Sonar Assists Searching for Missing Persons
Stanislaus County, USA, Sheriff’s Department dive team slowly motored their boat along the concrete lined drainage canal, periodically stopping and lowering their scanning sonar to see what was beneath the muddy water. They were searching for a 2003 Toyota Corolla belonging to alleged kidnapping suspect Jose Esteban Rodriguez.
They were using a variety of high tech equipment including ROVs and sonar systems. Teams spent ten days searching the 75-foot wide canal that was as deep as 50 feet in spots. They located and removed sixteen vehicles, including a pickup truck and a motorcycle. Rodriguez’s car was among those found, but the windows were down and no one was inside. Officers are continuing the search, in an attempt to determine if bodies are somewhere in the 117 mile long waterway.
Mark Cardoza, a sheriff’s department diver, reported their JW Fishers SCAN-650 scanning sonar was instrumental in locating a number of the vehicles. The sonar operates in water similar to the way radar operates in air. It sweeps a circle up to 250 feet in diameter with a sound wave. The wave reflects off any object on the bottom and is received by the sonar transducer. The data is transmitted topside where a detailed image of any underwater object is displayed on a laptop computer. Cardoza remarked, “This sonar will now be the go-to technology to help us better utilise our limited bottom time.”
California law enforcement officers are not the only ones using sonar to aid in their underwater searches. Cumberland County Emergency Management Agency in New Jersey, Tafton Fire Company in Pennsylvania, and Washington County Sheriffs Department in Minnesota are among the many groups now employing Fisher sonar. Washington’s Water Recovery Unit uses both side scan sonar and scanning sonar. “Our towed SSS-600K side scan system lets us cover large areas quickly”, says team member Jim Anderson. “It can help us find a sunken boat, a vehicle that went into the water, or a drowning victim.” Side scan images are displayed and stored on a computer along with position coordinates.
Records can be replayed back at the office and images blown up and emailed to other agencies if necessary. “We also have a SeaOtter-2 ROV equipped with SCAN-650 scanning sonar”, adds team leader Sgt. James Gribble. “The ROV saves time by letting us inspect targets located with the side scan, without deploying a diver. When we need to put in a diver to make a recovery, he knows what the underwater conditions are before getting into the water.” Scanning sonar helps manoeuvre the ROV in low visibility environments when the target is beyond the viewing range of the camera.
The scanning sonar proved invaluable in a recent search for a snowmobile that went through a frozen lake. The ROV was deployed through a hole in the ice. Using the SCAN-650, the operator was able to quickly locate the target and guide the ROV directly to it. A diver then entered the water and followed the ROV’s umbilical straight to the snowmobile, and found the victim nearby. “The sonar saves us time, and dramatically increases the safety factor for our divers”, says Gribble.
