Transcript Welcome [igic.org]

High-Accuracy GPS for GIS:
From 1 inch – 1 foot
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CHICAGO
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INDIANAPOLIS
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KANSAS CITY
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MILWAUKEE
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Seiler is….
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About Seiler
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
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Why High-Accuracy?
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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 surveygrade 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?
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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 Flow
Reference
station data
streams back
to server
through LAN,
Internet, or
radio links
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VRS Data Flow
Roving receiver
sends an NMEA
string back to
server using
cellular modem.
Virtual Reference
Station position
is established.
VRS
NMEA—GGA
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VRS Data Flow
Server uses
VRS position to
create corrected
observables and
broadcasts them
to the rover
VRS
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Indiana RTN/VRS Network
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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
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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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Multipath
Occasionally 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
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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
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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 System
Example - 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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Questions?
[email protected]
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CHICAGO
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INDIANAPOLIS
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KANSAS CITY
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MILWAUKEE
--- ST. LOUIS/ST. PETERS