Influence And Correction Of Multi-beam Backscatter Angle Factor

Multi-beam system has outstanding advantages such as high efficiency and stability.It can not only collect water depth information,but also collect backscatter intensity information of water body and seabed at the same time.It plays an important role in marine investigation and marine development and utilization in China.With the increasing demand for seabed imaging,seabed sediment classification,marine habitat investigation and many other aspects,efficient processing and application of multi-beam seabed backscatter data become the key.Due to the complexity of marine environment and multi-beam sonar system,there are various errors in backscatter data.Seabed backscattering data is affected by the incident angle of the beam,and the existing angle response correction models have poor adaptability at different bottom boundary with large difference in inherent scattering intensity.Therefore,an angle response correction method based on seabed point pre-classification is proposed in this paper.The main contents are as follows:1)The extraction method of multi-beam backscattering data is introduced,and the influence of seabed topography fluctuation on seabed incident angle and seabed acoustic illumination area is analyzed.Firstly,the processed water depth grid is used to calculate the dip angle of the seabed along the track direction and the dip angle perpendicular to the track direction,and then the actual incident angle of the seabed is obtained by calculating the included angle between the incident vector of the seabed beam and the normal vector of the seabed.Finally,the influence of the inclination angle along the track direction and the inclination angle perpendicular to the track direction on the incident angle and the area of the seabed acoustic illumination area is analyzed respectively.The analysis shows that the dip angle of the seabed along the track direction has a great influence on the incident angle of the seabed and the area of the seabed acoustic illumination area,which cannot be ignored in the calculation.The inclination angle along the track direction also has a great influence on the incident angle of the seabed,but has a relatively small influence on the area of the acoustic illumination area.2)This paper introduces the extraction method of multi-beam backscattering data,and analyzes the influence of seabed topography relief on seabed incident angle and seabed acoustic illumination area.Firstly,the seabed topographic grid generated by water depth data is used to calculate the seabed inclination angle along the track direction and vertical track direction,and then the actual seabed incidence angle is obtained by calculating the included angle between the seabed beam incidence vector and the seabed normal vector.Finally,the influence of the inclination angle along the track direction and the inclination angle perpendicular to the track direction on the incident angle of the seabed and the area of the seabed acoustic illumination area are analyzed respectively.The analysis shows that the submarine inclination angle perpendicular to the track direction has a great influence on the submarine incident angle and the area of submarine acoustic illumination area,which cannot be ignored in calculation.The inclination angle along the track direction also has a great influence on the incident angle of the seabed,but has a relatively small influence on the area of the acoustic illumination area.