Abstract: The invention is a process relating to the processing of the signals sent by passive buoys dropped from an aircraft so as to compile EGP (Energy Geographic Plot) maps. The process is split into three steps: the first makes it possible to produce an EGP map of the x,y positions of the noise sources, the second makes it possible to associate the velocities Vx,Vy with certain designated positions and the third makes it possible to eliminate the noise sources regarded as hampering the readability of the maps.

Abstract: The invention is a process relating to the processing of the signals sent by passive buoys dropped from an aircraft so as to compile EGP (Energy Geographic Plot) maps.

Abstract: In a method of formation of channels for a sonar, after having sampled at a frequency T=1/4f.sub.0 (where f.sub.0 is the receiving center frequency of the sonar) the signals from the hydrophones of the sonar and having translated them to baseband, the signals thus translated are subsampled with a period T.sub.SE =kT (wherein k is an integer) substantially equal to 1.25 B, where B is the reception bandwidth of the sonar. A first set of signals is subsampled at identical times to form a frontal sector. Two further sets of signals are subsampled with delays between the signals from two adjacent hydrophones equal to T, which determines two side sectors adjacent to the frontal sector. The subsampled signals are then transmitted serially by the towing cable of the sonar device towed array and are processed in FFT circuits which allow to form in each sector a set of channels covering the sector.