Past experience with wildly varying data has prevented me from trusting GPS-based devices for accurately logging distances while riding mountain bike trails, but after hearing reassuring reports of modern units and seeing how useful it could be to have one unit logging data for all three of my bikes and automatically aggregating it I decided to give it a go. I purchased a Garmin Edge 500 cycling computer and a GSC 10 wheel speed / pedaling cadence sensor a month ago and after beginning to use it things seemed quite accurate, but I continued to be a bit suspicious that it may not be providing as accurate of data as it could. So, I decided to do some tests.
The results of these tests have shown that when the Edge 500 is used in conjunction with the GSC 10 it is just as accurate as a wheel-based computer and can be relied on to provide sufficiently accurate distance measurements while riding curvy mountain bike trails. Coupled with all the extra data that the system can log (heart rate, location, temperature, cadence, etc) it’s quite a nice system for recording data.
Without the GSC 10 (using only GPS-based data recording) the Edge 500 showed drastic undermeasurement, 20.70% on a typical Southeast Michigan trail ride and 33.87% in a worst-case test scenario.