Integrating GPS and GIS: The Basics

6/19/12Presented By:

Doug Kotnik, GISPPrecision Laser and Instrument

•What is GPS?•How does it work?•Why use GPS to map my assets?•How do I get the best accuracy?

•Questions

What we will cover

Doug Kotnik, GISPPrecision Laser and Instrument

•20+ years in GIS/GPS•Have worked for some of the largest Engineering firms•Private consultant•GIS Director for Butler County•Precision Laser and Instrument

A Little About Myself

GPS: Global Positioning System•Developed and run by DoD•31+ satellites•24 Needed for global coverage•12,600 mi altitude•Orbit the Earth 2x day

What is GPS?

GNSS: Global Navigational Satellite System•Includes systems from other countries•GLONASS: Russian•European Union: Galileo (2020)•China: Compass (2020)

GNSS

Three Segments

How Does It Work?

How Does It Work?

•Need at least 4 satellites

Trilateration

Why Use GPS To Map Your Assets?

•Accurately Map New Assets

Why Use GPS To Map Assets?

•Field Verify Existing Assets

Why Use GPS To Map Assets?

•Navigation: Where is that valve?

Why Use GPS To Map Assets?

•Streamline Data Collection–Control Data Input

•Drop down menus (domains)•Ranges•Yes/No•Date Fields

•Drop down menus (domains)•Ranges•Yes/No

Why Use GPS To Map Assets?

•Incorporate Other Data Collection Devices–Cameras–Barcode Scanners–Utility Locators–Ground Penetrating Radar–Sign Reflectometers

Why Use GPS To Map Assets?

•Seamless integration with your existing GIS/Mapping or work order system

Why Use GPS To Map Assets?

•Return on Investment!!–Better understanding of your assets–More accurate information–More efficient field workers–Regulatory compliance

Why Use GPS To Map Assets?

Accuracy

Recreational: 10+ meters (30 ft)

Mapping Grade: 5 meters to 10 cm (4in)

Survey: <1-2 centimetres (< 1in)

Accuracy

Dual Frequency Receivers•L1 and L2 signal•Using two signals allows receiver to more quickly determine your position•More Accurate

Single Frequency•L1 only•Cost Less

Mapping Grade Accuracy

• Atmosphere Delay

• Signal Multipath

• Receiver Clock Errors

• Number of Satellites Visible

• Satellite Geometry and shading

• Selective Availability – Turned off

Error: It’s always something

Differential Correction

•Real Time Correction

•Post Processing

How Do We Get There?

Real Time Correction

• WAAS (Wide Area Augmentation System)– Initially developed for aircraft navigation– Required accuracy of 25 ft at least 95%

of the time– Typical accuracy of about 3 ft

How Do We Get There?

WAAS

Real Time Correction

• VRS (Virtual Reference Stations)– Operated by ODOT in Ohio– 50+ Base stations– Access is free (for now)– Uses an internet connection via hotspot

or phone

How Do We Get There?

Ohio VRS

Post-Processing– Done using desktop software– Retrieve base station data

• Trimble Pathfinder Office• Trimble GPS Analyst Extension for

ArcMap

How Do We Get There?

GIS/GPS Software Configurations

GIS Data Pathfinder Office TerraSync

GIS Data

ArcMapTrimble GPS Analyst

ESRI ArcPad

Trimble GPS Correct

QuestionsContact Info

Doug Kotnik, GISPPrecision Laser and Instrument614-588-7085dpk@laserinst.com