SONAR

Sound navigation and ranging is a technique

that uses sound propagation to communicate with or detect other vessels. There are 2 kinds of sonar: active and passive. Some uses of sonar are acoustic location and of measurement of the echo characteristics of targets in the water. Acoustic location in air was used before the introduction radar. Sonar is also used for robot navigation, and SODAR is an upward looking in-air sonar used for atmospheric investigations. The word sonar is also used for the equipment used to generate and receive the sound. Frequencies used in sonar range from very low to extremely high. The study of underwater sound is also known as underwater acoustics or hydro acoustics.

FISHING SONAR

Fishing with sonar is a very practical way to get the edge on finding fish. After all if you don't know where they are, you may be drowning your tackle in an area completely void of fish. There are any number of fishing sonar units available from a number of manufacturers and range from very elaborate (and pricey) to simple hand held units that can go with you where ever you go. In very simple terms, all sonar units send out a beam which is bounced back to the sonar unit and the time it takes to bounce back is calculated to determine the distance or depth of the fish.

SONAR MAPPING

Sonar mapping uses sound waves to map out the contours or the shape of the ocean bottom. Usually a pulse of sound is generated using a special "loudspeaker" towed behind a boat. The pulse of sound , or ping spreads through out the water and the sound is redirected back by objects in the water such as fish, the bottom or a submarine. Many sunken vessels have been located this way. An underwater microphone calculates how long the sound takes to return and processors determine the object being mapped. Complicated mathematics are needed as the ocean floor returns many different "pings" because of the variations in the ocean floor. It takes trained technicians and advanced computing to accurately compute the echos being received.

Sonar is crucial to naval forces through out the world to track and monitor other countries submarine activities and movements. There is also numerous underwater stations that aid in ocean temperature and and tide changes.