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I know that when I use .getAltitude() I get the height above the WGS84 reference ellipsoid. Now, there is an inaccuracy of more than 50 metres.

Furthermore, I know that the height can not be calculated so easy to the normal metres over sea. In my app, I can´t give the user such an inaccuracy. How can I handle that? Is there only the one way that I use a Web Service to get the exact height?

AlexWien
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user896692
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1 Answers1

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I can answer only a part of your question:

The GPS chip delivers the height above the WGS84 ellipsoid, but still usually this value is inacurate by typically 20-30m. So even the value related to the elliposid is wrong.

For an accurate height you must

  1. Correct the inacurate altitude (WGS84 ellipsoid) to the correct WGS84 height by using a web Service, where you send you lat,lon coordinates to.

  2. Convert the now acccurate height above WGS84 to height above mean Sea-level.

For point 2, I am not sure if there is a service and if you can do it locally.

I recomend that you read this post: How do I convert a geodetic location to an ECF position that works with the terrain model in Cesium

Update: Every GPS receiver can output height above mean sea level and height above ellipsoid, this means that there is a possibilty to convert without using much memory. Find out how they do, and please post here. (Add a comment if you found out) (The GPS NMEA GGA message contains both values)

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AlexWien
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