Segmented maps obtained for the models analyzed in Fig. 14, zooming in on a part of the two regions that was removed from the training namely, the l = 166.1–168.3° (top) and l = 350.3–353.5° (bottom; see the red zones identified in Fig. 3). The segmented images are displayed in the range [0,1] representing the classification value according to which a pixel belongs to the filament class. For each region, the first row shows results of the UNet segmentation, and the second row shows results of the UNet++ segmentation with initial learning-rate values of 10³ (left), 10⁻⁴ to 10⁻⁵ (right). The UNet++ with a learning rate of 10⁻² is not presented because of diverging results (see Sect. 4.1). The is shown at this position for each region. The regions are 0.45° × 0.45 ° wide.