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Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. [4] Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, [5] and sodar (an upward-looking in-air sonar
Sodar systems are in fact nothing more than sonar systems used in the air rather than in water. More specifically, since they operate using the Doppler effect with a multi-beam configuration to determine wind speed, they are the exact in-air equivalent to a subclass of sonar systems known as acoustic Doppler current profilers (ADCP). Other ...
Sonar (sound navigation and ranging) is a technique that uses sound propagation under water (or occasionally in air) to navigate, communicate or to detect other vessels. There are two kinds of sonar – active and passive. A single active sonar can localize in range and bearing as well as measuring radial speed.
Some species of hawkmoths (Sphingidae) produce ultrasound capable of sonar jamming. [25] Sonar jamming capability has evolved independently in at least six subfamilies. [26] Because sonar jamming seems to require high duty cycle ultrasound, it is believed to be a derived form of the simpler ultrasound used for aposematism and mimicry. [27]
Modern radar systems are generally able to smoothly change their PRF, pulse width and carrier frequency, making identification much more difficult. Sonar and lidar systems also have PRFs, as does any pulsed system. In the case of sonar, the term pulse-repetition rate (PRR) is more common, although it refers to the same concept.
The radar mile is the time it takes for a radar pulse to travel one nautical mile, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1,852 m, then dividing this distance by the speed of light (299,792,458 m/s), and then multiplying the result by 2 yields a result of 12.36 μs in duration.