altitudes are not real

I wrote on the forum :

start alt = 1591m, max alt =2706 ... It's wrong. My GPS noticed 1455 as start alt and ~2590 as max alt so it's not only a 60m drift

• 136m at start
• 116m at max alt

I've calculated another 20m at landing alt (534m for gaggle instead of 514 for garmin)

both are calculated with WGS-84 (which is used for each every GPS tool)

best regards

I think the problem has something to do with Geoid-correction. Gaggle measures altitude in AMSL instead of WGS-84 (if I understand it correctly). For the one of us who needs the WGS-84 altitude a switch in the preferences would be great! (XC-Soar running on the same device -> correct altitude - Gaggle -> ~50m to high)

XC Soar does wgs-84/egm96 correctino using an open source c library. For now I've provided a manual adjustment which should be good for most people, I think.

You can work out your geoid height difference by googling geoid height calculator and entering your lat/long into one of the available tools