The image of the test sample obtained in a dynamic mode of scanning. The characteristic distortions are caused by temperature drift of scanner and low-frequency vibration. The next structures are displaced in a vertical direction.

Alignment made by finding of an average line of structures of a surface with their subsequent subtraction. The standard algorithm, which works well for Gaussian surfaces. In other cases the similar distortions are observed.

The algorithm used in "Callisto" allows to minimize errors of alignment. The essence is consists in a finding of median mismatch of the next structures with its subsequent subtraction (median line correction). The distortions are minimal.