Why is my activity's average speed or pace different than my friend's?
Even if you and your friend do an activity together, it is possible to get different distance calculations on Strava. In most cases, this will be because one or both of your GPS devices recorded location (or other) data that does not accurately represent your activity. Things like GPS drift, GPS signal loss or a 'jumpy' GPS track can cause your activity to report more or less distance than you actually traveled. If for example, your bad GPS data tells Strava that you traveled a longer distance than your friend in the same amount of time you can expect different average speed calculations.
In addition to distance discrepancies, Strava uses moving time to calculate average speed and pace. It's possible that you and your friends calculated moving time may be different which will lead to different average speed or pace calculations.
Why is my activity's average speed on Strava different from my GPS device?
When uploading rides Strava will use the recorded GPS data to calculate our own version of your moving time. During the upload process, whether you recorded with our mobile app or a third party device, Strava relies on a speed threshold to determine whether or not you are resting. You can enable auto-pause on our mobile app to automatically pause during your activity when your GPS tells us you are resting. In general, Strava tends to be more strict about resting time so we remove less of it than other platforms. This means that even though the elapsed time is the same, the moving time can be a bit different, which can cause differences in average speed.
When uploading runs Strava relies on the recorded "timer time" which is the time the app or device was unpaused to determine moving time. As long as your device is recording conventional pauses, Strava will respect any pauses recorded in the file whether your device pauses automatically or you manually hit the pause button. If you do not pause at all our server will calculate moving time based on the recorded GPS data. Again, even though elapsed time may be the same, Strava may calculate moving time differently than other platforms. The other thing to keep in mind is that if you choose to pause you must do so consistently. If there are any pause events in your activity file our server will not remove any additional resting time.