Survey mask for the well-specified Model A. We added extinction linearly decreasing from 100% at the galactic plane to 0% at 60° galactic latitude (dash-dotted orchid line), along with 256 holes of approximately 0.1-degree radius (white crosses). The observed octant is delineated by the light orchid triangle. The colour scale represents the completeness function $C(\widehat{\mathbf{n}})$, with 0 indicating masked regions and 1 indicating unmasked regions, and any value in between indicating partial completeness. In the misspecified Model B, the same mask is used, except for the linear extinction which extends from 0 to 59° galactic latitude.