The National Aeronautics and Space Administration's Langley Research Center wants to find solutions to challenging tasks in GPS-deprived environments, so it put a group of MIT students on the problem. The students came back to NASA with a plan for a fleet of drones that can autonomously fly through a forest, communicate with one another and stitch together a 3D map of the environment—all without hitting trees or using GPS.
The quadcopters used in the experiment, which is described in a white paper that was presented at the International Symposium on Experimental Robotics, Nov 5-8, 2018, Buenos Aires, have onboard laser-range finders for positioning and planning their routes as they pilot themselves. They use a technique called simultaneous localization and mapping (SLAM) to position the drones in space and scan the environment at the same time. Algorithms guide the drones so they map efficiently and avoid re-mapping already covered ground. Captured data is sent via WiFi to the researchers' base station where all the drones' maps are stitched into one.