Unlike model-oriented generalization, which reduces the amount of information within a data base, cartographic generalization concerns the optimization of spatial data towards a certain scale with regard to visualization. As it occurs on the geometry level, the object’s shape is altered in the process, thus introducing geometrical distortions. The assessment of the rate at which the objects change can be seen as a quality evaluation of the generalization process. This paper is particularly interested in the simplification of building ground plans and the achieved accuracy when comparing the results to their original appearance. A classification of possible changes is given, as well as quali- ty characteristics and their graphical interpretation. The quality parameters are defined and norma- lized, so that they can be used separately, but also in combination with others, depending on the requirement of a certain application.