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Abstract

Method for determining the ranges between pairs of transceivers deployed underwater. According to a preferred embodiment, the transceivers transmit acoustic pulses to and receive acoustic pulses from other of such transceivers according to a coordinated schedule of individual transmission times and reception windows stored in each transceiver. Timers in each transceiver sequence the transceiver through its scheduled events. Periodic synchronization of all deployed transceivers keeps the transceivers synchronized. One- or two-way ranging between pairs of receivers is possible, with two-way ranging requiring only loose synchronization of transceivers. The preferred method of range determination includes a two-way range between pairs of transceivers, each transceiver transmitting pulses having preselected characteristics to the other on a different frequency channel. The times of reception of the pulses having the preselected characteristics received within open windows are compared with the times of transmission to determine the range. In the event of an occluded direct acoustic path between a pair of transceivers, the method uses sea-bottom reflected ranges to estimate the direct range or to qualify a suspect direct range measurement. A central controller in communication with all the transceivers compiles the individual schedules, collects the transmit and reception time data, and computes the ranges therefrom.

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First Claim