Retrieval of wave parameters from ERS-2 SAR imagery in shallow ocean area

Abstract

Inversing the surface wave spectrum from SAR (Synthetic Aperture Radar) is widely used to obtain the ocean wave parameters in a large ocean area. Considering that the ocean wave is affected by the water depth factor in coastalarea, this study focuses on the inversion of wave parameters in shallow ocean area from SAR images, and using the shallow water TMA spectrum as the first-guess spectrum to develop the inversion method presented by Hasselmann. The surface wave spectrum under swell-dominated case can be inversed from SAR image spectrum directly.So this paper selects 10 sub-images of one ERS-2 image which locates in Zhanjiang city sea area where under the wind-wave dominated cases. The wave lengths and wave directions are calculated from the inversion wave spectrums.Radon transform method is used to compare results. The result indicates that the wave lengths calculated by this inversion method and the radon transform agree with the bias of 4.07m, the standard deviation of 5.05m and the correlation coefficient of 0.953; the wave directions calculated by this inversion method and the radon transform agree with the bias of 1.93°; the standard deviation of 2.70°and the correlation coefficient of 0.955. When the water depth decreases, the change of wave length calculated by this inversion method is consistent with the change of ocean wave length.