Acoustic ranging system

Abstract

In an acoustic ranging system, an echo signal received following a shot is repeatedly sampled and the samples digitized to produce a statistical data base representing the received echo profile which can be analyzed by various methods to determine the point on the time axis of the profile which corresponds to a wanted echo, and the degree of confidence with which the wanted echo has been identified. The number of shots taken depends upon the conditions at the site being monitored and upon the degree of confidence with which the wanted echo has been determined, and the order in which points in a multipoint system are monitored is determined by an adaptive scanning system which directs shots to different points following a system determined by a predetermined hierarchy, by the results provided by previous shots, by the conditions existing at different points, and by the receipt of outside signals. In order to improve resolution beyond that permitted by the sampling rate selected, the data base produced may be used as an adjunct to an analog determination of the actual elapsed time before receipt of a wanted echo, either by using the data base to determine a temporal "window" within which a wanted echo may be expected, and the expected amplitude of that echo, so that an accurate analog determination of the receipt of a wanted echo becomes possible, or by using the data base to provide an adaptive time variant gain control signal for the echo signal receiver so as to facilitate analog detection of the wanted echo.

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