Version 8 (modified by knpa, 15 years ago) (diff)


Grafnav GNSS Processing for IPAS Pro

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

  1. If required convert the Plane and basestation GPS RINEX files to GPB files. (file>convert>Raw GPS to GPB)
  2. Add Remote file (file>add remote). This is the plane GPB file (probably in the extract directory)
  3. Add Master file. (file > add master). This is the basestation data.
  4. Load airborne settings (Settings > Load settings from > airborne)
  5. 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.
    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 Export -> Export Wizard. Select IPAS from profile. All other default settings should be ok, but check to see if sensible.
  6. Click finish to output the results to a suitable format for IPAS Pro.
  7. Save project and exit.
  8. Analyse the X, Y and Z accuracy of the exported ASCII file (.lat). Acceptable SD results are 3.5cm in XY, 5cm in Z. Excellent SD results are 2cm XY, 3cm Z. These assume basestations within 25km. These figures are from the user manual.

PPP Processing

If the PPP processing method doesn't work and gives the error "Cannot find epoch ... blah blah blah", then try this:

  1. Go to "Help" and "About Grafnav"
  2. Click download manufacturer files
  3. Re-try running the PPP

Exporting Grafnav Result to POSPAC

It is possible to do the GNSS processing in Grafnav and then export the result into POSPAC. This saves doing the GNSS processing two times (one for LiDAR IMU and one for Applanix IMU). The version of Grafnav is newer than the POSGNSS version and should be used instead of POSGNSS.

When the solution in Grafnav is ready to be exported, save the project and go into POSGNSS. Open the Grafnav project into POSGNSS, ignore warnings about being an older version. Then click the "combine GNSS" or "combine PPP" button. This will load in the previous solution. This can then be exported to POSProc as per usual. If the "combine" buttons are not highlighted, then you can goto the menu and select combine solutions, select the files and load in the forward and reverse ones.