Deriving Wave Height Using Image Shadow Feature and Extracted Principal Component

Benefiting from the merit of independent calibration without external reference, the shadow feature is investigated to retrieve wave steepness and wave height from X-band marine radar images. However, the wave period is currently required. Although the wave period could be achieved using the fundamental spectrum analysis technology from a radar image sequence, an external measuring device, like a wave buoy, is essential for the calibration of the wave spectrum. To solve this problem, an improved method for deriving significant wave height (SWH) is proposed by fusing the wave steepness extracted from the shadow feature of the radar image and the wavelength derived through rotated empirical orthogonal function analysis technology. Considering the attenuation relation of received echo in the distance direction, echo intensity calibration is adopted before extracting principal components. The collected X-band marine radar images are applied to verify the performance of the established SWH retrieval approach, with the observation of the wave buoy serving as the ground truth. Compared with the fundamental shadow statistical method, the correlation coefficient of the proposed approach rises by 0.08, while the root mean square error drops by 0.05 m.