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Abstract

A method of determining the bearing 'S' of a signal transmitter relative to a remote signal receiver. A signal pulse having a high signal to noise ratio is transmitted and sampled at closely spaced receivers displaced from the transmitter by a distance 'D'. Sampled phase components are derived at each receiver by deriving in-phase and quadrature components of the sampled pulse and by deriving the arctangent of each such component. The arrival time of the sampled pulses is measured by applying a least squares Gaussian fit to the modulus or to the amplitude envelope of the pulse samples. The difference '.delta.t' between the time of arrival of the pulse at each receiver is determined and then the approximate phase difference 2.pi..omega..delta.t between the sampled pulses is determined where '.omega.' is the carrier frequency of the transmitted pulse. The phase difference is then applied to resolve the phase ambiguity of the phase components and the bearing 'S' is then calculated. The method also facilitates correction of errors in the apparent transmitter bearing which are introduced by relative medium movement, in which the signal pulse is transmitted through a medium which moves with a component of velocity 'u' perpendicular to the acoustic path between the transmitter and receivers, thereby causing the bearing to appear to deviate from the actual bearing of the transmitter relative to the receivers; and, by small scale fluctuations in sound speed between the transmitter and each of the receivers.

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