Contact Fusion and Multi-Hypotheses Tracking for Low Frequency Active Sonar Data

Towed low frequency active sonar systems (LFAS) are used in Anti-Submarine Warfare (ASW) to detect submarines. LFAS systems are hampered by reverberation in shallow water environments because the interaction of sound with the sea bottom can lead to a large number of point-like sonar contacts resulting in a high false alarm rate. Reducing the false alarm rate under a non-decreasing probability of detection is preferable for further signal processing of the data, especially for target tracking. In a sea experiment with an LFAS system two different sonar signals have been transmitted within each ping. Fusion of the contacts obtained by processing these independent signals yields a reduction of the false alarm rate since only fused contacts are passed to the tracking stage. Contacts that have not been fused are assumed to being caused by noise. In addition to a reduced false alarm rate contact fusion provides a Doppler information of the considered contact. A different approach of fusing the sonar contacts and extracting its Doppler information is to use the data association scheme of a multi-hypotheses tracking (MHT) algorithm where different hypotheses for the association of contacts from the independent signals are stated. Thus, false alarms are distinguished from target contacts. This paper compares both mentioned fusion approaches by means of several trackingperformance metrics. A good tracking performance for a one-sensor-tracking scenario as it is analyzed here is a precondition for a high quality track fusion in a multistatic scenario which is subject to current research.