基于能量函数最优的海表面风向反演算法

针对灰度不变模型(BCM)光流法从海杂波图像中提取海表面风向存在较大误差的问题，根据海杂波图像特点，提出了基于局部灰度和梯度不变模型
(BGCM) 的能量函数最优海表面风向反演算法.首先，将图像灰度不变模型、梯度不变模型和时空平滑约束项有机组合起来，构造能量函数；然后，将能量函数对光流的两分量求偏导，得非线性欧拉-拉格朗日方程组；最后，通过迭代方法求解非线性方程组，得到光流场，求取主海表面风向.应用实测岸基海杂波图像序列进行实验，将BGCM、BCM模型反演的风向与风向标测得风向进行比较，结果表明，BGCM风向具有更高的相关系数和更小的误差，改进算法具有较好的性能.

Determination of Ocean Surface Wind Direction Using Energy Functional Optimization

To overcome the big error existing in the common optical flow technology for determining wind direction based on brightness constancy model (BCM), an energy function optimization method was proposed for determining wind direction which depends on brightness and gradient constancy model (BGCM) with the feature of sea clutter images. Firstly, energy function is constructed with the common brightness constancy assumption, gradient constancy assumption as well as spatio-temporal smoothness constraint. Secondly, by calculating the derivation of optical flow components from energy function, the nonlinear Euler-Lagrange equations are obtained. Finally, optical flow field and main ocean surface wind direction can be achieved with iterative method to solve Euler-Lagrange equations. The improved method is finally validated with the real shore based X-band radar image. The superior performance of the proposed method is demonstrated by smaller estimation errors and well correlation when compared with results of the previous technique.