GPS accuracy?

[Dabigguy]

How accurate is the MPH calculation on GPS systems? I'm trying to calibrate my speedometer and am wondering what is the fudge factor of GPS.

 

[TurboDave]

How accurate is the MPH calculation on GPS systems? I'm trying to calibrate my speedometer and am wondering what is the fudge factor of GPS.

As a rule of thumb, if you have a name brand unit the speed calculations, once moving, will be VERY accurate. As a matter of fact that's the most accurate portion of data produced by GPS devices.

You can rest assured that the speed accuracy will be out to the nearest 100th of a mph.

This all assumes a good signal and view of the sats.

 

[Dabigguy]

Darn, only accurate to 1/100 MPH huh? I was hoping they were REALLY accurate !!

 

[UNGN]

We have a $70 Ebay GPS Speedo in our 2+2 and it was within 1 mph of a 100 ft electronic LASER gated speed trap at 166 mph. My cars speedo is about 7 mph off at that speed (If it read that high, at 154 it says 160 which is as high as it goes)