GPS speed

[old skool iron]

My trucks speedometer well its not the best. I've replaced the sensor no luck. so i got a dash mount gps that projects my speed,mileage,and distances on the windshied.its great.OSI

[kanewolf]

A little background on the accuracy of GPS as a speedometer. http://gpsinformation.net/main/gpsspeed.htm

Most people don't realize that the GPS receiver is using Doppler shift for speed determination and not just distance from last reading and elapsed time.

[JDOFMEMI]

Good link kanewolf.

I think .5 mph is much better than any factory installed speedometer. That is a good fix for broken units, or with vehicles that have different tires or gearing installed.

[kanewolf]

I always "validate" the speedometer in my vehicles against GPS. It is really interesting in rental vehicles. Usually car speedometers read high -- over the GPS speed. My Nissan truck is pretty much right on. Of course, a change in tires could alter that.