Hi. I want ask you some information about altitude and his calibration. I did some test about DEM calibrate and I see that altitude have difference from official altitude, from Google Earth and from some app that give me altitude with same DEM data. And this is strange, because I test it in my city that is in a place without mountains or something else, and because in teory I wait same result that start from DEM and datum WGS84 for every program, or not? For example my central plaza have official altitude of 199m and with Google Earth I have 199m, but with another smartphone app and Garmin it have 204m. On another place, near my home, I have 209m with Google Earth, 216m with Garmin and 213m with this app, and those misures are the same is I try to misure every day. Barometer of my Garmin 945 I see that is ok, because there is allways 10m of difference from plaza to my home, but there is allways this difference. How is possibile? What change?
