To set the spatial calibration we go to Data> Pixel Size.

Here the user can see the width of pixels in each of the X ,Y and Z dimensions independently and to change them we can just enter the new value in each field as needed. 

Note that it is necessary to have units. If no unit is selected the field will be highlighted red to indicate that the units are missing.

Note that, as of arivis Vision4D 3.3, it is possible to add calibrations to every set in a batch simultaneously by selecting the [all image sets] option from the Image Set drop-down list.