Originally Posted by
kahn
I use Specialized Mission Control and Gaia to track my routes. They usually vary about .1 or .2 miles difference over a 15 to 20-30 mile rides. Elevation data is even more out of whack.
I also use Mission Control, plus rideWithGPS. The results are usually very, very close (last ride reads 46.10 miles in mission control, 46.1 in rwGPS, ride before that, 20.7 in rwGPS, 20.82 in mission control). zooming way in on the GPS track through known urban areas shows that the straight line segments between measured or interpolated points results in a slightly shorter distance than the actual arc the bike is traveling, plus the GPS based measurements are horizontal distances, while the bike's rear wheel sensor (used by mission control in combination with GPS) would show a longer distance over an incline. Just for kicks i once rode a very very wiggly route down a bunch of 20% streets here in SF, and the results were much more divergent between the two apps.
What I don't know is how an app like mission control (or a bike computer which has both wheel sensors and GPS!) integrates the conflicting data. Wheel sensor says 50 feet has passed in the last second (with no additional data), GPS says one second ago you were at XX,YY and now you're at UU,VV, and the distance between those two is 49 feet, not 50.... does anyone know how they reconcile that? Separate data streams which simply don't agree, and the application viewing the data simply chooses?