Abstract: The invention relates to a simple, cheap sonar system with high image rate, for the detection of objects and the imaging of sea bottoms. It consists in transmitting n uncorrelated successive codes in a sector of angular width exactly equal to n times the angular width of the reception sector .theta..sub.R, the reception antenna continuing to turn during this time whilst the first signal transmitted has not yet reached the maximum range dmax, and in receiving, in the sector of angular width .theta..sub.R, the echoes of these n codes, coming from n propagation regions which are adjacent in relation to the reception axis, and lying between 0 and dmax in space, each of them having a depth equal to dmax/n.

Abstract: Disclosed is a sonar for avoiding sub-surface underwater objects, for a surface vessel, having its directivity in elevation optimized to observe the surface and its surface reverberation reduced to the minimum. It consists in using an acoustic antenna having two columns of n transducers, the first column insonifying, at transmission, an elevation sector corresponding to the collision-risk zone and forming channels at reception, in the insonified elevation sector, the width of the channels being all the finer as the desired precision of the measurement of the position in elevation is high. The second column is necessary for the localization in relative bearing. The disclosure can be applied to the precise localization in elevation of objects located in the path of a vessel.

Abstract: An interferometric sonar in non-linear acoustics for high-resolution observations of objects located in the vicinity of the sea floor includes two end transducers for simultaneous transmission at two high frequencies F.sub.1 and F.sub.2 of the order of 200 kHz. Reception is performed by hydrophones placed between the sending transducers at the low frequency F.sub.2 -F.sub.1 of the order of 20 kHz. Angular channels are formed during two transmission sequences. Transmission takes place in phase at the frequency F.sub.2 -F.sub.1 in one sequence and in phase opposition in the other sequence in the case of the two sources generated by non-linear effects.

Abstract: Acoustic positioning device for a vessel comprising N transponders (B.sub.1 . . . B.sub.i . . . B.sub.N).A fixed acoustic transmitting means (E) periodically transmits acoustic pulses at frequency f. The responses of the transponders (B.sub.1 . . . B.sub.i . . . B.sub.N) are received by the acoustic array (A.sub.1, A.sub.2) of the vessels. The time origins are transmitted by a radio antenna to the surface vessel. In the case of submarines, two stable clocks are used, one of which is on board the submarine. Processing circuits make it possible to know the position of submarines.Application to the positioning of vessels in an oil production field or for oceanographic research.

Abstract: A device for measuring sea currents at great depths as a function of the depth.A spherical shaped plunger having negative floatability is dropped from a boat and descends to the bottom of the sea, releases its ballast and rises to the surface where it is recovered.Acoustic responding buoys positioned geographically receive pulses emitted by the plunger and respond. The plunger-buoy distances are determined sequentially and stored in the plunger. After recovery of the plunger by the boat a computer determines the currents at the different depths.

Abstract: A device for measuring in real time sea currents in deep water possibly exceeding 6000 m, as a function of the depth.A spherical shaped plunger having negative floatability is dropped from a boat and descends to the bottom of the sea, releases its ballast and rises again to the surface where it is recovered.Acoustic responding buoys positioned geographically as well as the contrivance receive pulses transmitted by the boat and respond to the boat. Furthermore, the contrivance also sends out a response intended for the buoys which reply to the boat; from the arrival times of these pulses, a computer on board the boat calculates the sequential positions of the contrivance in relation to the buoys as well as the velocities of the currents as a function of the depth.

Abstract: The invention relates to a device for measuring aquatic currents, placed on a moving boat comprising a Doppler effect sonar. The device comprises two sets of transducers and transmitting and receiving in the directions D.sub.1, D.sub.2, D.sub.3 and D.sub.4 forming an angle .+-..alpha. with the vertical z. A transmission circuit supplies impulses simultaneously at two frequencies f.sub.1 and f.sub.2. The receiving circuit processes the signals of the volume reverberation echos affected by the Doppler effect, corresponding to the frequencies f.sub.1 and f.sub.2, and the sea bed echo affected by the Doppler effect at the frequency F=f.sub.1 -f.sub.2, this frequency being generated by the non-linearity of the medium. Finally are obtained the profile of the horizontal velocities of the currents function of the depth.

Abstract: A system on board which provides measurement of flow rates of a liquid layers at different depths, the provided results being corrected from error due to the craft movement, said system being proper for location and establishment of an underwater drilling site.In this system arrangement, are combined to cooperate a Doppler sonar system providing the craft speed with respect to the sea bottom and a flow rate meter system providing the liquid flow rate by reference to the craft, a common electro-acoustic transducers unit being switched for sequential operation from sonar to flow rate system and an output data processing system derives from these two measures the values of flow rate with respect to the sea bottom.