I have the original Galaxy watch (42mm), which I was using fine with my S10+ phone.
After upgrading my phone to an S21 Ultra, I restored my Samsung Backup, then re-paired my watch with the new phone (wiping & reloading the watch.)
Since then the distance reported for a walk is off by something like 35%.
Using a 2nd phone app, I logged todays walk at 1.99 miles. The watch and the Samsung Health phone app show 1.3 miles, and that reaching 1 mile took 5 minutes longer than it actually did.
Also, the Health app used to log the GPS track of the route - I no longer see this.
I set the watch to use GPS only for location, and also re-entered profile info that was lost like my height and weight. Made no difference.
Solved! Go to Solution.
Tried the trial version of the Gear Tracker app - it logged the same route perfectly, while the Samsung Health app was 73% of the actual distance (1.41 miles vs 1.92 miles).
How can this watch app be this far off when a different watch app is accurate on the same hardware?
In the watch, Settings / Apps / Permissions / Samsung Health / Location
had gotten turned off. Now it is back to recording my GPS track, and doing a reasonable job of measuring distance and speed.