As far as GPS goes.....
There are about 5 different types of bands that come off them satelites, military uses A/B band which is accurate to about 7 meters and about 1% error on calculations....Civilians with store bought gps units use C-band which can have up to 150ft of error and 15% error on calulations with built in erroneus data thrown in just to make it even worse. Im not sure i'd believe anything as far as a speed calulation comin from a walmart gps unit.


My 0.02