I had a quick play wit hthe phone part of the software over the weekend, and while cycling round Herne Hill, with my phone in my back pocket it belived taht I mananged to peak at 43 mph.
That being nearly 20mph faster than my cycle computer recorded, I somehow don't belive it.
That happens to all GPS devices, even the high sensitivity ones. They usually go as low as 6m "accuracy".
If you look at the figures then:-
23mph = 10.28m/s.
So in one second you'll go about 10m. Now imagine in one second the GPS thinks you're 6m further back than you are, you then move 10m forward in that second, and then the GPS thinks gets it wrong by 6m the other way (i.e. further on).
So it thinks you've moved 22m in one second or 49mph.
On any long ride my Garmin eTrex claims I've done about 90kph at one point.
