An American defence research agency is developing a radar system, which will monitor vehicular movement across a city using a few uncrewed aircraft.

Pentagon's Defence Advanced Research Projects Agency (DARPA) is creating the experimental vehicle tracking system, called Multipath Exploitation Radar (MER), reports New Scientist.

With the use of the new radar system, DARPA is hoping to track vehicles across an entire city using just a few uncrewed aircraft as it could see around corners and down into "urban canyons".

Unlike traditional radar that relies on direct line of sight and fails to track a vehicle that keeps nipping behind buildings, the MER, by using buildings as mirrors, will identify a target vehicle from radar reflections.

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.

A DARPA spokesman said that MER is expected to be compatible with the radar systems currently used to track vehicles.

The team anticipates that using reflected radar would cover more ground than a line-of-sight system, making it possible to monitor a city of about 1000 square kilometres, such as Baghdad, with just three airborne radars.

The three-dimensional model of a city needed to make sense of the reflection pattern could be created using LIDAR, the optical surveying technology which is routinely carried on aircraft.

MER makes use of Ku-band radar - frequencies of between 12 and 18 gigahertz. It is sensitive enough to produce distinct signatures for apparently similar vehicles, by detecting slight differences, such as the angle of an aerial or a wing mirror.

The agency is also planning to develop an algorithm, which would enable the system to track multiple vehicles. (ANI)