Fishermen use sonar to find the big ones and the Navy uses it to track enemy submarines. Now, law enforcement has found it can crack open cold cases.
In Oklahoma, state troopers were on the Foss Reservoir, about 110 miles west of Oklahoma City. They were training with sonar equipment from a company called Humminbird. The sonar is a more sophisticated version of the type fishermen use routinely, and can "see" down to 350 feet below the water on either side of a boat.
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To generate the image, the sonar sends out a pulse of sound and measures how much time it takes for the pulse to come back. That signal is converted into an image. Unlike the sonar that appears in old war movies, though, this type can process many images quickly. By taking a thin image - a kind of "slice" as the boat moves, like an MRI or CT scan, a built-in computer can generate fine detail.
The troopers weren't looking for anything special. Local park rangers had asked them to look at the bottom of the lake to prepare for building an extension to a marina. But when they turned on the sonar's display, they saw two old cars. The images were sharp enough that one of the troopers told a local news outlet he could see the driver side door was open.