Originally Posted by
ItsJustMe
I actually rode a 20 mile course with a GPS on my handlebar and found that my computer was about 2% off, so I subtracted 2% from the setting in the computer. Do not do this if you're going over a course with lots of curves; the GPS will probably underestimate the distance a bit by cutting corners between samples.
You have got to be kidding - that GPS makes it's calculations, like 3 times a second. It's not averaging, or cutting corners, on anything.
Other than changes due to national (and military) security, it's as accurate as things can be!