In CCDPACK three methods for determining image feature correspondence are provided. Two of these rely on transformations between coordinate systems being `well modelled' by simple offsets. These methods have the advantage of automated and semi-automated processing. The third method relies on considerable interaction but can deal with transformations of scale, magnification and shear as well as offsets (i.e. general linear transformations).
If images are well modelled by simple offsets apart from a known transformation, for instance a rotation of the instrument between observations, then a coordinate system describing the known transformation can be added using WCSEDIT or ASTIMP, and the automated methods still used.