Sensors

An ROV Pilot's view of an ultrasonic thickness measurement of a ship's hull being recorded.

Sensors include a variety of measurement devices such as ultrasonic thickness gauges for measuring material thickness, radiation detectors and water quality sampling sondes for various parameters such as temperature, pH, salinity, dissolved oxygen and more. Sonars and specialized cameras can also fall into the sensor category.

Two of the most widely used sensors include Sonar (SOund Navigation And Ranging) and Position Tracking Systems.

Sonar

Sonar uses acoustic transducers to create an image of the surrounding area. They can be mounted on ROVs to assist with underwater detection and navigation. The most common types are scanning, imaging and side scan. Scanning sonars create an image similar to what you see on a radar screen. A single transducer sweeps through a circle to create a highly detailed image, however the sweep takes some time and these sonars have to remain stationary during the scan to create a clear undistorted image. Imaging sonars are also called multibeam sonars because they use multiple transducers to scan an entire area simultaneously. They are good for real time navigation because their display updates at near movie frame rates. Side Scan sonars are towed and create an image of the covered area one transverse line at a time. Side scan sonars are good for imaging large areas for searches and mapping.

Position Tracking Systems

Position Tracking Systems use acoustic or inertial measurements to calculate their position. While these measurements are relative, they can be integrated with GPS systems on the surface (GPS does not penetrate in water) to precisely locate the system in georeferenced coordinates. These system are ideal for marking or returning to previously marked points and can be integrated with control systems to provide autonomous operation.