Correlation wheels for PCs at v_LSR = 24.7 km s⁻¹ (panels a), − 105.9 km s⁻¹ (panels b), 2.0 km s⁻¹ (panels c), 7.3 km s⁻¹ (panels d), 31.6 km s⁻¹ (panels e), and 17.7 km s⁻¹ (panels f). The percentages in parentheses give the contributions of the PCs to the total variance. The ellipses around the arrow heads show the uncertainties estimated from 1000 realisations of the opacity cubes.