基于小波的多极化机载合成孔径雷达海面风向反演

摘要

为了实现从合成孔径雷达（SAR）图像本身提取高精度的海面风向信息,提高SAR海面风场反演精度,研究了多极化机载SAR海面风向反演技术,借助小波分析相对傅里叶分析和局部梯度更精细的时-频分析能力,将二维连续小波变换与快速傅里叶变换（FFI）相结合,提出一种新的机载SAR海面风向反演方法.为验证反演方法的有效性,通过海上同步飞行试验获取多极化机载SAR数据及同步调查船实测风向数据,用于反演试验的数据比对.采用本文提出的方法,利用多种小波基对机载C波段SAR的同极化和交叉极化数据进行风向反演,将反演结果与美国国家环境预报中心再分析资料以及调查船实测风向进行比对.结果表明,本文提出的基于小波分析的海面风向反演方法适用于机载SAR探测数据,反演精度优于二维FFT法和局部梯度方法;小波基的选择对反演结果影响较大,Mexican-Hat小波基是机载SAR海面风向反演的最优小波基,且同极化与交叉极化机载SAR数据均可用于海面风向的反演.%An ocean surface wind direction retrieval method from multi-polarization airborne synthetic aperture radar images is presented in order to retrieve high precision wind direction SAR image and improve the accuracy of ocean surface wind.The method relies on the ability of two-dimensional（2D） continuous wavelet technique with better time-frequency than Fourier transform and local gradient, which combines 2D continuous wavelet and FFT to exact the ocean surface wind direction from airborne SAR images.The proposed method is executed by using several kinds of mother wavelet functions for the C-band co-polarization and cross-polarization airborne sounding images,and the retrieved ocean surface wind direction is compared with NCEP data and buoy data.The verification results show that the wavelet based ocean surface wind direction retrieval algorithm is suited to retrieve wind direction from airborne SAR sounding data.The choice of mother wavelet function has a certain influence on the results,and 2D Mexican-Hat is the best mother wavelet for wind retrieval.Both co-polarization and cross-polarization airborne sounding images are suited to retrieve ocean wind direction.