Rotation of Polarimetric SAR Covariance Matrices

In multilook polarimetric synthetic aperture radar (polSAR) data dihedral targets unaligned with the radar line of sight cause cross-polarized reflections which can be confused with vegetation. To avoid this, rotation can be performed. For the covariance representation of polSAR data this is described in two different ways, namely 1. by minimization of the covariance matrix cross-polarization term $\left\langle {{S_{hv}}S_{hv}^{\ast}} \right\rangle $ , and 2. by means of the argument of the circular covariance matrix term $\left\langle {{S_{rr}}S_{ll}^{\ast}} \right\rangle $ .