Patent ID: 7133327

Claim:
A method for measuring a vessel's velocity relative to the bottom using a correlation velocity measuring sonar, the method comprising steps of (1) Select a transmit code for acoustic pulses; (2) according to the transmit code, transmitting acoustic pulses into a fluid medium, and receiving echo signals backscattered by flow layers and the bottom; (3) excute step (4) if the echo signals in step (2) includes bottom echo signals, otherwise return back to step (1) if the echo signals in step (2) do not include bottom echo signals; (4) Demodulate and filter the bottom echo signals, and calculate the data bottom medium temporal and spatial correlation function matrix according to the bottom echo signals; (5) Extract a data matrix for fitting from the data bottom medium temporal and spatial correlation function matrix derived from step (4); (6) set a search range of the unknown parameter ensemble Θ 1 ={{overscore (V)} 1x , {overscore (V)} 1y , γ}, wherein {overscore (V)} 1x , {overscore (V)} 1y are average values of vessel's velocities relative to the bottom in x, y directions respectively, γis width factor; (7) Fit the data matrix for fitting derived from the step (5) with a theoretical function in the search range of the unknown parameter ensemble Θ 1 ; the theoretical function being φ( d, Θ 1 , τ)= B J 0 (γ β 2 θ) wherein B is a constant, θ is the incident angle of the acoustic wave, τ is time delay, d is distance between receive elements of the sonar array, J 0 (•) is zero-rank Bessel function; β 2 = ω 0 c ⁢ ( ( τ ⁢ V _ 1 ⁢ x + d x ) 2 + ( τ ⁢ V _ 1 ⁢ y + d y ) 2 ) 1 / 2 , wherein ω 0 is the central frequency of the transmit signal, c is the velocity of sound, d x and d y are components of d in x direction and y direction respectively; (8) Attain average values {{overscore (V)} 1x , {overscore (V)} 1y ,} of velocities relative to the bottom derived from the fitting results, and storing the results.