Accuracy of Garmin vs. Strava

That's a fairly big difference which is not typical. Usually they will match within a few seconds if all the parameters equal.

Are the distances the same (or within experimental error)? If so, then check the "moving time" vs. "elapsed time" and check your autopause settings in Strava. It seems that it is likely subtracting more of the non-moving time (perhaps below a certain pace threshold) and thus calculating a faster moving pace.

edit: It also will depend on the satellite reception in your area. In general the accuracy of the Garmin should be higher but if both are losing signal frequently they will make different corrections and thus the data will look different. I normally get longer distance (and therefore faster pace) using the Strava app vs Garmin in areas with variable GPS reception, and in general the Garmin data is more reliable.

Edited by jennifer_runs 2016-05-29 1:46 PM

GPS signal is not very accurate, especially when using a cellphone (you have two variables, GPS positioning accuracy and cell signal strength... if you have intermittent signals, then it will calculate distance based on last known coordinate, speed at that point and then new coordinate). Another major challenge is that if you run in hilly terrain (which you can't do around London...), the height calculations based on GPS signal are really inaccurate...

The 910XT is using barometric pressure to calculate height, so that is much more accurate, plus it relies on the GPS signal, not a cell signal.

Garmin will be more accurate.