The US Pentagon's Defense Advanced Research Projects Agency (DARPA) is now developing a radar system that sees around corners & down into urban canyons. With just using a few uncrewed aircrafts, the agency could track vehicles across an entire city. So, the key to this is that they will be using the buildings as mirrors which will help them to identified a targetted vehicle due to radar reflections. This system is call Multipath Exploitation Radar.

They are aiming to combine the received radar data with a 3D map so that they can calculate how the radar reflects off & between vehicles & buildings. They also anticipate that using these reflected radar would cover more ground than a normal radar which will be able to monitor a city of about 1000 square kms. The frequencies used would be between 12 & 18 GHz.