GPS Speedometer Accuracy in GPS technology and devices Posted April 15, 2002 quote:Originally posted by BletchleyPark: Both cars read 3 mph faster that the radar speed as I would expect from this (German) manufacturer. Both cars had the ColorMap and Vista side-by-side reading the same 35 mph as the radar trailer indicated. I should note that I made 4 passes in each vehicle while the road was deserted. Not scientific, but good enough neurosurgical work! BP Radar guns always read less than actual, unless they're in the middle of the road. MajBach You can't have everything. where would you put it?