Side-scan sonar is a category of sonar system that is used to efficiently create an image of large areas underwater. This tool is used for mapping underwater for a wide variety of purposes, including creation of nautical charts and detection and identification of underwater objects and bathymetric features. It may be used to conduct surveys for maritime archaeology. Side-scan sonar imagery is also a commonly used tool to detect debris items and other obstructions on the reservior floor that may be hazardous to diving or to underwater installations by energy companies. Side-scan data are frequently acquired along with bathymetric soundings and sub-bottom profiler data, thus providing a glimpse of the shallow structure underwater.

Side scan uses a sonar device that emits fan-shaped pulses down toward the bottom across a wide angle perpendicular to the path of the sensor through the water which may be towed from a surface vessel or mounted on the ship’s hull. The intensity of the acoustic reflections from the reservior floor of this fan-shaped beam is recorded in a series of cross-track slices. When stitched together along the direction of motion, these slices form an image of the bottom within the swath (coverage width) of the beam.