i definitely get much cleaner results than that with my iPhone; i can't really find any in the last 20 or 30 rides that are grossly off except for going through tunnels. perhaps the iPhones augmented GPS is doing something, perhaps it's just luck. i've chalked up major differences (more than .5%) in rides to tire inflation changing the accuracy of the wheel sensor, and the GPS always being just a tiny bit short of the real distance thanks to the straight-line-interpolation.



i've