A comparison of the A_V estimates derived from the sub-millimetre emission (frame a), the column density converted to A_V with the assumptions listed in the text), the reddening of the background stars (frame b)), and the dust scattering (frame c)). All maps have been convolved to a common resolution of 40″. The frame d) shows the NICER A_V estimates (black points) and the estimates derived from the NIR surface brightness as the function of the values from sub-millimetre data. The blue and the red points are, respectively, the values north and south of declination −36°55′. The solid lines are least squares fits to the respective data points. The dashed line indicates the one-to-one relation.