用合成孔径雷达图像反演浅海水下地形的一种方法

An inverse method for underwater bottom topograghy by using SAR imagery

海流与海底地形的相互作用导致了海表面的粗糙起伏，从而引起对海面观测的雷达散射截面的变化．在浅海海流速度垂直分布廓线为均匀的假定下，由流体连续性方程和驰豫时间近似下流体力学弱相互作用的理论，已证明雷达散射截面的空间变化正比于海流方向上海流速度变化的梯度．研究了合成孔径雷达（ＳＡＲ）对海面的观测图像在无槽道信息和海流方向预知条件下，提出用散射系数的二维相关函数确定海流方向．在海流速度和方向已知条件下，推导了由雷达散射截面的空间变化迭推反演浅海水下地形的公式，并研究了航天飞机 ＳＩＲ—Ｃ ＳＡＲ在我香港特区海域的二维图像反演浅海水下地形的应用。

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 by using two-dimensional (2-D)correlation of spatial variation of backscattering measured by the SAR imagery, as the priori 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 area of Hong Kong, China is studied.