Cross-correlation functions for the pairs of wavelet-filtered maps from Fig. 2. Top panel: C_w(t,5 pix), bottom panel: C_w(t,45pix). The red crosses denote the centre of the offset plane t = 0, where one can read the wavelet cross-correlation coefficient r(l) = C_w(t = 0,l). The peak of the cross-correlation functions is displaced from the centre by τ(l) = τ_i as the WWCC recovers the input displacement of the structure in the second map.