Accurate Correction Of Environmental Influence In Multibeam Backscatter Measurement

The main purpose of multi-beam sonar system is to obtain high-resolution water depth information with full coverage of the seabed,but it can also obtain high-resolution back scattering information of the seabed at the same time to provide data support for seabed sediment classification.However,due to the complexity of the marine environment,there are various influences in the beam propagation process of multi-beam,which will inevitably affect the accuracy of backscattering intensity.Among them,the seabed terrain inclination and seawater turbidity in the propagation environment have great influence on the multi-beam,the former will affect the seabed incidence angle and the effective acoustic illumination area of the beam;The latter will affect the beam propagation loss.For this reason,based on the general treatment method of environmental influence in the backscattering intensity of the seabed,this paper deduces the calculation formula of the area of the acoustic illumination area under the inclination of the seabed topography,and focuses on the influence of suspended particles in turbid seawater on the propagation loss of the backscattering intensity,which is of great significance for improving the quality of multi-beam backscattering data.The specific work is as follows:(1)In this paper,the interaction between beam and sea water and seabed is analyzed,and a set of overall flow of multi-beam backscattering data processing is given.The backscattering data affected only by seabed sediment are obtained,including original data analysis,intensity point position calculation,sonar parameter correction,propagation loss correction,effective acoustic illumination area correction and incident angle effect correction.The multi-beam backscatter data imaging is realized.A complete set of multi-beam backscattering data processing flow is constructed.(2)The uncertainty factors affecting the effective acoustic irradiation area are analyzed.By analyzing the influence of terrain changes on the beam irradiation area,the accurate calculation formula of the effective acoustic irradiation area under inclined terrain is derived.(3)Aiming at the problem of poor adaptability of the existing back scattering intensity propagation loss correction methods in turbid waters,a calculation model of sound propagation loss in turbid waters is proposed.Firstly,acoustic absorption coefficient profiles are constructed by using marine environmental parameters at different depths,and then propagation losses are calculated for each beam layer along the beam propagation path.Experimental analysis shows that this method has good propagation loss correction effect,greatly weakens the correlation between multi-beam echo intensity and propagation distance in turbid waters,and effectively improves the quality of multi-beam sonar images.