Ocean Wave Parameters Retrieval from Polarimetric SAR Images

The ocean waves are the most common and obvious ocean phenomenon. Its parameters retrieval is particularly important for the development of marine resources, the construction of marine engineering and marine transportation. Synthetic aperture radar (SAR) is widely applied to the ocean wave observation and parameters retrieval with obvious advantages of all-day, all-weather. With the rapid development of SAR technology, the resolution of SAR images becomes higher every day. High-resolution SAR brings us more plentiful target details, but sea spikes are prone to appear when observing the ocean. It causes the information of ocean waves to be overwhelmed by sea spikes, which seriously affects the retrieval of the ocean wave parameters from SAR. As a step forward, an ocean wave parameters retrieval method from polarimetric SAR images is proposed in this paper. Firstly, the VV and HH dual-polarized data is used to remove the nonpolarized components of the SAR echo to suppress the sea spikes. The clear SAR image of ocean waves is obtained that is not disturbed by the sea spikes. Then, the azimuth cut-off, wavelength and propagation direction of ocean waves are estimated in the two-dimensional wavenumber domain. Finally, the three parameters are input into the empirical model. The significant wave height and the mean wave period are retrieval in combination with SAR system parameters. This method is applied to a field X-band SAR data. The significant wave height and the mean wave period of ocean waves are obtained. The results are similar to the European Centre for medium-Range Weather Forecast (ECMWF) data, which verifies the effectiveness of the proposed method.