the whole mosaic. The minimum overlapping area shall be at least 500m wide. Sufficient blending shall be applied to the seam line to ensure smooth transition from one strip to the adjacent. The original image strips shall also be delivered on top of the mosaic. 7.5.2.13 Block Adjustment In order for further block adjustment by CGIS or other authority, each image strips shall be accompanied by file(s) with information relating to the attitude, ephemeris, and camera model, suitable for triangulation with appropriate software. Alternatively, the equivalent information can be provided in the form of Rational Polynomial Coefficient (RPC).


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7.5.3 Deliverables The following materials shall be delivered for each project:

Table 7.12

Imagery Digital Files on CD-ROM TIFF 6.0 .TIF and .TFW world files

Mosaic Seams - Digital Files

Quality Control Reports • Production Flow Diagram • Camera model / RPC adjustment - RMSE • Rectification Quality - RMSE • Image Histogram

All materials provided by the CGIS are to be returned at the conclusion of the project. All materials derived from CGIS materials are likewise to be returned.


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7.6.0 Specifications for the Compilation of Digital Image Mapping 7.6.1 General These specifications supersede all previous documentation pertaining to the production of digital orthoimagery from aerial photography or satellite image for the Centre for GIS, State of Qatar. The Centre for GIS, State of Qatar (CGIS) shall be the final authority on the acceptance or rejection of digital imagery and hard copy products derived there from, produced under these specifications. These specifications detail digital orthoimagery produced from any scale of aerial photography or satellite imagery. The principal parameters governing digital orthoimagery at a given scale are the resolution and accuracy characteristics of the imagery. 7.6.1.1 Digital Orthoimagery 7.6.1.1.1 Definition A digital orthoimage is a raster image which has been derived from aerial photography of perspective projection or high resolution satellite imagery. The perspective image has been transformed to acquire the properties of an orthographic projection through the process of image resampling taking into account the relief displacement effect. Image displacements caused by the attitude of the camera, camera distortion, and the relief within the image have been removed. Therefore the rectified image has the geometric qualities of a map. The principal inputs to the orthoimaging process are:

1. Aerial Photography or satellite photography 2. Digital Elevation Models 3. Camera Calibration Data or Satellite camera model 4. Photogrammetric Control and Camera Orientation Parameters 5. Ground Control data

7.6.1.1.2 Quality Each of the above inputs will have a profound effect on the quality of the rectified imagery. For example, the quality is influenced by the following factors:

• quality of the original digital aerial photography/image (exposure, aircraft movement, image blur, developing, handling)

• scale of photography relative to the output products • orientation of the photography relative to the "map" extent • quality of diapositive production and handling • type of scanner employed and the mounting of the diapositive in the scanner • scanning resolution (if analog photograph) • quality and density of ground control • quality of the mensuration and adjustment • accuracy, density and design of the DEM • capture of breaklines within the DEM • interpolation algorithms employed and the final density of the DEM gridded for the rectification • care exercised in the space resection process • judgment required in the mosaicing process • rectification algorithms, resampling algorithms and the number of resampling steps to which the

imagery is subject

The CGIS philosophy is based upon achieving excellent quality and consistency in all products. Accordingly, the digital orthoimagery shall be produced in strict accordance with these specifications. Where the product or


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associated process is not fully defined by these specifications, internationally accepted professional practice shall govern. 7.6.2 Specifications 7.6.2.1 Projection, Datum, Coordinate System Refer to Table 7.3. 7.6.2.2 Project Extent Refer to Table 7.4, Figure 7.1 to Figure 7.3 7.6.2.3 Ground Sampling Distance (GSD) The horizontal ground sampling distance, GSD (the ground area represented by each pixel) in the delivered product shall be as indicated in the following table for each of the project classifications.

Table 7.13

Project Classification Ground Sampling Distance (GSD)

Large Scale 10cm by 10cm

Small Scale 50cm by 50cm

7.6.2.4 Data Conversion 7.6.2.4.1 Scanning if Analog Aerial Photography

If analog aerial photography is the source, then scanning of diapositive or negatives shall be performed. The scanning shall be accomplished utilizing a high accuracy, high precision micro-densitometer, providing a relative accuracy of 12µm to 25µm. The diapositives shall be scanned at a resolution which provides pixels representing ground dimensions less than or equal in size to those that will be delivered. The lowest possible scanning resolutions for the project classifications using the example photo scales are as follows:

Table 7.14


Example Photo Scale

Maximum Ground

Sampling Distance

Lowest Scanning Resolution

Large Scale 1:5,000 10cm 20µm

Small Scale 1:30,000 100cm 33µm

The scanning shall be effected at a radiometric resolution of at least 8 bits (256 intensity values). The intensity values shall be represented by integer values from 0 to 255 inclusive; zero representing the color black and 255 representing the color white with full color range in between.


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After scanning, the inner orientation of each photograph shall be performed, measuring at a minimum of 6 fiducial marks and fitting it to the known coordinates of the fiducial marks with affine transformation to an accuracy of less than 1 pixel. 7.6.2.4.2 Digital Photography or Satellite Imagery In the event that aerial photography is acquired with digital camera, the aerial photograph is already in digital form. Scanning is not required for digital aerial photography. For digital camera, the photography will have to be acquired with GSD of less than 10cm for large scale urban mapping, and less than 100cm for country wide mapping.

Satellite imagery with sufficient resolution may be used. At the time of writing, the resolutions for satellite imagery are:

i. 0.5 cm for GeoEye-1 ii. 0.5 cm for WorldView-1 (not suitable because it is only available in panchromatic mode, no

color) ii. 0.61 cm for QuickBird iv. 0.82 cm for IKONOS

From the above, satellite imagery at the moment can only support small scale countrywide mapping (GSD required is 100cm). 7.6.2.5 Processing Algorithms 7.6.2.5.1 Rectification The rectification shall be performed on a pixel-by-pixel basis. The photogrammetric collinearity equations (for aerial photography) or satellite camera model (for satellite imagery) shall be used in the solution for each output pixel. Replacement camera model (e.g. rational polynomial coefficient, RPC, model) may be used provided the replacement camera model is derived from the rigorous camera model or collinearity equations and the replacement camera model must match the rigorous camera model to accuracy of less than 0.02 pixel for the whole image. Algorithms based on simple polynomial warping between rectified “posts” shall not be utilized for the rectification. 7.6.2.5.2 Resampling

The number of times the imagery is subject to resampling shall be minimized. The resampling algorithms used shall employ cubic convolution, bi-cubic or superior strategies for deriving the output pixel intensity value. The output shall have a dynamic range similar to the input imagery. 7.6.2.6 Accuracy

Digital orthoimagery accuracy shall be judged on its ability to correctly portray the position of a well-defined object. The following three factors are seen as most significant in determining accuracy:

1. Scanner Accuracy or Internal Accuracy 2. DEM Accuracy 3. Pixel Size and Selection


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7.6.2.6.1 Scanner Accuracy As indicated in earlier section, the scanner will position the imagery to within 1 pixel. For satellite imagery (or digital aerial camera), care should be exercised in choosing the suitable satellite (or camera) data. IKONOS and QuickBird are designed for metric mapping. For these two systems, the internal relative accuracy is within 1 image pixel. For digital mapping camera, the internal relative accuracy is also less than 1 image pixel (1 GSD). 7.6.2.6.2 DEM Accuracy The critical input for rectification is the DEM. The effect of the DEM on horizontal position will depend on the off nadir angle α of the pixel in the image.

Figure 7.12

For off nadir angle α of 30º, the typical rectification errors due to DTM are:

Table 7.15

DTM Accuracy

1

Rectification errors due to DTM

(m)

Rectification errors due to DTM (Pixel)

Urban 30 cm 0.17 1.7

Whole Country 3m 1.7 1.7

1 DTM accuracy at post is 20cm and 2m for urban and country mapping. A factor of 1.5 times was included to account for interpolation

to required height not at the DTM post.


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7.6.2.6.3 Pixel Size and Selection

Of the 3 key factors to accuracy being identified in this specification, pixel size and selection is the one which reflects a human beings ability to read what the image portrays. In the follow pair of diagrams, a well defined object is shown along with how it appears as an orthoimage after zooming in to the point where individual pixels can be recognized. The actual location of the line defining that object is overlaid on top of the pixels to show how “fuzzy” the line becomes. The task of interpreting the correct position becomes a task of picking the right pixel. Chances are very good that for a well-defined object such as this, the pixel you pick will either be the right one, or next to the right one. If you always pick the middle of your selected pixel, then at worst you would be off by the diagonal of 1½ pixels. This equates to 15cm for large scale urban mapping and 1.5m for small scale country mapping.

Figure 7.13

7.6.2.6.4 Summary of Errors The total error is estimated from the following expression:

The following Table 7.16 summarizes the contributing factors to orthoimagery accuracy. The last column is simply the sum of the 3 columns preceding it, but is expressed as an accuracy (i.e. with “±”).

Table 7.16

GSD

Internal Error

Error due to DTM

Error due to pixel

selection

Total Error / Ortho

accuracy

Urban 10cm 0.1m 0.17m 0.15m 0.25m

Whole Country

1m 1m 1.7m 1.5m 2.5m

This total error / ortho accuracy is consistent with the planimetric accuracy required for 1:1000 and 1:10,000 mapping.


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7.6.2.7 Photo Selection Under normal circumstances, in the case of stereo aerial photography, every second exposure shall be used for rectification. The exception to this will be

• At the end of each flight line • Where there is substantial detail potentially obscured by tall buildings • Where there is substantial detail potentially obscured within narrow street canyons • Where there is significant radiometric imbalances to be resolved • Where there is a landmark of particular significance

In the case of monoscopic satellite imagery, all the images will be used for rectification. At the edges of blocks of imagery the exposure centered on the last tile edge shall be rectified. This will ensure that the image used to create the last map sheet of each row contains sufficient coverage beyond the block boundary to facilitate mosaicing the image to an image from a new block of photography. This last mosaic seam shall fall entirely outside the original project area. Where there are significant concentrations of tall buildings or narrow street canyons, the choice of photos shall be adjusted to utilize the exposure closest to the centre of the concentration of buildings or street canyon. This may mean using every photo in certain areas rather than every other photo. Or choosing satellite image with smaller off-nadir angle (e.g. 18º). Where there are significant radiometric imbalances resulting from using every second photograph, additional photographs will be used. This will be particularly necessary where the sun’s reflective glare repeats itself in the same position on each photo (this is especially visible on water). The CGIS may specify that images with the nadir point closest to specific landmarks be utilized in the mosaic. Similarly, the CGIS may specify that special photography be flown oriented to cover specific areas. In such case the special photography will be integrated into the mosaic from which the final sheets shall be cut. In no case shall the mosaic seam line exceed a distance that will cause the off nadir angle to be greater 30º. This is in order to limit the horizontal error associated with the DEM in the rectification process. It also limits the apparent building “lean”. The consultant shall deliver digital files containing all mosaic seam lines and/or lines defining edges of blend regions. These files may be formatted as either ARCGIS personal GEO-Database or shape files. 7.6.2.8 True Ortho For urban areas with high rise building, CGIS may wish to specify for “true orthoimage”. True ortho requires all building features to be measured and aerial photography flown with 60% sidelap. The building features dimension is required to correct for the “building lean”, while the 60% sidelap is required to provide supplemental imagery to fill-in the area patch obscured in the first image. CGIS may wish to additionally specify 85% overlap for the photography. This will allow us of only the near vertical portion for production of “true orthoimage”.


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Figure 7.14

7.6.2.9 Mosaicing Each rectified image shall be mosaiced to the adjacent images in order to form complete sub-tiles as described in earlier section. This mosaicing shall be performed using interactively defined, irregular seams. The seams shall be designed to minimize the effects of the mosaicing and shall not cross vertical objects above ground level except where absolutely unavoidable. The seams shall be designed to minimize the effects of differing radiometric characteristics (reflectivity) between adjacent images. The seam line should not be visible except in areas where it must cross an area of substantial change in feature reflectivity between images. An example of such a case is the mosaicing of two images over water, one of which contains specular reflection. The seam line shall also be chosen so as to minimize any spatial discontinuities across the seam. Therefore, the seam shall be placed on the imagery at ground level and located in areas where minor discontinuities of features are masked. Localized adjustment of the brightness and contrast of the images shall be performed so as to minimize tonal variations across the seam lines. Each aerial photography or satellite image shall be rigorously ortho-rectified using collinearity equation, rigorous satellite camera model or replacement camera model (e.g. RPC) and generated DTM or existing DTM. Ortho rectification should provide the highest radiometric and geometric quality assigning to each pixel its exact geographical position. Mosaic should be done along flat features and should not be crossing any tall

1. The Raw Image 2. Rectification with DTM will remove displacement due to relief, but leave buildings leaning

3. Providing building feature file will pull buildings upright. But ‘shadow’ will be left in the previously obscured area

4. Supplemental imagery that covers the obscured area will fill-in the ‘shadow’ area with valid imagery


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features like Building, Wall, Towers etc. Proper feature continuity and radiometric balance needs to be maintained along the mosaic. Any visual defects to be taken care originating during the ortho-rectification process. The mosaicing shall be performed in such a way that the entire area appears continuous. The individual sub-tiles shall be cut from mosaiced imagery. Therefore all photographic images to be used in the production of the final image data sets must be mosaiced one-to-another. Rectified images shall not be “butt joined” except where the above criteria describing spatial and radiometric matching can be met. The following diagram shows several photographs and the resultant four tiles. Note that each of these images would also be mosaiced to other adjacent images if the area were surrounded by a contiguous block of photography.

Figure 7.15

Figure 7.16


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7.6.2.10 Radiometry The radiometric characteristics of the imagery shall be adjusted to provide uniform contrast and brightness. This uniformity shall be evident within each rectified image, within each map sheet and across the entire area for which imagery is being prepared. The imagery shall be stretched to provide uniform contrast throughout the dynamic range. There should be detail evident both in the shadows and in the bright white areas. The data may utilize the full dynamic range. No specific “cut-off” values are prescribed owing to the inherent tonal variability within aerial photography. The frequency distribution of intensity values shall be adjusted to ensure that the mean falls within the range of 100~130 for 8-bit imagery or 1600~2000 for 12-bit imagery. The frequency distribution should be a relatively smooth curve with no evidence of radiometric anomalies or artifacts, which are attributable to the processing methodologies. 7.6.2.11 Data Format

The CGIS processing facilities are based on ARCGIS®

/ARCSDE®

from Environmental Systems Research Institute, Inc. (ESRI). The data format specifications are thus designed to ensure complete compatibility

between the data and the ARCGIS/ARCSDE®

product line. It is recognized that the ARCGIS/ARCSDE®

product is in continuous development and that the data format requirements may evolve with time. The data shall be delivered in files comprised of individual sub-tiles in GeoTIFF (based on TIFF version 6.0, Aldus Corporation) format. The tiling structure is described in earlier section. The data must be formatted such that an integer number of image rows are contained in each strip. The strip boundaries must match row boundaries. It should be noted that the data must be formatted such that all other GeoTIFF parameters are

set to conform to ARCGIS/ARCSDE®

requirements. Each GeoTIFF filename shall carry the extension “TIF”.

Each image file shall be accompanied by an ARCGIS/ARCSDE®

“world” file. This file shall embody the

georeferencing information necessary for ARCGIS/ARCSDE®

to display the image. The file shall contain the six parameters, which define the affine transformation from image space to QNG coordinates. The world file shall carry the same file name as the image with a “TFW” extension. The image data GeoTIFF files shall not be compressed.

7.6.2.12 Quality Control

The consultant shall institute comprehensive quality control procedures to ensure that the products delivered are in full compliance with these specifications. Each quality control process shall be documented in the form of a report to be delivered to the CGIS with the corresponding data product. 7.6.2.12.1 Reports The reports are to be delivered with the orthoimagery and are in addition to those specified for the documentation of other input products (aerial photography, aerial triangulation, DEM compilation etc.). 7.6.2.12.1.1 Production Flow The consultant shall deliver a production flow diagram and associated explanatory notes which describe each stage in the production process, the systems and software applied, the quality control procedures and the quality criteria.


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7.6.2.12.1.2 Fiducials A calculation of the RMSE of the fiducial marks identified in the scanned image relative to the true positions as described by the camera calibration report shall be made. The report shall show the deviations in both X and Y for each point as well as the RMSE calculation. If photography is acquired from digital camera or satellite imagery, this report will be omitted. 7.6.2.12.1.3 Space Resection A calculation of the RMSE of the photogrammetric control points (chosen in the image to define the resection in space) relative to the GCP coordinates shall be made. The report shall show the deviations in both X and Y for each point as well as the RMSE calculation. Similar process shall be performed if satellite imagery is used for rectification. 7.6.2.12.1.4 Rectification Quality (Spatial) The consultant will carry out a quality assessment of the geometric quality of each rectified image. The results of this assessment will be delivered to the CGIS. At least four GCP points will be withheld from the space resection. The position of these points in the rectified image will be evaluated relative to positions computed within the aerial triangulation process. A root mean square error will be computed for these points. The report shall show the deviations in both X and Y for each point as well as the RMSE calculation.


Table 7.17

Imagery Digital Files on CD-ROM

GeoTIFF .TIF and .TFW world files

Mosaic Seams – Digital Files

Quality Control Reports • Production Flow Diagram • Fiducial Report – RMSE • Space Resection – RMSE • Rectification Quality – RMSE

All materials provided by the CGIS (aerial film, calibration reports, aerial triangulation data, indexes etc.) are to be returned at the conclusion of the project. All materials derived from CGIS materials (diapositives etc.) are likewise to be returned.


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7.7.0 Specifications for the Compilation of Digital Geospatial Data 7.7.1 General These specifications supersede all previous documentation pertaining to the production of digital geospatial data from aerial photography for the Centre for GIS, State of Qatar. The Centre for GIS, State of Qatar (CGIS) shall be the final authority on the acceptance or rejection of geospatial data, attribute information, and hard copy products derived therefrom, produced under these specifications. These specifications detail the production of digital geospatial data from any scale of aerial photography. Compilation will be specified as being under one of the following classifications. Unless otherwise specified, the default nominal photo scale (for analog camera) or GSD (for digital camera) will be employed. Analog Camera

Table 7.18


Nominal Photo Scale Range

Default Nominal

Photo Scale

Final Digital Map GSD

Reference Map Scale

Urban Mapping Larger than

1:20,000 1:5,000 10 cm 1:1,000


Smaller than 1:20,000

1:30,000 0.5 m 1:10,000

Digital Camera

Table 7.19


Nominal Photo GSD Range

Default Nominal

Photo GSD

Final Digital Map GSD

Reference Map Scale

Urban Mapping Smaller than

30cm 10 cm 10 cm 1:1,000


Larger than 30 cm

0.5 m 0.5 m 1:10,000

The principal parameters governing digital line mapping are:

• Data Model - Vector Geospatial Data - Tabular Data

• Layers • Features

- Hierarchy - Structure and Topology - Attributes

• Accuracy • Temporal Status

These specifications define the compilation of digital maps and associated data in accordance with the Qatar National Geographic Information Systems Database Specifications and Data Dictionary.


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7.7.1.1 Digital (Vector) Geospatial Data 7.7.1.1.1 Definition For the purposes of these specifications a digital geospatial data is a vector representation of a topographic line map which has been derived from aerial photography or satellite imagery. The vector representation is compiled photogrammetrically on stereoplotters and carries specified attribute information. The vector data is represented in a structured format and in strict accordance with specified nomenclature. 7.7.1.1.2 Quality Each of the above inputs will have a profound effect on the quality of the digital line maps. For example, the quality is influenced by the following factors:

• quality of the original aerial photography or satellite image (exposure, aircraft movement, image blur, developing, handling)

• scale of photography relative to the output products • quality of scanning or digital aerial photography • type of stereoplotter employed • quality and density of ground control • quality of the photogrammetric point selection, mensuration and adjustment • skill of the photogrammetrist and the care exercised in the compilation process • data processing techniques, the algorithms used in the topological structuring of the data, the

processing sequence, and the procedures employed in the production of the final files • quality control procedures and the diligence of the editor

The CGIS philosophy is based upon achieving excellent quality and consistency in all products. Accordingly, the digital line mapping shall be produced in strict accordance with these specifications. Where the product or associated process is not fully defined by these specifications, internationally accepted professional practice shall govern. 7.7.2 Specifications 7.7.2.1 Projection, Datum, Coordinate System Refer to Section 7.1.3. 7.7.2.2 Project Extent For vector mapping, the whole country or city shall be managed as one seamless continuous map. 7.7.2.3 Accuracy Horizontal positional and vertical height accuracy requirements are dependent on the reference scale of the required map according to Table 7.20 below. This is based on ASPRS accuracy standard for large scale mapping. The rms error (RMSE) is the cumulative result of all errors including those introduced by the process of ground control survey, stereo plotting, map compilation and final extraction of ground dimensions from the map.


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Table 7.20

Reference Scale

Contour Interval

Elevation Acc. RMSE-Z

Positional acc. RMSE X-Y

1:1000 0.5m 0.17m 0.25m

1:2000 1m 0.33m 0.5m

1:5000 2m 0.67m 1.0m

1:10000 5m 1.7m 2.5m

1:20000 10m 3.3m 5.0m

The CGIS will verify the accuracy of each map sheet by field survey methods. Both GPS and conventional survey techniques will be utilized in the validation process. A minimum of ten well-defined and well-distributed horizontal and height checkpoints will be established. The points will be checked for absolute error, bias and precision in both X, Y and Z coordinates. 7.7.2.3.1 Coordinate Resolution All coordinates shall be full QNG values. Coordinates shall be represented to the nearest millimeter (meters, with 3 decimals) and stored in ARCGIS/ARCSDE double precision format. 7.7.2.4 Data Model The geo-database model supports an object-oriented vector data model. In this model, entities are represented as objects with properties, behavior, and relationships. The employed geo-database is used by ArcGIS products®, a Geographic Information System software platform produced by Environmental Systems Research Institute (ESRI). For further reference and latest information on vector data model, refer to the supporting documentation from ESRI on the ArcSDE® data model or visit www.esri.com. For more details on needed features, feature classes, feature datasets, tables, etc; refer to the topographic data dictionary.

7.7.2.4.1 Compilation Rules Specific definitions and compilation rules are contained in the Qatar National Geographic Information Systems Database Specifications and Data Dictionary. The data dictionary provides compilation examples and explanatory text and diagrams for each and every feature. The spatial data shall be cleaned and the topological relationships built. The individual data elements and features shall join and intersect at exact coordinate values i.e. the end point of one feature “snapping” to another feature shall have its end point coordinates duplicated in the line it joins or intersects. No features shall be displaced for cartographic reasons. Note that all points of features must be explicitly captured from the photography. No points are to be derived or interpolated from other points already established. For example, no corner squaring or perfect curve routines are to be applied, even if an object appears to be formed by right angles or perfect curves. Hydrographic features having a gradient shall be digitized in a downstream direction. 7.7.2.4.2 Control Points The CGIS shall supply a digital file of all ground control points and associated annotation falling within the mapping limits. This file shall be used to incorporate the control points within the hard copy product.


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7.7.2.4.3 Hard Copy The geospatial data shall be able to plot in GeoPDF format as produced by ESRI ArcGIS technology. The graphic overlay shall be integrated with the geospatial data and the combined file output on a film writer or scribed. The neat dimensions of the sheet shall be 50 cm by 100 cm. The CGIS shall provide the names to be reproduced on the hard copy. The names will be annotated on the site verification proof plot. 7.7.2.5 Deliveries and Production Process 7.7.2.5.1 Production Process The mapping will subject to comprehensive quality assurance processes applied by the CGIS. The work will adhere to the following sequence of activities:

• Aerial Triangulation • Photogrammetric Compilation • Site Verification • Final Edit • CGIS Quality Assurance • Final Inspection.

The CGIS shall approve each product or interim result prior to work beginning on the successive stages of the project. The mapping will be undertaken in blocks, the configuration and priority of which shall be determined by the CGIS. Each block will be tied to all existing mapping in adjacent blocks. The aerial triangulation adjustment will likewise be tied to each adjacent block. 7.7.2.5.1.1 Photogrammetric Compilation The planimetric and hypsometric data will be compiled by photogrammetric means on a model-by-model basis and then merged into tile (map sheet) format. 7.7.2.5.1.2 Site Verification Following photogrammetric compilation the consultant will produce two check plots of each sheet and submit them to the CGIS. These plots will be made on stable base material and will carry symbology defined specifically for the verification plots. The verification plots will extend 20mm beyond the nominal sheet neatline so as to show continuity of features across the neatline. At the same time the geodatabases will be delivered to support the evaluation of the horizontal accuracy of the planimetric features. The CGIS will first verify the horizontal accuracy by collecting coordinates for well defined objects (as defined by an independent survey of higher order than that utilized to control the aerial photography). Should the horizontal accuracy fail to meet the required standard (refer to Section 7.4.3), the tile (map sheet) shall be returned to have the photogrammetric compilation repeated. None of the spatial data from a failed horizontal coordinate accuracy submission may be used on a subsequent submission. Should the horizontal accuracy meet the required standards, the verification survey shall continue by adding field data to one of the verification plots. This will be returned to the consultant for inclusion in the map files. The field verification is used to identify:

• new features • obscured features • removed or destroyed features • miscoded or misinterpreted features


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At the same time attribute data will be acquired in the field and annotated on the verification plots. Where new features are to be added they will be surveyed in the field by the CGIS. The new information will be provided to the consultant in AutoCAD DWG or DXF format with a TXT file containing the text. [For Small scale projects (nominal photo scales smaller than 1:20,000 or GSD greater than 30cm), it may not be possible to compile small objects since they are not visible on the photography. Objects not visible on photography at a nominal scale less than 1:20,000 or GSD greater than 30cm will not be surveyed during the site verification survey. If an object is visible on the photography, it must be collected regardless of how small it is. For Large scale projects (nominal photo scales larger than 1:20,000 or GSD smaller than 30cm), all objects listed in the data dictionary (topographic vector data) will be surveyed during the site verification survey.] 7.7.2.5.1.3 Final Edit The consultant will perform a final edit to correct problems identified in the field verification stage and to incorporate the new information. A final proof plot will then be generated on stable base material for submission to the CGIS. This plot will carry final cartographic symbology with the exception of line weights. The digital data will be cleaned and the topology will be built to form the final digital deliverable. 7.7.2.5.1.4 CGIS Quality Assurance The CGIS will verify that all changes requested during the site verification phase have been completed properly. An inspection will be made of the final proof plot made during the Final Edit phase. The digital data will be subjected to a rigorous and exhaustive quality assessment by the CGIS. A complete report of all problems detected will be generated during this procedure. This report will be returned to the consultant to guide corrections to be made to the files. It should be noted that the CGIS quality assurance routines are not a substitute for the consultant’s own procedures. Individual tiles shall be rejected for any error. Tiles failed in Control Point Testing (CPT) check shall be rejected and The Consultant shall recompile that whole tile again. If the CGIS detects fewer than ten errors, none of which are major, it may elect to effect the corrections in-house. If more than ten errors are detected, CGIS quality assurance will be terminated before completion, and the sheet will be returned to the consultant for corrections and further quality assurance processing. 7.7.2.5.2 Materials to be Delivered

• Reports List

∗ Production Flow

∗ Aerial Triangulation Report

∗ Stereo Model Set-up

• Site Verification Proof Plots (2) • Interim Digital Files • Final Proof Plot • Final Digital Files • Original Negative Film• All Contact Prints • All Diapositives • Control Lists and Files (provided by CGIS)

7.7.2.5.3 Quality Control The consultant shall institute comprehensive quality control procedures to ensure that the products delivered are in full compliance with the specifications. Each quality control process shall be documented in the form of a report to be delivered to the CGIS with the corresponding data product.


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7.7.2.5.3.1 Reports The reports are to be delivered with the geospatial data files and are in addition to those specified for the documentation of other input products (aerial photography, aerial triangulation, DEM compilation etc.). 7.7.2.5.3.2 Production Flow The consultant shall deliver a production flow diagram and associated explanatory notes which describe each stage in the production process, the systems and software applied, the quality control procedures and the quality criteria. 7.7.2.5.3.3 Stereo Model Set-up Sheets Stereo Model set-up sheets shall be prepared for each model oriented for compilation. Model set-up sheets and model orientation histories shall be part of a permanent file for the project and shall be submitted to the CGIS following compilation.


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7.8.0 Specifications for the Compilation of Digital Elevation Models 7.8.1 General These specifications supersede all previous documentation pertaining to the production of digital elevation models from aerial photography for the Centre for GIS, State of Qatar. The Centre for GIS, State of Qatar (CGIS) shall be the final authority on the acceptance or rejection of digital elevation model information, and hard copy products derived from, and produced under these specifications. These specifications detail the production of digital elevation models. Compilation will be specified as being under one of the following classifications. Unless otherwise specified, the default nominal photo scale (for analog camera) or GSD (for digital camera) will be employed. Refer to Figure 7.18 and Figure 7.19 The digital elevation models are to satisfy two requirements:

• They shall serve as the basis of imagery orthorectification taken from nominal photo scales range of the same or smaller project classifications as that used to create the DEM.

• They shall support surface modeling applications. The principles contained herein are applicable to DEMs compiled from other scales of photography with appropriate modifications to calculated parameters. The principal parameters governing digital elevation models compiled from a given scale of photography are:

• Character • Density • Accuracy

The character and density refer to the spatial structure of the DEM and the techniques employed in compilation. These parameters govern how well a DEM describes the ground surface. The accuracy of the DEM refers to the degree of conformity of measurements with the actual elevations as measured in the field. 7.8.1.1 Digital Elevation Models 7.8.1.1.1 Definition For the purposes of these specifications a digital elevation model is a representation of a topographic surface which has been derived from aerial photography of perspective projection or high resolution satellite imagery with pseudo-perspective projection. The representation is compiled with softcopy digital photogrammetric workstation (DPW) and carries specified attribute information. The digital elevation models are comprised of points and line strings. The individual points carry X, Y and Z coordinates. The line strings are sequences of points each carrying X, Y and Z coordinates. The data is represented in a structured format and in strict accordance with specified nomenclature. The principal inputs to the process of compiling digital elevation models are exactly the same as those for digital line (vector) mapping:

1. Aerial Photography or Satellite Imagery 2. Camera Calibration Data 3. Ground Control Data 4. Camera Orientation Parameters, Camera Model of RPC

Each of these inputs is governed by a separate set of specifications by the CGIS.


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7.8.1.1.2 Quality Each of the above inputs will have a profound effect on the quality of the digital elevation models. For example, the quality is influenced by the following factors:

• Quality of the original negative image (exposure, aircraft movement, image blur, developing, handling)

• Scale of photography relative to the output products • Quality of diapositive production and handling • Type of stereoplotter employed • Quality and density of ground control • Quality of the photogrammetric point selection, marking, mensuration and adjustment • Skill of the photogrammetrist and the care exercised in the compilation process • Data processing techniques, the algorithms used, the processing sequence, and the procedures

employed in the production of the final files • Quality control procedures and the diligence of the editor

The CGIS philosophy is based upon achieving excellent quality and consistency in all products. Accordingly, the digital elevation models shall be produced in strict accordance with these specifications. Where the product or associated process is not fully defined by these specifications, internationally accepted professional practice shall govern. 7.8.2 Specifications 7.8.2.1 Projection, Datum, Coordinate System (Refer to 7.1.3, pp 253). 7.8.2.2 Project Extent (Refer to 7.1.4 pp 253,254) 7.8.2.3 Accuracy Horizontal positional accuracy requirements are dependent on the reference scale of required mapping.


Reference Map Scale

Default Nominal Photo Scale

Default GSD

(digital photo-graphy)

DTM Post-ing

Mass Point Accuracy

RMSE XY

RMSE Z

Urban Mapping 1:1,000 1:5,000 10cm 5m 0.25 cm 0.17 m


1:10,000 1:30,000 50cm 50m 2.5 m 1.7cm

Figure 7.20

In the case of DEMs, Breaklines may be compiled in similar manner as planimetric. The CGIS will verify the accuracy of each map sheet by field survey methods. Both GPS and conventional survey techniques will be utilized in the validation process. A minimum of ten well-defined and well-distributed horizontal check points will be established. The points will be checked for absolute error, bias and precision in both X and Y coordinates.


294

Vertically, accuracy is usually the limiting criteria for aerial flying flight. The C factor is the standard empirical factor that relate the contour interval plottable by the stereo plotting system to the flying height of the aerial photography. For modern DPW, the C factor of 2000 is commonly adopted. The standard for contour interval requires 90% of the mass heights to be within half contour interval. ASPRS accuracy standard for large scale mapping define the rms error for mass height to be one-third the contour interval. It is thus convenient to define the S factor, such that: RMS mass elevation error = flight height above terrain / S factor The S factor is thus 3x the C factor. i.e. S factor to be used is thus 6000. 7.8.2.4 Compilation Rules There are to be four different types of points collected:

Mass Points Points collected at regular gridded posting, which form the foundation of the DEM.

Single Points Points collected as supplementary heights and points of special significance e.g. hilltops, bottoms of depressions etc.

Breaklines Linear elements which mark a change in elevation and/or a change in the trend of elevations. Breaklines can be lines depicting abrupt change in slope, form lines, ridgelines, hydrographic features, roads, etc. They shall be categorized as one of three types: physical, hydrographic or transportation.

Building Heights Single points captured atop each building as a measure of the highest point in the building structure (not including masts, aerials, tanks etc.).

7.8.2.4.1 Feature Digitizing Rules The digital elevation model shall be compiled on a first order softcopy digital photogrammetric workstation (DPW). Mass points will be measured either automatically (with DPW template matching DTM acquisition software) or manually. If automatically measured, manual editing process is mandatory to eliminate erroneous height values that may arise due to cloud, water bodies, trees and buildings. The DTM height must be corrected to the ground level. Additional points of special significance shall be captured on top of the regular gridded DTM post. These points are necessary to depict elevation extremities. Spot heights shall also be captured at road intersections, along roads, on bridges, and on summits and depressions, and at water level on the ocean. All mass point and spot height DEM points must be explicitly captured from the aerial photography or satellite imagery. No points are to be derived or interpolated from other points already established.


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7.8.2.4.1.1 Transportation Breaklines All road extents, runways etc. shall be captured as transportation breaklines. Certain features, as listed below will always constitute breaklines whereas others shall only be included where they define a distinct change in slope or elevation

Breaklines Optional Breaklines

Road Accessway

Airstrip Assembly Area

Apron

Carpark

Footpath

Track

Race Track

Taxiway

Helicopter Pad

7.8.2.4.1.2 Physical Breaklines Physical breaklines shall be captured as form lines defining breaks in slope of natural landforms e.g. ridges, cliffs, gullies etc. and certain man-made features e.g. retaining walls, embankments etc. Certain features, as listed below will always constitute breaklines whereas others shall only be included where they define a distinct change in slope or elevation.


Embankment Bund

Pile Cultivated Area

Pit Plantation

Quarry Playing Field

Cliff

Sand Dune

Retaining Walls

Other breaklines shall be captured where necessary to adequately characterize the complexity of the terrain. These breaklines do not correspond to features captured in the vector mapping e.g. ridgelines, saddles, base of slopes etc. Several of the features captured as breaklines require that two breaklines be captured. A quarry, for example necessitates breaklines at the rim and at the base of the excavated area in order to define the topography.


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7.8.2.4.1.3 Hydrographic Breaklines All shorelines, shall be compiled as hydrographic breaklines. Certain features, as listed below will always constitute breaklines whereas others shall only be included where they define a distinct change in slope or elevation.


Beach Irrigation Ditch

Shoreline Pool

Wadi

Reservoir

Sabkha

Both banks of ditches and canals will be compiled and coded as hydrographic breaklines. 7.8.2.4.1.4 Building Heights Building heights shall be a component of the DEM. A single height will be measured atop each building. The uppermost part of the structure of the building will be depicted. The top of antennae, masts, water tanks etc. shall not be measured. The point must be positioned within the building polygon even if the height is measured at the edge of the polygon. The building heights shall be delivered as a separate file. 7.8.2.5 Quality Control The consultant shall implement a rigorous quality control process to evaluate, correct and verify the DEM data prior to submitting the data to the CGIS for inspection. The following inspections shall be undertaken at a minimum:

1. Inspection of the DEM in model formats prior to removal of the stereo model from the

photogrammetric instrument. An examination of a 3D representation of the model should identify significant anomalies.

2. The minimum and maximum elevations on each model shall be measured photogrammetrically.

These values shall be compared to the minimum and maximum values derived from the DEM file.

3. Ocean points, shorelines and other breaklines defining the ocean, ponds, and reservoirs must be

checked to ensure uniform heights. 4. Breaklines defining a watercourse must be verified to ensure continuous downhill flow. 5. Geo-database must be verified on a sheet-by-sheet basis and a plot must be produced.

6. Contour plots must be generated and inspected for anomalies. 7. Elevation values for all photogrammetric points on the sheet must be interpolated from the DEM.

An RMSE calculation shall be performed to quantify the deviation of the interpolated values from the adjusted values produced in the aerial triangulation process.

7.8.2.6 DEM Reports The DEM shall be accompanied by a report comprised of a vertical RMSE calculation based on the evaluation of interpolated values relative to the photogrammetric control points which fall within the DEM. In addition, the report shall include two plots prepared from the DEM. One plot will show all compiled breaklines (minus the


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building heights). The second plot shall depict contours derived from the DEM (minus the building heights) at an interval of 0.5m for urban mapping, 5m for whole country mapping. The contour plot shall be used as a quality control mechanism to identify anomalous data within the DEM. Reports to be submitted with each DEM:

a) Plot of breaklines; b) Contour Plot; c) RMSE Calculation for Photogrammetric Control in the DEM.


DEM GeoDatabase

DEM GeoDatabase with mass points, high low points, physical breaklines, transportation breaklines, hydrographic breaklines, and building heights.

DEM reports • Plot of breaklines. • Contour plot. • RMSE calculation.



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7.9.0 Specifications for 3D City Model Mapping 7.9.1 General These specifications supersede all previous documentation pertaining to the production of 3D City Model Mapping from aerial photography for the Centre for GIS, State of Qatar. The Centre for GIS, State of Qatar (CGIS) shall be the final authority on the acceptance or rejection of 3D city model information, and hard copy products derived there from, produced under these specifications. These specifications were compiled to prescribe the production of 3D city model, which will in turn be used to support the generation of different analysis by different applications on ESRI product lines for photogrammetrically compiled products in the State of Qatar. 7.9.1.1 3D City Models 3D city models allow for computer-based photo-realistic visualization of 3D urban environments for many applications like urban planning, telecommunication planning, engineering, architecture and 3D city information systems. There are five consecutive levels of detail (LoD) defined, where objects become more detailed with increasing LoD, both in geometry and thematic differentiation.

Table 7.21

LoD 0 – Regional Model 2.5D Digital Terrain Model

LoD 1 – City/Site Model “block model” without roof structures

LoD 2 – City/Site Model Textured, differentiated roof structures

LoD 3 – City/Site Model Detailed architecture model

LoD 4 – Interior model “walkable” architecture models

For city wide mapping, LoD 2, city/site model with textured and roof structure is recommended. 3D city models can be cost-efficiently generated using photogrammetric technique - in combination with 3D Digital Terrain Models (DTM) textured with high-resolution oblique aerial photography or terrestrial photography for texturing.


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7.9.1.1.1 Compilation For the purposes of these specifications a 3D model is a representation of a topographic ground surface with 3D features such as buildings, that has been derived from aerial photography of perspective projection. The representation is compiled with softcopy digital photogrammetric workstation (DPW) and carries specified attribute information. Compilation of the digital elevation models are described in earlier sections. The 3D model surfaces are handled through ESRI multipatch feature format. Multipatches are a type of geometry composing of planar three-dimensional ring or triangle faces, used in combination to model objects that occupy discrete volumes in three-dimensional space. These faces may contain texture information, such as oblique aerial photographs or terrestrial photographs, allowing the creation of photorealistic 3D views with appropriate software. For buildings, the highest point of the roof is to be measured, excluding temporary water storage tanks. The principal inputs to the process of compiling 3D models are similar to those for digital line (vector) mapping, with the addition of oblique or terrestrial photography for texturing:

1. Aerial Photography 2. Camera Calibration Data 3. Ground Control Data 4. Camera Orientation Parameters 5. Oblique Aerial or Terrestrial Photography

The first 4 inputs are governed by a separate set of specifications by the CGIS. 7.9.2 Specifications 7.9.2.1 Projection, Datum, Coordinate System Refer to Section 7.1.3. 7.9.2.2 Project Extent The project area will be defined by the extent of the city to be mapped to be defined by coordinates in QNG or WGS84 systems. The project files shall be provided to vendors in the form of ESRI compatible Shape file or text file containing the bounding coordinate value. 7.9.2.3 Accuracy Horizontal positional and vertical accuracy requirements are similar to that for Urban Mapping Vector and DTM as follows:

Table 7.22


Reference Map Scale

Default GSD (digital photography)

Horizontal Positional Accuracy (RMSE XY)

Vertical Accuracy (RMSE Z)

Urban Mapping 1:1,000 10cm 25 cm 17cm

The CGIS will verify the accuracy by field survey methods. Both GPS and conventional survey techniques will be utilized in the validation process. A minimum of ten well-defined and well-distributed horizontal check points per square kilometer will be established. The points will be checked for absolute error, bias and precision in both X and Y coordinates.


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7.9.2.4 Vertical Aerial Photography Vertically accuracy is usually the limiting criteria for aerial photography flying flight. The C factor is the standard empirical factor that relate the contour interval plottable by the stereo plotting system to the flying height of the aerial photography. For modern DPW, the C factor of 2000 is commonly adopted. The standard for contour interval requires 90% of the mass heights to be within half contour interval. The recommended contour interval for 1:1000 scale mapping is 0.5m. ASPRS accuracy standard for large scale mapping define the rms error for mass height to be one-third the contour interval. It is also convenient to define the S factor, such that: RMS mass elevation error = flight height above terrain / S factor The S factor is thus 3x the C factor. i.e. S factor to be used is thus 6000. 7.9.2.5 Oblique Aerial or Terrestrial Photography Oblique aerial photography or terrestrial photography is primarily used for texturing the building façade purposes. Small 35mm format digital camera may be used for such purposes. It is recommended that the camera used should have more than 22 million pixels per picture frame. The image shall be acquired with GSD less than 10cm (comparable with the vertical aerial photography). 7.9.2.5.1 Multi-Cameras Oblique Aerial Photography System For comprehensiveness, a multi(5)-camera systems may be used for acquisition of oblique aerial photography. The 5 cameras are organized such that 4 are tilted with oblique angles of 40 degrees from nadir and one is vertically mounted. The 5 cameras are connected to a dedicated data acquisition with integrated airborne GPS (ABGS) and inertial measurement unit (IMU). The photography flight lines shall be planned such that the 4 oblique photography are directed in the 4 cardinal directions – North, East, South & West. All oblique and vertical photographs shall have sufficient forward and side overlap to cover the entire project area individually. The ground sampling distance of the oblique photograph shall be better than 10cm for the front line of the photograph. Each camera (fully digital) shall have the following minimum specifications: i. Sensor size and type : > 36mm x 24mm CMOS ii. Focal length : 35mm to 50mm ii. No of pixels : > 11 million pixels iii. Bits per pixel : > 12 bits per pixel iv. Color bands: Red, Green, Blue 7.9.2.6 Quality Control The consultant shall implement a rigorous quality control process to evaluate, correct and verify the 3D city model data prior to submitting the data to the CGIS for inspection. The following inspections shall be undertaken at a minimum:

1. Inspection of the 3D city model prior to removal of the stereo model from the photogrammetric

instrument. An examination of a 3D representation of the model should identify significant anomalies.


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2. Interactive visualization of the 3D city model with texturing, view from all directions, shall be done to ensure correcting placement of textured image. At least 90% of the building façade should be textured.

3. An RMSE calculation shall be performed to quantify the accuracies of positional and vertical

accuracies.

7.9.2.7 3D City Model Reports The 3D city model shall be accompanied by a report comprised of a horizontal and vertical RMSE calculation with field surveyed check points to ensure accuracy of the deliverables. 7.9.3 Deliverables The following materials shall be delivered for each project:

Table 7.23

3D City Model 3D city model database at Level of Details of 2 (LoD 2), complete with texturing in format compatible with the current version of ESRI ArcGIS in CGIS.

Vertical Aerial Photography

Aerial photography in TIFF format with associated support/annotation file. Delivered in harddisk.

Oblique Aerial or Terrestrial Photography

In TIFF format unless otherwise specified

Reports RMSE calculation with field survey check points. CGIS will specify the number of check points per sq km.



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References The Manual of Photogrammetry, American Society of Photogrammetry, Fifth Edition, 2004. Engineering and Design Photogrammetric Mapping, Department of the Army, U.S. Army Corps of Engineers, Engineer Manual 1110-1-1000, 2002. ASPRS Accuracy Standards for Large-Scale Maps, ASPRS Professional Practicing Division 1990 Part 3: National Standard for Spatial Data Accuracy, Federal Geographic Data Committee. FGDC-STD-007.3-1998 Map Accuracy Standards, U.S. Geological Survey, Fact Sheet FS-171-99 (November 1999) Minimum Guidelines For Aerial Photogrammetric Mapping, State of New Jersey, Department of Transport, BDC98PR-009, 2005 Draft Standards for Aerial Photography, ASPRS Professional Practice Division Specifications and Standards Committee, 1995 Specifications for Aerial Triangulation, Province of British Columbia, Ministry of Sustainable Resource Management, Release 2.0 May 1998. CityGML: An Open Standard for 3D City Models, by Thomas Kolbe and Sam Bacharach, Directions Magazine, Jul 03, 2006 3D Building Visualisation – Outdoor and Indoor Applications, by Dieter Fritsch, University of Stuttgart, Photogrammetric Week 03, 2004 Standardization of 3D City Models, by Dr. Thomas H. Kolbe, Institute for Cartography and Geoinformation, Univ. of Bonn, EuroSDR Meeting in Bern 4/2005 IKONOS Imagery Products Guide, GeoEye, Version 1.5, 2006 QuickBird Imagery Products Guide, Revision 4.7.3, 2007 ADS40 Airborne Digital Sensor, ASPRS Potomac Region Chapter, Large Format Digital Camera Symposium, 29 August 2007 Geometric Handling of Large Size Digital Airborne Frame Camera Images, by Jacobsen, K. in Optical 3-D Measurement Techniques. Zürich, 2007, S. 164-171 DMC Practical Experience and Accuracy Assessment, by Madani M., Dörstel C., Heipke C., Jacobsen K., XXth ISPRS Congress, Commission 2, Istanbul, Turkey, p. 396 ff. 12-23 July 2004 Tests And Performance Analysis Of The Dmc At The Cartographic Institute Of Catalonia (ICC), by W. Kornus, R. Alamús, J. Talaya Institut Cartogràfic de Catalunya, Spain, Optical 3-D Measurement Techniques, Zürich, 2007 Flying the New Large Format Digital Aerial Camera Ultracam, by Franz Leberl, Graz University of Technology and Michael Gruber, Vexcel Imaging Austria, Photogrammetric Week 03, 2004 BAE Socet Set User’s Manual, Version 5.2, November 2004

Qatar Survey Manual – Chapter 8 – Geographic Information System

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Abbreviations CAD Computer Aided Design

CGIS Centre of Geographic Information System

DXF Data Exchange Format

GIS Geographic Information System


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8.1.0 State of Qatar Geographic Information System (GIS) The content of this section is extracted from the paper entitled “Qatar's GIS - Peering Beyond Objectives - Challenges and Future Vision” delivered by Head of The Centre for Geographic Information System (CGIS) in the 1998 ESRI User Conference. State of Qatar experienced rapid urban growth during the past three decades after the discovery of oil. Several hundred kilometers of roads, drainage networks, telephone lines, power and water networks, etc have been built accompanied by a spurt in new real estate developments. The government agencies were unable to keep up-to-date records of this rapid and large scale development. The lack of information together with inadequate inter-agency coordination led to poor and inefficient physical and utilities planning and management of resources. There was also lack of coordination between these agencies involved in physical and utilities planning which resulted in inharmonious infrastructure expansion and urban growth leading to large strain on government expenditures. The government soon realized the need for an innovative means of tapping and managing vast information resources that facilitate more constructive decision making required to sustain the developments and to maintain newly built infrastructure. Further, wastage of resources due to duplication of efforts had to be contained. To solve these problems, government decided to go for an innovative mean for managing such information. This aspect, together with the realization that eighty percent of this vast information was geographically related, prompted the government officials to look at various information technology options to transfer the maps/aerial photographs into electronic form. In 1988, a top-level government official Sheik Ahmed bin Hamad Al Thani, referred to as the champion of Geographic Information System (GIS) in the State of Qatar, pioneered the establishment and development of GIS to revolutionize the way information is managed in the country. In 1989, a government-wide user needs study was conducted to ascertain which areas of government would clearly benefit from the implementation of GIS. Three key recommendations resulting from the study were: that a Digital mapping database be implemented for the entire country; that a comprehensive fully integrated nationwide GIS be created; and that a high level National GIS steering committee be established to set standards and to oversee the GIS implementation. In 1990, acting on these recommendations, State of Qatar established a National GIS Steering Committee and The Centre for Geographic Information System (CGIS) with a mandate of implementing GIS across the country in an organized and systematic fashion. The objectives behind the decision to implement a nation-wide GIS program are: (a) Eliminate duplication of efforts causing wastage of resources by avoiding data redundancy and by

enhancing inter-agency co-ordination;

(b) Make right information available at the right time to the decision-makers for efficient planning and management;

(c) Foster teamwork among government agencies, especially those involved in physical and infrastructure planning, environment protection and local government authorities so that they all work towards common goals;

(d) Efficiently manage government expenses for future development requirements;

(e) Achieve consistency and uniformity in policies, standards and regulations for whole of Qatar; and

(f) Enable preparation of physical plans that are dynamic, flexible, easy to update, monitor and implement.

The strategies adopted to achieve the objectives are: (a) Gain support and commitment from the highest levels of government;


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(b) Make concerned agencies and officials aware of the potential and power of GIS;

(c) Encourage government departments for coordination and data sharing;

(d) Involve every government department in design and implementation; and

(e) Establish education and training programs and make GIS tools available to everybody.

This manual documents the Strategy Team, framework for the development of GIS, overview of geospatial data components and standard and the geospatial database specification. 8.2.0 Management of GIS Management of GIS in State of Qatar could be classified into Strategic Management, Tactical Management, Operation Management, Executive Management and Functional Users Management. Successful implementation of GIS in State of Qatar could be attributed to the successful managements. 8.2.1 Strategic Management

Strategic management begins with the identification and organization of a GIS Steering Group to examine the impact of transitioning to the technology. GIS in the State of Qatar is guided and supported by the highest levels of government (See Figure 8.1). In accordance with the Leadership’s wishes, Cabinet created the National GIS Steering Committee and the CGIS in October 1990. The National GIS Steering Committee plays the role of the GIS Strategic Management Team in the State of Qatar. Whenever possible, examination of the organizational process should encompass both a “top down” and a “bottom up” approach. The objective of the GIS Strategic Management Team is to evaluate the business process and establish a management framework within which the GIS Strategy can occur, ensuring that the development is efficient, effective, and useful to the organization. The National GIS Steering Committee plays a key role in Standardization and in fostering Cooperation amongst Government Agencies. Responsibilities of the National GIS Steering Committee include Development of:

• GIS Policies

• GIS Standards

• GIS training programs

• GIS database creation priorities

• Guidelines for data sharing and other GIS activities Experience has shown that failure to succeed in the development and management of geographic information lies not in the technology, but in organizational behavior. Successful adoption of geospatial technology has to be perceived as more than successfully acquiring the hardware and software, it includes the awareness for the value of planning, establishing objectives, and developing evaluation programs. A team approach then becomes a necessary function of planning. It also allows management to distribute the burden associated with this task while concurrently developing in-house expertise.


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8.2.2 Tactical Management The CGIS has the responsibility of the GIS Tactical Management Team effecting the implementation of GIS in all departments. The synergy role of the National GIS Steering Committee and the CGIS would be to organize the efforts of Qatar's Ministries & Agencies such that Qatar could realize the rewards of a nation-wide Geographic Information System implementation. The Mission Statement of CGIS is: “To coordinate a systematic implementation of GIS in Qatar, which simplifies data transfer between all agencies, minimizes data redundancy, and ensures suitably trained personnel are available to operate and manage the various components of the system.” (http://www.gisqatar.org.qa/new/all.html)

The CGIS also ensures continued cooperation amongst all agencies in Qatar. For this, they meet on regular basis (at present every 3

rd Monday) to discuss the communication, coordination and cooperation strategies for

acquisition, maintenance, sharing and dissemination of geospatial data among their respective authorities. Responsibilities of the CGIS include Development of:

• Point of reference for the Steering Committee

• Maintaining and updating Basemap for the state

• Authorized Mapping agency of the State

• Positioning services (geodetic network + GPS)

• National GIS standards and specifications

• Inter-agency coordination

• Technology transfer and keeping abreast technology at international level As the GIS Tactical Management Team, comprised of key directors and policy makers for the installation, CGIS has the overall responsibility to:

• Obtain funding

• Identify policy requirements and prepare recommendations for review/action

• Approve resource allocations and timetable for development

• Solve interdepartmental conflicts The objective of GIS Tactical Management Team is two-fold, the first is to fund and support the implementation process, and the second is to build commitment, hence the high level guidance. Only at this level can funding support be ensured. This level also demonstrates management commitment toward the

Figure 8.1: Management of GIS in the State of Qatar


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project, lending credence to the project. While not ensuring the success of the endeavor, experience shows that if staff members perceive that GIS is a management priority, they have vested interest to make it work. So, support from executive management increases the likelihood of success. Building commitment also includes getting the entire organization involved. The GIS Tactical Management Team is in a unique position to provide the necessary support to ensure organizational involvement. Getting everyone to be a part of the solution helps alleviate the fear experienced in transitioning to a new technology. It decreases the amount of resistance and encourages cooperation within the organization. If done properly, morale rises, and unit cohesiveness evidenced by esprit de corps is noted. 8.2.3 Operation Management After the formation of the National GIS Steering Committee and the CGIS, each member agency set off to implement their own GIS with the condition that it must be capable of integrating its data with any other member agency's GIS. Central to their goal of implementing GIS was the establishment of GIS Working Groups by each agency to provide the Operation Management of GIS in the State of Qatar. Membership of Agency Working Group includes:

• Senior Agency Technical & Management Staff - Leadership in defining agency specific responsibilities, demands, and priorities for GIS implementation.

• Agency GIS Coordinator - primary organizer of agency GIS implementation

• Agency GIS Technologist - to carry out, and report on implemented technical GIS activities

• Centre for GIS Staff - act as coordinating agent among all Agency Working Groups. These working groups had before them, the following basic objectives to achieve before they could reach their goal:

• Perform a detailed technical User Needs Study

• Compose a Data Dictionary

• Appraise existing records

• Collect data (either from records, or from site)

• Enter the data into the GIS

• Designing of Applications

• Develop GIS Applications Each member agency is set off to implement their own GIS with the condition that it must be capable of integrating its data with any other member agency's GIS. To facilitate this, a single GIS software platform was selected as the standard for Qatar. Figure 8.2 depicts the working relationship between the National GIS Steering Committee, the CGIS, and each of the Agency Working Groups. 44 government agencies in Qatar (see Appendix 8A) are using fully integrated GIS in their day to day activities. Agencies providing the following government services today functioning on the integrated GIS system are: Urban Planning and Development Authority, Roads, Electricity, Drainage, Water, Police Services, Agricultural Services, Telecommunications, National Statistics, Environment, Land Registration, Education, Health, Fisheries and Qatar University. 8.2.4 Executive Management

The GIS Coordinators Group for the Inter-Agency Project is the coordinators group to the GIS Working Groups. The GIS Coordinators Group (see Figure 8.3) addresses and acts upon, as part of a national effort, issues of common concern to all Agency Working Group. This group was organized within the CGIS, and offered Coordinators the opportunity to exchange ideas. In fact, many GIS Coordinators held offices within the CGIS premises, allowing further interaction.


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Figure 8.2: The Working Relationship between the National GIS Steering Committee, the CGIS, and each of the Agency Working Groups

1

1 Extracted from State of Qatar – GIS Database Specifications and Data Dictionary.

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(UNS)(UNS )GIS Coordinators

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Figure 8.3: Qatar GIS Coordinators Group1


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The GIS Coordinators supports objectives of the GIS Executive Management Team, i.e. CGIS, in providing Executive Management. Personnel assigned to this group should have an in-depth understanding of their area of expertise, databases, GIS software/hardware, networking, etc. This team has the overall responsibility to:

• Help develop strategy

• Meet tactical management team objectives

• Identify resource requirements

• Provide technical insights and experience

• Identify and evaluate operational processes that can be automated

• Identify GIS priorities

• Manage data structure CGIS is the chairing body of GIS coordinators group, and by setting regular meetings with representatives from every ministry/corporation, it encourages cooperation, sharing and coordination of GIS activities and ensures compatibility of all GIS standards. This group works to create and sustain a spirit of harmony in the community of GIS users in Qatar, which is a major goal of CGIS. This is achieved by bringing together and providing required support and training for all candidate people from involved GIS Ministries/Corporations. GIS Coordinators, who are responsible for setting up and maintaining the GIS databases in their respective Ministries/Corporations are focused on to receive a variety of GIS training classes, learn about implementation techniques. GIS Coordinators meetings are held at CGIS every three weeks regularly; it never stopped for the last 20 years. At these meetings ideas are shared, problems are solved, technical policies are formulated, and work initiatives are explored. The technical support and services offered by CGIS to the entire GIS community in the State of Qatar go a long way to cement friendships and strengthen the spirit of community. Cooperation, sharing and coordination of GIS activities are all encouraged by CGIS, particularly when it comes to the development of applications. There is a mutual agreement to clearly document any tools, utilities and scripts that anyone develops so they can be shared by all. Such efforts, in the long run, save time and money for all and help to ensure the reliability as well as the suitability of the products developed. Finally, by enforcing adherence to all GIS standards, CGIS has ensured compatibility throughout the GIS databases in Qatar. Compatibility itself tends to encourage and sustain cooperation because the data is readily transferred and easy to use. Moreover GIS has been successful in fostering teamwork among government agencies especially those involved in planning, environment protection and local government authorities so that they all work towards common goals. High resolution, fully integrated GIS is available to all agencies and the public. The agencies make use of the same base information, so all new data collected are also integrated. CGIS sets standards, provides training, supports the National GIS steering committee, creates data sets, and in general coordinates all aspects of GIS development and use throughout Qatar. The GIS Coordinators have jointly developed a volume set of National GIS Database specifications and data dictionaries consisting of 16 volumes, one for each agency. All specifications and data dictionaries are approved and administered by the National GIS Steering Committee in order to ensure that the compatibility necessary for data sharing is never jeopardized.


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The CGIS staff as coordinating agent among all Agency Working Groups has responsibility to:

• Prepare development strategy and implementation plan

• Manage the Agency Working Groups

• Provide technical insights and expertise

• Facilitate end user involvement in appropriate analysis, design, and development efforts

• Assemble the proper people and skills necessary for the Agency Working Groups

• Create an environment of open communication among groups and teams This single point of contact serves as a liaison to all teams and groups, internal and external to the process. This position is imperative because a knowledge void typically exists between the user and management. The CGIS staff acting as coordinating agent bridges that void. The CGIS Coordinator possesses a detailed understanding of the political environment and the technology. The CGIS Coordinator as Executive Manager acts as a facilitator or negotiator, solving problems as they arise. The CGIS Coordinator has the technical background and can assist management in aligning the technology with the strategic direction of the mission. A common cause for failure in developing a GIS has been the lack or absence of expert guidance. 8.2.5 Functional Users Management

The Functional Users Group is a subordinate group to the Agency Working Group. Personnel assigned to this group are the users who gather, process, analyze and disseminate geographic information. The Functional User Group is tasked to:

• Assist in developing strategy

• Identify resource requirements

• Identify data requirements

• Identify those processes that can be automated This is the group that is intimately familiar with the data that are collected and the output products the data supports. It’s the user for whom geographic information applications are written. It’s the user who accesses and shares data. The key point to remember is that Geographic Information System is user driven. The user is the client! 8.3.0 Structural Framework for the Development of Geographic Information Systems Building and implementing a full-scale GIS is a long and complex process. It impacts every organization on the installation and requires a substantial investment to construct and maintain. Figure 8.4 displays the structural framework for constructing a GIS. The entire process, beginning with the decision to implement the technology through its completion, can be divided into six logical phases, i.e. Initiation (Section 8.3.1), Evaluation (Section 8.3.2), Preliminary System Design (Section 8.3.3), Implementation Management (Section 8.3.4), Maintenance (Section 8.3.5) and Feedback (Section 8.3.6). Each phase is discussed below.


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8.3.1 Initiation (a) Strategic Plan Review The process begins with a review of the Strategic Plan. The strategic plan is a document that provides the installation with general guidance. It is usually comprises several sections including the mission statement, a set of guiding principles, goal statement, and program direction. The strategic plan defines the purpose of the installation (mission statement), in general terms of what it is the installation is tasked to accomplish (goal statement), and it provides specific direction for subordinate units (objectives). Each unit that comprises the enterprise also has a “plan” that provides guidance to the unit. Examine these as well and determine where they fit into the overall direction of the enterprise-wide process. (b) Analyze the Business Process The purpose of this analysis is to understand the existing organizational framework, how it operates, how the new technology will change the structure, and to create a framework under which the impacts of change can be managed. This analysis is an opportunity for management to tune-up virtually every job and function that is performed on the installation. GIS Strategic Management (See Section 8.2.1) must determine if information flow can be streamlined using a GIS. What information is gathered within the organization? In broad terms, examine the information and determine whether this information can best be displayed as locational information or as tabular data. Do spatial relationships exist with other data? Can these relationships be portrayed more efficiently with GIS? Is redundant information being gathered and maintained within the organization? Do multiple agencies collect the same data? Does information within the organization conflict? Are these duplicate data files necessary? Do they hinder dissemination of accurate information or hamper communications within the organization? If efficiency and efficacy are issues, is GIS the appropriate mechanism to solve the problem? Providing answers to these questions allows management to determine organizational needs and allows management the opportunity to identify and examine alternative solutions.

Phase 1

Initiation

Phase 2

Evaluation

Phase 6

Feedback

Phase 5

Maintenance

Phase 4

Implementation

Phase 3

Preliminary

Design

Figure 8.4: Structural Framework for Building a GIS


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(c) Feasibility Assessment Feasibility falls into three basic categories – technical, financial, and organizational. To determine whether or not a project is feasible, GIS Tactical Management (See Section 8.2.2) must examine and answer the following questions:

• Technical. Is the necessary technology available? Can it be procured at a reasonable cost? Is the required staffing available? Can it be obtained with a reasonable amount of funding? With a reasonable amount of training, can it be used by the staff?

• Financial. Is cost within the realm of resources that can be obtained? Does the return on investment (ROI) justify the investment? Can funding be allocated and sustained over the entire planning horizon?

• Organizational. Are organizational impacts (structural and processes) within acceptable parameters? Can performance measures be determined that satisfy management and policy requirements? Can funding be sustained throughout the planning horizon?

Answers to the above questions determine whether or not the installation should proceed with the implementation. If the answers to all three parameters indicate feasibility can be supported, then the current business process should be examined for efficiency and effectiveness. This examination is time consuming. GIS Tactical Management must determine whether or not information flows efficiently throughout the organization. Identify where the bottlenecks to information flow occur. Identify processes that are uniquely geospatial in nature, e.g., data that pertain to locational features and their related attributes – buildings, roads, land parcels, real estate. 8.3.2 Evaluation The primary concern during this phase is to obtain an accurate and detailed assessment of the present method of operation coupled with a complete inventory of equipment and resources. This will provide a baseline against which all actions will be measured. (a) System Investigation Building on the steps initiated with the analysis of the business process, the system inventory, i.e. the computers (both hardware and software) and the peripherals (digitizers, plotters, scanners, digital cameras etc.) are examined. Also examined are the established communication links – determine how computers and peripherals communicate with one another and the networking capabilities of the organization. (b) Site Survey The site survey employs a variety of techniques that can include (but are not limited to) interviews, workshops, questionnaires, and modeling. The goal of the site survey is to obtain an accurate depiction of the organization’s requirements – both present and future. The survey should examine not only the computer needs, but also personnel requirements e.g., skills available, skills needed, training requirements, and past investments that support geospatial technology. During the site survey the Tactical Management assesses what data the organization collects, activities that collect the data, and mapping and graphic needs of the organization. This survey should include all collected data, e.g., tabular data, graphic data, charts, and maps. Compare data collection with present mission requirements and identify extraneous data and data voids (data that should be but is not collected). Examine future needs of the organization. Is a mission change scheduled? What data are needed to support this tasking? (c) Identify Input and Output Identify and list the products (inputs and outputs) generated by the organization. What is produced? Why is it produced? How is it produced? Who produces the product? How often is this product produced? What data is needed to support the product? How does this product support mission accomplishment? To answer these simple questions it is imperative that the Tactical Management thoroughly understands the installation mission and have an in-depth understanding of the requirements the organization will place on the new system.


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After compiling “current products inventory” meet with the customer and develop a detailed listing of the products the system should produce. Combine the two lists and prioritize the inventory based upon some functional criterion e.g., mandatory product, product aids mission accomplishment, internal use only etc. Using the product list as a guide, determine the specific data requirements for the system – are data spatially related? Are they maps, reports, images? Are tolerances or accuracy specified? What mapping scales are required to adequately present the data? If the product is a map, attach a sketch and itemize the visual aspects (features) on the map. If it’s a report, define the information that is needed, including the headings and other common data fields – if possible; obtain a copy of the product. Identify the relationships between the data elements and the database. Finally, examine the tolerances and accuracy that are needed for the data. Error tolerance impacts the cost of the system. Determine how much error can be allowed and still retain the integrity of the final products. The less tolerance acceptable the higher the cost – cost of data precision is exponential. (d) Define Scope Analysis of the site survey and inventory of available resources allows the Tactical Management to define the scope of the proposed project. Knowing the mission requirements, available resources, data needs, and product requirements, allows the Tactical Management to prepare a requirements document. The requirements document should include all of the information discussed above, i.e., results of survey, results of inventory, current practices, current resources, needed resources, current training status, and a history of past investments toward the technology. It should also include a listing of output products – including examples of maps and map scales, reports and graphs etc., data requirements, types of data collected, logical linkages and error tolerances, and cost projections for the technology. Finally, a projected timetable should be developed and provided to the Strategic Management. This document, including recommended priorities, is presented to the Strategic Management for approval – remember the Strategic Management has the responsibility to set priorities and align the project with the overall organizational goals and objectives. 8.3.3 Preliminary System Design During this phase, the Tactical Management will develop a preliminary system design based on the information compiled during the mission review and the needs analysis. This step allows the Tactical Management and the users to optimize the system based on input received from the users and to examine the system design to ensure it is developed along a logical path. While the basic components of the system – data, hardware, software, and maintenance are discussed as disaggregated elements, they are not mutually exclusive – each has an impact on the other and is typically accomplished at the same time. They are separated below only to facilitate discussion.

• Database issues are concerned with data storage - where and how the data is stored, data access, data security, data accuracy, data standards, and data conversion.

• Software issues relate to what software should be used, and the modules necessary to support the GIS.

• Hardware concerns configuration requirements, communications (networking), type of equipment, location of equipment, and system performance.

• Maintenance is concerned with support issues e.g., responsibilities for maintenance and updates, procedures, and access.

(a) Database Database issues are a major concern because they are the most cost intensive factor of the system. Seventy percent of the total cost of a GIS is attributed to data collection, standardization, and conversion. Adoption of a spatial data standard provides a relational database schema and a naming convention that is compatible with most software and eliminates the cost of data conversion. Using the standards also facilitates data sharing across services – this means that applications can be readily shared between the services with little or no modification reducing the cost of application development. Reference could be made to the website of the International Cartographic Association (ICA) http://ncl.sbs.ohio-state.edu/ica/3_spatial.html.


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Database issues also need to address how data will be stored. Is it centralized or decentralized. Where will the data be stored? Who has access to the data? What level of access – read only, read and write? Not everyone has a need! Access should be granted only to those who have a legitimate need for the data. Finally, the level of accuracy or error tolerance must be specified for the GIS. It is impossible to develop a GIS without error. Error is built into the system! It comes from a variety of sources. Algorithms are used to convert images from raster to vector – error occurs. Vector images, complete with their errors, form the foundation for many CAD drawings. These drawings are “stretched and warped” to force-fit drawing to the digital geometry - increasing error. Error cannot be avoided – it can be minimized and an acceptable level of error can be prescribed. It is important to understand the needs of the end product and not over specify accuracy requirements. The more accuracy required the higher the cost of the GIS. The cost increases geometrically. Be cautious of vendors who prescribe centimeter accuracy! (b) Metadata Metadata is nothing more than data about the data. Metadata describes the content, quality, condition, and other characteristics of a data. Metadata serves three important functions. First, it provides end-users if data sets with adequate information for proper use of the data (documentation). Second, it provides a listing of work that can be shared with others (inventory). Third, it supports search capability of a data set based on its extended properties for others to find (catalog). (c) Software Software, too, is a critical element. The software chosen to support the GIS must consider the interoperability between the software packages e.g., CAD, GIS, spreadsheet, word processor, database etc. The applications developed for the system will also have a bearing. Identify programming needs. Automate routine functions. (d) Hardware Again, consider operability between software and the computer hardware (memory, ram, speed of processor, video card, compact disk, etc) and peripherals (scanner, digitizer, plotter, printer, camera, etc.). (e) Preliminary Design Report As a minimum, this report should address two functions - data and system. Based on the inventory, compile a list of data layers needed to support the GIS. Annotate data availability e.g., available, partially available, not available. How much of the available data is usable with the planned system? How much data conversion will be required? Prioritize this list. The systems section should include a description of the existing system and a description of the planned system and a map explaining how the organization will transition from one to the other. A description of the hardware and software components should be provided to include communications and interface requirements. This report will serve as the guideline for the development of the GIS. As with all reports that support this undertaking, send to the Tactical Management for their concurrence and approval. 8.3.4 Implementation Management The purpose of the implementation plan is to ensure the implementation process is efficient, effective, and useful to the organization. The process involves transforming the implementation process into specific tasks that can be accomplished within the constraints identified during the initiation and evaluation phases. It allows Tactical Management the opportunity to schedule time and resources against a logical sequence of events. The focus now shifts to the realm of application development – transitioning from the conceptual model to the practical application – translating the previously gathered information into a working GIS. (a) Detailed Design The detailed design is a continuance of the preliminary design. During this phase the preliminary design is translated into a specific functional system aligned with the organization’s business process. The database architecture is finalized and data compiled and converted to work within the architecture. Acquisition and


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assemble hardware and software components. Personnel are trained and position to receive the final product. The organization work process is restructured and production is transferred to the new process. (b) Compile and or Convert Data. A database schema is required to be developed. Spatial data standard forms the foundation of the approved schema for use on installations. Additionally, it provides a data dictionary. The standard reduces the cost associated with the development of a schema and it facilitates data sharing within the unit, the installation, and between major commands, and services. Data sharing is a key concept of the system. Data compilation began with the survey and inventory discussed in the evaluation. A list of all the data the organization uses was compiled. Now that data is reviewed for its quality and appropriateness. If it is compliant with the database structure then the data is uploaded. If not, the data must be converted. Conversion includes taking manual maps, engineering drawings, plans, as-builts and digitizing them in a standard format. Existing digital files are converted to a single format, flat files are converted to relational files, raster files to vector, tabular sets are geo-coded, and images sets are geo-referenced to their relative position on the earth’s surface. As the data is gathered it will become readily apparent that it is not standardized. This results in increased cost in data conversion. Data conversion is typically the most expensive portion of the GIS development. (c) Select and Acquire System Components Procurement of the system components is dependent upon the individual service policies and procedures. It’s beyond the scope of this guide to evaluate or make recommendations related to their individual practices. (d) Pilot During this phase, hardware and software are delivered, assembled, and tested according to some formal acceptance testing procedures – preferably stated in the functional specifications of the project. These procedures are designed to ensure the operability of the system, validate the database, its structure and format, create a benchmark, and provide hands-on training. This is not a complete system but rather a sampling or a cross-section of the entire system. It should allow the user to validate digitization routines, data entry, data retrieval, map production, functionality of specific applications, and its analysis capability. As the system undergoes the testing procedures technical problems will arise. This is one of the major functions of the pilot project, it ensures the operability of the system, that the system accomplishes what it was designed to do. Training is also provided during this phase. Training is provided by the contractor (if one was used), the vendor, or the team responsible for the system development. Ideally, this training is conducted on base, using the installations system, data, and applications. Training should consist of application familiarity, commands, product generation, system operation and system maintenance. It is important that training include long-term data maintenance and procedures on how to update the database.

(e) Load Database After the pilot project is thoroughly tested and all identified errors or technological problems corrected, the remaining applications and complete data files should be loaded. It is imperative that the data files undergo a quality control measure prior to loading into the system. The quality control measure should allow the database administrator the opportunity to evaluate the data contents, accuracy, continuity, and data consistency. The administrator should also examine the structure for integrity of the layering scheme and ensure the definitions for each of the elements are present and accurate. (f) Training An integral aspect of designing a Geospatial Technology is the development of an effective training plan. The training plan outlines a basic curriculum that allows the student to achieve a stated level of competency in GIS. The training process involves all staff and support personnel throughout the organization. It must recognize that there are at least three distinct levels of proficiency that must be addressed in the GIS Profession. Each of these is unique and requires a specific set of skills. The three levels are:


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• Doer. The doer is the most highly trained GIS technician within the organization. These are the experts who create the data and write the applications.

• User. The user’s focus is on manipulating and analyzing the data. This person creates derivative data sets from the parent database.

• Viewer. The viewer views, extracts, analyzes, and displays data for communication purposes. The training plan must also address the source of training, e.g., vendor, university, on-the-job training, consultant, or government based courses. GIS technology is not limited to a single discipline but rather encompasses a variety of skills across a multitude of practices. In reality, GIS is an inter-disciplinary tool, drawing its knowledge from several fields of study consequently, the GIS technician must have an understanding of several disciplines. The CGIS has developed a recommended curriculum for the GIS professional and has provided a list of training sources. The training plan must also target the student based on the level of interaction. Training demanded of senior management (viewer) differs from that required for middle management (user) and again for the training necessary for the operator (doer). Each has a specific need that must be met. Senior management is concerned with issues that relate to how the technology will impact the budget, personnel, policies, and procedures. They will be concerned with how the system will be implemented and what their specific role is to ensure the success of the endeavor. Middle management is also interested in these items. They also need more specific knowledge on how it works, what makes it successful, what tasks need to be performed, and what impact this technology will have on the business process. Operators need to know how to use the specific programs, enter data, generate reports, and maintain the system. The vendor usually provides GIS training for vendor specific programs. However, due to the complexity of the technology, education should go well beyond vendor supplied training. They should also receive training in computer-aided design and drafting, cartography, coordinate geometry, spatial relations, information technology - programming, database management, systems administration, and presentation skills. Providing the user with in-depth the knowledge base will help alleviate problems during the implementation of the technology. It will provide the user with the skills necessary to recognize and avoid product bias. (g) Staffing GIS is an inter-disciplinary field. Consequently, there are various full-time skills that are necessary to ensure the success of this endeavor. Some of these skills have been identified and can be stated as positions, e.g., GIS Manager, GIS Analyst, Computer Programmer, Systems Administrator, Database Manager, and a CAD Operator or Draftsman. These positions can be filled with existing personnel who have the stated skills or existing personnel can be trained to accomplish these tasks. The option also exists to go outside the organization and hire personnel with the requisite skills or the function can be outsourced to a contractor. Consequently, a combination of contracting and existing personnel, working together is prudent. Initially only the GIS Manager, working in concert with the Executive Management (See Section 8.2.4) should be sufficient. However, as the system evolves other skills are brought into play. For example, application development should involve the programmer; database design should involve the database manager. A definitive schedule should be developed to allow this transition. If contractors are initially used, then a scheduled transition from contractor to in-house personnel should be explicitly built into the process. The training plan should ensure that personnel are identified and provided the necessary training to ensure they are capable of assuming the assigned tasks and responsibilities. (h) Transition to Technology Everything known to mankind has a beginning and an end. Just as every project has a beginning and an end, somewhere along the line the GIS Implementation reaches fruition - the project ends and the system becomes operational. Exactly when this change occurs varies from base to base depending on a multitude of factors. Whenever the transition occurs there is a corresponding change in the business process. The focus shifts from planning and education to operation and maintenance of the system. (i) System Operation Budgeting for a GIS is related to (1) labor, (2) hardware, (3) software, (4) maintenance of existing system, and (5) miscellaneous expenditures.


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• Labor cost includes the annual salary of the personnel assigned to the GIS functions. While the salary is set, the manager may prefer to track internal costs in separate categories such as direct and indirect labor costs. Direct costs are associated with time spent on project management or project completion. Indirect costs are costs not directly attributable to the GIS such as time spent in training and administrative functions.

• Hardware cost should include all existing maintenance and or service contracts for all hardware necessary to support the GIS function to include the CPU’s, modems, digitizers, scanners, etc. It should also include indirect costs of replacement and modernization of equipment. Computer hardware life cycles run about eighteen months and become truly obsolete every three to five years.

• Software cost should include funds associated with the purchase and or lease of software packages including periodic upgrades of software. In general, GIS software tends to be upgraded on an annual basis. For planning purposes, a GIS life cycle for management applications is about five to seven year life cycle, after which much of the technology and many of the procedures should be replaced.

• Maintenance cost should include time spent maintaining the system. Maintenance includes preventative maintenance, backup of system files, system repairs, and changing parts (if assigned to this function). A general rule of thumb estimate for an annual budget is to fund fifteen percent of the systems total purchase price.

• Miscellaneous cost includes all other costs. As a minimum, these should include administrative support, office supplies, and travel and per diem costs.

At this point, an operational GIS is available. This implies that more than just hardware and software are functional. It also means that the system is making a difference in how the organization is meeting its mission tasking. Being operational means the customer is receiving the products they have been promised in the implementation plan. 8.3.5 Maintenance Maintenance includes that of hardware, software and data: (a) Maintenance of Hardware and Software Maintenance of hardware and software includes: determine where equipment will be located, and identify who is responsible for the maintenance of the equipment; develop operating procedures for maintenance, (schedules, instructions, etc.) and determine access requirements. It is imperative that line item funding for system upgrades be part of the budget. Schedule system upgrades annually. For example, computer technology changes render computers obsolete every five years – the budget should allow for a fifteen-percent turnover of computers annually. Software upgrades will be needed annually in some cases and semi-annually in others. Ensure these items are included in the budget. (b) Maintenance of Data Building a database consists of two distinct steps. The first step is inputting the initial data and the second step is maintaining the data. Inputting the data consisted of acquiring from multiple sources the data necessary to support the selected geospatial applications. Maintenance consists of keeping the data current. Data is the heart and soul of any information system. It provides the foundation upon which decision-makers plan their activities. Sound data and maintenance procedures are essential to ensure that data and the information derived from the data are above reproach. Once the quality of the data is questioned then the value of the geospatial system is negated. Data are of little value if they cannot be trusted. It has been stated that the most significant costs attributed to the development of a GIS lies in the data and data-related activities. Conversely, the greatest savings are gained from data and data related activities. A significant saving is realized by reducing the number of times a piece of data must be entered and manipulated. For example, savings are realized when data are shared from a single data file rather than from multiple inconsistent entries. This also leads to increased efficiency in data processing, increased data reliability, and better decisions based on accurate and current data. An underlying goal of information technology is to increase the efficiency of data entry and serve consistent, accurate, and current information to the decision-maker.


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Data maintenance is probably a larger problem than data collection mostly because data maintenance is an on-going process. Not only is it on-going, maintenance cost over the long haul are just as (or more) expensive than the initial data gathering. But, it also provides a platform from which the user may realize significant savings through gains in efficiency. 8.3.6 Feedback Even the best laid plans change. The implementation process must remain flexible to accommodate evolving missions, technological advances, and personnel changes. Short-term focus may redirect the course of the implementation plan. Consequently, a systematic review can ensure the implementation remains on track or reflects its direction as mission needs change. The initial review of the system should entail some sort of formal appraisal. It should be channeled toward specific, pre-defined aspects of the system comparing the original design to the delivered or manufactured product. Is this system accomplishing the tasks as designed? Does it function as expected? Is it more efficient than the “old way”? Does it follow the parameters established in the Delivery Order? Is it producing the designed products? Remember that the GIS is a tool that provides the decision-maker with the tools necessary upon which they can base decisions. Decisions are based on their confidence in the data provided. In order for the GIS to remain a viable tool, it must continue to meet these expectations. Plans do change. The GIS must remain flexible to meet these changes. As mission change and evolve, so too should the GIS. Periodic reviews of the system are in also in order. The frequency of these reviews remains at the discretion of the GIS Manager. However, every change in installation plans should be reflected in the GIS. The GIS Manager must constantly re-evaluate the GIS to ensure its integrity. 8.4.0 Geospatial Data Overview and Standards GIS technology helps users to perform a variety of tasks. It is important to focus on standardizing data and data life-cycle management to meet the many challenges today and tomorrow. This focus on standards and life-cycle management enables interoperability and provides an effective tool to manage the investments made in GIS technologies. The cost of developing and maintaining geospatial data is the most expensive and crucial part of implementing geospatial strategies. Standardization will enable the data collected to be used throughout the organization in an enterprise implementation. In addition, strict adherence to national and international standards will extend their usefulness to local, national, and international agencies. Strict compliance will also ensure that the data these other agencies collect will be compatible and interchangeable with CGIS data sets. 8.4.1 Geospatial Data Components It is not the intent to describe in detail geospatial data. There are numerous books and published reference materials on geospatial data. It is the intent of this paragraph to describe geospatial data and identify applicable standards. An entity or feature is a real-world phenomenon, such as a lake, river, house, etc. It can be modeled as a point, polygon, line, raster; but it is the thing being described. Entities, features, and geospatial data in general can be broken into three parts: the spatial component, the attribute component, and the metadata (See CGIS Topographic Data Dictionary). (a) Spatial Component – All geospatial data has a spatial component or locational information associated with it. Locational information can take the form of latitude/longitude, state plane coordinates, universal transverse Mercator coordinates, etc., but in order for it to be integrated with other data sets, it must have locational information tied to a geographic information system. Traditionally, survey data have been tied to local coordinates rather than a geographic reference system. CAD drawings for architectural, structural,


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mechanical, and electrical disciplines have not been tied to a geographic coordinate system. CAD civil/site layout drawings are traditionally tied to a state plane coordinate system. In order for CAD and survey data to be used in a GIS solution, the data need to be referenced to a geographic coordinate system. (b) Attribute Component – The attribute component, or the non-graphical component of the geospatial data, is the information about the geographic phenomena. For example, the information associated with a lake, such as the name of the lake, volume, discharge rate, etc., are all attribute information. Without the attribute information, the ability to perform spatial analysis is limited to automated mapping. (c) Metadata – Geospatial metadata refers to the documentation of geospatial data sets. Geospatial metadata describes the content, quality, condition, and other characteristics of data.

8.4.2 Geospatial Data Standards1

Standards may be catalogued in several ways. Usually they are developed in either an informal or formal process, in reaction to or in anticipation of need. An informal process is developed by source of authority. An informal standard, or de facto standard, is exemplified by AutoCAD DXF. This is when the user community, through constant use, adopts a practice without any formal certification. A formal process for developing a standard requires certification by a government body or a professional organization. Types of geospatial data standards include the following:

• Data modeling – Either a conceptual or logical description of data organization.

• Data content – A definition of feature, attribute and values.

• Data symbology – Specifies display and output symbol libraries.

• Data quality reporting – Provides a standard for data set quality reporting.

• Metadata – Data that describes the data set and includes information on its usage.

• Data exchange and transfer – Standards that define how data are exchanged or converted from one format to another.

8.5.0 Geospatial Database Specification

2

A database specification should be established to serve two purposes: provide a firm set of rules for data collection and database construction, and describe the database in sufficient detail to permit application development. This specification will permit use of the database inside and outside of the producing organization and result in a substantial cost savings to users. At a minimum, the specification should include the following sections:

• Scope – A concise abstract of the coverage of the specification.

• Applicable Documents – A bibliographic listing of the standards and references used in developing the specification.

• Database Description or Collection Criteria – A summary of the information contained in and the structure/format of the database and the intended use of the data. What features/entities need to be collected. Reference appropriate data content standard.

• Metadata – A listing of the static metadata elements, including accuracy, datum, scale/resolution, source, and projection (if applicable).

• Data Format – A detailed description of the data format.

• Data Accuracy – Reference the appropriate accuracy standard.

• Data Symbology – Identify symbology to be used.

• Data Dictionary – A dictionary of the feature and attribute codes used in the database. Reference appropriate data content standard.

A database should be built to meet the requirements of the database specification. Before the design of a database is finalized, it is advisable to create a prototype database and distribute it to potential users, along with a copy of the draft specification. This procedure is valuable, even if only for internal use.

1 Reference: Metadata Details document of CGIS, CGIS Data Dictionary and Specifications and CGIS Database Design Document.

2 Reference: CGIS Data Dictionary and Specifications.


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8.5.1 Vector Data Equivalence The geodatabase model supports an object-oriented vector data model. In this model, entities are represented as objects with properties, behavior, and relationships. The employed geodatabase is used by ArcGIS

products®, a Geographic Information System software platform produced by Environmental Systems Research Institute (ESRI). Geometric data types used in this dictionary are as follows: For further reference and latest information on vector data model, refer to the supporting documentation from

ESRI on the ArcSDE® data model or visit www.esri.com. Data Mapping: All feature class and attribute item types in coverages are mapped to geometry and field types in the geodatabase. More than one feature class type in a coverage will map to the same geometry type in the geodatabase. For example, points, tics, and nodes all map to geometry type point. Following Table 8.1 illustrates the mapping of feature class type to geodatabase geometry type between coverage and the geodatabase.

Table 8.1: Geometry Type Mapping between Coverage Feature Class and Geodatabase

Coverages Feature Class Geodatabase Geometry

Point Point

Arc line (polyline)

Polygon Polygon

Node Point

Tic Point

Region Polygon

Route line (polyline) with measure

Annotation Annotation1

Section Polygon

1 Annotation in the geodatabase is not a geometry type but is implemented as a feature type.


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Table 8.2: Field Mapping between Coverage (INFO Item) and Geodatabase:

Coverage Field GDB field Range/format/notes

Type Width Type Width GDB supports seven generic data types

B 4 Long integer 4 -2,147,483,648 to +2,147,483,648

C 1-320 Text Varies Text

D 8 Date 8 mm/dd/yyyy hh:mm:ss am/pm

F 4 Float 4 About -3.4e38 to +1.2e38 (~7 significant digits)

F 8 Double 8 Double

I 1-4 Short

integer 2 -32,768 to +32,767

I 5-9 Long integer 4 -2,147,483,648 to +2,147,483,648

I 10-16 Double 8 Double

N 1-9 Float 4 Float

N 10-16 Double 8 Double

BLOB Varies Store images or other multimedia

Table 8.3: Geometry Type Mapping between Shape File and Geodatabase

Shapefile Geodatabase geometry

Point Point

Point M point with measures

Point Z point with Zs

Polyline line (polyline)

Polyline line (polyline) with measures

Polyline line (polyline) with Zs

Polygon Polygon

polygon M polyline with measures

polygon Z polyline with Zs

Multipoint Multipoint

multipoint M multipoint with measures

multipoint Z multipoint with Zs

Table 8.4: Field Mapping between Shape File (dBASE Field) and Geodatabase:

Field type Field width Geodatabase field type

Date - date

string 1-255 Text

boolean - Short integer

number 1-4 (decimals=0) Short integer

number 5-9 (decimals=0) Long integer

number 10-19 (decimals=0) Double

float 1-13 Float

float 14-19 Double

number 1-8 (decimals >0) Float

number 9-19 (decimals >0) Double


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Table 8.5: Geometry Type Mapping between CAD and Geodatabase:

CAD feature class Geodatabase geometry

Point Point

Polyline Line (polyline) with Zs

Polygon Polygon with Zs

Table 8.6: Field Mapping between CAD Field and Geodatabase:

Filed type Geodatabase field type

String Text

Integer Long integer

Double Double

Table 8.7: Legacy Data and Geodatabase Equivalents

Coverage Geodatabase Description

Workspace Geodatabase RDBMS that contains data

Coverage Feature dataset Contains topologically related feature classes

Feature class Feature class Contains feature of same geometry

Tic N/A GDB does not use; may import as points

Bnd N/A Extent is a property of the spatial reference

Arc Line Line may be multipart, like routers

Node Point GDB does not use; may import as points

Point Point Points may be multipart

Polygon Polygon Polygons are "simple", not chains of arcs

Polygon Label N/A GDB does not use; may import as points

Route Line Lines with m (measure) coordinates

Region Polygon Polygons may be multipart, like regions

Annotation Annotation1 Feature linked or not

N/A Dimension A type of graphical annotation

Network Network Topologically related lines and points

Topology Topology A set of rules defining spatial relationships

1 Annotation in the geo-database is not a geometry type but is implemented as a feature type.


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8.5.2 Tabular Data Model The use of tabular data model depends on the Database Management System (DBMS) in which the table is

stored such as Oracle®. The geodatabase supports only the following seven generic field data types, data types not in the table cannot be used:

Data Type Bytes Range/format/notes

Short integer 2 -32,768 to +32,767

Long integer 4 -2,147,483,648 to +2,147,483,648

Float 4 About -3.4e38 to +1.2e38(~7 significant digits)

Double 8 About -2.2e308 to +1.8e308(~14 significant digits)

Text Varies Up to ~64,000 characters

Date 8 mm/dd/yyyy hh:mm:ss am/pm

BLOB Varies Store images or other multimedia

Oracle® Data types used in Oracle

® are as follows:

CHAR Character A fixed-length character string up to 2000 bytes in length. It will pad unused bytes with spaces.

VARCHAR2 Character A variable-length character string up to 4000 bytes. It will not consume storage space for unused bytes.

NUMBER Number A variable-length number field, either with or without decimals. There is a maximum of 38 significant digits.

DATE Date A fixed length, 7-byte field, includes both calendar date and time of day.

LONG Long Text A variable length character string of up to 2GB (231 bytes).

RAW Raw A variable-length binary data, only 2000 bytes.

LONGRAW Binary Large Object (BLOB) A variable-length field used for binary data up to 2GB (231 bytes).

BLOB BLOB Binary large object, up to 4 GB in length

8.5.3 Qatar National GIS Data Dictionary Specifications These specifications are administered under the authority of the National Geographic Information Systems (GIS) Steering Committee. It is the responsibility of this committee to provide national standards and specifications for all GIS databases in the State of Qatar that are compatible, and provide for effective sharing/exchange of data where such sharing is warranted. The Qatar National Geographic Information Systems Database Specifications & Data Dictionary is a multi-volume set of “Information Resource Catalogues”.


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Each GIS Data Dictionary is one volume in a series, of which focuses on a particular resource. The full series includes the following:

Table 8.8: GIS Data Dictionaries

Volume 1 Topographic Volume 6 Water Volume 11 Real Estate

Volume 2 Drainage - PWA Volume 7 Police Services Volume 12 Environment

Volume 3

Urban & Regional Planning and Development

Volume 8 Agricultural Services Volume 13 Fisheries

Volume 4 Roads - PWA Volume 9 Telecommunications Volume 14 Education

Volume 5 Electricity Volume 10 National Statistics Volume 15 Health

Geodatabase is a container of geographic data objects and often refers to as workspace. The various types of objects it contains such as Tables, Feature classes, Subtypes, Feature datasets, Raster datasets, Relationship classes, Geometric networks, Topologies, and rules. Geodatabase addresses both geographic and non-geographic data issues. They are organized as follows:

Table 8.9: Organization of Geodatabse Components

(a) Data Model

Data modeling plays an important role in all software environments. Data models can be used as simple representations of reality. The focus of most geographic information systems (GIS) is on the spatial relationships between entities in the real world. Having an accurate and structured dataset is crucial to the validity of the complex spatial analysis that is to be performed by a GIS. In order to maintain the integrity of data imported and edited by the end user, strict controls must be imposed via the model. Place all schematics of Object Oriented data models created either using CASE and UML for designing and building a geo-database e.g. Visio or any latest tool available/supported by ESRI technology to specify UML model.

Data Model List of all required data models

Feature Datasets Description of all required Feature Datasets and listing of Feature Classes, Topology layers, Geometric Network, Annotation FC, Dimensions (geographic object classes), and features' hierarchy

Feature Classes Description of all required features classes

Annotation Classes Description of all required annotation classes

Topology Description of all required topologies

Domains/Subtypes Description of required domains and subtypes

Tables/Object Classes Entities (non-geographic object classes) and their attributes, if applicable

Relationship Classes Description of relationship classes, if applicable

Geometric Networks Description of all required Geometric Networks

Network Datasets List all required Network Datasets

Raster Dataset Description of all raster datasets; if applicable

Raster Catalogs Description of all raster catalogs; if applicable

Others Indexes/Other Object Classes, optional

Features Description of features (geographic object classes)


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(b) Feature Datasets The purpose of this section is to identify all feature datasets, topology layers, geometric network and geographic object classes including Annotation and Dimension object classes required for each datasets. These should be listed alphabetically by the classes name in respective Feature Dataset. Feature Datasets is a collection of feature classes that shares the same spatial reference. To model or maintain spatial relationships in feature classes using a topology or geometric network, the feature classes must reside in a feature dataset. Feature classes that store simple features (not part of a topology or network) can be organized either inside or outside a feature dataset. � Feature class stores features with the same type of geometry and the same attributes. In geo-database,

an object class that stores features and has a field of type geometry. For naming convention, please refer to Feature Class section.

� Topology: Identification of the spatial relationships that meet the needs between features in one or more feature classes or subtypes that meet the needs of data model. The following types of rules are available:

� Point rules � Line rules � Polygon rules

Separate one or more pages should be devoted to list the names of feature datasets, feature classes, and topology layers or any object classes those are participating in the geo-database. Following illustrates a list of feature datasets, feature classes, and topology layers for topographic database.

For example: List of Feature Datasets, Feature Classes and Topology Layers

1. Landscap

• Landscap_Arc

• Landscap_Polygon

• Landscap_Topology

2. Landuse

• Landuse_Arc

• Landuse_Polygon

• Landuse_Topology

3. Veg

• Veg_Arc

• Veg_Polygon

• Veg_Topology

4. Landchng

• Landchng_Arc

• Landchng_polygon

• Landchng_Topology

5. Urban

• Urban_Arc

• Urban_Polygon

• Urban_Topology

6. Trnsport

• Trnsport_Arc

• Trnsport_Polygon

• Trnsport_Topology


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7. Landmark

• Landmark_Point

8. Height

• Height_Point

Topology Rules for Urban Feature Dataset Rule Feature Class Associated Feature Class Must Not Overlap URBAN_ARC

Must Not Intersect URBAN_ARC

Must Not Self-Overlap URBAN_ARC

Must Not Have Dangle URBAN_ARC

Must Not Have Pseudo URBAN_ARC

Must Not Intersect Or

Touch Interior URBAN_ARC

Must Not Self-Intersect URBAN_ARC

Must Not Overlap URBAN_POLYGON

Boundary Must Be Covered By URBAN_POLYGON URBAN_ARC

The Feature Datasets must be described in alphabetic order by its name. The description of particular feature dataset should be started from separate page. One or more pages should be devoted for each feature dataset. Each page (or group of pages) is of the same format. At the top of the page is the full feature dataset name. This must be unique of any length, but is generally kept of 10 characters. The feature dataset is then described in the following headings:

♦ Description: A long description of the feature dataset's contents in terms of what criterion was used to define it. This will generally be the theme by which compulsory physical relationships were examined.

♦ Name: Write a name of feature dataset which will be used in other naming conventions such as for feature classes, topology layers, etc.

♦ Feature Classes: A list of feature classes that can be found under this feature dataset.

♦ Feature List: A list of features (classes of objects) those can be found in a feature class are listed with each feature name and its Feature GFCODE

1. The feature list should be further

subdivided into separate lists based on the geometric representation of the feature. Each of these lists is sorted in alphabetical order on GFCODE. The geometric representation has been classified into the following categories:

♦ Point primitive feature

♦ Line primitive feature

♦ Polygon primitive feature

♦ Line with measure system

♦ Point events

♦ Linear events

♦ Polygon � Known Redundancy: Notes regarding any features in this layer for which their geometry exists

redundantly in other layers.

1 Features and Feature GFCODEs are explained further in the Features – Section 8.5.3 (j).


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� Hierarchy: An indication of any topological hierarchy that may exist. For example, polygonal features may be bounded only by those linear features greater than a defined level in a hierarchy of linear features. A similar relationship may also exist between linear and nodal features.

� History Notes: If geometric history is maintained, the means by which it's done is identified. � Owner: The agency which owns (or has been appointed as custodian for) the geometry in this layer. � Update Rights: The agencies entitled to submit changes to the geometry in this layer. The list of features' hierarchy under a respective feature dataset should be started from separate page. One or more pages should be devoted for the same. Write at the top of the page "Feature Hierarchy" then feature data set name and followed by list of all features with their hierarchy. (c) Feature Classes The purpose of this section is to identify all feature classes required for each datasets. Here details explain business table of feature class. List and order all the identified feature classes by its name and describe them accordingly. One or more pages are devoted to the description of a feature class. Each page (or group of pages) should have same. At the top of the page is the feature class's full name. The feature class is then described under the following headings: � Name: The entity name, for primary geographic feature tables (business table) of type point, arc, or

polygon, the Name assigned must be (<feature dataset>_<feature type>). For example, table landscape_arc would have this Name for arc feature class of landscape feature dataset.

� Description: A long description of the feature class. � Feature Dataset: Name of the feature dataset that contains this feature class, if applicable. � RDBMS: The name of the Relational Database Management System within which this business table

resides. � Known Redundancy: An indication if there is any data in the table which exists redundantly in other

tables.

� For the primary geographic feature attribute tables (business tables) in ArcSDE®1

, a number of mandatory columns exist. Some fulfill GIS software requirements, whereas others fulfill national feature inventory requirements.

� Column Data Types: The breakdown of each column in the table should be identified in the following

headings such COLUMN (name of the column), TYPE (what kind of value does it accept), WIDTH (how much is the width of column to accommodate the required values) and DECIMALS (number of decimal

places) for Oracle®2

tables, and CHARACTERISTICS to define domain and constraints such as acceptable values, range, validation checks, constraints for further limiting column values, unique key, primary key, foreign key etc. Note that column names can only be of maximum 10 characters in length,

and must not conflict with any reserve word identified within ArcSDE® or Oracle® DBMSs. For the

primary geographic feature attribute tables (business tables) in ArcSDE®, a number of mandatory columns exist. Some fulfill GIS software requirements, whereas others fulfill national feature inventory requirements.

� Column Definitions: A description of what each column represents.

1 Refer to ArcSDE® documentation for further details

2 Refer Oracle® documentation for further details


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� List of Features: Provide a list of all features lie in this feature class in a table format with two columns under heading of GFCODE and definition, for feature details refer Features – Section 8.5.3 (j).

� Owner: The agency that owns (or has been appointed as custodian for) the data in this table. � Update Rights on Columns: The agencies which are entitled to submit changes to the data in

specific columns of this table. � Relate Table: A table which contains a list of all direct relationships for the given table. In case of

many-to-many relates via a link table, both sectors of the relate table are shown on the same row. Diagram methods: Design documents are often simplified (abstracted) so they may be easily read and understood. Use Unified Modeling Language which is independent of process and language under the Visio environment or any latest visual tools for data and software modeling available at ESRI. ESRI provides Visio templates needed in order to build designed model. They contain ArcObject geodatabase classes, their interfaces, and ESRI extensions to UML. Provide Data Model depicting relationship between feature classes, subtypes for a respective feature dataset. Also list out all domains applied for each feature class/subtype for a feature dataset. For clarity, Link Tables may be omitted. The Lookup Table that does not have its own Appendix C listing must be shown on in the model Master Tables it’s referenced with. A Lookup Table that has its own Appendix C listing must either have its own model, or be shown on the models of Master Tables it’s referenced with. The following class diagrams illustrate the representation of Feature Datasets used for developing topographic model.

LANDSCAPE VEGITATION

LANDCHANGE

LANDUSE

URBAN TRANSPORT

LANDMARK HEIGHT

Figure 8.5: Feature Datasets for Topographic Geo-database


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The following illustration depicts the modeling of Feature Dataset, Feature classes, subtypes, and domains in UML/Visio, showing an example for Urban Feature dataset and its feature classes, subtypes and domains used for modeling topographic database.

URBAN FEATURE DATASET

URBAN_POLYGON

+ OBJECTID

+ GFCODE+ TYPE+ GFCODE1+ TYPE1

+ ARURBN_KY+ DATE_LUPD+ METHOD

+ AGENCY+ ARURBN_KY1+ SHAPE

+ SUBTYPECOD

URBAN FEATURE DATASET

URBAN_ARC

+ OBJECTID+ GFCODE+ LNURBN_KY

+ DATE_LUPD+ METHOD+ AGENCY+ SHAPE

+ SUBTYPECOD

FEATURE DATASET

FEATURE CLASS

SUBTYPES

CODED VALUE DOMAIN

Pool

Swimming 001

Water Fountain 002

Tower

Water 001

Tank

Oil 001Natural 002

Water 003

Sanitation 004

Building

School 001

Refinery 002

Clinic 003Light House 004

Mosque 005

Stadium 006Hospital 008

Police Station 009

Fire Station 010

Government 011Bank 012

Hotel 013

Souq 014Co-operative 015

Building

+SUBTYPECOD = 14

+GFCODE =TGARBLDG

+GFCODE1

+TYPE

+TYPE1

Pool

+SUBTYPECOD=145

+GFCODE = TGARPOOL

+GFCODE1

+TYPE

+TYPE1

Tower

+SUBTYPECOD=129

+GFCODE = TGARTOWR

+GFCODE1+TYPE

+TYPE1

Tank

+SUBTYPECOD =113

+GFCODE = TGARTANK

+GFCODE1

+TYPE

+TYPE1

Generalization

Binary Association

Figure 8.6: Modeling Feature Datasets, Feature Classes, Subtypes, Domain in UML/Visio


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(d) Topology Layers Topology: Identification of the spatial relationships that meet the needs between features in one or more feature classes or subtypes that meet the needs of data model. The following types of rules are available:

� Point rules � Line rules � Polygon rules

The primary purpose of geo-database topology is to define spatial relationships between features in one or more feature classes. It stores edited area, rules, errors, and exceptions. The primary spatial relationships to model are adjacency, coincidence, and connectivity. More than one topology rules may be applied in one feature class. Provide a list of all feature classes and/or subtypes affected by topology rules. All topology rules those are going to be applied on feature classes of a feature dataset should be listed under a same feature datasets. List and order all the identified topology layers by its name and describe them accordingly. One or more pages are devoted to the description for each topology layer. Each page (or group of pages) is of the same format. At the top of the page is the full name of topology layer. The topology layer is then described in the following headings: Name: Following naming convention should be followed for topology layers:

<Feature Dataset Name>_<Feature Class Name>_Topology

Feature Class Name: is the name of feature class whose rank is the highest in the topology relationship. If there is only one feature class in topology then same name should be used. Description: Long description of topology layer's contents in terms of what spatial relationships is maintained and why. Cluster Tolerance: Define a distance in which all vertices and boundaries are considered identical, or coincident. The default is the inverse of the precision of the feature dataset. Feature Dataset: Name of the feature dataset which contains this topology layer. Feature Classes: List out all feature classes those will participate in the topology. Ranks: Ranks allows controlling how vertices move during validation process. Determine the number of ranks (up to 50) based on data, and the priority of the rank of each feature class in the topology. Rules: These define conditions in the topology, and are used to specify and constrain the topological relationships that must exist within the topology. Specify topology rules those will be applied and corresponding feature classes. (e) Domains/Subtypes Domains: Attribute domains define additional rules/constraints for fields in table, feature class, or subtype. They are created as properties of the geo-database, and then are assigned to fields by editing the field properties of a feature class or table. The same domain may be assigned to many fields in different tables. Also, domains may be applied to all records, or to specific subtypes of records. These are used in defining legal values or defining split or merges policies for features. Following are the types of domain:

• Range Domain

• Coded-value domain Range domain specifies a valid range of values for a numeric attribute. A coded value domain can apply to any type of attribute – text, numeric, date, and so on.


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List and order all the identified domains needed for database by its name and describe them accordingly. Description of each domain should start from separate page. One or more pages should be devoted to the description of each domain. On the top of the page is the name of the domain and it must be unique of any length. Then describe domain as follows: domain properties, codes/ranges and values. The naming conventions for the domains are as follows:

(i) If domain is specific to a feature class then –

AgencyCodeFeatureClassName_DomainName

(ii) If domain is applicable to more than one feature class –

AgencyCode_DomainName

Description: A long description of domain including need and objective. Following example shows the naming convention used, domain properties, coded values for specifically arc feature class of vegetation feature dataset in topographic database. Name: Veg_Arc_GFCode

Domain Properties

Field Type Text

Domain Type Coded Value

Split Policy Duplicate

Merge Policy Default Value

Coded Values

GFCODE Description

TGLESCRB Scrub Extent

TGLEWDAR Wooded Area Extent

TGLNHDGW Hedgerow

TGLNTRLN Tree Line

TGLVMPLT Mapping Limit Extent

TGLVNEAT Neatline Extent

Subtypes: The geodatabase has several data integrity and data management capabilities, one of them is subtypes. The objects stored in a feature classes or table are organized into subtypes and can have set of validation rules associated with them. When to use subtypes it depends upon business requirements. For example, if we are trying to distinguish objects by their default values, attribute domains, connectivity rules, and relationship rules, it is recommended to create subtypes for a single feature class or table. If we are trying to distinguish objects based on different behaviors, attributes, access privileges, or whether the objects are multi versioned, we must create additional feature classes. The description of each subtype should start from separate page. One or more pages can be devoted to the description of each subtype needed to database. Use following subtype values and associated features those are common to all feature classes:

0 - New feature 999 - Empty feature (applicable to polygon feature class only)


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Order and description of subtypes is as follows: Feature Dataset Name: Write the name of feature dataset that will contain these subtypes. Feature Class/Table Name: Specify the name of feature class/table where these subtypes will be applied. Description of Subtypes: Write the description of each subtype and respective code. (f) Tables The purpose of this section is to identify all tables. List and order all the identified tables by its name and describe them accordingly. One or more pages are devoted to the description of a particular table. Each page (or group of pages) is of the same format. At the top of the page is the RDBMS table name. Other than the primary geographic feature

attribute tables in ArcSDE®, there are 3 different types of tables indicated in this document. These are: MST Master Table - A primary table representing an entity and maintaining its characteristics. Master Table names are given the following structure

1:

LNK Link Table - A table which only maintains foreign keys for the purpose of allowing relates between Master Tables (usually when a many-to-many relationship exists between them). Link Table

names are given the following structure1

:

LKP Lookup Table - A table which maintains a single column2 of long text, along with its

abbreviation. This abbreviation is essentially a primary key to substitute for long text in Master Tables

thus minimizing data storage requirements. Lookup Table names are given the following structure1

:

1 The underscore ("_") delimiter is used with Oracle®. In INFO®, a period (".") is used as its delimiter.

2 A Lookup Table may maintain two columns of long text where one is in Arabic, and the other in English.

<GFCODE>_MST

Where GFCODE is the feature/entity GFCODE. e.g. ZZZZSTUF_MST

<Resource Area>ZZ<sequence>_LNK

Where Resource Area is the first 2 characters from GFCODE, and sequence is a sequential value between AAAA and ZZZZ (i.e. AAAA, AAAB, AAAC, etc.) such that

the full 8 characters before the extension (LNK) are unique.

e.g. TGZZAACL_LNK

<Resource Area>ZZ<abbrev>_LKP

Where Resource Area is the first 2 characters from GFCODE, and abbrev is an abbreviation to represent the file such that the full 8 characters before the

extension (LKP) are unique.

e.g. TGZZCHPT_LKP


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The table is then described under the following headings: � GFCODE: An 8 letter identifier to nationally identify a unique entity or feature (geo-entity). Refer to the

previous section FEATURES description (page) for generating GFCODE and more details. For primary geographic feature attribute tables (.AATs, .PATs, etc.), the GFCODE assigned must not have PV, LV, LE, LX, RV, AV, GV, or CV in character positions 3 and 4 (i.e. basic geometric representation without the qualifiers “virtual” or “extent”).

� Name: The entity/feature name. � Description: A long description of what the entity is in its true existence. � RDBMS: The name of the Relational Database Management System including version number within

which this table resides. � Normalization: Mention what degree of normalization such as first, second, third, etc. could have

been achieved by normalizing a table, if applicable; or specify clearly why de-normalization is preferred.

� Known Redundancy: An indication if there is any data in the table which exists redundantly in other

tables. � Column Data Types: The breakdown of each column in the table should be identified in the following

headings such COLUMN (name of the column), TYPE (what kind of value does it accept), WIDTH (how much is the width of column to accommodate the required values) and DECIMALS (number of decimal

places) for Oracle®1

tables, and CHARACTERISTICS to define domain and constraints such as acceptable values, range, validation checks, constraints for further limiting column values, unique key, primary key, foreign key etc. Note that column names can only be of maximum 10 characters in length,

and must not conflict with any reserve word identified within ArcSDE®2

or Oracle® DBMSs. For the

primary geographic feature attribute tables (business tables) in ArcSDE®, a number of mandatory columns exist. Some fulfill GIS software requirements, whereas others fulfill national feature inventory requirements.

� Column Definitions: A verbal description of what each column represents. If a Lookup Table (LKP)

is to be referenced, and it does not have its own Appendix C entry, the Lookup Table's Column Data Types must be listed.

� Owner: The agency that owns (or has been appointed as custodian for) the data in this table. � Update Rights on Columns: The agencies which are entitled to submit changes to the data in

specific columns of this table. � Relate Table: A table which contains a list of all direct relationships for the given table. In case of

many-to-many relates via a link table, both sectors of the related are shown on the same row. � Diagram Methods: Design documents are often simplified (abstracted) so they may be easily read

and understood. Use Unified Modeling Language which is independent of process and language under the Visio environment or any latest visual tools for data and software modeling available at ESRI. ESRI provides the Visio templates needed in order to build designed model. They contain the ArcObject geo-database classes, their interfaces, and the ESRI extensions to the UML. Provide Data Model depicting relationship between feature classes, subtypes for a respective feature dataset. Also list out all domains applied for each feature class/subtype for a feature dataset. For clarity, Link Tables may be omitted. The Lookup Table that does not have its own Appendix C listing must be shown on in the model Master Tables it’s referenced with. A Lookup Table that has its own Appendix C listing must either have its own model, or be shown on the models of Master Tables it’s referenced with.

1 Refer Oracle® documentation for further details

2 Refer to ArcSDE® documentation for further details.


334

(g) Relationship Classes Geodatabase relationship classes manage the relationship between pairs of classes in the geodatabase. Relationship rules restrict the type of objects in the origin feature class or table that can be related to a certain kind of objects in the destination feature class or table. A relationship is implemented as a class in the geodatabase. Geodatabase relationship classes provide many advanced capabilities not found in ArcMap joins and relates such as read-write access, versioning support, all cardinalities, relationship rules, simple or composite, referential integrity. These are created in ArcCatalog and use them in ArcMap. Relationships are established between a pair of classes, one of which is the origin and the other is the destination. Objects in two classes are matched based on the values found in their key fields. The key fields may have different names, but must be of the same data types and contain the same kind of information. Fields of all data types except BLOB and Date may be key fields. Maintaining relationship classes requires more computer processing to maintain than joins and relates. Use them only when you need their advanced capabilities. List and order all the identified relationship classes by its name and describe them accordingly. One or more pages are devoted to the description of a particular relationship class. Each page (or group of pages) is of the same format. At the top of the page is the full relationship class name. The relationship class is then described in the following headings: Name: Relationship classes have names, like tables and feature classes, and their names must be unique within the geo-database. Use descriptive naming conventions; a label is easiest to use when its name is descriptive, like ToOwner and ToParcel. You might preface the name with the relationship, like OwnerToParcel:ToParcel. Description: A long description of the relationship class's in terms of what type of relationship, the objective, relationship rule, cardinality, need of intermediate key table, and so on. Origin Class: Write a name of origin class with breakdown of its all fields, which has an impact on referential integrity enforcement. Destination Class: Write a name of destination class with breakdown of its all fields. Key Fields: Write name of fields, data type, and their width from origin and destination classes those are going to be used for matching the values between classes. Types of Relationships: Relationship type should be written here such as simple, composite, or other types. (h) Geometric Network Classes There are two types of network: geometric and topologic. A geometric network is a topological relationship between line and point feature classes in a feature dataset, and a feature class can participate in one geometric network. Each feature has a role in the geometric network of either an edge or a junction. The point and line features acquire more behavior and become junction and edge features in a single, integrated dataset. Junction is of two types: simple and complex. Geometric network satisfies the needs of vector datasets required to model utility networks to support tracing through a set of connected lines and points. List and order all the identified geometric networks by its name and describe them accordingly. One or more pages are devoted to the description of a particular geometric network class. Each page (or group of pages) is of the same format. At the top of the page is the geometric network class name. The geometric network class is then described in the following headings: Name: Geometric network classes have names, like tables and feature classes, and their names must be unique within the geodatabase. Use descriptive naming conventions such as WaterNet, DrainageNet. Description: A long description of the geometric network class's in terms of what type of network such as simple or complex, the objective, and so on. Feature Dataset: Write the name of feature dataset that will contain the network.


335

Feature Classes: List out all feature classes those will participate in the network. A geometric network doesn't have to include all feature classes in a feature dataset. Snapping Tolerance: Specify the map units that features are going to be snapped to and the features classes that are going to be snapped. Moreover, specify some feature classes to snap while others remain stationary. It would be required if one feature class is more accurate than another, and want the less accurate class to snap to the more accurate feature class. Connectivity Rules: Specify the network connectivity rules those constrain the type of network features that may be connected to one another and the number of features given type that can be connected to features of another type. For example, in a water network, 10-inch transmission main can only connect to an 8-inch transmission main through a reducer. Network Weights: Identify the names and type of weights will have in network and fields those weights are associated with it. Network weights are required to control tracing operations. These are three types: Ratio, Nominal, and Bitgate. (i) Raster Datasets The purpose of this section is to identify all raster datasets. List and order all the identified raster datasets by its name and describe them accordingly. One or more pages are devoted to the description of raster images. Each page (or group of pages) is of the same format. At the top of page is the full name of raster image such as satellite images, ortho images, etc. Description of each type of images should be started from separate page. The image is described under the following headings: � Name: It is the same name as of business table which will be stored in the database. Naming convention

should include the following:

Area Name: Image name should be preceded by including the meaningful name of area to which this imagery belongs such as DOHA, ALKHOR, QATAR, etc. Year: After preceding by underscore, include 4 digits for year in which image was taken such as 1994, 2003, 2009, etc. Month: After preceding by another underscore, include 2 digits for the name of a month in which image was taken such as 01 = Jan, 02 = Feb, 03 = Mar, ……, 12 = Dec. Resolution: After preceding by another underscore, include resolution of image in centimeter such as C20, C100, C2000, etc in the part of name. Source of Image: After preceding by another underscore, include three characters code suitable for the source of Image such as ORT = Ortho, IKS = Ikonos, LNT – Landsat, SPT = Spot, QKD = Quikbird, etc as a last part of full image name.

For example: RASTER.ALKHOR_2008_05_C080_IKS

� Description: A long description of raster image, it may include resolution of image, name of the source,

date of image, source type (continuous, discrete), area of image, etc. � Storage Type: Specify the appropriate raster storage type needed such as Mosaic, catalog or any other

type. � RDBMS: The name of Relational Database Management System within which this image will reside. � Known Redundancy: An indication if there is any raster dataset in the database which exists

redundantly.


336

� Compression Method: Specify compression method needed and used to store raster image into the geo-database such as LZ77, JPEG, JPEG2000, etc, along with type of compression or percentage of compression respectively.

� Data Depth: Specify the data depth of image such 8, 16. � Owner: The agency that owns (or has been appointed as custodian for) the raster dataset. � Update Rights on Columns: The agencies which are entitled to submit changes to the raster

dataset. (j) Features The purpose of this section is to identify all required geographic features for respective data dictionary. These are listed first by Geometric Representation (in the order shown under GFCODE below, excluding Section and Not Geographic), and then alphabetically by the Feature Name. One or more pages should be devoted for the description of a particular feature. Each page (or group of pages) is of the same format. At the top of the page is the feature name. This may be of any length, but is generally kept short. The feature name is given in the following structure:

The feature is then described under the following headings: � GFCODE: An 8 character identifier to nationally identify a unique entity or feature (geo-entity).

Uniqueness is only present using the full 8 characters). GFCODE is structured as follows:

♦ The first two characters in positions 1 and 2 combine to represent the Resource Area from which the entity/feature was identified. The available Resource Area values are:

Table 8.10: Resource Areas of Entity/Feature

AG Agriculture/Water EN Environment SW Sewer

CD Civil Defense FS Fisheries TE Treated Sewage

Effluent

CI Crime Investigation IM Immigration &

Residence TG Topographic

CS Control Survey NS National Statistics TL Telecommunications

DA Drainage PD Municipal Planning &

Development TP Traffic & Patrol

DI Demographic PS Police Services TR Traffic Management

ED Education RD Road WT Water

EI Economic RE Real Estate ZZ Common

EL Electricity SG Surface Ground Water

<Feature Name>(<Geometric Representation>)

Where Feature Name is given with all first letters in upper case, and Geometric Representation (see under GFCODE below) is given inside round brackets, and with all

letters in lower case. e.g. Guard Rail (line)


337

♦ The characters in positions 3 and 4 combine to represent the Geometric Representation of the entity/feature. The available Geometric Representations are as follows:

PT Point PV Point Virtual LN Line LE Line Extent LX Line Extent Virtual LV Line Virtual ND Node NV Node Virtual AR Area AV Area Virtual GN Region GV Region Virtual RT Route RV Route Virtual EP Event/Point EL Event/Linear EC Event/Continuous TX Text

1

CX Complex Object CV Complex Object Virtual PX Pixel Cell SC Section ZZ Not Geographic

♦ Given the Resource Area and Geometric Representation identifiers, the characters in positions 5, 6, 7, and 8 combine to identify a particular entity/feature. If numbers are to be used in positions 5, 6, 7, or 8, in order to avoid confusion between letter “O” and the number zero, the only valid configurations of letters (“L”) and numbers (“N”) are as follows:

Position Remarks

5 6 7 8

L L L L

L L L N no letter “O” in position 7

L L N N no letter “O” in position 6

L N N N no letter “O” in position 5

N N N N

♦ Virtual applies to objects which require geometric representation, but do not physically exist (e.g. Administrative areas or boundaries).

♦ Extent applies to linear objects which only exist to delineate the limits of areas. � Definition: A long definition of the feature. This will describe what the feature is in its true existence

(not how it will be geometrically represented). � Aliases: A list of any aliases or alternative spellings for the feature name. � Feature Dataset: Name of feature dataset within which the feature can be found.

1 Text is available as a Geometric Representation since it fulfills cartographic demands that can't be satisfied by other means. However,

it should be noted that where the text string labels characteristics for a coded geometric object, the content of that text string must not be considered as the primary source of that characteristic. The characteristic's primary source is its attribute association with the geometric object.


338

� Feature Class(es)/Object(s): Name of feature class(es)/Object(s) within which the feature can be found. A list of more than one feature classes/object(s) represents the presence of redundancy in feature geometry.

� Geometric Representation: An explanation of how an object's true shape and position (and possibly

orientation) are geometrically represented. � Sharpness: An indication of how fixed & distinct the feature is. This essentially classifies features in

terms of their potential to have a significant degree of positional accuracy associated with them1. Valid

options are: Well Defined – always having a very fixed & distinct shape. Not Well Defined – never having a fixed & distinct shape. Mixed – fixed & distinct in shape in some cases, but not in others. Not Applicable – feature for which Sharpness does not apply (such as cartographic text). � Examples: Any diagrams, images, etc. which add to the clarity of how the feature is to be identified

either on site, or in the GIS Database.

8.5.4 Accuracy of GIS Database The issue of accuracy is dealt with in this section under 4 general headings. These are:

1. Positional Accuracy (correctness) 2. Characteristic Accuracy (correctness of attributes) 3. Data Currency 4. Completeness

(a) Positional Accuracy

For determining positional accuracy, one undertakes computation of the exact range from an object's measured position within which its true position will fall. This is dependent on numerous factors. In the data dictionary, the computed positional accuracy is not recorded for any objects. However, there are three values which are stored against each which allow the user to gauge the data's positional accuracy. These are:

SOURCE

The unique identifier of a specific positional data capture history, which has generated the current positional values. The source of capturing data could be such as CGIS (Surveyed by their team), Outsourced company, digitized from ortho images, digitized from Satellite images, digitized from scanned document and so on.

RELIABLE

A subjective estimate of a position's reliability as indicated by the layer owner. It is indicated as a plus or minus value in the same units as the positional data. As of today, the acceptable values are Reliable, Moderate and Fair.

CONFIDENCE

The expected frequency, expressed as a percentage, with which the position will be within the tolerance expressed by RELIABLE. We are choosing a level of certainty or a level of confidence such as 99%, 95%, 90%, and so on.

1 Positional accuracy requirements for future “survey / data collection” exercises of a particular feature are listed in the Qatar National

GIS Survey Specification (not yet produced at the time of this document’s printing).


339

Most applications will be able to rely on the RELIABLE and CONFIDENCE values alone. More rigorously determined accuracy could be established by interrogating the details available via the SOURCE field. This field allows linkage to the following details, defining how a position was established:

� Other sources used � Tasks performed � Methods used � Equipment used � Specifications under which each source was produced � Agencies involved

The means by which these details are accessed are mapped out in the ERD in Figure 8.7.

Source

Resource

Custodianship

Appointment

Resource Type

Specification

Task

Project

Method

Equipment

Equipment

Custodianship

Appointment

Agency

Equipment

Requirment

Equipment

Type

Equipment

Purchase

constitute

part ofconsist of

have

available

of

be used by

use

be

created

by

create

conform to

define

be used by use

be issued to

receive

issue be issued by generate

be

generated

by

be used

byusebe qualified

to perform

be a qualified

service of

have

be for

divide into

be a division of

spawn

be spawned by

be credited with be credited to

make

be made by

consist of

constitute

part of

consist of

constitute

part of

be of

form part of

be

classified as

identify the

classification of

be used by use

have donehave been

done by

manufacture

be

manufactured

by

Figure 8.7: Entity Relationship Diagram of Positional SOURCE Details


340

(b) Characteristic Accuracy

If they are required, accuracy for characteristics will be recorded in separate columns. Typically, measured values (which includes date & time values) will have their accuracy recorded in columns much like RELIABLE and CONFIDENCE in the previous Positional Accuracy section. Columns carrying text (alpha, numeric, or both) may have their accuracy recorded in columns that indicate "Verified/Unverified" values. In the case where translations are involved, additional columns may be used to indicate if the translation is phonetic, or based on meaning. (c) Data Currency

Via the SOURCE column, all tasks associated with the establishment of an object's position can be queried. The START and FINISH date characteristics recorded for these tasks indicate when an object was positioned, but they do not give any indication of whether or not anything has happened since. Has it since been destroyed? Has something new gone up in the vicinity? To determine when an area was last examined for any changes, a change verification START and FINISH date exist as characteristics against each tile

1. In some cases, changes may take place in a portion of a tile

during the examination for changes. If that change is in an area already examined, it will not be picked up. Thus, the change verification START date for a tile is the date one can rely on as an indication of how current a position is. Where required, the currentness for any characteristic of any entity or feature, are established by one or more date last examined columns. These reflect the last time when one or more characteristics were verified. One last date characteristic which is of particular importance is the date a piece of data became available on the database

2. For position, this is stored in the DATE_LUPD (date of last update) column of the business

table of feature class. Where required for characteristic values, similar date fields are added.

1 A Layer can extend, geographically, to infinity. It is often more practical to geographically partition a layer into more manageable

areas. Each of these is referred to as a Tile. 2 For historic data, the date of removal carries a similar level of significance.


341

References CGIS Topographic Data Dictionary

Metadata Details document of CGIS

CGIS Data Dictionary and Specifications

CGIS Database Design Document


342

Appendix 8A

Eligible GIS Member Agencies

Center for GIS (CGIS)-State of Qatar

Serial # Agency Name

1 Real Estate Registration Department (RERD)/Ministry of Justice

2 Statistical Department/Planning Council

3 Electricity/Qatar General Electricity and Water Corporation (KAHRAMAA)

4 Water/Qatar General Electricity and Water Corporation (KAHRAMAA)

5 Qatar Telecommunication (QTEL)

6 Roads/Drainage Public Works Authority (PWA) Ashghal

7 Qatar Petroleum Corporation (QP) (it Includes around five sectors/departments)

8 Lands Affairs Sector/Urban Planning and Development Authority-UPDA (It includes three Departments)

9 Planning Affairs Sector/Urban Planning and Development Authority-UPDA (It includes three Departments)

10 Agricultural Information center (AIC)

11 Ministry of Interior (MOI)

12 Supreme Council For Environment and Natural Resources

13 Department of Agricultural and Water Research (DAWR)

14 Department of Agriculture and Development (DAD)

15 Qatar University

16 Building Engineering Department/Public Works Authority (PWA) Ashghal

17 Ministry of Education (MOE)

18 Civil Defense Department

19 Ministry of Awqaf and Islamic Affairs

20 Olympic Games Committee

21 State Security Intelligence (SSI)

22 Internal Security Force

23 Qatar Armed Forces (Head Quarter)

24 Al-Daayen Municipality

25 Doha Municipality

26 Rayan Municipality

27 Al Khor Municipality

28 Al Wakrah Municipality

29 Al Shamal Municipality

30 Technical Affairs- Doha Municipality

To continue


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Appendix 8A (continue)

Eligible GIS Member Agencies

Center for GIS (CGIS)-State of Qatar

Serial # Agency Name

31 Health Affairs- Doha Municipality

32 Umm Salal Municipality

33 Mechanical Engineering Department

34 Animal Health Affairs

35 Agricultural Central Lab

36 Central Market - Salwa Road

37 Fisheries Department

38 Ministry of Municipal Affairs and Agriculture (MMAA) Head Quarter

39 Building Permit Complex (It includes UPDA, Kahrammaa, PWA, Civil Defense, Qtel, Doha Municipality Offices)

40 State Audit Bureau

41 Courts

42 Private Engineering Office (Ameri Dewan)

43 Hamad Medical Emergency Services (Ambulance)

44 Hamad Medical Corporation (HMC)-Head Quarter

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Document Control Page

Document version: 1.0

Document status: Current

Document owner: Urban Planning & Development Authority, Qatar

Date printed: 30 May 2009

Document name: Qatar Survey Manual

Revision history of this document:

Version Number

Revision Date

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Qatar Survey Manual

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Transcript of Qatar Survey Manual