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Diver Detection Sonar (DDS) systems are sonar and acoustic location systems employed underwater for the detection of divers and submerged swimmer delivery vehicles (SDVs). The purpose of this type of sonar system is to provide detection, tracking and classification information on underwater threats that could endanger property and lives. Further, this information is useful only to the extent that it is made available to authorities in time to make possible the desired response to the threat, be it deterrent or defensive action. Subsurface threats are a difficult problem, because reliable detection is available to date chiefly by use of high-resolution active sonar or trained dolphins or sea lions.〔TECHNICAL DOCUMENT 3138 May 2002, Non-Lethal Swimmer Neutralization Study. Applied Research Laboratories, The University of Texas at Austin.〕 The threat of an underwater terrorist attack is a concern to the maritime industry and port law enforcement agencies. Ports face a range of threats from swimmers, boat-delivered ordnance such as limpet mines and other forms of improvised underwater explosive devices.〔Underwater Terrorism Prevention Plan Informational Bulletin〕 DDS systems have been developed to provide underwater security for ports, coastal facilities, offshore installations, pipelines and ships. Due to the variety of life and objects that exist under the water, it is desirable that a DDS system be capable of distinguishing between large sea mammals, shoals of fish; a ship's wake; a diver with an open circuit scuba set and a stealth diver with a rebreather. DDS systems have been developed that can be mounted on the seabed, on a pier or on the hull of a vessel. For complete port security these systems are integrated with the surface surveillance and security systems employed at ports, coastal facilities and offshore installations. Various systems provide specialized features to facilitate their use in port security systems including automatic detection features. ==Evaluation of DDS systems== In 2006, in a NATO report given by Dr. R. T. Kessel and R. D. Hollet at the NATO Undersea Research Center, it was stated that sonar gives by far the lowest cost per square meter of underwater coverage of all other means of surveillance (radar, video, visual). This is because sound waves have a low attenuation and long propagation distance in turbid harbor waters relative to other means of sensing (electromagnetic waves, visual light, temperature, magnetism). The leading sonar technology for detecting and tracking underwater intruders is active, monostatic sonar, using principles of conventional beam forming in its signal processing. These sonars are now available from a number of different manufacturers who recommend their use for surveillance against underwater intruders, whereas, other sonar technologies, such as active multi-static or passive sonar, possibly with model-based signal processing, remain at best in the development stage so far as intruder detection is concerned.〔Underwater Intruder Detection Sonar for Harbour Protection: State of the Art Review and Implications. Ronald T. Kessel, Reginald D. Hollett, October 2006〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Diver Detection Sonar」の詳細全文を読む スポンサード リンク
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