Effect of the angle rotation on the Planck Stokes parameters using Eq. 3. The original data at FWHM=80' are shown in the left column and the maps rotated with respect to ℓ_ref = 20 in the right column. The Stokes parameters are shown in the top and central panels with the same color bar displayed on the left, while polarized intensities are shown in the bottom panels in the background of the drapery patterns tracing the magnetic-field orientation obtained through LIC. The 80% sky mask is applied (see Fig. 1).