Method for determining depth values of a body of water

Abstract

For mapping and exploring bodies of water, fan depth finders are used that emit ultrasound pulses and receive-echo pulses in a number of tightly-bundled receiving sectors. Because the predominant number of receiving directions is oriented diagonally downward instead of straight down, these ultrasound pulses propagate on bent paths due to sound refraction. Sound refraction is caused by different sound velocity layers, the precise knowledge of which is necessary for determining an average sound velocity. The method of the present invention does not require a separate measuring probe to measure the sound velocity at different depths; rather, the average sound velocity is determined using a regression method based on the travel time measurements of the ultrasound pulses. In this method, first the floor profile that forms the basis of the measured travel times is determined with an assumed average sound velocity and compared with a floor profile model composed of partial functions modeled in a specific manner. Because a correction value for the average sound velocity can be determined from the partial functions, improved depth values of the floor profile can be determined iteratively with the measured travel times and the corrected sound velocity. A method of this type can advantageously be implemented on research and survey vessels for attaining the high precision required in surveying technology.