Originally Posted by
69chevy
Add the GPS function as another means for speed detection and I doubt a garmin is more accurate.
I can't say about other apps, but at least compared to Strava my 810 is a lot more precise. On Strava I always get average and maximum speed and altitude exaggerations, and that's not only compared to the 810 (I got the same results using my old eTrex Vista and a cycle computer).