The Effect of Orientation Angle Compensation on Coherency Matrix and Polarimetric Target Decompositions

Abstract

The polarization orientation angle (OA) of the scattering media affects the polarimetric radar signatures. This paper investigates the effects of orientation compensation on the coherency matrix and the scattering-model-based decompositions by Freeman-Durden and Yamaguchi et al. The Cloude and Pottier decomposition is excluded, because entropy, anisotropy, and alpha angle are roll invariant. We will show that, after orientation compensation, the volume scattering power is consistently decreased, while the double-bounce power has increased. The surface scattering power is relatively unchanged, and the helicity power is roll invariant. All of these characteristics can be explained by the compensation effect on the nine elements of the coherency matrix. In particular, after compensation, the real part of the (HH − VV) · HV * correlation reduces to zero, the intensity of cross-pol |HV| always reduces, and |HH − VV| always increases. This analysis also reveals that the common perception that OA compensation would make a reflection asymmetrical medium completely reflection symmetric is incorrect and that, contrary to the general perception, the four-component decomposition does not use the complete information of the coherency matrix. Only six quantities are included-one more than the Freeman-Durden decomposition, which explicitly assumes refection symmetry.

On the Use of Generalized Volume Scattering Models for the Improvement of General Polarimetric Model-Based Decomposition

“…As this parameter γ describes the elements of the volume matrix components, we first apply Lee's polarimetric orientation compensation [30] in order to lower the coupling to the volume component of other scattering sources not originated within the canopy. For every pixel, as γ is computed, the corresponding volume model will be determined according to Equation (4), hence no new unknowns are added to the inversion step.…”

An Improved Sar Radiometric Terrain Correction Method and Its Application in Polarimetric Sar Terrain Effect Reduction

“…In sloped areas, the azimuth slope causes shift of POA, thus changes the polarization state of scattered wave, and distorts the analysis of scattering characteristics of the targets. According to [12][13][14], POA shift η can be calculated using DEM data…”

“…(3) Polarization states distortion. The azimuth slope causes polarization orientation angle (POA) shift, thus causes rotation of the polarimetric backscattering matrix [11][12][13][14].…”

“…Small et al [17,28] proposed a correction method by normalizing the backscatter coefficient with the local illuminated area projected onto the plane perpendicular to the radar line of sight. For polarization distortion, researchers proposed to perform the correction through polarization orientation angle shift compensation [12][13][14]29]. The effects of polarization orientation angle shift compensation on polarimetric SAR data have been studied [14,29,30].…”

“…For polarization distortion, researchers proposed to perform the correction through polarization orientation angle shift compensation [12][13][14]29]. The effects of polarization orientation angle shift compensation on polarimetric SAR data have been studied [14,29,30].…”