A video camera at known distance from the ground can be used to compute speed. If combined with a magnetic compass, you get direction too. This should work with most ground materials that shows some form of structure. It would probably fail badly in case of rain. Quality of magnetic sensor, external magnetic fields or low-quality lens if lots of distortion would affect precision.

Another option - set up visible image markers, and film them. Image sensor information can triangulate angle and distance. Weak spot here would be fog, or the work measuring where to place the markers.