The pitch: current systems exclusively rely on above ground sensors like GPS, lidar and cameras to identify the exact position of the vehicle, but those can be confused and handicapped by poor visibility issues and adverse weather conditions such as snow, heavy rain, fog, sand and dust. But more reliable and stable data can be tapped beneath the road's surface where unique subsurface textures can be mapped and leveraged to accurately position a car on a track, regardless of the weather conditions and visibility above ground.
The technology, initially developed by researchers at the MIT Lincoln Laboratory for military applications (accurately detecting and mapping mines and other sub-surface explosives) is described by WaveSense's CTO and co-founder Byron Stanley in a 2015 paper "Localizing Ground Penetrating RADAR: A Step Toward Robust Autonomous Ground Vehicle Localization" published in the Journal of Field robotics.
The localizing ground-penetrating radar (GPR) consists of a 152cm×61cm plate array of 12 antennas (just under 8cm thick) sequentially pulsing RF patterns across the 100MHz to 400 MHz range. Just about the width of the car and positioned under the vehicle, behind the front wheels, the GPR operates at a sweep rate (across all its channels) of 126Hz, detecting underground features at a 2 to 3m depth to generate baseline maps on a first pass, tied with GPS tags.