The SAR Ocean Image Correlation Model and Its Validation by MultiBand SAR Ocean Images

摘要

The correlation characteristic plays an important role in the SAR ocean image mechanism. The radiometric resolution of high correlation SAR images is lower than that of the SAR images with lower correlation. The correlation length of SAR ocean images is usually assumed simply to be the same as the size of the resolution cell in the previous studies. However, in this paper, a new correlation function model of SAR ocean images is present, which shows that the correlation length in range direction is depend only on the range resolution, but the azimuth correlation length is rather complex, it depends on azimuth resolution, ocean scattering coherent time and platform velocity. According to this model, the azimuth correlation length can be shorter than SAR azimuth resolution if the coherent time is short enough and the platform velocity is sufficiently low. In the ocean image of airborne high frequency band (such as X or Ku band) SAR, the azimuth correlation length is significant shorter than range resolution because that the scattering coherent time of high band is shorter and the velocity of airborne platform is relatively low. However, the azimuth correlation length of spaceborne SAR images are very close to the range correlation length because of its high velocity. Some airborne multiband (L, X, and Ku band) and spaceborne SAR ocean images are used to validate and support this model.