Sample RA–v (left) and v–Dec (right) maps to demonstrate that the apparently very complex and chaotic appearance in the zeroth and first moment maps shown in Figs. 2 to 5 can easily be resolved in the third dimension. The two top panels represent an area where all three layers of ¹²CO3–2 emission (see text) that we found in the pathfinder are visible, the centre panels were taken towards DR 21, and the bottom panels towards W 75 N.