side-scan sonar

A remote sensing tool used in underwater archaeology to provide a plot of the features on the sea-bed. An acoustic emitter sending out sound waves in a fan-shaped beam is towed behind a vessel. The sound waves reflected from the sea-bed are detected by a transducer on the vessel and recorded on a rotating drum. The time taken by the sound to reach the transducer depends on the distance travelled and thus a three-dimensional plot of the sea-bed surface can be produced.