GW probability versus galaxy-weighted probability in wide-field observations. Comparison between the LALInference GW sky localisation probability density (P_2D) integrated over the tiles of our wide-field observations and the sum of individual galaxy probabilities P_gal (Sect. 3.7) over galaxies that fall in the same tile. The data are reported in Table B.2. Due to the wide field of view of these facilities, the galaxy density averages out, and the probabilities computed in the two ways are very similar. We note that the larger scatter for Pan-STARRS observations is due to the fact that observations are divided into smaller “sky cells”. Grouping sky cells in the same observation would reduce the scatter.