Research On The Model And Method Of Multibeam Bathymetry Adaptive Sound Velocity Correction

As a high-tech product in contemporary ocean surveying and mapping,the multibeam bathymetry system has been widely used in the field of ocean topography and geomorphology with its characteristics of full depth,high precision and high integration.The multibeam bathymetry system obtains narrow-beam measuring points perpendicular to the ship's course distribution through two sets of directionally orthogonal transmitting and receiving transducer arrays,and calculates the vertical depth and lateral horizontal distance of each measuring point according to the travel time of Sound signals of each beam and the corresponding Sound Velocity Profile(SVP).Due to seawater medium's inhomogeneity,the propagation velocity and direction of acoustic signal in sea water will be changed continually,sound waves will be refracted at the interface of different seawater medium's physical properties and it will change the ray-line trajectory,the speed of sound change rate determines the sound ray bending degree,therefore during the sound ray tracking process the accuracy and precision of sound velocity profile directly affect the depth points' accuracy,reliability and operation efficiency.Usually,the measured area of most multi-beam projects has a wide range,and even the sound velocity profile of the same measured area in the same period is not the same.Therefore,the reasonable construction of equivalent sound velocity profile and the study of adaptive sound velocity correction method are particularly important.Based on the construction of three-dimensional sound velocity field and equivalent sound velocity profile,this paper discusses the multi-beam sound velocity correction method,proposes a set of adaptive multi-beam accurate sound velocity correction model,to some extent,realizes the adaptive streamlining processing of multi-beam sounding data,and improves the accuracy and reliability of data post-processing.In this model,a number of measured sound velocity profiles in the test area are used to construct three-dimensional sound velocity field based on empirical orthogonal function(EOF),and the sound velocity profile data within the test area are encrypted at certain distance intervals.In order to reduce the computational redundancy caused by a large number of sound velocity profile data,the Douglas Peucker algorithm was used to conduct adaptive equivalent reconstruction of each representative sound velocity profile,and the sound velocity node was adjusted according to the water depth value error in the overlapping area of adjacent sounding swaths,so as to minimize the influence of the sound velocity profile error on the sound velocity correction.In order to improve the efficiency of seabed beam point homing operation,the look-up table(LUT)method was used to replace the acoustic tracking algorithm to calculate the location and depth of water depth point quickly.The example shows that the method has the characteristics of high precision,high efficiency and self-adaptation.