Patent ID: 8730765

Claim:
A method for measuring a profile of the ground ( 6 ) by means of a transmitting arrangement ( 20 ) attached to a watercraft ( 2 ) for the targeted emission of sound signals into an underwater area ( 8 ) and by means of a receiving arrangement ( 28 ) attached to said watercraft ( 2 ) having at least two transducers for receiving the sound waves reflected by the profile of the ground ( 6 ) inside the underwater area ( 8 ), from which the transducers each generate a received signal ( 40 ; 42 ), which is sampled, digitised and stored at predefined sampling times and wherein a sound signal with a plurality N of predefined frequencies that are different from one another is successively emitted into the underwater area ( 8 ) by means of said transmitting arrangement ( 20 ) and components of said sound signal reflected by the profile of the ground ( 6 ) are received by means of the receiving arrangement ( 28 ) and the N different frequencies are filtered out of the received signal ( 40 ; 42 ), and wherein for a plurality of the sampling times and for the N frequencies of the received signals ( 48 1 , 48 2 , 48 3 , . . . , 48 N ; 50 1 , 50 2 , 50 3 , . . . , 50 N ), both a phase difference (Δφ) and a transit time (τ) of these received signals are determined, wherein the electroacoustic and/or optoacoustic transducers of the receiving arrangement ( 28 ) are arranged at a distance ( 30 ) greater than half the wavelength (λ) of the received signal ( 40 ; 42 ), via the phase differences (Δφ), determining path differences of the received sound waves resulting therefrom between two transducers of the receiving arrangement ( 28 ) and associated receiving angles ( 66 ), determining incidence coordinates (x, y, z) for these sampling times and for the N frequencies, by means of the transit times (τ) and the receiving angles ( 66 ), determining a data density for the incidence coordinates (x, y, z) within a predefined surface element containing the incidence coordinate (x, y, z), wherein the data density represents a measure of the number of previously determined incidence coordinates (x, y, z) within this surface element, and selecting the particular surface element in which the data density becomes maximal and the incidence coordinate (x, y, z) belonging to this surface element is determined as the true incidence coordinate (x, y, z) of the profile of the ground ( 6 ).