Illustration of the selection function projected in ϕ–R space for the case without dust at Z_GC=0 kpc (midplane). Panel a shows the map of the selection fraction computed using the sub-binning method, panel b shows the same for the method without sub-binning, while panel c shows the distance to all voxels that are within a distance of d_max < 12.94 kpc of the Sun. Panel a also shows the additional voxels that would be missed by assuming the median values of observables (l, b, G). In all panels, the location of the Sun is indicated by the black star.