WaveSense uses ground penetrating radar – GPR to create a reference map of the subsurface conditions below the pavement of a highway. This can be accomplished because the return GPR signal creates a unique electromagnetic signature.
From an article in Motortrend.
Waymo, which recently launched its autonomous ride-hailing service in the Phoenix area, is betting big on traditional sensing technologies—including cameras, GPS, radar, and those super-expensive spinning lidar sensors on the roof.
These Waymo cars are essentially beta-testers, which means they are not fail safe. (Remember Uber?) If Waymo happens to have an accident and the fault is found to be with the sensor array, it’s a safe bet Waymo won’t be able to blame a blizzard or pea-soup fog.