Base station orientation calibration in 3-D indoor UWB positioning

A method is proposed to correct three-dimensional (3D) positioning error due to base station antenna orientation that takes into account non-boresight electrical length differences due to antenna phase center errors. An automated algorithm is used to calibrate an ultra-wideband (UWB) system using only a starting estimate of the base station position and acquired positions central to the base stations. The true positions of the acquired 3D calibration points are unknown to the calibration algorithm. Upon completion of the algorithm, the base station orientation is estimated, along with estimates of electrical length offsets due to potential cable length differences. This method is designed to minimize small errors due to base station position and orientation uncertainty. The algorithm is shown to be robust given the availability of accurate 1D ranging can be provided by the system.