Messages

[Disabling "Google Services assisted location" solved the problem.]

Hi Menion,
Thank you very much for your suggestion.

Disabling "Google Services assisted location" solved the problem.

I've tested it on two more flights, and the unfiltered altitude readings usually match that of the "GPS test" app within one meter. The filtered readings have delays, but this is expected as the activity type was set to walking.

final attachment

further attachment

another attachment

Last Monday, I took a flight from London Stansted to Belfast International Airport and decided to record the track (in Airplane Mode). GPS connection was fine, and my horizontal position was displayed correctly, but soon after takeoff, I noticed that the displayed altitude of about 400m seemed to be too low for the view from the window. So, I opened a GPS Test app, which showed an altitude of over 4km. After about 20 minutes, the altitude on Locus Map reached the correct value in a nonuniform and inconsistent fashion (going up and down tens if not hundreds of meters for no reason while GPS Test displayed sensible and consistent values). The same happened on the descent with the altitude reading of 1765m at Belfast International Airport's runway (while 136m in GPS Test). I also compared the GPS Test's altitude readings with that of the Garmin's Earthmate app, and they were consistent.
Note that the activity type was set to walking, but I tried different filtering modes and then disabled filtering completely. This didn't help. I made sure these were actual GPS-based (not barometric) readings.
Attached (in multiple forum entries due to the attachment size limitations) are the screenshots from my phone showing Locus Map alongside other apps displaying the altitude. Note that for some reason, GPS Test reports a higher number of used satellites than Locus Map. The recorded track split into two .gpx files (because I restarted the recording trying to fix the issue) is also attached.
Let me know if you need more information.