Variation of underwater bathymetric features on SAR images and relation to environmental factors

Abstract

In this study, we analyze a series of SAR images over Gyeonggi Bay in the eastern Yellow Sea off the western coast of Korean Peninsula to investigate variations of the tidal channel signatures on SAR imagery. Most of the SAR images show obvious bathymetric features irrespective of acquisition frequency and polarization state while the tidal channel signatures in the study area are imaged in various shape and brightness. For statistical analysis, the underwater topographic features are extracted by the objective method. Comparison of the extracted underwater topographic signatures and tidal currents shows a tendency of NRCS variations to primarily increase with magnitude of tidal current component normal to ridges. Although parallel current flows generate certain convergence and divergence over the ridges for underwater topographic feature imprints, it is believed that the intensity modulation depends strongly on the interaction by across currentflows. Furthermore, the modulation of NRCS over tidal channel tend to be degraded as wind speed increases. The result of the study confirms degradation of underwater topography imaging through the decrease of NRCS variations under high winds.