An indoor absolute positioning system with no line of sight restrictions and building-wide coverage

Accurate sensing of vehicle position and attitude is required in many mobile robot applications, but is a very challenging problem in real office building or warehouse environments. Many existing indoor positioning systems are limited in workspace and robustness because they require clear lines of sight, have insufficient coverage area, or do not provide absolute measurements. This work presents a new absolute position and attitude sensing system with no line of sight restrictions and an operating area that can span an entire office building or warehouse. The system uses beacons fixed at known locations throughout a building to create dipole magnetic fields. All of the beacons produce fields at all times, and a code division multiple access (CDMA) method is presented to distinguish between the fields produced by the individual beacons. This method provides advantages over existing magnetic field techniques in coverage volume, accuracy, and resistance to distortion. Initial experimental results demonstrate centimeter-level positioning accuracy