Track Initiation in the Presence of Multipath Effect and Reflecting Point Uncertainties

Track initiation for a low observable target with multipath measurements can be very challenging due to reflecting point uncertainties (e.g., with Over-the-Horizon Radar (OTHR) systems and underwater target tracking). Existing algorithms cannot handle multipath measurements with reflecting point uncertainties. In OTHR tracking, reflecting point uncertainties amount to reflecting height uncertainties. Existing methods assume that this height is exactly known a priori. In practice, however, the reflecting height is time varying slowly. To initiate tracks, initial target parameters and the reflecting height are considered jointly since they depend on each other. Then an approach by embedding joint smoothing (JS) into an expectation-maximization (EM) algorithm is proposed, where the information contained in measurements and the prior information about this height are utilized. An approximate solution is presented, where a closed form is derived for track initiation based on the latest estimated reflecting height and then the current estimated reflecting height is obtained by a smoother, which has a recursive form by using the current estimate of initial target parameters. The performance of our JS-EM approach is further improved through iterative update. Simulation results show that the JS-EM approach outperforms the approach using a specific value of the reflecting height.