Watch: A UAV chases a person running in a dense forest without GPS, without internet and without a person to navigate it. The UAV flies about 2 meters off the ground at running speed, builds a 3D map of the trees while moving, and guesses where the person's face is headed when trees block his view. Everything works on board the UAV itself. Purdue's IDEAS Lab built the hardware, but the software relies on open source tools, mostly from the University of Hong Kong, so it's not completely built from scratch. The same lab also has a separate $1.5 million Army research deal for robots that work without GPS.