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i senta chousa 
f Aichi.(1999). 
senta  chousa 
— 
CHALLENGES AND SOLUTIONS ON THE GENERATION OF DIGITAL 
SURFACE MODELS OF FACADES USING IMAGE PROCESSING TECHNIQUES 
Albert Wiedemann 
FPK Ingenieurgesellschaft mbH 
Feurigstr. 54, D-10827 Berlin, Germany 
a.wiedemann@fpk.de 
Commission V, WG V/5 
KEY WORDS: Architecture, Cultural Heritage, Matching, Orthoimage, Surface, DSM 
ABSTRACT: 
Digital Surface Models (DSM) are essential for the differential rectification. But whereas there is a lot of experiences with the 
generation of Digital Surface Models of topographic terrain, only a few experiences exist in the determination of DSM of 
architectural objects. This may be a result of the high demands to the DSM in architectural photogrammetry. The paper describes 
approaches to determine the required data for the DSM of facades based on image matching in already oriented images and 
strategies for interpolation of the DSM of faces with in-continuities in the surface and her derivation. 
KURZFASSUNG: 
Digitale Oberflächenmodelle (DOM) sind für die differentielle Entzerrung von entscheidender Bedeutung. Aber während es eine 
Menge Erfahrungen bei der Erstellung von Oberflächenmodelle topographischer Geländeoberflächen gibt, existieren nur begrenzte 
Erfahrungen bei der Erstellung von Oberflächenmodelle von Architekturobjekten. Dies kann eine Folge der harten Anforderungen 
an DOM in der Architekturphotogrammetrie sein. Der Aufsatz beschreibt Ansätze um die erforderlichen Daten für DOM von 
Fassaden mit Hilfe der digitalen Bildzuordnung in orientierten Bildern zu gewinnen und Strategien für die DOM-Interpolation von 
Flächen mit Unstetigkeiten in der Oberfläche und in der Ableitung der Oberflächenfunktion. 
1. DIGITAL SURFACE MODELS OF FACADES erosion. Both approaches also require an enormous amount of 
interactive work. In only a limited number of projects resources 
1.1 Requirements for Digital Surface Models as described in Dallas (Dallas et al., 1995) are available. 
Some people call simple rectified images orthoimages. 
Therefore some authors have developed the term true 
orthoimages to describe orthoimages determined under the 
knowledge of the geometric surface structure (Dequal & Lingua 
1.3 Special Requirements 
Some special requirements on faced DSM distinguish them 
  
2002). In my texts and lectures only this true orthoimages are 
orthoimages at all. 
There are several methods to provide the required surface data 
for the generation of digital orthoimages of facades. If there is a 
CAD model consisting of volumes or faces with the necessary 
accuracy and level of detail already existing or derived from 
geodetic or photogrammetric measurements (Wiedemann 
1996), it is possible to derive a Digital Surface Model (DSM) of 
the facades (Fig. 2). Another approach to determine the data for 
the DSM is the usage of a laser scanner (Wiedemann 2001). 
Both approaches are tedious or expensive and may not be 
available in all situations. 
1.2 Photogrammetric Data Acquisitions 
In these situations only photogrammetric approaches may come 
into account. In many cases no equipment for stereo 
photogrammetry is available and bundle based restitutions may 
fail due to the lack of exact defined features, like on facades of 
natural stones or facades suffered from a long time weather 
from topographic DSM. In architecture the relation of height 
differences to image acquisition distance is much bigger than in 
aerial photogrammetry. Therefore the horizontal displacement 
resulting from height differences is bigger than in aerial 
photogrammetry. The surfaces are not continuous. The 
curvature stays identical over large areas but changes abrupt. 
Therefore it is necessary to mention break lines or acquire the 
data with a very high density, in the ideal case the same grid 
with like the raster with of the orthoimages to be derived from 
the DSM. 
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