asked 2014-05-13 15:06:50 +0200
I noticed a height difference of about 50 meters, when I move to points of known height (absolute altitude above sea level) in Germany, even when the accuracy is high (a few meters) and the horizontal position (i. E. in a maps app) is given very precisely. Jolla's value is higher than the real one. Android Apps and "GPSInfo" from warehouse give identical values, so I think it's the system. Someone able to confirm?
Michael
answered 2014-05-13 18:51:09 +0200
From my point of view it's a tough task to get altitude information right just from satelite navigation. It's based on trilateration (http://en.wikipedia.org/wiki/Trilateration) and if you take the satelite's orbits into account the altitude is the dimension with the highest uncertainity in the resulting intersection figure. That's why other positioning solutions use additional sensors to get a more precise altitude.
The displayed accurracy is usually an estimation from the tracked satelite's positions and the received signal.
answered 2014-09-10 19:27:51 +0200
Can confirm (also in Germany). It's possible that this is somehow influenced by the reference system. http://www.ottmarlabonde.de/L1/Pr1.Applet1.html shows a difference of about 50m between IfE89 (whatever that is, IfE = Institut für Erdforschung?) and geodesic systems closer to WGS 84. The original applet doesn't seem to be available anymore.
Just to push it up... compared with my backup Jolla (marginal note: is it enthusiasm or idiocy to buy the same device twice, just because a fear of breakdown?): that second one adds further ~20 meters. So, in my patio: real height (from map) -> 224m, Jolla 1 -> 273m, Jolla 2 -> 292m. Nominal accuracy on both better than 15m. With Jolla you are always on top.
Robomike ( 2015-06-03 22:52:51 +0200 )editAsked: 2014-05-13 15:06:50 +0200
Seen: 556 times
Last updated: Sep 10 '14
You've confirmed it's not GPS in common that's causing the issue? I would guess other GPS-devices can/would do the same...
RobNas ( 2014-05-13 23:33:28 +0200 )edit