Corresponding to the models in Fig. 7, the accuracy of the recovered peak column densities (left frames) and FWHM values (right frames). The relative errors of method B (cyan and magenta crosses for cold and warm sources, respectively) and method E (blue and red plus signs for cold and warm sources, respectively) are shown relative to idealised observations at 18.3″ resolution. The noise levels k_n are indicated in the frames. Values with relative errors outside the range of [–0.6, 0.6] are plotted at those boundaries. To reduce overlap between plot symbols, some jitter was added to the x-coordinate values of the FWHM plots.