spally

leasaunce, You are right. Is is better the other way. I did correct my first posting to reflect thet the speedo was higher than the GPS. What can I say, It was late at night when I entered my post :)

Make that 100 on the speedo and 97 on the gps. ;) That is not bad at all. I mean the speedo. What sort of GPS is this? Is that bluetooth or via serial bus? It is a $35,000 Leica GPS Sensor. It uses both United States' GPS satellites andthe Russian GLONASS sats. It augments its position from fixed base stations via corrections sent over the internet. I am a Naitonal Tech Support person for the survey equipment we sell and I was out looking at satellite coverage on the Gateway Arerial upgrade here in Brizzy. To get over 5hz, you have to go away from bluetooth as BT only supports serial data at a maximum of 5hz. If you are really serious about getting accurate GPS positions at a high updatae rate, let me know.

Make that 100 on the speedo and 97 on the gps. ;)

I have access to Survey grade GPS. It runs RTK corrections (30mm positional accuracy) and updates at 20hz. At 100 kph on the GPS, my spedo reads 97kph. Also be aware that "GPS" distance (known as Ellipsoidal Distance") is different to "Ground" distance. The difference depends on your Latitude and Elevation.