Underwater GPS (UGPS) Introduction
The underwater GPS (UGPS) takes its name from the similarities that it shares with its terrestrial cousin. The purpose of the UGPS is to provide a low-cost solution for providing positioning data to a large number of vehicles simultaneously. Traditionally, underwater vehicles use a long, short, or ultra-short baseline system for navigation. These systems all require two-way communication between the components. This can become prohibitively complicated and expensive for large fleets of underwater vehicles. |
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UGPS System Architecture
The UGPS is comprised of three segments: the surface segment, the underwater segment, and a control/monitoring station. The surface segment is comprised of four or more surface buoys (SB) which broadcast position and timing data using acoustics. The underwater segment is comprised of any number of receivers which can be mounted to moving or stationary platforms.
The control station ensures that the SBs are working correctly and sending the most current information to the underwater receivers. The SBs broadcast information about their own position into the ocean. This message signal is then received by the underwater receivers. Once the receiver has resolved signals from four or more buoys it can determine its position.
Surface Buoy (SB)Design
 The surface buoys (SB) are the backbone of the UGPS. The electronics are sealed in a waterproof cylinder shown on the left. The floatation is provided by an adapted mooring buoy. The buoy has wireless ethernet communication for communication with a command centre, and a WAAS GPS for determining its own position. Inside of the cylinder, there is also a PC-104 stack for data processing and an ITC-1032 acoustic transceiver for transmitting the navigation message out through the ocean to the receivers.
The acoustic signal that is broadcast by the transceiver is modulated with a navigation message. The navigation message contains the position of the buoy and the time that the message was sent. The timing information is used to determine the range to the buoy, which in turn can be used to triangulate the position of the receiver and its clock bias.
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