Retrieval of Sea Surface Range Velocities From Envisat ASAR Doppler Centroid Measurements

The processing steps and error corrections needed to retrieve estimates of sea surface range Doppler velocities from Envisat Advanced Synthetic Aperture Radar Wide Swath Medium resolution image products are presented. Retrieval accuracies based on examination of the corrected Doppler shift measurements are assessed. The root-mean-square errors of the Doppler shift after bias corrections are found to be 4.7 and 3.9 Hz in VV and HH polarizations, respectively. At 35 degrees incidence angle, this corresponds to horizontal Doppler velocities of 23 and 19 cm/s.