Geoid Height Extension

Starting form version 2.7.0 (published on the 14th of June 2015) new extension called “Geoid Height” has been added to allow recording of altitude as orthometric height (height above EGM96 geoid which approximates mean sea level).

The Geoid is a model of the Earth’s surface that represents the mean global sea level.  Its shape passes through the Earth’s crust and is determined from data collected all over the world about the Earth’s gravity field.  The vertical distance between the geoid and the ellipsoid is called the geoid height.  This height can be either negative of positive.  Differences in height between the geoid and ellipsoid (geoid heights) range from roughly -100 to +100 meters.

If you would like to record the orthometric height instead of the ellipsoidal GPS height which assumes the Earth to be totally homogeneous as if there be would no mountains or trenches this extension will do the job and no post processing is needed.

The picture below explains the differences between the ellipsoidal and orthometric height.


Orthometric height (Mean See Level)


The extension is using Worldwide 15 Minute Binary Geoid Height File to calculate the geoid offset.

You can check the difference between the WGS84 (GPS) altitude and the Mean See Level using the program on this website: .


More information:




If you can’t explain it simply, you don’t understand it well enough.

Albert Einstein

8 Responses

  1. Rempu Rayat says:

    Hi, i just bought extension software for geoid height. Where do can see the height in map? Thanks.

    • osedok says:

      Hi there, go to Survey Settings and enable “Show speed & altitude”. If you have it already enabled the altitude displayed will be automatically adjusted to include geoid differences.
      As long as the ‘Geoid Height for GPS’ is switched on in Survey settings – all altitudes will be automatically recorded with geoid correction. You can compare your readings for the option switched on and off to see the difference.

  2. Kuloba Aron says:

    Hi provide me with Calculations about the geoid

  3. Daniel Flint says:

    How accurate is the measurement?

    • osedok says:

      Hi Daniel, high measurement accuracy is depending from number of factors – most important are the GPS device itself which I am not able to comment on, the second one is the Earth Gravitational Model itself. For the purposes of MapIt I am using the one published here by NASA, but I am not able to provide more information in terms of accuracy in your area. You may get directly to the Earth Gravitational Model publishers to get some more information.

  4. Bruce Hedquist says:

    I’m not sure which geoid model I’m using. I tried importing the 2.5′ x 2.5′ one. I downloaded it off the net and put it in a folder as instructed. But the folder may not be under the program.

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