Underwater sonar tech aids evidence recovery and protects police divers

     Drug smugglers constantly seek new ways to fly under the radar of law enforcement and counter-drug surveillance personnel while delivering loads of contraband. Their latest method: going underwater using "cocaine" submarines or divers to avoid...

     Drug smugglers constantly seek new ways to fly under the radar of law enforcement and counter-drug surveillance personnel while delivering loads of contraband. Their latest method: going underwater using "cocaine" submarines or divers to avoid detection.

     The need to patrol the soft underwater belly of the nation's coastlines is growing. Two years ago, U.S. counter-drug surveillance members spotted just three semi-submersible submarines, but that number jumped to 40 by 2007, and in 2008, officials estimate numbers could climb as high as 120, according to a report in the St. Petersburg Times in Florida.

     And while using semi-submersibles in narco-trafficking is a new phenomenon, employing divers to traffic drugs is not. Back in 2001, United Kingdom police arrested two divers under a boat in the Thames River and seized cannabis with a street value of £2.5 million.

     The attraction to move operations underwater lies in the fact that the water itself is the weakest link in the air, land and sea police system that protects U.S. harbors, ports and ships from criminal and terrorist activity. While extensive security precautions apply to air travel and important land installations, the civilian maritime industry remains virtually unprotected. Ports can be entered easily by vessels, especially small- and medium-sized ones, and there are virtually no restrictions controlling the presence of scuba divers and what they do once they're in the water.

     "Criminal elements attempting to use underwater routes are not as easily perceived as if they were coming into the airport, down the freeway or in a ship," explains Phil Andrew, manager of underwater security for Kongsberg Mesotech, a global provider of underwater sonar technologies and sonar supplier to the San Bernardino County (California) Sheriff's Department dive team. "The rise of terrorist threats, combined with drug smuggling, makes the need even greater to monitor the underwater lanes of our ports and ships using sonar detection technologies."

Advances in sonar

     One technique smugglers use involves bolting a drug shipment to a ship's outside hull in a foreign port. When the ship arrives in North America, the drug cartels' diver swims up to the hull undetected and unfastens the drugs. Change the above scenario from diver to terrorist delivering a bomb, and the importance of securing a port's underwater flanks becomes even more urgent. Advanced sonar technologies enhance underwater security by spotting hull anomalies and enabling police officials to set up underwater "stakeouts," such as the one carried out on the Thames River.

     Since its invention and usage beginning halfway through the 20th century, some key trends improving underwater sonar include greater portability, expanded image resolution, and enhanced processing capabilities for incoming data.

     Side-scan and scanning sonar are the two main sonar technologies, both of which have different but complementary applications. Side-scan sonar emerged in the late 1960s and is useful for mapping large targets or areas, and for seabed surveys that go on for thousands of feet. In the mid-1980s, scanning sonar emerged, enabling detailed and rapid examination of complex geometric structures such as bridge foundations, piers, ship structures and others. These systems help create detailed pictures of cracks or other weak spots that can be examined more closely by divers and engineers.

     New sonar technologies now allow surveillance operators to set up a system that can track movements by divers and other small targets of interest in harbors, and around ships and piers. A single sonar head with a 360-degree field of view can monitor 500,000 square yards, detecting and tracking movements of targets exhibiting diver-like characteristics. One significant advance is the application of state-of-the-art computer processing speeds, which enable users to better analyze and organize incoming signals and data from the sonar.

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