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What's Sonar Used For?
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text See a fish finder image. Sonar, which stands for SOund NAvigation and Ranging, is usually used to "see" objects in the water or to determine the distance to something. For example, people who fish sometimes use simplified forms of sonar, called depth sounders or fish finders, to find how deep the water is where they are or to locate schools of fish. A depth sounder sends out a pulse, measures the time it takes to receive a return signal, and—using the speed of sound in saltwater (about 1,500 meters per second)—calculates the distance to the object or sea floor.

See a sidescan sonar image. Marine scientists may use sidescan sonar to map the hills, valleys, and other features of the ocean floor. This sophisticated sonar returns very detailed "pictures" of objects in the water and can be used to locate submarines, underwater mines, shipwrecks, or aircraft crash debris. Sonar can also be used to inspect pipelines, cables, or bridge foundations.

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