The trace itself can express any integer value for distance (integer because the trace reader assumes an integer) and the program can handle arbitrary distances as well. The "bucketing" is actually an artifact of the size of the (original) large 16k-sample radar inputs (each being 8-10MB) and the desire to keep a more manageable dictionary size. The units are also intentionally abstract here; while the radar is actually calibrated in meters the mini-era plan-and-control functionality interprets the distances as a much shorter abstract unit. It is presumed that the final radar, etc. would be calibrated to the plan-and-control distancing, and here we are focused on avoiding vehicles near the subject car.
The trace itself can express any integer value for distance (integer because the trace reader assumes an integer) and the program can handle arbitrary distances as well. The "bucketing" is actually an artifact of the size of the (original) large 16k-sample radar inputs (each being 8-10MB) and the desire to keep a more manageable dictionary size. The units are also intentionally abstract here; while the radar is actually calibrated in meters the mini-era plan-and-control functionality interprets the distances as a much shorter abstract unit. It is presumed that the final radar, etc. would be calibrated to the plan-and-control distancing, and here we are focused on avoiding vehicles near the subject car.