Hey rsiesta, the GPS receivers we use are accurate enough for what we need them to do. As you've been advised, adding a speed sensor to your wheel will improve this. I know that is not a satisfying answer, but to get one that gives the kind of precision you are hinting at, you'd have to spend more on the GPS receiver than the bike you're riding. Think about it like this: if you aren't guiding bombs and artillery, don't sweat the loss of a few meters here and there.