Example H I self-absorption extraction. The left panel shows the observed THOR-H I emission channel map toward a (100 × 100)pixel subsection of the giant filament GMF20.0-17.9 at the velocity 44.5 km s⁻¹. The middle panel shows the map of the self-absorption baseline obtained with optimized smoothing parameters. The right panel gives the resulting HISA map, which is the difference between the baseline map and the H I emission map. The HISA feature in the bottom half of the map could be successfully recovered by astroSaber, while the strong continuum source in the top left was masked during a quality check of the spectra.