Unmanned surface vessels are vehicles that operate on the surface of the water without a crew.

Unmanned underwater vehicles sometimes known as underwater drones, are any vehicles that are able to operate underwater without a human occupant. There are two categories of UUVs: AUVs and ROVs.

Ultra short baseline is a method of underwater acoustic positioning. A complete USBL system consists of a transceiver, which is mounted on a pole under a ship, and a transponder or responder on the seafloor, a towfish, or on an AUV or ROV. A computer, or “topside unit”, is used to calculate a position from the ranges and bearings measured by the transceiver.

Refers to the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality.

A tethered or towed UUV that has a constant power and data connection to the support ship. Towbodies do not require batteries like AUVs.

Typically used to refer to command and control, or processing electronics, for subsea sensors and vehicles, that reside onboard the ship (above water).

The electromechanical component of a sonar system that is mounted underwater and converts electrical energy to sound energy and vice versa. The transducer formation determines the beam shape and is the basis for image formation in side scan sonar. Its condition and stability help determine the final image quality. Transducers can be surrounded by various types of acoustically transparent urethanes or epoxies, or can be within an oil-filled assembly. For the purposes of side scan, transducers are almost always mounted on a towbody which also contains firing and amplifying circuitry. They are towed over a cable instead of hull mounted in order to maximize stability by de-coupling them from ship motion.

The lateral coverage of side scan sonar on the seabed. Because side scan sonar projects a beam out to the side of the towpath it creates a wide region of insonified seafloor. Both right and left sonar channels make up the swath. Swath width changes with range settings and is a factor in determining coverage and lane spacing.

Side scan sonar. A specialized system for detecting objects on the seafloor. Most side scan systems cannot provide depth information. Like other sonars, a side scan transmits sound energy and analyzes the return signal (echo) that has bounced off the seafloor or other objects.