We got on the plane, take off, as usual, after 15 seconds it switches to climb mode, at that time it showed about 120-130 meters. After a minute, he returns to ground mode. And that’s it - for 2-3 minutes, then it switches back to the climb mode, but the difference with the altimeters of other skydivers is 180-200 meters.
@Macabre96 so developers have investigated this and for transparency I will post their findings here -
Barometers and GPS functioned as intended throughout the flight/jump.
Note for anyone joining the convo, the weather conditions had declined considerably between loads, ground level pressure appears to have dropped about 4mbar. I assume that there was a storm brewing and the pilot chose to fly under 190m for approx. 4 minutes before beginning to climb. This played a part in confusing the device about what the ground level was.
Plane mode started normally but aircraft only ascended to 150m within the first 60s. This tricked the
device into thinking it was a false start and returned to ground mode.
The plane kept ascending very slowly (+240 meters in 3 minutes) and ground speed was as slow as
44 knots. This confused the device about what the ground level is.
Eventually at around 400 meters ASL or 310 meters AGL, the plane got to 85 knots ground speed
and 2-3 m/s climb rate. Until this point a new ground level was being computed by averaging some
last measurements and at this point device already thought ground was at 280 meters ASL, but the
ground level should’ve been 90m which gives a ~190m difference
This circumstance is obviously a very rare one but all of the information you have kindly provided will help developers tweak and refine the device algorithms to avoid a similar situation in the future. Thank you!