Sonar is a remote sensing technique based on the echolocation of sound waves in water. The name Sonar is short for SOund Navigation And Ranging and is closely related to the technology of RADAR (RAdio Detection And Ranging). The basic principles behind both technologies are the same. RADAR employs the transmission and reflection of radio waves in air to detect objects in the atmosphere. Similarly, SONAR employs sound waves rather than radio waves to detect underwater objects. Sound waves are preferable in underwater applications because radio waves lose too much energy when they propagate through the water. Likewise, the propagation of sound waves in air is also inefficient.

SONAR was originally motivated by the desire to detect icebergs after the sinking of the Titanic in 1912. World War I subsequently stimulated the development of further SONAR technology in order to detect enemy submarines. However, SONAR now has tremendous civilian...