Acoustic log

Apparatus for measuring a vessel's velocity relative to a reference location, comprising:

• transmitter means on board a vessel and including at least one transmitter and at least one transmitting transducer coupled to said at least one transmitter for transmitting a coherent signal toward the reference location from where the coherent signal is reflected;
• receiver means on board the vessel and comprising at least four spaced-apart receiver transducers coupled to at least one receiver, said at least four spaced-apart receiver transducers all being stationary relative to the vessel and each having an elongated sensing area and being arranged in pairs beside each other, the transducers of each pair being situated such that the direction of measurement of one pair is oriented at a predetermined angle relative to the direction of velocity measurement of the other pair, the longitudinal axis of the vessel being substantially parallel to the binsectrix of the angle between said directions of velocity measurement so that two velocity components of the vessel's velocity can be determined when there is a certain angle between the direction of travel of the vessel and its longitudinal axis;
• said coherent signal transmitted by said transmitter means being within a lobe range that is substantially common to said at least four spaced-apart stationary receiver transducers, the signals reflected by said reference location and received by said receiver means comprising at least two acoustic signals that are similar in character but different in timing from each other, the difference in timing between said at least two acoustic signals being a function of the distance in the direction of measurement between said spaced-apart stationary receiver transducers and further being a function of the vessel's velocity, said received signals comprising reflections from every point on the reference location within said lobe range;
• each of said reflected acoustic signals received by said receiver means being representative of the instantaneous position of each of said stationary receiver transducers relative to said reference location, said received signals being modulated as a function of the vessel's movement relative to said reference location;
• and
• operating means coupled to said receiver means for comparing said reflected acoustic signals with each other and for generating an output signal which is a function of the timing difference between said two signals, said output signal further being indicative of the vessel's velocity relative to the reference location.

Apparatus for measuring a vessel's velocity relative to a reference location, comprising:

• transmitter means on board a vessel and including at least one transmitter and at least one transmitting transducer coupled to said at least one transmitter for transmitting a coherent signal toward the reference location from where the coherent signal is reflected;
• receiver means on board the vessel and comprising a plurality of receivers and a plurality of receiver transducers arranged in an array, said receiver transducers being stationary relative to the vessel, at least some of said stationary receiver transducers being spaced-apart, pairs of said spaced-apart ones of said stationary receiver transducers forming a unit comprising a number of pairs of receiver transducers, alternate paired combinations of said receiver transducers being oriented and connected to respective receivers to provide various directions of velocity measurement so that two velocity components of the vessel's velocity can be determined when there is a certain angle between the direction of travel of the vessel and its longitudinal axis;
• said coherent signal transmitted by said transmitter means being within a lobe range that is substantially common to said spaced-apart receiver transducers, the signals reflected by said reference location and received by said receiver means comprising at least two acoustic signals that are similar in character but different in timing from each other, the difference in timing between said at least two acoustic signals being a function of the distance in the direction of measurement between said spaced-apart stationary receiver transducers and further being a function of the vessel's velocity, said received signals comprising reflections from every point on the reference location within said lobe range;
• each of said reflected acoustic signals received by said receiver means being representative of the instantaneous position of each of said stationary receiver transducers relative to said reference location, said received signals being modulated as a function of the vessel's movement relative to said reference location;
• and
• operating means coupled to said receiver means and being responsive to the outputs of said receivers for comparing said reflected acoustic signals with each other and for generating an output signal which is a function of the timing difference between said two signals, said output signal further being indicative of the vessels velocity relative to the reference location, said operating means being further responsive to the receiver outputs to measure various direction components of the vessel's velocity.

Apparatus for measuring a vessel's velocity relative to a reference location, comprising:

• transmitter means on board a vessel and including at least one transmitter and at least one transmitting transducer coupled to said at least one transmitter for transmitting a coherent signal toward the reference located from where the coherent signal is reflected;
• receiver means on board the vessel and comprising six spaced-apart receiver transducers coupled to at least one receiver, said six spaced-apart receiver transducers each having an elongated sensing area and being arranged in pairs beside each other, the transducers of each pair being situated so as to provide three directions of velocity measurement, each pair being oriented at an angle of approximately 120.degree.with the other pairs to enable velocity components of any arbitrary direction to be measured, the longitudinal axis of the vessel being substantially parallel to the bisectrix of the angle between said directions of velocity measurement;
• said coherent signal transmitted by said transmitter means being within a lobe range that is substantially common to said six spaced-apart receiver transducers, the signals reflected by said reference location and received by said receiver means comprising at least two acoustic signals that are similar in character but different in timing from each other, the diffrence in timing between said at least two acoustic signals being a function of the distance in the direction of measurement between said spaced-apart receiver transducers and further being a function of the vessel's velocity, said received signals comprising reflections from every point on the reference location within said lobe range;
• each of said reflected acoustic signals received by said receiver means being representative of th instantaneous position of each of said receiver transducers relative to said reference location, said received signals being modulated as a function of the vessel's movement relative to said reference location;
• and
• operating means coupled to said receiver means for comparing said reflected acoustic signals with each other and for generating an output signal which is a function of the timing difference between said two signals, said output signal further being indicative of the vessel's velocity relative to the reference location.