Relation between degree of polarization and Pauli color coded image to characterize scattering mechanisms

Abstract

Polarimetric image classification is sensitive to object orientation and scattering properties. This paper is a preliminary step to bridge the gap between visible wavelength polarimetric imaging and polarimetric SAR (POLSAR) imaging scattering mechanisms. In visible wavelength polarimetric imaging, the degree of linear polarization (DOLP) is widely used to represent the polarized component of the wave scattered from the objects in the scene. For Polarimetric SAR image representation, the Pauli color coding is used, which is based on linear combinations of scattering matrix elements. This paper presents a relation between DOLP and the Pauli decomposition components from the color coded Pauli reconstructed image based on laboratory measurements and first principle physics based image simulations. The objects in the scene are selected in such a way that it captures the three major scattering mechanisms such as the single or odd bounce, double or even bounce and volume scattering. The comparison is done between visible passive polarimetric imaging, active visible polarimetric imaging and active radio frequency POLSAR. The DOLP images are compared with the Pauli Color coded image with |HH-VV|, |HV|, |HH +VV| as the RGB channels. From the images, it is seen that the regions with high DOLP values showed high values of the HH component. This means the Pauli color coded image showed comparatively higher value of HH component for higher DOLP compared to other polarimetric components implying double bounce reflection. The comparison of the scattering mechanisms will help to create a synergy between POLSAR and visible wavelength polarimetric imaging and the idea can be further extended for image fusion.