SONAR

Date: April 07, 2015

Sonar ( 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. Sonar uses the echo principle by sending out sound waves underwater or through the human body to locate objects. 

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There are two types of sonar sets: active and passive. An active sonar set sends out sound pulses called pings, then receives the returning sound echo. Passive sonar sets receive sound echoes without transmitting their own sound signals.

Sonar is also used to measure the depth of water, by means of a device called a Fathometer. (One fathom equals 6 feet, or about 1.8 meters.) The Fathometer measures the time it takes for a sound pulse to reach the bottom of the sea and return to the ship. Fishing boats use Fathometers to locate schools of fish.


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