High-Accuracy GPS for GIS: From 1ft to 4in. CHICAGO --- INDIANAPOLIS --- KANSAS CITY --- MILWAUKEE --- ST. LOUIS/ST. PETERS

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: 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

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.

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)

GeoXH (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.

GeoXH’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

ProXH <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.

ProXH 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

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 30-60 seconds at each point 3-foot accuracy in the field with WAAS/Beacon Omnistar/GLONASS capable Designed for use on a rangepole

Data Collector Options

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

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

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.

Iowa RTN www.iowadot.gov/rtn

Iowa DOT RTN

Iowa DOT RTN – District 1

Iowa DOT RTN – District 2

Iowa DOT RTN – District 3

Iowa DOT RTN – District 4

Iowa DOT RTN – District 5

Iowa DOT RTN – District 6

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.

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

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

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

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

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)

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.

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.

GPS – The First Global Navigation System

Questions. www. seilerinst. com/mapping/support Questions? www.seilerinst.com/mapping/support.asp jriester@seilerinst.com CHICAGO --- INDIANAPOLIS --- KANSAS CITY --- MILWAUKEE --- ST. LOUIS/ST. PETERS