Mitigation of biased measurement in location estimation

The distance measurements are biased for various reasons in location systems, e.g. non-line-of-sight path, propagation speed, and sensor calibration error. The impact of measurement biases is investigated in the time of arrival (TOA) systems and time difference of arrival (TDOA) systems. The TDOA estimator is robust to biases when measurements bias their true values toward the same direction, either positive or negative. We thus present group biased-TOA difference (GBD) method to combat the mix of biased and unbiased measurements in location systems. The distance measurements are divided into biased group and unbiased group and time difference operation is conducted in the biased group. We verify the effectiveness of GBD through simulation and experiment by using an ultrasound location system.