Illustration of the Galactic regions located at 160–171° (left) and 349–356° (right) of the four input maps used for the supervised learning. From top to bottom, we show the column density map, the input filament masks, a background localization map, and the missing-data map (0 in purple, 1 in yellow). All these maps were obtained as explained in Appendix A. The filament and background mask maps are multiplied by the missing-data map before they were used in the training process. The red rectangle shown in each column density map represents the region we extracted to compute the performance of the training (see Sect. 4.1).