The results of the successive calculations can visualized with the 'uvmat' interface by selecting the check boxes 'civ1', 'civ2' on the left. The vectors removed by the 'fix' operations are indicated with the magenta color: they are not erased but flaged in the files, so that the fix is reversible. However these flagged vectors are not taken into for further processing, for instance in 'patch'. They can be suppressed from the display by unselecting the check box 'see false' on the upper right. Here false vectors are obtained only under the mask, as the image quality is excellent.
The velocity field resulting from the patch operation is displayed by selecting the 'filter1' or 'filter2' check box. One can observe that the vector origins are on a regular grid, unlike for civ1 and civ2. Indeed the vectors are positioned at a position averaged between the position on the first image, set by the measurement grid, and the position on the second image, depending on the particle displacement. Furthermore the vectors are all blue, corresponding to perfect correlation, since their origin has been lost by the interpolation process. The fields 'interp1' or interp2' correspond to pure interpolation, with no smoothing.
In summary, for analyzing velocity, 'civ2' (or by default 'civ1') is the most precise and reliable, with no smoothing or interpolation, while 'filter2' (or by default 'filter1') is needed for spatial derivatives. When no field is selected, the 'view_field' display of 'uvmat' chooses this best option automatically, and indicates it by the yellow color. To impose the choice, select the corresponding check box .