Testing approaches to deal with random noise. An input datacube with a S/N of 100 (i.e. 1% random noise contribution – first row) was reconstructed with the basic method ignoring the noise (second row), ad-hoc regularisation with a set of values of regularisation parameter (third to fifth row) and the Wiener-like filtering approach (last row). The correlation coefficient for the whole cube between the input velocity field and the reconstruction is given in the titles of the plot panels. Colour-bars have the units of km s^-1 (violet indicates fast variations from pixel to pixel) and the field-of-view shown here covers 38 Mm × 38 Mm in the horizontal directions.