Thrumapper: Through-Wall Building Tomography With A Single Mapping Robot

Vision- and LIDAR-based Simultaneous Localization and Mapping (SLAM) techniques can build indoor building floorplans with ease, but require line-of-sight into every room of a building. We are developing a radio microwave-based system for building indoor floor plans using SLAM techniques, but without the requirement that the mapping robot has access to every room in the building. Our system uses multiple antennas to direct radio energy through walls in particular directions, and joint time- and angle-of-arrival estimation techniques to estimate their backscatter returns from the walls of the building. Wide bandwidth (120 MHz) transmissions combined with an iterative transmit nulling and receive cancellation strategy allows ThruMapper to isolate individual walls and measure the location of a non-line-of-sight wall hidden behind another wall and office clutter to within a 50-centimetre RMS error.