UNDERWATER ACOUSTIC TRACKING AND TWO WAY MESSAGING SYSTEM

摘要

A system where a large number of underwater devices can transmit their precise position relative to a fixed underwater beacon, by transmitting two short duration, precisely timed acoustic tones (pings). The arrival time of the pulses at the fixed underwater transceiver beacon will relay the transmitter's precise position relative to that beacon. The two pings code for two numbers; either the range and bearing or an X, Y coordinate of each object with respect to the beacon. Data messages can be sent to and received from the beacon, used for command, control and status. The pulses can be a single frequency and have duration of around a lms and operate one or many frequencies to allow multiple cycles to be overlapped in time. This coding scheme allows many devices to send the data simultaneously in the cycle for group tracking from last position or as independent cycles for unambiguous tracking. The transducers used in the system can be omni-directional hydrophones. The tracking grid size is a function of the acoustic frequency chosen and range from 1000 m for 40 KHz and 6000 m for 8 kHz. The system requires that all nodes in the system keep precise synchronized time.

主权项

1. A method for tracking a position of an underwater device, comprising:
providing a beacon on or below the surface of the water, the beacon being located in a known position; providing a device-to-track below the surface of the water, the device-to-track being located in a known position with respect to the beacon; providing each of the beacon and the device-to-track with a synchronized time base; sending a range acoustic pulse from the device to locate to the beacon, the timing of the range acoustic pulse representing a range from the device to locate to the beacon; sending a bearing acoustic pulse from the device to locate to the beacon, the timing of the bearing acoustic pulse representing a bearing from the device to locate to the beacon; calculating the location of the device to be tracked based on the range from the device to locate to the beacon, the bearing from the device to locate to the beacon, and the known position of the beacon.