chicago --- indianapolis --- kansas city --- milwaukee --- st. louis/st. peters high-accuracy gps...
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CHICAGO --- INDIANAPOLIS --- KANSAS CITY --- MILWAUKEE --- ST. LOUIS/ST. PETERS
High-Accuracy GPS for GIS:From 1 inch – 1 foot
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Seiler is….
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Seiler Instrument Company is a family owned, multi-divisional firm headquartered out of St. Louis, Missouri. We are industry leaders with
technology sales, training, service and implementation solutions.
Seiler works with a variety of vendors to provide value added turn-key solutions for our primary markets; Engineering, Architecture, Surveying, Construction,
Government, Utilities, and GIS. Our team of experienced professionals is passionate about understanding your needs, challenges, and current goals.
Committed to excellence since 1945
About Seiler
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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?• 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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Why use a real-time network?
• Do not need post-processing software if you are working with shapefile format.
• Increased accuracy– Much better than WAAS and Beacon– Doesn’t degrade with distance from the base– Even better than post-processing
• Instant accuracy– Desired accuracy typically achieved within seconds
• All users in common, established coordinate frame– Best fit of GIS data with survey/cadastral framework
• Integrity monitoring– QA/QC increasingly important for contractors
• Availability in places where other RTCM doesn’t reach– Inner cities are well served by mobile phone networks, but don’t tend
to be WAAS-friendly
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VRS Data FlowReference station data streams back to server through LAN, Internet, or radio links
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VRS Data 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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VRS Data FlowServer uses VRS position to create corrected observables and broadcasts them to the rover RTCM or C
MR+ VRS
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Indiana RTN/VRS Network• Growing list of networks• Check with Seiler for status
in your area• Subscription Service in IL
and IN• Free service in IA, IN, MO,
WI• Must have cellular coverage• Works with specific, newer
models for high-accuracy in the field
• Excellent for relocates
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VRS Conclusions• VRS is coming …
– Large and recent expansion in the Midwest• The cost of using VRS is declining or is free
– Cellular costs dropping; coverage improving• The benefits of VRS are significant
– Data quality and consistency• Once availability and cost get to the right level, VRS is
expected to be the DGPS source of choice for many applications– Particularly urban/suburban
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Configuring for RTN/VRS
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Cellular Coverage• Must have cellular service in your
work area– Verizon, AT&T, Sprint, T-Mobile,
etc.– Data Plan is needed (differs from
a voice plan)• Make sure “tethering” is enabled• Carry spare batteries or bring an
external battery• SIM card option:
– AT&T and T-Mobile only
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Know your hardware
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Antenna Height
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Best Practices: In the field
• Horizontal/Vertical and In the Field/Post Processed accuracy settings.
• Post Processing Distance from Base.
• Estimated Accuracy icon on the status bar (click on it to display) TerraSync and GPS Correct.
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Best Practices: In the field
• 1 second logging – “Averaging”
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Know Your Sky
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MultipathOccasionally multipath errors occur
• GPS Signal is being delayed/disrupted. “Chain Link Fences, Automobiles, Metal
& Glass buildings and bodies of water.”
• Estimated error may not always include multipath.
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Collect good GPS measurements between features
– Collect good quality data before and after you collect your feature (maintain GPS/Initialization - lock).
– In theory, you don’t have to collect too many positions in a point feature, once the accuracy indicator readings are good enough.
– But if you collect for about 20 to 30 seconds, you increase the chance of acquiring more satellites or cancelling out short-term multipath errors.
– If the accuracy indicator readings are poor, you should log more positions or cancel and start again.
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Log Now or Later• Log Now – start a feature and
simultaneously start collecting
GPS position.
• Log Later – start a feature, enter
attributes and start collecting GPS
positions later. Use this for lines and areas too.
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Pause/Resume
– Allows you to concentrate on positioning:• Holding the antenna over the location to be
measured.• Holding the antenna horizontal with a good view
of the sky.
– It is not easy to do this while concentrating on entering attribute information.
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GPS Product Review• Centimeter on a Pole• Decimeter in your Hand• Modular system (integrate to another device)
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Centimeter on a Pole
• Example:– Geo XH 6000 Centimeter
• Results available only with external antenna
• CM firmware update• TerraSync Centimeter• Integrated GSM modem option
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Centimeter Solution for Water
• Mapping of pipes, culverts, inlets, open channels, and retention ponds
• Capture infrastructure as it is built
• Hydrological modeling or network analysis
• Data collection for permits and resource allocation
• All gravity-fed systems
…All using attribute-rich datasets
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Decimeter in your Hand
• Example:– GeoXH 6000
• Handheld unit• Results available with external
antenna or handheld• CM firmware update path• TerraSync or ArcPad• Integrated GSM modem option
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Modular SystemExample - Pro 6 Series
• High accuracy GNSS positioning system
• Exceptional GNSS positioning performance in difficult environments
• A modular data capture solution for flexibility in configuration
• Optimized for mapping and GIS data collection activities
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High Accuracy Sample
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What about older equipment?
• Depends on the specification of the unit after post-processing, but no better than submeter (WAAS/Beacon accuracy).
• May be better but no official specification.
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Some Applications
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CHICAGO --- INDIANAPOLIS --- KANSAS CITY --- MILWAUKEE --- ST. LOUIS/ST. PETERS