Ocean Surface Currents Determination from X-Band Radar Image Sequences

An algorithm for retrieving ocean surface currents using nautical radar-image sequences is presented in this paper. The image sequences are acquired by common marine X-Band radar. With the Fast Fourier Transformation the image sequences are transformed to the wave number frequency domain and produce a three dimensional image power spectrum. In the absence of the sensorpsilas velocity and the near surface current the spectral energy in this three-dimensional wave number frequency space will lie on a shell defined by the dispersion relationship. Any deviation from the expected dispersion relationship can be interpreted as a current induced Doppler shift of the wave frequency. A weighted least squares curve fitting technique is used to determine the surface current. For validation of the algorithm, the surface current derived from the inverted radar data sets and from ground truth data are compared. It is shown that the radar-retrieved surface currents are within the accuracy of the conventional instrumentation.