A sub-bottom geophysical imaging apparatus includes a carriage assembly having at least one acoustic transmitter, and at least one acoustic receiver proximate the transmitter. A position determining transponder is mounted on the carriage. A plurality of position transponders is disposed at spaced apart positions to communicate with the transponder mounted on the carriage. A pair of tracks is provided for moving the carriage to selected positions above the bottom. Electrodes are provided for a resistivity sensor and a shear acoustic transmitter and receiver disposed in at least one of the pair of tracks. A signal processing unit is configured to coherently stack and beam steer signals detected by the line array, the electrodes and the shear transmitter and receiver. The signal processing unit is configured to record signals detected by the line array of acoustic receivers, the electrodes and the shear acoustic transmitter and receiver.

The application relates to bi-static or multi-static holographic navigation systems, including methods of localizing an emitter or receiver with high precision relative to the sea floor. The system and methods can be used with a fully active sonar or radar system using well synchronized transmitters and receivers. The system and methods can be used with a passive sonar or radar system localizing a transmitter or a receiver based on poorly timed received signals.

Techniques for determining coherency between composite images having phase and amplitude components are disclosed. The coherency can be determined based on the amplitude components of the images, by providing first and second amplitude images indicative of amplitude values of pixels of a respective first and second composite images, applying to each of the first and second amplitude images a first directional derivative operator and a second directional derivative operator, thereby generating for each of the amplitude images respective first directional derivative image and second directional derivative image thereof, and generating a first coherency map based at least on the directional derivative images of the first and second amplitude images. The first coherency map is indicative of decorrelation between the first and second composite images.

A system for detecting and locating submerged underwater objects having neutral buoyancy comprising mechanically steered sonar to image the water column comprises mechanically steered sonar with a single emission channel, to perform the insonification of a first individual sector in a first pointing direction by a single first acoustic pulse, the sonar forming a single reception channel suitable for acquiring a first acoustic signal resulting from insonification, the mechanically steered sonar being mounted on a carrier to advance in a main direction, the first pointing direction substantially lateral to the carrier and the first individual sector exhibits a wide relative bearing aperture and a narrow elevation aperture, the mechanically steered sonar comprising a mechanical pointing device to tilt the first pointing direction about an axis of rotation substantially parallel to the main direction allowing the sonar to acquire first acoustic signals resulting from insonifications performed in different pointing directions.

A method and system for mapping a target region (60) of space with signal scatterers. The method involves moving a signal transmitter (26) and/or signal receiver (46) along a respective trajectory (34, 54) relative to the target region, and meanwhile transmitting a probing signal (62) towards the target region, this probing signal including a pseudo-random-noise sequence modulated onto a carrier signal, receiving a response signal (76) composed of components resulting from scattering of the probing signal (62) by respective portions of the target region, and repeatedly determining positions (Q.sub.T, Q.sub.R) of the transmitter and/or receiver. The method further involves transforming the probing signal (62) into multiple test signals, each test signal being associated with a propagation path via a portion of the target region, and correlating each of the test signals with the response signal (76) in the time domain, to generate a map of correlation strength values associated with the portions of the target region.

A method and system for mapping a target region (60) of space with signal scatterers. The method involves moving a signal transmitter (26) and/or signal receiver (46) along a respective trajectory (34, 54) relative to the target region, and meanwhile transmitting a probing signal (62) towards the target region, this probing signal including a time sequence of noise (70) with a predefined bandwidth, receiving a response signal (76) composed of components resulting from scattering of the probing signal (62) by respective portions of the target region, and repeatedly determining positions (Q.sub.T, Q.sub.R) of the transmitter and/or receiver. The method further involves transforming the probing signal (62) into multiple test signals, each test signal being associated with a propagation path via a portion of the target region, and correlating each of the test signals with the response signal (76) in the time domain, to generate a map of correlation strength values associated with the portions of the target region.

Systems and methods are disclosed herein for a pressure tolerant energy system. The pressure tolerant energy system may comprise a pressure tolerant cavity and an energy system enclosed in the pressure tolerant cavity configured to provide electrical power to the vehicle. The energy system may include one or more battery cells and a pressure tolerant, programmable management circuit. The pressure tolerant cavity may be filled with an electrically-inert liquid, such as mineral oil. In some embodiments, the electrically-inert liquid may be kept at a positive pressure relative to a pressure external to the pressure tolerant cavity. The energy system may further comprise a pressure venting system configured to maintain the pressure inside the pressure tolerant cavity within a range of pressures. The pressure tolerant cavity may be sealed to prevent water ingress.

A computer apparatus determines a highly accurate displacement of a sonar array in real time using multiple processors and data objects. The processors receive multiple sonar pings from a sonar array, instantiate the quasi-unique sonar objects, beamform, and update the objects using time-delay functions. Each object includes properties such as a time of flight value associated with a first ping, time-delay values associated with a second ping, a speed of sound value associated with the pair of consecutive pings, a sonar beam angle value associated with the first ping, and the displacement value. Processing code in each object utilize these properties to update the displacement value and provide it for SAS imaging.

The present disclosure relates to a method for generating a synthetic image. In the method, image data is generated using a receiving dynamic beamforming method, image data is generated using a synthetic aperture beamforming method, and the image data generated using the receiving dynamic beamforming method and the image data generated using the synthetic aperture beamforming method are synthesized with being applied with weighting factors according to advancing distances of ultrasonic waves. By using a zone blending method, in which image data according to a receiving dynamic beamforming method is mainly used for an ultrasonic image having a predetermined depth or less, and image data according to a synthetic aperture beamforming method is mainly used for an ultrasonic image having any other depth, a grating lobe and distortion of image brightness are eliminated. In addition, the non-uniformity of the image is compensated, and a uniform energy density is acquired even in an area near a virtual transmission sound source.

Encoded transmit signals are provided to an ultrasound array such diverging ultrasound waves are sequentially transmitted. Each diverging ultrasound wave is generated by a respective set of encoded transmit signals, where each set of encoded transmit signals is encoded by a respective row of an N?N invertible orthogonal matrix. Only a selected subset of M rows, with N<M, is employed to encode the transmit signals. Sets of receive signals detected in response to the transmitted diverging ultrasound waves are decoded via a transposed matrix generated based on the invertible orthogonal matrix, with each set of decoded receive signals being associated with insonification via a subset of the ultrasound array elements in the fixed aperture. Synthetic aperture beamforming is performed on the decoded receive signals to generate an ultrasound image.