Mode identification and location improvement based on data association of OTHR and azimuth-only sensors

Target tracking of over-the-horizon radar (OTHR) faces the challenge of low detection probability, low sampling rate, low measurement precision and multipath propagation. Identification of propagation modes and improvement of target location accuracy will significantly affect both data association and estimate updating, and thus they become the key concern on OTHR target tracking. In this paper, a scheme of measurement fusion of OTHR and azimuth-only sensors is presented to identify propagation/clutter modes and improve location accuracy. Measurements of azimuth-only sensors are first fused to obtain the preliminary estimates of location position via the standard least square method. Then, based on the above position estimate and OTHR measurements, a maximum-likelihood-estimation-based data association rule is proposed to identify the propagation modes and clutter mode. Finally, a minimum variance estimation method is given to improve the estimate of target position by fusing the associated data from OTHR and azimuth-only sensors. In simulation, it is found that the identification of propagation/clutter modes is satisfactory, and there is significant improvement on azimuth. However, the method does not result in significant improvement in the accuracy of geographical distance from the OTHR receiver to the target.