When weapons such as IEDs (improvised explosive devices) are hidden along the roadside, they do visually change the environment, but in a manner which is subtle enough that it will likely be unnoticed by the human eye. The US Army Research Laboratory's Dr. Christopher Reardon set out to address that problem.

Working with colleagues from the University of California, San Diego, he equipped a small autonomous wheeled robot with LiDAR sensors – these detect objects and measure distances by emitting laser beams, then measuring how long it takes for the laser light to be reflected back by whatever it strikes.

In Reardon's system, the robot had initially LiDAR-scanned an environment once, in order to establish a baseline for what everything should look like. When it went back through that environment again, the robot was able to detect even very slight changes in the placement of three-dimensional objects.