
 
the semantic context to simplify the automatic 
reconstruction. 
The following section gives background 
information on projects that aim to reconstruct a 3D 
model of a building from survey data. In these 
projects the semantic information that describes the 
context of the building takes an important place. 
Section 3 describes our approach inspired from these 
projects. Section 4 focuses on this method by 
explaining all the important parts of the 
reconstruction process.  
2  BACKGROUND 
Today, computer-driven evaluation of spatial data 
sets is limited by the complexity of the objects to be 
extracted. As a matter of fact it is complicated and 
time consuming to formulate rules in order to detect 
and extract objects geometrically correct. It is due to 
one essential reason that the objects are broken 
down into many small geometrical pieces. Even if 
each piece can be treated in an isolated way, it is not 
possible to treat all data at one time. Therefore, the 
use of knowledge and its introduction into the 
process of evaluation is promising for global 
interrelations. The impact of semantic information 
on the reconstruction process depends on the 
structure of the raw data that has to be handled. 
Therefore, it is necessary to study those structures 
and reconstruction processes. A short survey is 
given in the two following subsections. The first 
subsection is concerned with reconstruction methods 
based on photogrammetric data and the second 
considers reconstruction methods based on scanning 
data. Each method has its own characteristics and 
advantages but the best choice depends on the 
material available, the object to be captured, the 
required precision, and the time available (Grün, 
2002), (Bryan, 1999), (Balletti, 2004), (Boehler, 
2004). 
2.1  Photogrammetry 
Reconstruction methods based on photogrammetric 
data are of two kinds. The semi-automatic methods 
consist of the interaction with the user during the 
whole process. The automatic methods consist in the 
initiation of the process by the user at the beginning 
so that later the process runs without user 
interaction. Semi-automatic reconstruction methods 
can be found in the projects: Realise (Zitova, 2003), 
TotalCalib (Robert, 1995), (Bougnoux, 1997), 
(Faugeras, 1997), Marina (Cantzler, 2002), 
(Nüchter, 2003) and Rekon (Frasson, 1999), 
(Loscos, 1999), (Poulin, 1998). Automatic 
reconstruction methods have been developed by 
Pollefeys et al. (Pollefeys, 2000) and Zisserman et 
al. (Werner, 2002). They use the projective 
geometry on non-calibrated images. Pollefeys' 
system combines various algorithms from computer 
vision, like projective reconstruction, auto-
calibration and depth map estimation. Of special 
interest for our work was the project Aida (Weik, 
1996) because it uses a semantic network to guide 
the reconstruction. This method opens a new way by 
using semantic information. The automatic 
reconstruction remains a difficult task in spite of 
many years of research (Backer, 1981), (Fleet, 
1991), (Grimson, 1981), (Jones, 1992), (Marr, 
1979), (McMillan, 1995). The major problems are 
the impact of the viewpoint onto the appearance of 
the object in the image. This is due to the changes 
with respect to geometry, radiometry, occlusions and 
the lack of texture. Strong variations of the 
viewpoint may destroy the adjacency relations of 
points, especially when the object surface shows 
considerable geometrical variations. This 
dissimilarity causes confusion in the determination 
of correspondence and it is worse when partial 
occlusions result in a disappearance of object parts. 
In cases of weak texture the algorithms do not have 
sufficient information to solve the correspondence 
problem correctly. Usually, this is the reason why 
the reconstruction fails.  
2.2  Scanning 
Accurate reconstruction of a surface model from 
unorganized points of clouds provided by scanning 
systems are complex and are still not completely 
solved. Problems arise from the fact that the points 
are generally not organized, contain noise and do not 
reflect directly the object characteristics, for 
example. Computer-based processes of object 
extraction are therefore limited in their efficiency. F. 
Remonido gives a good overview of existing 
algorithms (Remondino, 2003). Close attention is 
given to the work of Cantzler et al. (Cantzler, 2002) 
and to the work of Nüchter et al. (Nüchter, 2003) 
because these projects use semantic information. 
Planes which are being reconstructed are associated 
to a semantic interpretation which has to fit to a 
network model (Grau,1997). A tree of 
“backtracking” allows to find the best mapping 
between the scene interpretation and the semantic 
network model. A coherent labelling exists if all 
surfaces are labelled.  
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