Wrong Altitude on Track Recordings

[Daniel]

Hi all,

I’ve recorded several tracks recently which show wrong altitudes (e.g. going to -24m for several seconds while not changing altitude at all; see attachments).

I’m pretty sure it’s not Trails fault but am still wondering where this issue can come from.

I’m on an iPhone X with iOS 11.3.1.

Anybody any idea?

Thanks!
Daniel

[trails-support]

Hi Daniel,

this is a known issue and while we’re investigating this issue (and have been for a while), we do not have a solution yet.

Our observation is that this issue is worse on recent phones (iPhone 7 and later) and recent versions of iOS (10 and later), but we cannot reproduce it on demand.

Generally, Trails relies heavily on the GPS signal. We try to detect/filter obvious jumps, but it’s not trivial to tell actual movements from these errors automatically. We have a couple of sample recordings with this issue and the recording accuracy (as reported by the GPS) isn’t significantly different in spots that the human eye easily detects as inaccuracies.

[Daniel]

Thanks for your reply!

Please let me know if I can help somehow. The effect you’re describing appears in all my recordings.

Best,
Daniel

[HPS]

Hi,
I have the same issue with my iPhone 8. And also calculation of the ascend and descend is wrong.
Maybe the integration of the barometer in a “altitude filter” in the GPS measured altitude could improve the accuracy.

Regards
HPS