Our app allows you to record trails on Apple Watch. It uses CMAltimeter to get the elevation for the recorded trail and HKWorkoutSession to record the user's workout.
Some of our users started reporting huge punctual elevation spikes when pausing the app in Apple Watch. After a thorough investigation, it turns out the altimeter reports wrong data while the workout session is paused.
CMAltimeter starts reporting offsetted relativeAltitude values while the HKWorkoutSession is paused. This offset, in our experience, ranges from 1.5 meters to +1000 meters. When the HKWorkoutSession is resumed, after a couple of seconds, the reported relativeAltitude value goes back to a similar range to the values before pausing. Strangely, the pressure value seems to be unaffected by this problem.
I've been able to reproduce this on my Series 5 Apple Watch with watchOS 6.2.8. Is this a known issue?
I've already submitted a bug report: FB7972487
RogerWikiloc
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