Dependence of the variation coefficient of nautical radar image sequences on the grazing and azimuth angle and consequences for the calibration

With the Wave Monitoring System (WaMoS) based on a nautical radar as sensor the significant wave height is determined. For the calibration of the radar image spectra an algorithm with empirically deduced parameters is used. The algorithm is based on the determination of the signal to noise ratio, where the signal belongs to the long wave modulation and the noise is induced by speckle. This method has been developed for synthetic aperture radar at moderate incidence angles and has been extended for use at grazing incidence. The dominant backscatter mechanism depends on the incidence angle which is linked to the grazing angle. It has to be proved if the different backscatter mechanisms have an influence on the calibration of systems working under grazing incidence.