Column density structure of the Spiral Cloud. The figure presents ring-averaged column density as a function of cloud radius. The blue line stands for the data and the red line stands for the analytical model (Eq. (1)). The telescope resolution is ~2.2pc at a distance of 9.8kpc. The resolution of the plot (2.7 pc, limited by the widths of the rings) is indicated as the blue horizontal bar. See Sect. 3.2 for details.