Left panels: Spatial distribution of the four toy systematics. Systematics A1 and A2 are uniform in each tile, but differ across tiles (type A); Systematics B varies within each tile (type B); Systematics C is tile-independent (type C); Right panels: Black curves in the colour bar show the selection function of each systematic and the shaded region is the normalised distribution of the systematics. The numbers on the right show the selection rate values.