i went to a trip around the mountains yesterday and since then my watch keeps telling me a wrong altitude (whereas my phone altitude is right). Now at my home the altitude is wrong of about 700 meters. If i download a third party app the altitude is right. What is the problem here? What do I do? Just wait for the next update?
anyway I have a watch se 40mm gps + cellular
Apple Watch SE, watchOS 7
The first (and simplest) thing to try if something isn’t working right is to restart your Apple Watch and its paired iPhone. If necessary (device not responding), try a forced restart. Both methods can be found here:
How to restart your Apple Watch - Apple Support
Restart your iPhone - Apple Support
If that doesn't help, the next steps would be to unpair and pair your watch again and restore from the backup just created. This should result in no loss of data. It deletes all temp and corrupted files and re-indexes the file system.
Unpair and erase your Apple Watch - Apple Support
Set up your Apple Watch - Apple Support
Also from:
Use Compass on Apple Watch (Apple Watch SE and Apple Watch Series 5 and later only) - Apple Support
"Note: Compass won’t display elevation or coordinates if Location Services is turned off. To turn Location Services on or off, open the Settings app 
on your Apple Watch, tap Privacy, then tap Location Services."
The first (and simplest) thing to try if something isn’t working right is to restart your Apple Watch and its paired iPhone. If necessary (device not responding), try a forced restart. Both methods can be found here:
How to restart your Apple Watch - Apple Support
Restart your iPhone - Apple Support
If that doesn't help, the next steps would be to unpair and pair your watch again and restore from the backup just created. This should result in no loss of data. It deletes all temp and corrupted files and re-indexes the file system.
Unpair and erase your Apple Watch - Apple Support
Set up your Apple Watch - Apple Support
Also from:
Use Compass on Apple Watch (Apple Watch SE and Apple Watch Series 5 and later only) - Apple Support
"Note: Compass won’t display elevation or coordinates if Location Services is turned off. To turn Location Services on or off, open the Settings app on your Apple Watch, tap Privacy, then tap Location Services."
I've have the same issue.
I went to the mountain walking for a difference of height of 900 meters and tracking the walking outdoor activity with Apple Watch. I dit it only going up but I did't tracked the same activity going down.
Since then, the altimeter shows around 900 meters more than the real altitude.
I did an hard reset of the Watch and the recalibration ad described by the support, walking again for 20 minutes.
The issue still exists. Only the accuracy in now 20 meters instead of 350 meters.
Apple watch altimeter
