Correlation plot of position angles in emission, ψ_S, and in extinction, ψ_V, for the merged sample, for lines of sight satisfying the first three selection criteria. Data for lines of sight failing the fourth angle criterion are marked in red; those finally selected are in black. The central diagonal solid line indicates perfect agreement (orthogonal polarization pseudo-vectors), and other lines are for offsets of 10° (dashed) and 20° (dotted). We note that when the arithmetic difference in angles falls outside the allowed ± 90° range for ψ_S (filled zones), the plotted ψ_V is adjusted by ± 180° (Eq. (9)).