Which is accurate sat nav or vehical speedo?
Think about it, and you will realise that Sat-Navs get the speed wrong if you are travelling up or down a hill – you appear to be not moving very far to the satellite observing you from above, as it is seeing your journey as a two-dimensional trip, not factoring in the extra distance you are climbing or descending, as the hypotenuse of a triangle. It is a small error, and yes, car speedos aren’t 100% accurate by any means.
