Transformations describe a mapping between two
coordinate systems. Moslty, both coordinate systems have the same
type. Transformation parameters are determined a posteriori by
measurements and have an accuracy.
Transformations have geometric conditions
straights are mapped to straights
conformity (e.g. Helmert- transformation)
Often transformation methods are chosen based on
the conditions on the geometric properties.
When applying transformations to coordinate
reference systems, in the most cases the datum changes.