Version 4 (modified by edfi, 10 years ago) (diff)


Verify GPS Base station position

When processing the aircraft navigation using differential GPS it is vitally important that the base station coordinates are added correctly. Sometimes it appears that the stated position can be out by the order of a few metres, so we should do static PPP processing on the base station data to get a fix on it's position. If we use as much data as available (48hrs appears max in GrafNav) then the solution can get to accuracy of a few cms.


  • Open GrafNav and do the PPP processing (see Processing/GrafNavProcessing)
  • Add the base station as remote file
  • Download the precise clock and ephemeris data (4th or 5th tab under PPP processing settings)
  • Check Datums in the General tab
  • Process->PPP

When the solution is available left click the GPS point to query the lat/lon/hei and make a note of it.

If there are multiple base stations to use for the navigation processing repeat for all base stations.

Make sure that you save the result in posatt/basestation/ppp_result as this will be used in automatic scripts to check solution. Saved filename should follow the usual conventions, which at the time of writing, is "YYYYJJJ_baseppp", e.g. "2013123a_baseppp".