Texture-based detection of sea wave direction

Various phenomena in the radar imaging mechanism, such as velocity bunching, azimuthal cutoff, tilt modulation, range dependence etc affect the SAR image. Among them, velocity bunching and azimuthal cutoff, straightly related to SAR azimuth direction, have been most investigated. However, in this study, the range factor, mainly due to lower radar image intensity for far range, is proved to be more pronounced. In the study framework, 2nd order texture analysis was performed in order to investigate a) the potential of texture to detect wave direction, b) wave range dependence, and c) velocity bunching effects. For this purpose, the Haralick Cooccurrence matrix was calculated on a despeckled ERS2 image for four directions. Eight texture images were generated and compared to the wave direction resulting from the TOPEX/POSEIDON model. The comparison showed that a) the texture image produced in the range direction detected sea wave direction efficiently, and b) accuracy was affected by the range factor. Thus, a range correction was proposed and implemented on the despeckled texture images. Following this correction, an accuracy of 88.6% was achieved for wave direction detection, if texture is calculated along the range direction and 74.9% if texture is calculated along the azimuth direction.