An inverse method for underwater bottom topograghy by using SAR imagery

Interaction between current and underwater bottom topography modulates roughness of the sea surface,which in turn yields variation of the radar scattering echo.By using the continuity equation and weak hydrodynamic interaction theory in the relaxation time approximation,the spatial variation of the radar scattering cross-section has been proved as proportional to the gradient of current velocity.The current direction is first determined byusing two-dimensional (2-D)correlation of spatial variation of backscattering measured by the SAR imagery,as thepriori knowledge of the current direction is not available.The inverse algorithm to successively derive 2-D underwater bottom topography from the SAR imagery is developed.As an application,the SAR SIR-C image over the sea areaof Hong Kong,China is studied.