ESRI’s Cadastral Extension to Survey Analyst

ESRIs Cadastral Extensionto Survey Analyst

CLSA, Reno, NV, March 11, 2006

Introduction

This presentation will describe development work currently underway for the new Cadastral Extension to Survey Analyst.

ALICE Project


Introduction and Overview

System Design and Concepts

Links with NSRS and CRTNTopics of Discussion


Introduction and Overview


GOAL

To build a simple extension to ArcGIS to improve and maintain the positional accuracy of boundary geometry and associated GIS layers.


MotivationMultipurpose GIS is often pinned on the cadastral layer

Cadastral base map governs other associated GIS layers

Accurate and consistent spatial data significantly extends GIS usefulness


Well, it looks good but its of little value for surveyors!


One Important Driver GPSGPS enabled systems ARE ubiquitous

GIS currently provides comprehensive underlying mapping information

But to make GIS more useful and GPS more valuable, this information must be accurate

GIS needs to improve here!


Cadastral Extension RequirementsSurvey Analyst Cadastral Extension:

Is extendable (data models & tools)

Follows survey methods for managing geometry

Incrementally improves positional accuracy of existing GIS datasets

Maintains spatial relationships between the Cadastral base map and associated GIS layers


ComponentsCadastral fabric geometry

+ geodetic control coordinates

+ weighted least-squares adjustment

+ accumulated displacement vectors

= ACCURATE FEATURE LAYERS


Cadastral fabricThe fabric is a continuous surface of connected parcels

It is also a dimensioned boundary network

Follows explicit geometric constraints such as common parcel corners

Parcels are also constrained by their relation to other parcels

Constraints are inherent in the model and enforced during data entry


Survey measurementsOnce upon a time measuring bearing and distance was easier than fixing a position

So land surveys are described by parcel dimensions

Precision of these measurements is generally known

So, measures and connections were known, but true coordinates were not


Existing LISMost LIS databases derived from scanning or heads-up digitizing of plat maps

Accuracy poor even after rubber-sheeting to control

Most importantly, original record measures are stored but not used

Instead, they are often distorted after a rubber-sheeting adjustment


From Measures to CoordinatesWe need accurate coordinates for the fabric and associated GIS layers

Accurate fabric coordinates are derived from: geodetic controlsurvey measurements

Like control, fabric points have:A physical location (monument)Reliability information (level of confidence)


AdvantagesA dimensioned cadastral fabric can be made very accurate using limited control

A least-squares adjustment uses all of the survey information, including historic, to distribute error

In Cadastral Extension, coordinates are a derived quantity, stored as a transient attribute of a point rather than a definition of the point


More advantagesCoordinates as attributes means historical coordinates can be retained, just like historical survey measurements

Datum re-adjustments and epoch updates are facilitated when measurements are retained and used in a least-squares adjustment


Fabric as Control for GISOften, associated GIS layers are created and maintained in context with the cadastre

An accurate cadastre then can serve as control for the rest of the GIS

If we capture the shifts in coordinates of the parcel cornerswe can use these to adjust the associated layers and maintain spatial relationships

The result is more accurate coordinates all around


Who wants this?Measurement CadastresSurvey measurements have definitive roleSpecifically designed for this

Coordinated CadastresUse fabric and geodetic control to move from measures to coordinatesCustomize to work with coordinates as the source


System Design and Concepts


Simple data model


Plans

Parcels

Points

Lines

Line Points

0-M

1-1

1

2-1

1-M

1

1-M

Control

0-1

1

1-M

Fundamental design conceptDifferentiate Source information from Derived information

Differentiate Survey Rules information from GIS Rules


Measurements

Coordinates

ESRI Shapes

Survey Rules

GIS Rules

Edited by Fabric Tools

GIS Operations

From Survey(held by Lines)

Calculated(held by Points)

Generated from Points

Central Design Concept Diagram

Fabric as a networkParcels are the basic unit of workCreate and edit parcelsJoin parcels to the fabric

Control points fix and geo-reference the fabric

Connected (and historic) parcels provide redundancy of measurements

Fabric network is constrained to control points and adjusted by least-squares


Historical parcelsParcels updated with new record information are never deleted from the fabric, they are simply marked as Historic

4 different types of historic information maintained:State of the Cadastre on a particular date State of the Fabric on a particular date Lineage of a ParcelHistory of adjustments to the fabric


Parcel creation and editingParcel is unit of work

Parcels are created by entering a loop traverse of the parcel boundary

Parcel closure is reported on-the-fly

At this stage corner coordinates are in an arbitrary local coordinate systemFirst Level QA check


Parcel JoiningJoining is an interactive point and click operationMatch shared points

Automatic 2D translation-rotation-scale performedFrom local project coordinate spaceTo projected coordinate space (SPCS)

Additional Q/C check provided by the transformation residuals resulting from Joining

Parcel Joining enforces the cadastral specific geometric constraints between parcels


Parcel Joining - 1


Parcel Joining - 2


Parcel Joining - 3


Parcel Joining


Build fabric using JoiningJoining is the easiest and fastest way to build the fabric

Joining ensures best fit to the existing fabricNo slivers or overlaps possible Can transfer basis-of-bearing

Provides approximate coordinates needed by the adjustment


Least-squares adjustmentFabric + Control + LSA = Good Coordinates

LSA does more than improve coordinatesShows where control is neededHelps isolate errors in the data (e.g. incorrectly entered measurements)

Post-adjustment analysis reports

LSA only estimates coordinates, never changes the original measurement values


Adjustment history maintainedAfter LSA the software creates a set of adjustment vectorsEach points coordinate residual generates a vector

This in turn generates a residual vector field

Vector sets are stored as a history of coordinate shifts based on each sequential LSA

GIS layers may be adjusted using the vector fieldYou decide when to adjust a GIS layer to the fabric

This is possible because the fabric maintains its adjustment history via the vector field


Accumulated Adjustment Vectors


Example of Feature AdjustmentUtility line features incorrectly located with respect to the fabricUsing LSA vector field, utility line features are adjusted to the fabric.


Whats the RESULT of all this?A cadastral fabric that is:Accurate to the same mathematical integrity as the original survey measurementsComplete by preserving all observed dataCoordinated in the NSRS

A GIS database of original survey measurements

Ability to correctly geo-reference GIS feature layers to the fabric

Ability to keep apace with NSRS re-adjustments and epoch updates using LSA


Why this approach is betterOriginal data are preserved

Data model adheres to cadastral specific geometric constraints

Provides incremental accuracy improvements:Of the fabricOf associated GIS feature layers

Highly user customizable with a simple model

Deep integration with ArcGIS


Links with NSRS and CSRS


GIS in support of CORS?Mission: The mission of Stark GIS is to develop the most accurate mapping system possible, enabling all current and future mapping to be referenced to a common framework. Stark GIS also is charged with disseminating the data created and encouraging Stark County's townships, cities, and villages to develop and utilize their own GIS.


Height modernization and GISZilkoski, D. & D. D'Onofrio. GEODETIC PHASE OF NOS' SAN FRANCISCO BAY DEMONSTRATION PROJECT states:

Explicit Objectives A modernized height system primarily based on the CORS will ensure a common foundation for all spatially related geographic data, including land and marine GIS data, and provide reliable height information for FEMA's Flood Plain Mapping program and for local surveyors, engineers, and planners. It will also support GIS requirements for regional and national transportation GISs, and provide data critical to monitor watershed planning and protection.


GIS and height modernizationTHE CONTRIBUTION OF GEODETIC DATA TO THE NATIONAL SPATIAL DATA INFRASTRUCTURE Rear Admiral J. Austin Yeager, NOAA, Director, Coast and Geodetic Survey; Captain Lewis A. Lapine, NOAA Chief, National Geodetic Survey, C&GS; and John F. Spencer, Jr., Chief, National Geodetic Information Branch, NGS states:

In the 1993 National Research Council (NRC) report, Toward a Coordinated Spatial Data Infrastructure for the Nation (1), it was exemplified that geodetic control is required to systematically register all spatial information to allow their integration into Geographic Information Systems (GIS). Such GIS systems have application in wetlands delineation, mineral assessment, renewable resource management, public health, urban and regional planning, disaster response and recovery, and national defense, among others.


Unrealized visionGIS was not ready Until Now!


Accurate fabric aids height modernization goalsPennsylvania Height Modernization Forum Report July 16, 2004 Sponsored by the National Geodetic Survey and the Pennsylvania Department of Transportation Co-sponsored by the United States Geological Survey and Herbert, Rowland & Grubic, Inc. A positionally accurate cadastral fabric can truly modernize FEMA FIRM maps by adjusting the flood plain boundary to the fabric, bringing about significant improvements in the insurance assessment process.


GIS Making coordinates usefulBut the mere application of geodesy alonedoesnt create order out of chaos. Geodesyshapes our lives today through a combination ofthree innovative tools:the Global Positioning System (GPS), whichsupplies the coordinates;NOAAs National Spatial Reference System(NSRS), which gives the GPS coordinatesintegrity; andGeographic Information Systems (GIS), which make the coordinates useful.As our society and economy become increasinglydependent on complex technologies, theneed for precise positioning and consistent, reliabledata intensifies. This imaginative trio of GPS,NSRS, and GIS is providing the order needed forensuring public safety, enhancing economicprosperity, and protecting environmental qualitythroughout the nation.


A unique unionSurvey Analyst for Cadastres with Low Distortion Projections (LDP)

LDP is a mapping projection that minimizes the difference between distances depicted in a GIS when compared to the real-world distances at ground elevation

Standard mapping projections are at sea level (ellipsoid)

Distortion increases with elevation

NGS is considering supporting registered LDP as an addition to their Geodetic Tool Kit


Why use LDP?The value of a GIS increases directly as a function of its accurate portrayal of items of interestLocal govt. GIS managers are realizing the benefits of incorporating survey measurements (COGO)

Leads to better decision support from the GIS

There is virtually no cost to using LDP in GISOn-the-fly re-projection is routine in ArcGIS

Standard Projections are not good enough for local GIS UTM distortion is 1:2,500 (2.1 ft per mile)SPC distortion is 1:10,000 (0.5 ft per mile)But in both cases distortion at ground usually much greater


Why will NGS support LDP?Local GIS will increasingly use LDP for their data

The fundamental purpose of the NSRS is to support mappingSPCS is not adequate for many applications

Use of well-defined registered projections can encourage use of the NSRS rather than local control

OPUS option for positions in LDP coordinatesData sheets could include LDP coordinates

The LDP tool encourages state and local government to utilize the NSRS as their GIS basis

Eventually LDP will replace current SCPS in state regulations


A CRTN Application with Survey AnalystSurveyAnalystWeb ServicesRTD ProCOMMIntegrating DataPDAPDARTD RoverRTD RoverBubba to Boss Bubba to Boss Hey Bubbas, thanks for the coordinates. I just ran the LSA and I need you to pick up points


Technology crouches at our doorMost of the nations infrastructure ourtransportation, utility, energy, and communicationssystems depends on the teamwork providedby GPS, GIS, and the National Spatial ReferenceSystem.

but we must master it!


Contact InformationESRI380 New York St., Redlands, CA

Kevin M. Kelly, Geodetic [email protected]; 909-793-2853 x1162

Tim Hodson, Product [email protected]; 909-793-2853 x2077


ESRI’s Cadastral Extension to Survey Analyst

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