The percentage of erroneously mapped pixels in today's orthophotos mainly depends on the density d and height h of the buildings. Influence of building height and building density on the percentage of erroneously mapped pixels 2. This paper presents a method to overcome these problems. Additionally to the DTM a model defining the shape of the buildings will be introduced. This digital building model distinguishes between roofs and walls.
Walls are vertical plane surfaces and therefore invisible in the orthophoto.
In the process of data capturing for the DBM in most cases it is sufficient to digitize the roofs only. In developing countries many buildings in new urban regions are of similar shape. It is important to model the real shape of a building although it is sometimes easier to create a new but wrong shape of the building with a CAD-system. The data structure for the storage of buildings is based on coordinate lists and topologigal information. The Z-buffer is a matrix, that stores for each building pixel of the digital photo its object distance.