Abstract: In an embodiment, a correlation SONAR system is adapted for use in shallow water. A pulse generator transmits an initial burst of pulses towards a bottom of a body of water. Echoes of the initial burst of pulses are received on a hydrophone array. After the receiving the echoes of the initial burst of pulses, a second burst of pulses is transmitted towards the bottom of the body of water. The echoes of the second burst of pulses are received on the hydrophone array, and a SONAR processor correlates a pulse from the initial burst of pulses and a pulse from the second burst of pulses to calculate a velocity estimate.

Abstract: A method for improving the accuracy of velocity-measuring spatial correlation SONAR or RADAR is disclosed. The method uses data from multiple receiver pairs for each velocity vector, thereby providing improved utilization of a fixed sized receiver array.

Abstract: In an embodiment, a process measures a velocity of a vessel using a spatial correlation sonar hydrophone array. The process includes the step of selecting a correlation time such that a correlation occurs between an early pulse and a later pulse on a first hydrophone and a second hydrophone respectively, wherein the first hydrophone and the second hydrophone are maximally separated in the spatial correlation sonar hydrophone array. The process further includes the step of selecting a time spacing between a first pulse and a second pulse such that the spacing is a function of the correlation time and a constant, wherein the constant is proportional to a size of the spatial correlation sonar hydrophone array, and wherein the correlation time is an approximate multiple of a sum of a time between the first pulse and the second pulse and a time between the second pulse and a next first pulse.

Abstract: A method for improving the accuracy of velocity-measuring spatial correlation SONAR or RADAR is disclosed. The method uses data from multiple receiver pairs for each velocity vector, thereby providing improved utilization of a fixed sized receiver array.

Abstract: In an embodiment, a correlation SONAR system is adapted for use in shallow water. A pulse generator transmits an initial burst of pulses towards a bottom of a body of water. Echoes of the initial burst of pulses are received on a hydrophone array. After the receiving the echoes of the initial burst of pulses, a second burst of pulses is transmitted towards the bottom of the body of water. The echoes of the second burst of pulses are received on the hydrophone array, and a SONAR processor correlates a pulse from the initial burst of pulses and a pulse from the second burst of pulses to calculate a velocity estimate.

Abstract: The present invention is a system that mathematically simulates acoustic waves that are reflected off an ocean floor from a SONAR transducer mounted on a ship, submarine, or other water navigable craft. By varying the number of mathematical equations, the form of the equations, and the parameters of the equations, many different conditions may be simulated in the laboratory before testing and implementing a SONAR system at sea. The system can simulate either a spatial hydrophone SONAR system or a temporal hydrophone SONAR system for all ship speeds (i.e. all velocity components). The novel equations used in the system are based on the physics of correlation SONAR, and are applied in real time simulation environments to provide for accurate SONAR simulation of a ship's velocity.

Abstract: A system is disclosed that provides a sonar system featuring combined spatial and temporal correlation array processing. The disclosed system merges spatial-based velocity errors with temporal-based velocity errors by using a combining algorithm that is based on the optimization criteria that the output after combining has no bias error and has a minimized mean square error. With these criteria, the combining algorithm takes the form of a weighted summation of the spatial data stream and temporal data stream inputs with the weights being a function of the relative velocity errors. In combining spatial and temporal processing in this manner, the disclosed system provides improved velocity measurements for a wider range of ship's speeds. In particular, the system achieves performance levels of a spatial correlation sonar for low ship's speeds for which a temporal correlation sonar solution might not be available.

Abstract: In an embodiment, a process measures a velocity of a vessel using a spatial correlation sonar hydrophone array. The process includes the step of selecting a correlation time such that a correlation occurs between an early pulse and a later pulse on a first hydrophone and a second hydrophone respectively, wherein the first hydrophone and the second hydrophone are maximally separated in the spatial correlation sonar hydrophone array. The process further includes the step of selecting a time spacing between a first pulse and a second pulse such that the spacing is a function of the correlation time and a constant, wherein the constant is proportional to a size of the spatial correlation sonar hydrophone array, and wherein the correlation time is an approximate multiple of a sum of a time between the first pulse and the second pulse and a time between the second pulse and a next first pulse.

Abstract: A system is disclosed that enables the use of an incomplete SONAR array matrix in a correlation SONAR system. An improvement is achieved through the generation of a correlation-array model matrix of hydrophone correlations, based on an independent estimate of the ship's velocity, such as from an inertial navigator. Meanwhile, estimates of the missing values are generated based on one or more values from the model matrix, an interpolation of values from the SONAR array matrix itself, or some combination thereof. Regardless of how the missing values are generated, the model matrix provides a basis for comparison with the SONAR array matrix, which is populated with the estimated values, wherein subsequent comparisons are made between successive iterations of the model matrix and the SONAR array matrix. By applying the disclosed technique, a correlation SONAR system with incomplete data is able to continue working, and in the presence of a greater number of hydrophone failures than before.

Abstract: A system is disclosed that provides an improvement in detecting a faulty hydrophone channel in a hydrophone array. The disclosed technique operates on pairs of hydrophones or, to generalize, on groups of two or more hydrophones; this is in contrast with operating on only one hydrophone at a time. As a result, the technique is able to use correlation data from the multiple hydrophones, in order to detect a fault. The technique also operates on received echo signal information that is associated with ongoing SONAR solution processing. The use of the relatively deterministic, echo signal information further enhances the performance. By using correlation products made up of the received echo signal information, the disclosed technique is able to leverage the SONAR solution processing that already relies upon the hydrophone array, such as spatial or temporal correlation SONAR, thereby reducing the additional processing incurred.

Abstract: Methods for mitigating errors in velocity estimates obtained from correlation SONARs when the SONARs are operated over irregular ocean-bottom terrain are disclosed.

Abstract: A system is disclosed that provides a sonar system featuring combined spatial and temporal correlation array processing. The disclosed system merges spatial-based velocity errors with temporal-based velocity errors by using a combining algorithm that is based on the optimization criteria that the output after combining has no bias error and has a minimized mean square error. With these criteria, the combining algorithm takes the form of a weighted summation of the spatial data stream and temporal data stream inputs with the weights being a function of the relative velocity errors. In combining spatial and temporal processing in this manner, the disclosed system provides improved velocity measurements for a wider range of ship's speeds. In particular, the system achieves performance levels of a spatial correlation sonar for low ship's speeds for which a temporal correlation sonar solution might not be available.

Abstract: A method of estimating velocity with a correlation SONAR that provides improved velocity estimate due to a reduction in random and bias errors is disclosed. The method generates a velocity estimate based on a weighted average of pulse-pairs that includes processing of those pulse-pairs based on an optimal correlation time as well as pulse-pairs based on sub-optimal correlation times.

Abstract: A sonar system comprises a transmitter adapted to provide pulse sequences, wherein each of the pulse sequences includes pulses that reflect off an object, a receiver adapted to receive the reflected pulses, and a processor. The processor is configured to transmit a first pulse sequence via the transmitter to obtain a first distance to the object in a first distance range and to transmit a second pulse sequence via the transmitter to obtain a second distance to the object in a second distance range. The processor is configured to transmit the second pulse sequence in response to being unable to obtain the first distance to the object in the first distance range.

Abstract: In accordance with the illustrative embodiment, a diagnostic method for use with multi-element transducers includes determining an acoustic center of a transducer and determining an offset of the determined acoustic center from a theoretical acoustic center of the transducer. In some embodiments, the method also quantifies the impact that the offset has on performance of a transducer array. In some embodiments, the offset is used to correct signal processing calculations that rely on assumptions about the acoustic center of each transducer in the transducer array. A diagnostic system for use with multi-element transducers includes a projector, wherein the projector generates a sound; and a mechanical fixture, wherein the fixture aligns the projector with the transducing elements in the transducer so that in combination, the projector selectively ensonifies each of the transducing elements in the transducer.

Abstract: A system is disclosed that enables the use of an incomplete SONAR array matrix in a correlation SONAR system. An improvement is achieved through the generation of a correlation-array model matrix of hydrophone correlations, based on an independent estimate of the ship's velocity, such as from an inertial navigator. Meanwhile, estimates of the missing values are generated based on one or more values from the model matrix, an interpolation of values from the SONAR array matrix itself, or some combination thereof. Regardless of how the missing values are generated, the model matrix provides a basis for comparison with the SONAR array matrix, which is populated with the estimated values, wherein subsequent comparisons are made between successive iterations of the model matrix and the SONAR array matrix. By applying the disclosed technique, a correlation SONAR system with incomplete data is able to continue working, and in the presence of a greater number of hydrophone failures than before.

Abstract: A system is disclosed that provides an improvement in detecting a faulty hydrophone channel in a hydrophone array. The disclosed technique operates on pairs of hydrophones or, to generalize, on groups of two or more hydrophones; this is in contrast with operating on only one hydrophone at a time. As a result, the technique is able to use correlation data from the multiple hydrophones, in order to detect a fault. The technique also operates on received echo signal information that is associated with ongoing SONAR solution processing. The use of the relatively deterministic, echo signal information further enhances the performance. By using correlation products made up of the received echo signal information, the disclosed technique is able to leverage the SONAR solution processing that already relies upon the hydrophone array, such as spatial or temporal correlation SONAR, thereby reducing the additional processing incurred.

Abstract: Methods for mitigating errors in velocity estimates obtained from correlation SONARs when the SONARs are operated over irregular ocean-bottom terrain are disclosed.

Abstract: A correlation SONAR that provides improved velocity estimates due to a reduction in random and bias errors is disclosed. Rather than basing the velocity estimate on a single set of primary receiver pairs, one or more additional velocity estimates are generated based on one or more available receiver pair sets having the same velocity vectors as the primary receiver pairs set. Additional velocity estimates also provide a reliability and accuracy improvement by enabling identification and subsequent elimination of erroneous velocity estimates.

Abstract: A temporal correlation SONAR calculates the velocity and position of a water navigable craft. A first pulse and a second set of pulses are transmitted towards an ocean bottom. A tetrad of hydrophones on the craft receives echoes of the pulses. A correlation between the first pulse received on one hydrophone with the second pulses received on another hydrophone produces correlation points, for which a correlogram is generated. The distance between the hydrophones is divided by twice the time value at the peak of the correlation to calculate the velocity of the vessel. Another correlation is generated for hydrophones pairs that are positioned diagonally from one another, and maximum correlation values, along with hydrophone angles, are used to calculate athwart-ship velocity.