Custom geoid for orthometric height measurements in Android with Mapit GIS or Mapit Spatial

earth geoid

For some applications you may need to use a high quality orthometric height (height above mean sea level) measurement in real time with your Android smartphone or tablet.
In this tutorial we will explain step by step how to do it.

Before starting, you will need the following:

  • Smartphone/tablet with Android
  • Mapit GIS or Mapit Spatial app for Android.
    App is free but the custom geoid option is not.
  • simpleRTK2B GNSS receiver
  • Geoid conversion tool from eye4software, you can download it from their site or directly from here
  • Custom geoid in any of the following formats:
    • Eye4Software Geoid File Format (GEO Files)
    • Trimble Geoid File Format (GGF Files)
    • Carlson Geoid File Format (GSF Files)
    • US National Geodetic Survey (NGS) File Format (BIN Files)
    • Natural Resources Canada Files (BYN Files)
    • Surfer V6 Binary Grid Files (GRD Files)
    • NOAA VDATUM grid file (GTX Files)
    • AusGeoid File Format (Australian Geoids)
    • French ASCII Geoid Files (MNT Files)
    • ASCII Geoid Files

Step 1: Prepare the custom geoid

  1. Get the geoid of the area where you plan to do your measurements.
  2. If you don’t know where to look, we suggest to search in your national geodetic survey service website.
  3. In our example, we will use the geoid from the Spanish National Geographic Institute.
  4. In our case we have the geoid in Trimble format: EGM08_REDNAP.ggf
  5. Run the Geoid conversion tool
  6. Select source file format to match our original geoid file format: *.ggf
  7. Click Browse and select Source File
  8. Select destination file format to US National Geodetic Survey (*.bin)
  9. Click Browse and select Destination File name and folder
  10. Click Start button and you are done!

Step 2: Connect your simpleRTK2B board to Mapit GIS or Mapit Spatial

  1. Connect your simpleRTK2B GNSS receiver to your Android smartphone/tablet via Bluetooth and Lefebure NTRIP app and enable mock locations.
  2. You can find here a tutorial explaining how to do it.
  3. Remember to connect to a NTRIP server to get the best accuracy.
  4. Now your Android device is using the simpleRTK2B as if it was its internal GPS!
  5. Open Mapit GIS/Spatial application, by default it uses the internal GPS which is now the simpleRTK2B receiver. You should see already your position in the map.
  6. Go to Settings, select Survey
    mapitgis settings
  7. Enable the following options:
    1. Orthometric height
    2. Accuracy & GPS Quality on the map
    3. Show speed&altitude
  8. Select geoid model option: Custom geoid *.bin format
    mapitgis orthometric
  9. If you go back to the main screen you will already see the orthometric altitude based on your custom geoid and clicking on the antenna icon will show you additional information
mapitgis details