Apparent shifts, δv, in source positions caused by the two polarisation components of a plane GW propagating towards the centre of the maps, i.e. the ‘+’ component (top) and ‘×’ component (bottom). The background colour encodes the magnitude of the shift, |δu |, in units of the maximum shift ∆_max. This and all other full-sky maps use the Hammer-Aitoff projection in equatorial coordinates, with α = δ = 0 at the centre, north up, and α increasing from right to left.