How is sonar used in submarines?

Underwater, the submarine uses inertial guidance systems (electric, mechanical) that keep track of the ship's motion from a fixed starting point by using gyroscopes. The inertial guidance systems ... by the target. Sonar systems can also be used to realign inertial navigation systems by identifying known ocean floor features . read more

Submarines also use fathometers and sounders, which are self-contained secure or unsecure active sonar systems to find the depth under the keel or above the ship to an overhead obstruction such as another ship or ice. read more

Active sonar emits pulses of sound waves that travel through the water, reflect off the target and return to the ship. By knowing the speed of sound in water and the time for the sound wave to travel to the target and back, the computers can quickly calculate distance between the submarine and the target. read more

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 to extremely high . read more