Originally Posted by
Seattle Forrest
I don't really use Strava, in Garmin you can make the X axis time or distance, but that's not what I mean. What I mean is this. You have more data points in your file than you have pixels on the X axis on that chart. Each pixel in the chart represents some amount of time, it might just be the highest or lowest value. My suspicion as a developer who fixes bugs for a living is that the average speed shown next to the chart comes from the Y values and they're being summarized incorrectly. I don't have a way to test that hunch, but in terms of how software is put together, it feels pretty likely.
Yes, I got that, and I understand that you know what you are talking about. OTOH, my point, developed disparately across this thread, is that smoothing alone doesn't explain a *systematic* bias, unless "slow" data are preferentially filtered by the smoothing. There is reason (see post above) to suspect that this could be the case.