High-resolution beamforming for multibeam echo sounders using raw EM3000 data

This paper deals with high-resolution beamforming for multibeam echo sounders with a linear receive-array. A fundamental limitation of the conventional beamformer is that the angular resolution depends upon the size of the receive-array. The use of subarray interferometry may increase the mapping resolution for oblique beams, but this method is not valid in the case of multiple scatterers. Therefore, it is interesting to examine how modern high-resolution beamformers work for multibeam echo sounders. Early research for this purpose, based on data simulation, showed promising results. The authors apply high-resolution beamformers to raw sonar data recorded at the receiver elements of Simrad EM3000 multibeam echo sounders. The estimation of spatial covariances plays an important role in high-resolution beamforming. A method to improve the estimation by subtracting noise covariances is applied. Among several beamformers they tested, MUSIC and ESPRIT gave the best results. Compared to the Fourier transform beamformer, high-resolution beamformers clearly improved the resolution. However, the noise level might also increase. It seems that a combined use of conventional and high-resolution beamforming may improve the sonar performance.

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