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Underwater GPS Positioning Systems: GIB
Among its range of products, ALSEAMAR has developed the GIB systems (GPS Intelligent Buoys). There are the first and only positioning systems to offer true underwater D-GPS tracking capabilities in real-time. GIB systems perform extremely well in various underwater environments (harbor, shallow as deep waters…) and are used worldwide in civil or military applications (UUVs guidance, torpedoes evaluation, MCM, oceanographic, survey, search & recovery, divers’ monitoring…).
How does the system work?
The GIB portable tracking system is based on a network of surface buoys that measures the time-of-flight of acoustic signals emitted by an acoustic transmitter mounted on a AUV, ROV, diver, etc.
Every cycle (typically 1 second), the acoustic transmitter transmits two successive signals, one synchronous to GPS time and the other delayed proportionally to the depth. Each buoy measures the GPS time of arrival of the two signals and transmits this information together with its own D-GPS position to the Control and Display Unit (via a radio link).
The propagation time is directly converted into the pinger/buoy distance, knowing the sound velocity. As the depth is known precisely (measured on each buoy), the position of the acoustic source is derived by triangulation.
The positions of the buoys and the acoustic source are known in WGS-84 coordinates.
The GIB systems are composed of:
- a set of 4 to 12 buoys. Two designs of buoy are available, one small (15 kg) for coastal areas and one spar buoy (6-m height, 60 kg) for offshore operations
- acoustic pingers. The frequency range of pingers compatible with GIB systems ranges from 8 to 50 kHz
- a Control and Display Unit (a laptop with deck unit containing all the necessary electronics and three antennas)
The main advantages of the GIB system are:
- fast installation on board non dedicated ships
- easy to deploy & recover, no calibration
- real-time multi-mobiles capabilities
- 1-metre accuracy in 3D
- accurate time stamping of positions and payload data
- high repetition rate and real-time Quality Control