Facades are not always in a single plane. Figure 16 presents a typical example of a building side consisting of various details such as extruding staircases and awnings. The application of the previous workflow to this type of facade will fail because there will not be useable edge histograms, and the process will deliver a failed classification. A possible elimination of these problems could be a splitting of the facades into multiple facade fragments. However, for our experimental data set of 104 buildings with 225 facades this method would result in a quadruple number of facades, and each image would only show a small element. One will have to cope with ambiguities because of the small size of the facade elements. The biggest problem is that the building classification that is used for the determination of building footprints is not always accurate enough due to misclassifications.