Visualisation of the border effect produced by the KDE technique on the δ_Σ map of the NEXUS simulations. Upper panel: scheme of the different configurations of the local (small squares) and global (large squares) scanning windows with respect to the boundary between a medium of uniform density Σ₀ (grey area at negative Y) and the vacuum (white region at positive Y). Lower panel: values of δ_Σ for the mentioned configurations (red curve), assuming h = 0.5 kpc (vertical dotted lines) and H = 2.0 kpc (vertical dashed lines) bandwidths for the local and global kernels, respectively.