Extended Object Tracking with Exploitation of Range Rate Measurements

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1 December 2017
Steven Bordonaro, Peter Willett, Yaakov Bar-Shalom, Marcus Baum, Tod Luginbuhl

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In active sonar and radar target tracking, measurements consist of position and often also include range rate. Tracking algorithms use these measurements over time to estimate target state comprising position, velocity and, where applicable, turn rate. In most cases there is an underlying assumption in the tracking algorithm that the target is a “point target” (i.e. the target has no physical extent). Another common assumption is that at most one measurement per scan originates from the target. For certain combinations of transmitted waveform and target type, the resolution of the waveform is such that the target is “over-resolved” (i.e. the sensor resolution is high enough that closely spaced scatter centers can be resolved). For such cases the point target assumption must be replaced with an extended target assumption. This work provides a methodology to exploit the extended nature of the target for the case of a rigid target whose spatial characteristics are fixed with respect to the line of motion. By employing a combination of the expectation maximization (EM) algorithm and allowing more than one measurement per scan to originate from the target, a technique is developed that uses a single scan of raw measurements that include range, bearing and range rate to provide an estimate of target position, velocity, heading and turn rate. This single scan estimate is then used in a nearly constant turn rate extended Kalman filter to provide a multi-scan estimate of the target state.