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"Sonar" can refer to one of two types of technology: passive sonar means listening for the sound made by vessels; active sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. [4]
Sonar systems are generally used underwater for range finding and detection. Active sonar emits an acoustic signal, or pulse of sound, into the water. The sound bounces off the target object and returns an echo to the sonar transducer. Unlike active sonar, passive sonar does not emit its own signal, which is an advantage for military vessels.
Side scan sonar is used to image large areas of the seafloor quickly. Applications include surveys for marine archaeology, shipwreck hunting, search and recovery (SAR), and environmental monitoring. [1] In conjunction with seafloor samples, it is able to provide an understanding of the differences in material and texture type of the seabed ...
Synthetic-aperture sonar (SAS) is a form of sonar in which sophisticated post-processing of sonar data is used in ways closely analogous to synthetic-aperture radar. Synthetic-aperture sonars combine a number of acoustic pings to form an image with much higher along-track resolution than conventional sonars.
Bistatic sonar is a sonar configuration in which transmitter and receiver are separated by a distance large enough to be comparable to the distance to the target. Most sonar systems are monostatic , in that the transmitter and receiver are located in the same place.
The speed of sound will vary slightly depending on temperature, pressure and salinity; and for precise applications of echosounding, such as hydrography, the speed of sound must also be measured, typically by deploying a sound velocity probe in the water. Echo sounding is a special purpose application of sonar used to locate
Pulse compression is a signal processing technique commonly used by radar, sonar and echography to either increase the range resolution when pulse length is constrained or increase the signal to noise ratio when the peak power and the bandwidth (or equivalently range resolution) of the transmitted signal are constrained.
USBL (ultra-short baseline, also known as SSBL for super short base line) is a method of underwater acoustic positioning.A USBL system consists of a transceiver, which is mounted on a pole under a ship, and a transponder or responder on the seafloor, on a towfish, or on an ROV.