S147, the SNR, as a test of HAGRID position selection. Upper panel: comparison between the pattern of final HAGRID positions, in red, and the VTSS (Dennison et al. 1998) arbitrarily scaled continuum-subtracted Hα surface brightness map shown in grey scale. A good correspondence is achieved. Lower panel: zoom into a 0.27 × 1.00 sq. deg. area within the remnant superposing HAGRID positions on the IGAPS Hα mosaic at full ∼1 arcsec resolution (shown in full in Fig. 8). This shows how the fine filaments making up the remnant are accurately traced by the HAGRID selections (green dots): Those with surface brightness exceeding 10⁻¹⁵ erg cm⁻² s⁻¹ arcsec⁻² are encircled in red. Both panels use Galactic coordinates such that latitude increases upwards and longitude towards the left.