Question #1ace5
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SO und N avigation A nd R anging, or Sonar, was first used as a military technology for detecting (enemy) submarines. It has come a long way since then.
Explanation:
As we can see from the above, Sonar doesn't just map the ocean floor. It maps anything that can echo or produce sound waves, such as submarines or fish.
We often imagine Sonar as sending out sound waves and listening for echoes to detect things. That is active Sonar. Alternatively, we can just listen for sounds and identify their source, an approach called passive Sonar. Passive Sonar is limited by the need to rely on external sound sources that stand out from surrounding noise, but it has the environmental advantage of not adding artificial "noise pollution" to the ocean. Accordingly both modes of Sonar have found widespread use.
A detailed description of the history and use of Sonar is found at https://en.wikipedia.org/wiki/Sonar.
