3D Sonar Imaging or Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is 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. Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR (an upward looking in-air sonar) is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.
Active sonar uses a sound transmitter and a receiver. When the two are in the same place it is mono-static operation. When the transmitter and receiver are separated it is bi-static operation. When more transmitters (or more receivers) are used, again spatially separated, it is multi-static operation. Most sonars are used mono-statically with the same array often being used for transmission and reception. Active sonobuoy fields may be operated multi-statically.
Passive sonar listens without transmitting. It is often employed in military settings, although it is also used in science applications, e.g., detecting fish for presence/absence studies in various aquatic environments. In the very broadest usage, this term can encompass virtually any analytical technique involving remotely generated sound, though it is usually restricted to techniques applied in an aquatic environment.
3D Sonar Imaging is useful in Civilian applications such as Fisheries, Echo sounding, Net location tracking, ROV and UUV, Vehicle location tracking, Prosthesis for the visually impaired. 3D Sonar Imaging also useful in Scientific applications such as Biomass estimation, Wave measurement, Water velocity measurement, Bottom type assessment, Bathymetric mapping, Sub-bottom profiling, Synthetic aperture sonar, Parametric sonar and Sonar in extraterrestrial contexts. 3D Sonar Imaging also used in Military applications such as Anti-submarine warfare, Torpedoes, Mines, Mine countermeasures, Submarine navigation, Aircraft, Underwater communications, Ocean surveillance, Underwater security, Hand-held sonar, Intercept sonar.
