Synthetic aperture radar imaging of ocean-bottom topography via tidal-current interactions: theory and observations

Abstract

A numerical model has been developed for the purpose of explaining and quantifying the relationship between the SEASAT synthetic aperture radar (SAR)signatures and the bottom topography of the ocean in the Southern Bight of the North Sea and Nantucket Shoals. The model uses environmental data (wind, current and depth changes)and radar system parameters (frequency, polarization, incidence angle and resolution cell size)as inputs and predicts SAR-observed backscatter changes over topographic changes in the ocean floor. The model results compare favourably with the actual SEASAT SAR-observed backscatter values. The comparisons between the model and the actual data are all within 1·5 dB except for one limiting geometry. The model suggests that for bottom features to be visible on SAR imagery, a moderate to high current velocity (0·4 m/s or greater) and a low to moderate wind (between 1·5 and 7·5 m/s) must be present.