Abstract: A small aperture acoustic velocity sensor and a method for velocity measurement are disclosed. In one aspect, the disclosed technology uses spatially-shifted sub-arrays for projection and/or hydrophone receipt and cross-correlation of successive pulses to improve correlation and reduce bias. The spatial shift can be created physically by selection of groups of elements or virtually by weighting the contributions of fixed sub-arrays. Spatial modulation can be used to form a projected signal and measured spatial phase of slope across the set of sub-arrays allows correction of both long- and short-term errors. The disclosed technology uses spatial and/or temporal interpolation.

Abstract: A small aperture acoustic velocity sensor and a method for velocity measurement are disclosed. In one aspect, the disclosed technology uses spatially-shifted sub-arrays for projection and/or hydrophone receipt and cross-correlation of successive pulses to improve correlation and reduce bias. The spatial shift can be created physically by selection of groups of elements or virtually by weighting the contributions of fixed sub-arrays. Spatial modulation can be used to form a projected signal and measured spatial phase of slope across the set of sub-arrays allows correction of both long- and short-term errors. The disclosed technology uses spatial and/or temporal interpolation.

Abstract: A small aperture acoustic velocity sensor and a method for velocity measurement are disclosed. In one aspect, the disclosed technology uses spatially-shifted sub-arrays for projection and/or hydrophone receipt and cross-correlation of successive pulses to improve correlation and reduce bias. The spatial shift can be created physically by selection of groups of elements or virtually by weighting the contributions of fixed sub-arrays. Spatial modulation can be used to form a projected signal and measured spatial phase of slope across the set of sub-arrays allows correction of both long- and short-term errors. The disclosed technology uses spatial and/or temporal interpolation.

Abstract: A small aperture acoustic velocity sensor and a method for velocity measurement are disclosed. In one aspect, the disclosed technology uses spatially-shifted sub-arrays for projection and/or hydrophone receipt and cross-correlation of successive pulses to improve correlation and reduce bias. The spatial shift can be created physically by selection of groups of elements or virtually by weighting the contributions of fixed sub-arrays. Spatial modulation can be used to form a projected signal and measured spatial phase of slope across the set of sub-arrays allows correction of both long- and short-term errors. The disclosed technology uses spatial and/or temporal interpolation.

Abstract: A system and method of remote sound speed measurement are disclosed. In one embodiment, a system for estimating a sound speed comprises a plurality of transducers configured to i) transmit a first acoustic signal from a first location, ii) receive a first scattered signal at a second location, iii) receive a second scattered signal at a third location, and iv) receive a third scattered signal at a fourth location; and a microprocessor configured to i) estimate a travel time based on at least one of the first, second, or third scattered signals, ii) generate a cross-correlation signal comprising a product of at least two of the first, second, and third scattered signals, iii) estimate a travel time difference based on at least the cross-correlation signal, and iv) estimate a sound speed based on at least the estimated travel time and the estimated travel time difference.

Abstract: A system and method of remote sound speed measurement are disclosed. In one embodiment, a system for estimating a sound speed comprises a plurality of transducers configured to i) transmit a first acoustic signal from a first location, ii) transmit a second acoustic signal at a second location, iii) receive a first reflected signal at a third location, and iv) receive a second reflected signal at a fourth location, the reflected signals comprising at least one echo from at least one of the acoustic signals; and a microprocessor configured to i) estimate a travel time based on at least the first or second reflected signals, ii) estimate a travel time difference based on at least the first and second reflected signals, and iii) estimate a sound speed based on at least the estimated travel time and estimated travel time difference.

Abstract: A system and method of remote sound speed measurement are disclosed. In one embodiment, a system for estimating a sound speed comprises a plurality of transducers configured to i) transmit a first acoustic signal from a first location, ii) transmit a second acoustic signal at a second location, iii) receive a first reflected signal at a third location, and iv) receive a second reflected signal at a fourth location, the reflected signals comprising at least one echo from at least one of the acoustic signals; and a microprocessor configured to i) estimate a travel time based on at least the first or second reflected signals, ii) estimate a travel time difference based on at least the first and second reflected signals, and iii) estimate a sound speed based on at least the estimated travel time and estimated travel time difference.

Abstract: A system and method for measuring velocity in a fluid medium utilizing a transducer are disclosed. In one aspect, the method comprises transmitting an acoustic signal comprising N (where N is integer and N>1) pings for each of a plurality of beams, receiving echoes from each ping, obtaining a velocity estimate for each of the N pings based on echoes of the ping, and calculating a velocity based on the sum of the N velocity estimates such that the velocity is substantially free from error caused by cross-coupling between the beams.

Abstract: A system and method of horizontal wave measurement is disclosed. The system for measuring the directional spectrum of waves in a fluid medium having a substantially planar surface may include a sonar system having a plurality of transducers for generating respective acoustic beams and receiving echoes from one or more range cells located substantially within the beams, at least one of the plurality of acoustic beams being angled non-orthogonally to at least one other of the plurality of acoustic beams. The method may calculate the directional spectrum associated with the waves from the received echoes.

Abstract: A system and method for measuring the directional spectrum of one or more waves in a fluid medium using a multi-beam sonar system. In an exemplary embodiment, range cells located within a plurality of acoustic beams are sampled to provide current velocity data. Optionally, wave surface height and pressure data is obtained as well. This velocity, wave height, and pressure data is Fourier-transformed by one or more signal processors within the system, and a surface height spectrum produced. A cross-spectral coefficient matrix at each observed frequency is also generated from this data. A sensitivity vector specifically related to the ADCP's transducer array geometry is used in conjunction with maximum likelihood method (MLM), iterative maximum likelihood method (IMLM), or other similar methods to solve a the wave equation at each frequency and produce a frequency-specific wave directional spectrum.

Abstract: A system and method for measuring velocity in a fluid medium utilizing a phased array transducer are disclosed. The phased array transducer comprises a plurality of transducer elements arranged to form a single two-dimensional array. In one aspect, the method comprises receiving echoes of a plurality of beams generated by the transducer, calculating raw velocity estimates based at least in part on the echoes, and removing substantially a bias related to a first velocity from the raw velocity estimates. The first velocity is orthogonal to the face of the two-dimensional array.

Abstract: A system and method of horizontal wave measurement is disclosed. The system for measuring the directional spectrum of waves in a fluid medium having a substantially planar surface may include a sonar system having a plurality of transducers for generating respective acoustic beams and receiving echoes from one or more range cells located substantially within the beams, at least one of the plurality of acoustic beams being angled non-orthogonally to at least one other of the plurality of acoustic beams. The method may calculate the directional spectrum associated with the waves from the received echoes.

Abstract: A system and method of horizontal wave measurement is disclosed. The system for measuring the directional spectrum of waves in a fluid medium having a substantially planar surface may include a sonar system having a plurality of transducers for generating respective acoustic beams and receiving echoes from one or more range cells located substantially within the beams, at least one of the plurality of acoustic beams being angled non-orthogonally to at least one other of the plurality of acoustic beams. The method may calculate the directional spectrum associated with the waves from the received echoes.

Abstract: A system and method for measuring velocity in a fluid medium utilizing a transducer are disclosed. In one aspect, the method comprises transmitting an acoustic signal comprising N (where N is integer and N>1) pings for each of a plurality of beams, receiving echoes from each ping, obtaining a velocity estimate for each of the N pings based on echoes of the ping, and calculating a velocity based on the sum of the N velocity estimates such that the velocity is substantially free from error caused by cross-coupling between the beams.

Abstract: A system and method for measuring velocity in a fluid medium utilizing a phased array transducer are disclosed. The phased array transducer comprises a plurality of transducer elements arranged to form a single two-dimensional array. In one aspect, the method comprises receiving echoes of a plurality of beams generated by the transducer, calculating raw velocity estimates based at least in part on the echoes, and removing substantially a bias related to a first velocity from the raw velocity estimates. The first velocity is orthogonal to the face of the two-dimensional array.

Abstract: A system and method for measuring the directional spectrum of one or more waves in a fluid medium using a multi-beam sonar system is disclosed. In an exemplary embodiment, range cells located within a plurality of acoustic beams are sampled to provide current velocity data. Optionally, wave surface height and pressure data is obtained as well. A sensitivity vector specifically related to the ADCP's transducer array geometry is used in conjunction with maximum likelihood method (MLM), iterative maximum likelihood method (IMLM), or other similar methods to solve a the wave equation at each frequency and produce a frequency-specific wave directional spectrum. The frequency-specific spectra are combined to construct a complete two-dimensional wave directional spectrum.

Abstract: A system and method of horizontal wave measurement is disclosed. The system for measuring the directional spectrum of waves in a fluid medium having a substantially planar surface may include a sonar system having a plurality of transducers for generating respective acoustic beams and receiving echoes from one or more range cells located substantially within the beams, at least one of the plurality of acoustic beams being angled non-orthogonally to at least one other of the plurality of acoustic beams. The method may calculate the directional spectrum associated with the waves from the received echoes.

Abstract: A system and method for measuring the directional spectrum of one or more waves in a fluid medium using a multi-beam sonar system. In an exemplary embodiment, range cells located within a plurality of acoustic beams are sampled to provide current velocity data. Optionally, wave surface height and pressure data is obtained as well. This velocity, wave height, and pressure data is Fourier-transformed by one or more signal processors within the system, and a surface height spectrum produced. A cross-spectral coefficient matrix at each observed frequency is also generated from this data. A sensitivity vector specifically related to the ADCP's transducer array geometry is used in conjunction with maximum likelihood method (MLM), iterative maximum likelihood method (IMLM), or other similar methods to solve a the wave equation at each frequency and produce a frequency-specific wave directional spectrum.

Abstract: A system and method for measuring the directional spectrum of one or more waves in a fluid medium using a multi-beam sonar system. In an exemplary embodiment, range cells located within a plurality of acoustic beams are sampled to provide current velocity data. Optionally, wave surface height and pressure data is obtained as well. This velocity, wave height, and pressure data is Fourier-transformed by one or more signal processors within the system, and a surface height spectrum produced. A cross-spectral coefficient matrix at each observed frequency is also generated from this data. A sensitivity vector specifically related to the ADCP's transducer array geometry is used in conjunction with maximum likelihood method (MLM), iterative maximum likelihood method (IMLM), or other similar methods to solve a the wave equation at each frequency and produce a frequency-specific wave directional spectrum.

Abstract: A system and method for measuring the directional spectrum of one or more waves in a fluid medium using a multi-beam sonar system. In an exemplary embodiment, range cells located within a plurality of acoustic beams are sampled to provide current velocity data. Optionally, wave surface height and pressure data is obtained as well. This velocity, wave height, and pressure data is Fourier-transformed by one or more signal processors within the system, and a surface height spectrum produced. A cross-spectral coefficient matrix at each observed frequency is also generated from this data. A sensitivity vector specifically related to the ADCP's transducer array geometry is used in conjunction with maximum likelihood method (NLM), iterative maximum likelihood method (IMLM), or other similar methods to solve a the wave equation at each frequency and produce a frequency-specific wave directional spectrum.