Had a few PC probs so haven't been on here properly for a bit. I still have my Astra but also still saving for my Bora.
Anyway, I seem to be using the Sat. Nav a lot lately and have found a major difference between the speed readings.
On my speedo I might be doing 70mph but the GPS is reading 64mph and at 30mph on the speedo, the GPS is reading 26mph?
I personally think the GPS is more accurate as it claculates where you are etc using normally around 6 satellites.