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Error in altitude indicated about +50 meters (and his cause)

Alberto
over 2 years ago

In the Explorer app, the indicated altitude is the geodetic (or ellipsoidal), however, the correct altitude should be the orthometric (mean sea level), which is the one indicated on all maps and the altitude that, correctly, indicates any GNSS receiver, app mobile or also my recent Inreach Mini 2 in the navigation page (with which I am delighted, by the way).

The approximate error (depends on the geoid of the earth) is about 50 meters more.

Just suggested via https://www.garmin.com/en-US/forms/ideas/ :)

  • 0 over 2 years ago

    I am quite sure Explore uses SRTM elevation data, at least in my area (Tyrol, Austria). Explore reports my altitude within 10m of my real altitude (derived from a high resolution DEM) and GPS elevation, so well within the error margins. I don't think that there is something wrong in general. 

  • 0 over 2 years ago

    Mmm, the SRTM is another system and have about 16 m vertical precision, but the GNSS receivers dont use DEM data ... internally use the ellipsoidal height but externally they show the correction corresponding to the geoid, giving the orthometric height, which is indicated by all the maps and the reference altitude.

    The Explore app shows ellipsoidal instead of orthometric. It's easy to compare on any open site. You will see that the app indicates approximately 50 meters more than the one indicated by the Mini 2 (or any other GNSS or mobile receiver)

    I have the official data of the orthometric altitudes of the geodesic points and I have been checking in several places, but specifically on a very clear summit and the altitude indicated in the Explorer app was clearly the ellipsoidal altitude, which, depending on the area of the earth, it is approximately +45 to +55 m above the orthometric altitude, which is the official one indicated on all the maps, ... and which, as I have mentioned, correctly indicates the Mini 2, my mobile in its multiple positioning apps ( Osmand, Oruxmaps,..).

    I just checked it right now on my site: it indicates 52m more, while Osmand and Mini 2 indicate the correct altitude.

    It's not important because I think the people dont use this data of the app