1. High-Accuracy GPS for GIS: From 1ft to 4in.
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2. GPS Resources GPS Information: H-Star White Paper:
GPS Tutorial:
National Geodetic Survey (NGS):

3. Why High-Accuracy? Utilities Collecting assets/features accurately:
collecting existing features or
‘as-built’ surveys
Relocating assets/features
Local & city government
Urban asset databases
Road centerlines
Construction
Preliminary site surveys
As-built surveys for collecting asset information
Environmental impact reports

4. Why Mapping-Grade?
If your applications only require 4in-12in, these systems are built for that level of accuracy.
Cost of the high-accuracy mapping systems are typically about half to a third of the cost of a survey-grade unit.
The Trimble Mapping/GIS products are designed to work well with attribute-intensive GIS data collection projects.
They integrate seamlessly with ESRI software such as ArcGIS.

5. Accuracy Levels 12 inches GeoXH’05 GeoXH’08 or ProXH 8 inches
GeoXH’05 /Pro XH with Zephyr Antenna
4 inches
ProXRT / GeoXH’08 with Zephyr (close to base station)

6. GeoXH (2008) Handheld
<12 inch accuracy after post-processing or VRS
Typically requires about seconds at each point
3-foot accuracy in the field with WAAS
Integrated unit can be carried in your hand. No need for cables or a pole/backpack.

7. GeoXH’08 with Zephyr
4 inch accuracy after post-processing…depends on distance to base station
Typically requires about seconds at each point
3-foot accuracy in the field with WAAS. 4 inches when connected to VRS.
Designed for use on a rangepole

8. ProXH <12 inch accuracy after post-processing
Typically requires about seconds at each point
3-foot accuracy in the field with WAAS
Use with a mobile data collector, tablet, or laptop.
Communication via Bluetooth or serial cable.

9. ProXH with Zephyr <8 inch accuracy after post-processing
Typically requires about seconds at each point
3-foot accuracy in the field with WAAS
Use with a mobile data collector, tablet, or laptop

10. ProXRT <4 inch accuracy after post-processing (<6in vertical)
ALSO…<4 inch accuracy in the field (<6in vertical)
Dependent on base station distance
Typically requires about seconds at each point
3-foot accuracy in the field with WAAS/Beacon
Omnistar/GLONASS capable
Designed for use on a rangepole

11. Data Collector Options

12. Post-Processing Pathfinder Office GPS Analyst for ArcGIS
Baseline Requirements:
50 miles for subfoot
18 miles for 4 inches (must use zephyr antenna)
2 options for real-time decimeter (4in) data collection:
Using real-time H-Star technology (VRS)
OmniSTAR HP (ProXRT only)
Real-time data collection
Allows for in field verification...knowing that a feature has been captured to the desired accuracy level streamlines workflow and reduces the risk of recollecting data
For relocating assets accurately and efficiently

13. Post processed Differential
Corrections applied in Pathfinder Office software or GPS Analyst software

14. H-Star Processing
Corrections applied in GPS Pathfinder Office software or GPS Analyst
Multiple CORS used
Carrier phase float solution generated
One base station within 50 miles or three within 120 miles.

15. Iowa RTN

16. Iowa DOT RTN

17. Iowa DOT RTN – District 1

18. Iowa DOT RTN – District 2

19. Iowa DOT RTN – District 3

20. Iowa DOT RTN – District 4

21. Iowa DOT RTN – District 5

22. Iowa DOT RTN – District 6

23. Why use VRS for GIS? Do not need post-processing software
Increased accuracy
Better than WAAS and Beacon
Doesn’t degrade with distance from the base
Integrity monitoring
QA/QC increasingly important for contractors
Focused on GIS benefits. The main barrier to adoption by GIS users has been the cost per position of cellular corrections. But as covered later, as cellular costs are falling, more GIS users are adopting VRS instead of other DGPS mechanisms.

24. VRS Data Flow
Reference station data streams back to server through LAN, Internet, or radio links

25. VRS Data Flow
Roving receiver sends an NMEA string back to server using cellular modem. Virtual Reference Station position is established.
VRS
NMEA—GGA

26. VRS Data Flow
Server uses VRS position to create corrected observables and broadcasts them to the rover
VRS
RTCM or CMR+

27. Real-time Settings
Configuration for VRS is all centered around the “External source” selection on the Real-time settings dialog.

28. Cellular Connection Must have cellular service in your work area
Verizon, AT&T, Sprint, T-Mobile
Data Plan is needed (differs from a voice plan)
Make sure “tethering” is enabled
Carry spare batteries or bring an external battery
A bluetooth cell phone is better
A Nomad “GX” series is best! (AT&T and T-Mobile)

29. Datum's Choosing the wrong datum can greatly shift your data!
NAD83 (CORS96)
Choosing the wrong datum can greatly shift your data!
NAD27 to NAD83 could mean 50 feet or more.
“NAD83” has different versions
NAD83 (86)
NAD83 (91)
NAD83 (97)
NAD83 (CORS 96)
I’m in “NAD83”
This slide illustrates the next step – Confirming the GPS reference Frame. Knowing which reference frame can be the difference between a meter plus and mean life or death to your otherwise complacent GIS manager.

30. Datum Shift Know your correction source.
WAAS and Beacon are different!
Confirm your base station if post-processing.
Find one base station that works and stick with it.
Do a test point on a known location before starting.

31. GPS – The First Global Navigation System

32. Questions. www. seilerinst. com/mapping/support
Questions?
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