Version 24 (modified by mark1, 5 years ago) (diff)

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Grafnav GNSS Processing for IPAS Pro

Similar to Applanix GNSS processing. (See that wiki page if these notes dont make sense :))

  1. Create a new project in Grafnav (File-New Project->Filename). Call it YYYYJJJ
  2. If required convert the Plane (from the extract folder) and basestation GPS RINEX files to GPB files. (file>convert>Raw GPS to GPB)
    IMPORTANT- When doing the conversion, go into options and make sure that 'Make all epochs kinematic' is ticked for the airplane data and UNticked for the basestation data.
  3. Add Remote file (file>add remote). This is the plane GPB file (probably in the extract directory)
  4. Add Master file. (file > add master). This is the basestation data.
  5. Load airborne settings (Settings > Load settings from > airborne)
  6. Process differential GNSS.
    1. Change settings as required to get a good result (green line). iterate until best solution obtained.
    2. Check combined seperation graph. We want this small. Ideally under 0.05m for green, red and blue (though blue (vertical) is the least important).
    3. Check number of satellites. The more the better (Need at least 4 to even get a solution, more for an adequate one)
    4. When happy, click Output -> Export Wizard. Select IPAS from profile. All other default settings should be ok, but check to see if sensible.
  7. Click finish to output the results to a suitable format for IPAS Pro.
  8. Save project and exit.
  9. Analyse the X, Y and Z accuracy of the exported ASCII file (.lat). Acceptable standard deviation results are 3.5cm in XY (SDNorth, SDEast) 5cm in Z (SDHeight). Excellent results are 2cm XY, 3cm Z. These assume basestations within 25km. These figures are from the user manual.

Back to IPAS processing

PPP Processing

If the PPP processing method doesn't work and gives an error about not finding epochs, then try this:

  1. Check you are using the latest version of grafnav (8.1 at time of writing)
  2. If you are, then try downloading the latest manufacturer files:
    1. This doesn't appear to work using the GUI so log on as admin2000 (see mggr)
    2. Go to website: http://www.novatel.com/support/info/documents/569
    3. Download latest manufacturer files
    4. Unzip and place contents in the C:\novatel\WaypntGPS810\
    5. Log out from admin

Troubleshooting

If Grafnav crashes as soon as you open it, this could mean that auto updating has been selected. To remedy this, move the preferences.ini file out of the grafnav install folder and see if it fixes the problem. If it does, then you can delete the old preferences.ini file (a new one should exist now - feel free to copy over any different preferences if you wish).