| 摘要 |
Autonomous underwater seismic acquisition devices 7 are dropped from a vessel 5 and guided to target locations 9 on the seabed by receiving signals from an acoustic navigation system comprising acoustic sources (beacons) 3 on the seabed. The acquisition devices have a hydrodyamically shaped body, and are steered towards their target positions using rudders or by transversely displacing the battery within the device to displace the centre of gravity of the device and therefore alter its trajectory. The beacons transmit ultrasonic pulses at known times, using timepieces synchronised to a common time reference system. The navigation system may also use GPS acoustic relay buoys to communicate with the beacons on the seabed and equipment on the surface. An autonomous underwater vehicle 29 may be used to determine the exact positions of the beacons 3 and the acquisition devices 7. When the acquisition devices 7 have all been located on the seabed, the beacons are released from their ballast, by remote control, and return to the surface. When the seismic acquisition is complete, the acquisition devices 7 return to the surface.
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