Patent ID: 9389331
Filing Date: 2016-07-12
CPC Classification: G01V

Claim Text:
1. A long baseline navigation system, the system comprising: a vessel; a deep-tow transmitter/interrogation unit configured for towing near a floor of a body of water, the transmitter/interrogation unit comprises an electromagnetic transmitter configured for emitting an electromagnetic signal for coupling with structures on the floor of the body of water to generate electric field gradients detectable by a plurality of antennae disposed on the floor of the body of water, and an acoustic transmitter/receiving configured to generate an acoustic interrogation signal and to receive responses thereto; a deep-tow cable attached to the vessel for towing the transmitter/interrogation unit; at least one tail acoustic transponder trailing behind the transmitter/interrogation unit, the at least one tail acoustic transponder adapted for receiving the acoustic interrogation signal and generating a tail response; and a pair of surface acoustic transponders towed by the vessel on the surface of the body of water, wherein the surface acoustic transponders of the pair are separated from each other by a pre-determined separation, and wherein the surface acoustic transponders each receive the acoustic interrogation signal and generate a surface response; wherein the transmitter/interrogation unit receives the tail response and the two surface responses and triangulates its position therefrom.