General Four-Component Scattering Power Decomposition with Unitary Transformation of Coherency Matrix

This paper presents a new general four-component scattering power decomposition method by implementing a set of unitary transformations for the polarimetric coherency matrix. There exist 9 real independent observation parameters in the 3 x 3 coherency matrix with respect to the second order statistics of polarimetric information. The proposed method accounts for all observation parameters in the new scheme. It is known that the existing four-component decomposition method reduces the number of observation parameters from 9 to 8 by rotation of the coherency matrix, and that it accounts for 6 parameters out of 8, leaving 2 parameters (i.e., real and imaginary part of T13 component) un-accounted for. By additional special unitary transformation to this rotated coherency matrix, it became possible to reduce the number of independent parameters from 8 to 7. After the unitary transformation, the new four-component decomposition is carried out that accounts for all parameters in the coherency matrix including the remaining T13 component. Therefore, the proposed method makes use of full utilization of polarimetric information in the decomposition. The decomposition also employs an extended volume scattering model, which discriminates the volume scattering between dipole and dihedral scattering structures caused by the cross-polarized HV component. It is found that the new method enhances the double bounce scattering contributions over the urban areas compared to those of the existing four-component decomposition, resulting from the full utilization of polarimetric information