Effect of a larger pixelisation when computing the structure function. Pixel size ranges from ℓ = 4, 17, 34, 69 kpc (from left to right). All four panels represent the same projected velocity field (injection scale at 100 kpc) in a galaxy cluster represented by a Xbeta model of core radius 21 kpc. In general, larger pixels reduce the power in the two-dimensional velocity fluctuations and roughly act like a smoothing convolution filter on the high-resolution centroid map.