Doppler positioning with orientation estimation by using multiple transmitters for high-accuracy IMES localization

A Doppler positioning method with orientation estimation for an indoor messaging system (IMES) is proposed. With this method, both position and orientation of a receiver are estimated simultaneously by using Doppler shifts produced by moving a receiver antenna under the use of two or more IMES transmitters. The proposed method is evaluated through an experiment in which the interval of two transmitters is varied. The results of the experiment demonstrate that centimeter- to decimeter-level positioning accuracy and orientation-estimation accuracy of ±3 degrees are achieved; these results were largely consistent with the theoretical values calculated from dilution of precision. In addition, magnetic-compass error indoors was experimentally investigated; the results show that a magnetic-compass is a large error source if it is used indoors. Lastly, which initial values of a nonlinear least-square used for the proposed method converge to appropriate position and orientation solutions is analyzed; the results of the analysis suggest that if an initial position is set to the midmost of two transmitters, a proper solution is obtained except in the case that initial orientation is 180 degrees opposite from the correct orientation.