Hitchhiker s s Guide Global Position System. Global Position System

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1 Hitchhiker s s Guide Global Position System Myles Sutherland Craig Greenwald Mike Shaw John Rogers Hitchhiker s s Guide Global Position System (GPS)

2 Myles Sutherland - ESRI Craig Greenwald ESRI John Rogers - Trimble Mike Shaw - ESRI

3 Key topics in today s s session Global Navigation Satellite Systems GIS Solutions Receiver Technologies Data Capture Best Practices Demonstrations

4 Global Navigation Satellite Systems

5 Global Navigation Satellite Systems Global Positioning System Differential GPS Systems GLONASS Galileo Positioning System

6 Global Positioning System (GPS) Unanswered question of Where am I? US Department of Defense project Worldwide radio-navigation system Explosion of Civil sector adoption

7 How do these man-made made stars work? Control Segment - Ground stations Control and position satellites in orbit Space segment Satellites Broadcast radio signal PRN code and orbit position User segment Receivers Measure distance and calculate positions

8 Space Segment Segment User Segment Control Segment

9 Control Segment Provides worldwide coverage and control 365/24/7 Master Control station Colorado Four support stations Hawaii Kwajalein Diego Garcia Ascension Island

10 Space Segment GPS satellite constellation 24 satellites Replenishment occurring Satellite design Lifetime 7.3 years 16 satellites over 9 years old 28 Satellites in GPS Constellation Number Under Age (Years)

11 User Segment Equipment produced by Military and Private companies Receives signal and computes Position Time Velocity

12 How do we position ourselves? Simple Geometry Velocity times travel time Determine Radio Wave Time Travel Accurate timing Measure Distances Known orbit locations Trilateration Distances not angles

13 Sources of Positioning Error Environment and Multipath Ionosphere and Troposphere Ephemeris Data Satellite Clock Bias Receiver Issues

14 Differential GPS Four or more satellites viewed by two receivers Rover adds error to its measured position to obtain the corrected position Error data is sent to rover with radio Reference station - a high performance GPS receiver placed in a fixed location whose position is accurately known. The GPS measured position is compared sec by sec against the known position, and an error calculated. Autonomous GPS = 10 meters Differential GPS = 1 meter This error is assumed to be the same error at the rover, and is sent to the rover as a differential correction.

15 Differential Systems Postprocessing Systems Online File Servers NGS CORS Realtime Systems National Differential GPS Program Satellite-based Augmentation Systems TCP/IP Networks

16 NGS CORS Programs

17 Coast Guard NDGPS Program

18 FAA Wide Area Augmentation System

19 TCP/IP Networks Virtual Reference Systems (VRS) Network of web-enabled enabled receivers Central server processing corrections TCP/IP broadcast of corrections Data Services over cellular networks

20 Galileo Positioning System European Satellite Navigation System Worldwide availability Complementary to GPS 27 satellites Fully operational 2008 onwards Free of charge

21 Advantages for Civil Users Galileo + GPS Double Number of Satellites Improved Urban Canyon reception Increased Signal Strength Improved reception under foliage Three Signals Instantaneous RTK positioning

22 GPS Satellite Visibility

23 GPS + Galileo Satellite Visibility

24 GLONASS Russian Navigation System Very similar to GPS In a state of disrepair 11 Satellites most with lifespan of 3 years Investment planned 24 Satellites by 2010

25 GPS Products

26 Mapping and GIS solutions Broad range of products Black box receivers Pole and Backpack receivers Integrated GPS handhelds Targeted at GIS industry Moderate to High cost Designed for the field Highly accurate

Black box receivers Products Accuracy Trimble ProXH Trimble ProXT Subfoot to Submeter Filter multipathed and weak signals Ensures quality

27 Black box receivers Products Accuracy Trimble ProXH Trimble ProXT Subfoot to Submeter Filter multipathed and weak signals Ensures quality positions Ruggedness and Reliability IP54 plus All day batteries GIS use-case Critical layers Data collection and maintenance Long term deployment strategy

Pole and backpack receivers Products Accuracy Trimble ProXT Trimble ProXH Trimble ProXRS Topcon GMS 110 Sokkia Axis3 Subfoot to Submeter Filter multipathed and weak

28 Pole and backpack receivers Products Accuracy Trimble ProXT Trimble ProXH Trimble ProXRS Topcon GMS 110 Sokkia Axis3 Subfoot to Submeter Filter multipathed and weak signals Ensures quality positions Ruggedness and Reliability IP54 plus All day batteries GIS use-case Critical layers Data collection and maintenance Long term deployment strategy

Integrated GPS Handhelds Products Accuracy Trimble GeoXH Trimble GeoXT Trimble ReconGPS Subfoot to Submeter Filter multipathed and weak signals Ensures quality positions Ruggedness and

29 Integrated GPS Handhelds Products Accuracy Trimble GeoXH Trimble GeoXT Trimble ReconGPS Subfoot to Submeter Filter multipathed and weak signals Ensures quality positions Ruggedness and Reliability IP54 plus All day batteries Operating System Data Storage Windows Mobile 2005 Onboard Add-in GIS use-case Critical layers Data collection and maintenance Long term deployment strategy

30 In-car navigation solutions Expanding range of products Black box receivers Integrated GPS handhelds Targeted at in-car navigation market Very inexpensive Designed for the car

when static Ruggedness and Reliability Non-existent GIS use-case Non-critical layer

31 Black box receivers Products Accuracy Holux GPSlim236 Garmin GPS10 Many others Five to twenty meters Highly smoothed when in dynamic mode Repeatedly reports same position when static Ruggedness and Reliability Non-existent GIS use-case Non-critical layer data collection Inspection and incident reporting applications Throw away deployment strategy

Integrated GPS handhelds Products Accuracy Garmin ique Mitac Mio168

smoothed when in dynamic mode Repeatedly reports same position when

Storage Windows Mobile 2003 Onboard Add-in GIS use-case Non-critical

32 Integrated GPS handhelds Products Accuracy Garmin ique Mitac Mio168 Pharos Traveller GPS 525 Holux GPSmile60 Five to twenty meters Highly smoothed when in dynamic mode Repeatedly reports same position when static Ruggedness and Reliability Non-existent Operating System Data Storage Windows Mobile 2003 Onboard Add-in GIS use-case Non-critical layer data collection Inspection and incident reporting applications Throw away deployment strategy

33 Receiver Technologies

34 Positioning Engines Calculate and report positions End-use determines how positions calculated Low-end Navigation products Smoothing of positions in a dynamic mode Filtering of positions in static mode Precise data!!! High-end Mapping and GIS products Filtering of multipath signals Filtering of weak signals (SNR) Accurate data!!!

35 Scatter Plot Navigation product HRMS: VRMS: Bias: Std dev: CEP: Max Error:

36 Scatter Plot Mapping and GIS product HRMS: VRMS: Bias: Std dev: CEP: Max Error:

37 Position by Position Shootout Recreational vs Professional DGPS distance from truth location in open static environment Distance from truth in meters Trimble GeoXT Garmin Map Position Count

38 Best Practices

39 Accuracy vs Precision Accuracy Measurement vs. Known Truth Strong dependency on environment Precision Relative accuracy Consistency of data

40 Environment is a very big deal Both in accuracy... and how accuracy improves with occupation time Accuracy vs Occupation Time RMS Error (m) RMS Error (Open) RMS Error (Canopy) Occupation Time (s)

41 How is Accuracy Related to Yield? Yield = actual positions / potential positions In poor environment you must choose Precision / Accuracy and Yield If you filter out lower quality positions Accuracy improves Yield declines

42 How is Accuracy Related to Yield? When is yield important Collecting line / area features Avoid cutting corners In tough environments Avoid waiting too long When is accuracy important Averaging point features 30 good measurements are preferred to 120 okay measurements

43 Is DOP an error source? Dilution of Precision is a metric for accessing satellite constellation DOP is not an error source - it is an error multiplier!!! Poor DOP equals decreased accuracy Accuracy vs PDOP RMS Error (m) PDOP RMS Error (Open) RMS Error(Canopy)

44 An Accuracy vs Yield tip Use PDOP mask of 6 for 3D Use HDOP mask 4 for 2D If you don t t care about height precision Gives better yield for similar horizontal precision PDOP 2 = HDOP 2 + VDOP % 90.0% 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% PDOP yield PDOP precision HDOP yield HDOP precision

45 Demonstrations ArcPad ArcGIS GPS Analyst Extension ArcGIS Server Mobile ADF

46 ArcPad: Where is GPS used? GPS support is ubiquitous Navigation to a location How far am I from my target? What direction do I travel to reach my destination? Tracklog Where have I been? Data capture/maintenance Capture a new feature using the GPS location Update an existing feature/vertex to the GPS location Averaging, streaming, offsets

47 What is exposed to developers? GPS Extensions (plug-in modules) GPS Object GPS Capture/Editing commands

48 GPS Extensions Written in C/C++, compiled as DLLs Support additional GPS Protocols Control the GPS port or let ArcPad manage it Log raw data for post processing (DGPS) GPScorrect is an example Support additional NMEA sentences Several complete examples included with ArcPad Application Builder SONY IPS1000, SONY IPS3000, NMEA-0182, STF ArcPad GPSOpen( GPSParse( GPSClose( Extension DLL HGPS GPSOpen( LRESULT GPSParse( LRESULT GPSClose(

49 GPS Object Exposed to scripts (VBS / JS) Fires events as GPS status changes Reports position and quality status Two way communication with GPS receivers Activation and deactivation Access to NMEA sentences as they arrive

50 GPS Commands GPS Point GPS Vertex GPS Streaming Vertices Select at GPS location Activate / Deactivate GPS Center map on GPS location

51 DEMO

52 What is the GPS Analyst extension? ArcGIS Desktop extension that allows you to work directly with GPS data in the office and in the field MB

53 GPS Analyst Key Features View, edit, and analyze GPS data inside ArcMap and ArcCatalog Improve productivity by eliminating extra file conversions and processing steps outside ArcGIS Improve GPS position accuracy by differentially correcting data from supported Trimble GPS receivers Store detailed quality information for GPS data Set up and run validation on GPS positions to ensure features meet the required accuracy

54 GPS Analyst Key Features Collect features and GPS data directly into the geodatabase with Trimble or NMEA receivers Built with ArcObjects and GPS Analyst Objects customize GPS Analyst workflows and data processing develop extensions to support other GPS receivers develop field data collection UI to meet your needs

55 GPS Analyst Demo Built-in in vs. Custom Field Data Collection

56 Server Technology Mobile ADF Mobile and Desktop Clients Released with ArcGIS 9.2 Developer Kit Components Object Classes Samples Easy to Use Drag and Drop SmartClient Occasionally Connected

57 Mobile ADF Pairs input from GPS receiver with a Serial Port Supports the NMEA standard GpsDisplay buddies with the Map Current Location based on Pdop Number of Satellites being Tracked Trail and Length Components FileGpsConnection SerialPortGpsConnection

58 Mobile ADF GPS Demo

59 Session Evaluations Reminder Session Attendees: Please turn in your session evaluations.... Thank you

Introduction to the Global Positioning System

GPS for Fire Management - 2004 Introduction to the Global Positioning System Pre-Work Pre-Work Objectives Describe at least three sources of GPS signal error, and identify ways to mitigate or reduce those