Acoustic Underwater Navigation System

Background:
Pilots used a navigation system based on sound to find pre-determined destinations. When the chief scientist and other researchers decide what area the dive will explore, transponders, or underwater beacons that make a special pinging sound, are dropped in a triangular pattern to the ocean floor. Once submerged, the submersible sends sound signals to each transponder in sequence. Using echo sounding and analytic geometry, computers on board the submersible determine the distance the ship is from each transponder and its exact location. When the dive is completed, the research vessel will send a special release signal to the transponders so they rise to the surface for recovery and use again.