A Kongsberg EM Multibeam Backscatter Strength Beam Pattern Residual Correction Method

For the Kongsberg EM multibeam sonar systems, a discrepancy between the beam directivity and factory calibration can lead to radiation distortion coupled with the sector in backscatter strength. This study introduces a multi-sector beam pattern residual correction method based on a directivity model. Firstly, the method constructs a multisector directional radiation model for EM sonar by analyzing the beam transmission and reception processes. Secondly, a specific survey line is chosen, and an empirical acoustic model is employed to estimate the backscatter strength-angle curve, effectively separating the beam pattern residual signals for each sector. Finally, the method corrects the echo intensity to obtain backscatter strength that is independent of the acquisition sector. Calculation results from case study demonstrate the method can effectively reduce the interference from multi-sector directional residuals in backscatter measurements, thereby enhancing the utility of EM series multibeam sonar for seabed bottom type analysis.