Break lines exist for topographic objects with any sharp breaks. The edges of a pedestrian strip or of a ditch are examples of break lines. These types of edges influence how the TIN is created and how the contour lines are calculated.
Form lines are used to describe special topographic surface forms, e.g. ridges or contour gradients. They influence how the TIN is created and how the contour lines are calculated.
Voids are areas which are not taken into account when creating a TIN or calculating the contour lines. In general, buildings or stretches of water are taken into account as voids.
The outer boundary of a DTM can be defined as a hull. A hull must exist for special calculations, e.g. volume calculations according to the German guidelines REB-VB 22.013.
