Importance

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Abstract

The positions of one or more underwater divers or vehicles are determined through an underwater acoustic communication link and at least a base buoy and one remote buoy with acoustic transponders and GPS position locating equipment. The location of the buoys is determined by the GPS equipment. The underwater diver or vehicle each carries an acoustic tracking unit transponder which emits a tracking unit message specifying its identity and its last known position at an assigned time slot. Upon reception of the tracking unit message by the base buoy, an acoustic base buoy message is emitted which includes the buoy position. The tracking unit receives the base buoy message, and marks the time of arrival to determine the propagation delay between the tracking unit and the base buoy. A predetermined delay after the receipt of the tracking unit message by the remote buoy, it sends an acoustic remote buoy message specifying its location. The tracking unit receives the remote buoy message, marks its time of arrival, and determines its location from the times of arrival and the positions of the buoys. The base buoy can communicate with a base station, passing along all received tracking unit messages so that the base station can keep track of the locations of all tracking units. Commands from the base station can be encoded into the base buoy message, to provide instructions to the various divers and underwater vehicles.

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First Claim