An Improved Three-Component Decomposition Method for $\pi$/4 Mode Compact PolInSAR Using Refined Volume Scattering Models

In this article, an improved three-component decomposition method for $\pi /4$ compact polarimetric synthetic aperture radar Interferometry (PolInSAR) is proposed to interpret the scattering mechanisms of various terrain types. In the proposed method, refined volume scattering models proposed in fully polarimetric synthetic aperture radar (SAR) is applied to the compact SAR system through certain transformation relations, which can be used to interpret the scattering mechanisms of various land covers. Meanwhile, compact polarimetric interferometric similarity parameter is proposed. This parameter is used to modify the refined volume scattering models, which can overcome the overestimation of volume scattering (OVS) due to the large angle between the building and the radar line-of-sight direction. In addition, extractors for building and nonbuilding regions are proposed, which can be used for adaptive selection of the volume scattering models. The performance of the proposed method is demonstrated and evaluated using $C$-band and $L$-band airborne PolInSAR data acquired at different study sites, and the fully PolInSAR data are converted to $\pi /4$ compact PolInSAR data. The experimental results show that the proposed method can be used to reasonably interpret the scattering mechanism of various terrain types (especially the built-up areas with large orientation angles) and overcome the OVS problem, which is an important supplement to the target decomposition method of $\pi /4$ compact PolInSAR.