The speedometer may be driven off the transmission, wheel speed sensors, or something else. It doesn't take into account slip.

Well, yes, a speedometer is perfectly fine if all you care about is "speed".

The point of the technique, however, is dead-reckoning of position which means integrating speed, which is prone to accumulate errors over time if you just look at the wheels.

The title of the paper, I think, could be better.