Top left: fBm map (Fig. 17a, left) filtered on scale of 17 pix. Top right: fBm map displaced on scales >10 pix by τ_i,x = −10 pix and τ_i,y = 15 pix (Fig. 17a, right) filtered on scale of 17 pix. Bottom left: product map of two fBm maps (top left and top right). Bottom right: product map of the top left and top right maps, where the latter is reversely shifted by τ_x = −10 pix and τ_y = 15 pix (Eq. (30)).