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High-Accuracy GPS for GIS: From 1ft to 4in. GPS Resources. GPS Information: H-Star White Paper: http://www.trimble.com/geoxh_wp.asp GPS Tutorial: www.trimble.com National Geodetic Survey (NGS): www.ngs.noaa.gov. Why High-Accuracy?. Utilities Collecting assets/features accurately: - PowerPoint PPT Presentation
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CHICAGO --- INDIANAPOLIS --- KANSAS CITY --- MILWAUKEE --- ST. LOUIS/ST. PETERS
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High-Accuracy GPS for GIS: From High-Accuracy GPS for GIS: From 1ft to 4in.1ft to 4in.
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GPS ResourcesGPS Resources• GPS Information:
– H-Star White Paper:http://www.trimble.com/geoxh_wp.asp
– GPS Tutorial: www.trimble.com
– National Geodetic Survey (NGS):www.ngs.noaa.gov
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Why High-Accuracy?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
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Why Mapping-Grade?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.
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Accuracy LevelsAccuracy 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)
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GeoXH (2008) HandheldGeoXH (2008) Handheld• <12 inch accuracy after
post-processing or VRS• Typically requires about
30-60 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.
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GeoXH’08 with ZephyrGeoXH’08 with Zephyr• 4 inch accuracy after post-
processing…depends on distance to base station
• Typically requires about 30-60 seconds at each point
• 3-foot accuracy in the field with WAAS. 4 inches when connected to VRS.
• Designed for use on a rangepole
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ProXHProXH• <12 inch accuracy after post-
processing• Typically requires about 30-60
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.
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ProXH with ZephyrProXH with Zephyr• <8 inch accuracy after
post-processing• Typically requires about
30-60 seconds at each point
• 3-foot accuracy in the field with WAAS
• Use with a mobile data collector, tablet, or laptop
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ProXRTProXRT• <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 30-60
seconds at each point• 3-foot accuracy in the field
with WAAS/Beacon• Omnistar/GLONASS capable• Designed for use on a
rangepole
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Data Collector OptionsData Collector Options
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Post-ProcessingPost-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
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Post processed Post processed DifferentialDifferential
• Corrections applied in Pathfinder Office software or GPS Analyst software
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H-Star ProcessingH-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.
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Iowa RTNIowa RTN
• www.iowadot.gov/rtn
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Iowa DOT RTNIowa DOT RTN
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Iowa DOT RTN – District 1Iowa DOT RTN – District 1
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Iowa DOT RTN – District 2Iowa DOT RTN – District 2
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Iowa DOT RTN – District 3Iowa DOT RTN – District 3
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Iowa DOT RTN – District 4Iowa DOT RTN – District 4
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Iowa DOT RTN – District 5Iowa DOT RTN – District 5
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Iowa DOT RTN – District 6Iowa DOT RTN – District 6
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Why use VRS for GIS?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
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VRSVRS Data FlowData FlowReference station data streams back to server through LAN, Internet, or radio links
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VRSVRS Data FlowData FlowRoving receiver sends an NMEA string back to server using cellular modem. Virtual Reference Station position is established. NMEA—GGA
VRS
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VRSVRS Data FlowData FlowServer uses VRS position to create corrected observables and broadcasts them to the rover RTCM or C
MR+ VRS
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Real-time SettingsReal-time Settings
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Cellular ConnectionCellular 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)
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I’m in “NAD83”
NAD83 (CORS96)
Datum'sDatum's• 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)
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Datum ShiftDatum 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.
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GPS – The First Global GPS – The First Global Navigation SystemNavigation System
CHICAGO --- INDIANAPOLIS --- KANSAS CITY --- MILWAUKEE --- ST. LOUIS/ST. PETERS
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Questions?Questions?
www.seilerinst.com/mapping/support.aspwww.seilerinst.com/mapping/support.asp
[email protected]@seilerinst.com
