Top 12 GPS Tips and Tricks

  1. Is your battery fully charged?  Do you have a spare or a car charger?
  2. Does your device have the Current Operating System and GPS Firmware installed?
  3. Are the Field and Office software versions compatible?
  4. Ensure correct Internal/External Antenna height settings.  Is the correct Antenna Type selected?
  5. Check your “PLAN” in GPS Controller, TerraSync or GPS Correct for GPS Satellite availability and PDOP spikes within the next 12 hours.  Verify the GPS Almanac file date via the Status/Sat Info screen.  Is it older then 1 week?  If it doesn’t update itself automatically within 20-30 minutes of collection then – Reset the GPS Receiver:  “Setup Screen” *Options* “Reset GPS Receiver”.
  6. Face the internal Antenna toward open Southern, SW, SE sky depending on GPS Satellite coverage.  In North America there a fewer GPS Satellites to the North.  Check your “PLAN”.  If using an External Antenna – raise it above your head and other objects while keeping it level during GPS averaging.
  7. Avoid Obstructions and Multipath Environments if possible i.e. any buildings, trees etc.  Multipath signals can come from metal, glass or other shinny objects.  Avoid standing next to a Building, Parked vehicles, Chain linked fences , bodies of water etc.  These objects will reflect GPS signals causing signal delay (GPS is a time stamped based signal.  The moment it left the GPS satellite it is live and directed at the earths surface).  Use an External Antenna or try using Offsets to assist in avoiding or limiting Multipath.  This will not be accounted for in your “PLAN” but you need to be aware of it influencing your “DOP” values.
  8. Maintain good GPS form between features as not to lose GPS lock or pick up Multipath i.e. keep your antenna level.  If you are in and out of a vehicle pause for a few moments in an open setting to allow your device to receive a quality 3D GPS lock.   Maintain “Carrier Lock” if you are trying to acheive sub foot with XH’s and ProXRT.
  9. Average your GPS position data collection.  By default TerraSync will do this, but ArcPad will not unless you go into GPS Preferences and click on the “Check Box” and type in a number to average.  Trimble recommends a minimum of 30 positions at a 1 second interval.  Always collect longer if you are in a harsh GPS environment.
  10. Collect GPS first and then fill out attributes.  In ArcPad this is your only option but in TerraSync you could always click “Pause” if needed.  You could always re-average your GPS Position in either software if you are not satisfied without having to delete the entire feature.
  11. Observe your “In the Field vs. Post Processed” estimated Accuracies for a guide of the quality of your GPS data collection (Horizontal arrow in upper right of newer versions of TerraSync and GPS Correct).
  12. Datum’s (everyone’s favorite).  Know your Datum for your project.   Incoming Datum can be selected when using a VRS/RTN Real-Time correction in the field.  If Exporting via GPS Pathfinder Office select your Datum wisely.  You can always re-export if it was not correct.

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