My father was a missile radar guidance technician for a living. He says radar on a car makes almost no sense, especially for navigating in inclement weather, due to how radar tends to reflect off of anything to some degree.
Radar works fine in rain and snow. You can use it to detect rain and snow, but the reflection is very weak compared to the reflection from a solid object, especially at the 0-500m range that these operate at. Big weather radars go out to a couple of hundred miles.
For a vehicle, it will be far less than ideal. It will have problems distinguishing between heavy rain and a solid object, especially at night, without a lot of other high-precision high-refresh sensor data and a good computer to put it all together in realtime.
Every sensor, man-made or natural, sucks at detection when it comes to operating in heavy inclement weather. That's why we need tons of processing power and filtering algorithms. If they were any good, we'd not need those higher-order algos and filters. The sensors could simply generate reliable data.
Automotive radar are in the ~80ghz range, giving it a wavelength on the order of about 4mm. Car radar can definitely see through rain and snow. All radars receive a range of reflections from many objects, rain included, but the return off of rain is nothing compared to the return off of a solid object. The filtering then becomes choosing the peak amplitudes of the radar return signal. Rain will manifest itself as a smearing of the signal and lowering the peak a little bit, but usually much less than a solid object.
Optical and lidar work miserably through rain/fog, with wavelengths in the ~1000nm range, but have much higher resolution.
Any real self-driving solution in the near to medium future is going to involve sensor fusion of as many sensors the car manufacturers can afford and cram in. This means cameras, ultrasound, lidar, radar, etc. Anybody telling you that there is only one true sensor to rule them all is either selling you something or ignorant of the state of the industry
Is this based on data you've seen or worked on? In general radar performs a lot better than lidar because the wavelength of automotive radar is reasonably large relative to the size of a raindrop.
https://www.weather.gov/media/publications/front/14dec-front...
My father was a missile radar guidance technician for a living. He says radar on a car makes almost no sense, especially for navigating in inclement weather, due to how radar tends to reflect off of anything to some degree.