Array Beamforming Algorithm for Estimating Waves and Currents From Marine X-Band Radar Image Sequences

A new algorithm using array beamforming for estimating waves and currents from marine X-band radar image sequences is proposed. Array beamforming is used to extract the wave directional spectrum from the image sequences; the image intensity time series is considered as the signal received by the “antennas” in conventional array beamforming. To retrieve the current velocity, the following feature is utilized: the total power reaches a maximum when a suitable current is used in the beamforming calculation. Because the new algorithm is based on individual pixel points, as opposed to the full image in the conventional method, the coordinate transformation procedure can be avoided. Because of the filter capacity in beamforming, moving vessels and shadowing have little effect on the estimate results, and the empirical modulation transfer function is not required to amend the wave spectrum. The wave and current retrieval scheme is validated using a simulation and by comparing results with data from an in situ buoy.