Method and a system for monitoring a sea area

Abstract

Three or more listening devices (A1, A2, A3) are dispersed over the water area where the location of a sound source is to be determined, and transmit radio signals over respective channels to a master station upon detecting sound. The master station correlates the signals from selected ones of the listening devices to derive the position of the sound source relative to those listening devices. If the positions of those listening devices are unknown, for example if the devices are floating free, their positions are determined by the master station by comparing the relative times at which an identifying radio signal transmitted by each listening device is received by the master station directly and relayed from each of two stationary radio stations with known positions. The listening devices may also be provided with receivers for receiving radio command signals from the master station, for example relating to activation of certain listening devices and assignment of radio channels.