Comparison of column densities derived from radiative transfer models of continuum and line emission. The dots correspond to all the pixels within the central 15′ × 15′ areas of the G26.34+8.65 (blue dots) and G195.74-2.29 (red dots) models. The coloured circles correspond to the positions of the clumps listed in Table 1. The crosses denote the column density estimates obtained assuming T_ex = 14 K.