Broadband Active Sonar Swimmer Detection and Identification

This paper proposes a viable solution to the port security swimmer detection/identification problem using a broadband active sonar system with TCP/IP interface. Broadband active sonar, characterized by compressed pulse and wide-ranging spectral features, offers the ability to locate an underwater target accurately and classify it as a swimmer (diver) apart from fish or marine mammals, thus considerably reducing the false alarm rate compared with existing energy-based detection systems. Coupled with tracking algorithms, the fusion output detector can further reduce false alarms, allowing high-probability automatic alerts to security forces that can´t continuously and consistently monitor this sector. Applications of conventional back-propagation algorithms or probabilistic neural networks in cooperation with track-based averaging technique show promising performance to this real-world classification problem. Several testing efforts conducted in both Alaska and Washington state waters have demonstrated the applicability of the technology and highlighted aspects of deployment around facilities such as ferry terminals and cruise ship docks for homeland security.