Doppler Positioning with a Movable Receiver Antenna for High-Accuracy IMES Localization
Yoshihiro SAKAMOTO, Takuji EBINUMA, Kenjiro FUJII, Shigeki SUGANO
A method for dramatically improving positioning accuracy of an indoor messaging system (IMES), whose accuracy is normally 10-20 m, was developed. This method uses Doppler shifts (produced by moving a receiver antenna) and three-dimensional attitude of the receiver to determine the receiver's position. Since trilateration is not used, positioning is possible even if the number of visible IMES transmitters is only one. A rotation-type Doppler-measurement system applying this method was developed. To evaluate the system, two experiments were conducted: in one, the rotation radius of a movable receiver antenna was varied; in the other, the position where positioning is conducted was varied. The experimental results show that the method can achieve centimeter-to decimeter-level positioning accuracy. As for design reference for setting up an IMES, the initial value of the non-linear least squares that converges to a proper solution was determined, and the influence of magnetic-declination error for the proposed positioning method was analyzed.