WHY jump in a cab to "follow that car" when an airborne drone could do the job for you? The US Pentagon's Defense Advanced Research Projects Agency is developing a radar system which sees around corners and down into "urban canyons". DARPA hopes to be able to track vehicles across an entire city using just a few uncrewed aircraft.

Traditional radar relies on direct line of sight, so it's tricky to track a vehicle that keeps nipping behind buildings. But DARPA believes that by using buildings as mirrors, it will be possible to identify a target vehicle from radar reflections. The experimental system is called Multipath Exploitation Radar.

The agency has been exploring how MER might work by driving vehicles around a simulated urban area and collecting returns from an overhead radar. Its researchers are aiming to combine the radar data with a three-dimensional map of the test environment to calculate how the radar reflects off and between vehicles and buildings. This process should highlight which signals in the returning radar data can be used to plot the target vehicle's path.

MER is expected to be compatible with the radar systems currently used to track vehicles, a DARPA spokesman told New Scientist.

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www.newscientist.com/article/mg20527524.600-spy-in-the-sky-that-sees-round-corners.html?DCMP=OTC-rss&nsref=online-news