CI P A 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
301 
To dissect the façade elements, we use the knowledge that 
facing is always surrounded by oak beams which are much 
darker spectrally. This is reflected by an important mean 
difference to darker neighbours. 
Figure 5. Rule established for the discrimination of 
the class “facing” (yellow). 
Nevertheless, the rule is not sufficient (Fig.5). So another 
feature is introduced according to the mean difference to 
general neighbours. The reasoning continues with the beams : 
beams, but not only beams, are characterised by dark colours. 
Thus we introduce a second criterion according to the 
distance separating them from previously classified objects. 
Indeed, one beam is always in direct contact to facing, so that 
distance is placed to zero. 
Each class of interest is analysed in this way. Tiled roof and 
freestones (composing the foundations of that house) are 
elements of the same parent class and, in addition to their 
own feature, inherit the area criterion from their parent class. 
After rule development, a classification based on fuzzy logic 
is performed over the entire image, without any training 
sample. Fig.6 illustrates the resulting classification. 
Figure 6. First result of the rule based classification 
Fig.3 sums up all experiments and results. Obviously, 
although the last classification provides the best results, it 
needs to be improved by refining the membership rules. 
Considering the last set of rules, other photographs are used 
for testing the reliability of the formalisation. Fig 7 shows a 
lot of correspondences, but also raises new problems which 
will help us to refine the initial set of rules by further 
investigations. 
Figure 7. Same set of rules directly applied on other 
datasets. 
4. CONCLUSION AND OUTLOOK 
Conventional classification techniques are not anymore 
accurate for high resolution imagery. Trying to extract 
information automatically from these images, one is 
confronted to the difficulty to formalise human knowledge. 
Nevertheless, interpretation of this knowledge allows to 
sustain a set of rules describing different elements of interest. 
Thereby, once the rules are established, they might enable 
further automatic classifications of other half-timbered 
Alsatian façades and help supplying architectural information 
systems. 
References 
Baatz M.& A. Schäpe (2000): Multiresolution Segmentation: 
an optimisation approach for high quality multi-scale image 
segmentation. In: Strobl, J.&T. Blaschke (Hrsg) : 
Angewandte Geographische Informationsverarbeitung XII. 
Beiträge zum AGIT-Symposium Salzburg 2000. 
Bianchin, A. & Barvin, L. (2003) : Land use in urban context 
from IKONOS image : a case study. The International 
Archives of the Photogrammetry, Remote Sensing and 
Spatial Information Sciences, Vol.XXXIV-7, Regensburg, 
Germany, 27-29 June 2003. 
Buck, A., De Kok R., Schneider, T., Ammer, U, (2000) : 
Integration von Fernerkundung und GIS zur Beobachtung 
und Inventur von Schutzwäldern in de Bayerischen Alpen, 
In: Strobl, J.&T. Blaschke (Hrsg) : Angewandte 
Geographische Informationsverarbeitung XII. Beiträge zum 
AGIT-Symposium Salzburg 2000. 
Kauffmann, M. (2002): Facade Interpretation for Damage 
Detection, In: PCV02 Photogrammetric Computer Vision - 
ISPRS Comission III - Symposium Graz 2002. 
Lang, S., Schöpfer, E., Blaschke, T. (2003): Object-specific 
change based on assisted feature extraction : a case study of 
an expanding suburban area. The International Archives of 
the Photogrammetry, Remote Sensing and Spatial 
Information Sciences, Vol.XXXIV-7, Regensburg, Germany, 
27-29 June 2003.