The satellites of Global Positioning Systems are often unavailable when users need them most: in mountain valleys, in subterranean caverns and in urban canyons where tall buildings block signals. To help people in these situations, DARPA- and US Air Force-funded engineers at Carnegie Mellon and North Carolina State universities have developed a tiny radar that attaches to a shoe and measures the distance between the heel and the ground.
Coupled with an in-shoe accelerometer and gyroscope, the radar reports how far the user has walked in each direction. Without the radar, the accelerometer would lose accuracy every time the shoe stopped moving. The researchers envision the system integrated into military survival equipment – for example, helping downed pilots navigate to safety – and into gear for adventure sport enthusiasts and first responders. – Alex Hutchinson