Re:RP don't know a whole lot about sonar apparentl (Score 1)

I guess the US Navy did too good a job of classifying SOSUS, it's now declassified as of the early 90's, after the end of the "cold war"; it used arrays on the ocean bottom employing passive sonar to detect Soviet submarines. It was highly successful, and had been in operation since the 1950's. The arrays were a series of hydrophones strung out in a approximate linear arrangement at an optimum depth. The arrays were able to determine the bearing of the sound source by the phase delay of the sound waves received, and triangulation from simulataneous detection by several stations, each with its own set of arrays. Depth, location, orientation, was all carefully planned to improve the signal-to-noise ratio to allow maximum detection capability. The accuracy of bearing determination (direction) was calibrated by US Navy ships towing a sound source, keeping a continuous record of time vs. ship's position, then comparing the ship's actual position with the SOSUS arrays data. SOSUS is now reincarnated as a research tool used by civilian oceanographers.