Polarimetric states analysis of forest backscattering

摘要

The polarimetric radar image analysis is giving a great impulse in understanding the physical mechanisms involved in the interactions radiation-matter. In the summer 1991 the multifrequency polarimetric SAR on board the NASA AIRSAR flew over the Black Forest site in South Germany. The Institute for Remote Sensing Applications of the Joint Research Center is exploiting the SAR capabilities in extracting information on forest spatial structure and water content by implementing a systematic approach in which Particular Polarimetric Configurations (PPCs) characterizing the backscattering of the forest stands are obtained. The PPC is defined as the polarimetric configuration of the transmit and receive channels which produces a particular set of values of the statistical parameters (i.e. mean, standard deviations, maximum and minimum extremes) of the return power of the targets belonging to a variable-size moving window. In this way we could create a thematic information for the imaged scene and try understanding the reasons beyond the found PPC combinations. Preliminary results show that the polarimetric orientations generating maximum and minimum powers are related to the spatial orientation of the trees' branches. Investigations are still on going on the information contained in the ellipticity configurations, possibly regarding the dielectric constant of the forest components.