406 
Weferling 
a) Photogrammetric image bundle 
provided by photogrammetrists 
b) Photogrammetric evaluation system for the evaluation 
done by architects 
Figure 7: Concept of a dense geometric reference system realised by a photogrammetric image bundle 
The second possibility to realise a geometric frame is the use of modem photogrammetric methods where the orientated 
photogrammetric model provides the reference-system (fig. 7a). When the position and orientation as well as the inner orientation of 
the photogrammetric images are computed in a bundle adjustment the photogrammetric images are representing a very precise 
reference system in which all building related evaluation can take place (fig. 7b). Today there are easy handling digital 
photogrammetric evaluation software packages on the market that provide single-image evaluation as well as multi-image and 
stereoscopic evaluation. The integration of digital photogrammetric systems in conventional CAD-Systems facilitates the easy use by 
architects or archaeologist. 
Digital rectification is also a well established method to provide a geometric reference system. To guarantee a high geometric quality 
the used geometric reference figure have to correspond with the actual object shape. Especially irregular differences from the actual 
shape to the mathematical one have to be considered during the evaluation process. 
For all these evaluation strategies a second revision of the object model in front of the real object is essential for the model quality 
under architectural, archaeological, historic, constructive or conservation aspects. 
5. FINAL CONCLUSIONS 
Finally some aspects should be discussed which follow from the consequent consideration of the modelling theory. Following the 
modelling theory one central demand for a successful modelling process is to define the modelling purpose. The definition of the 
modelling purpose has to be done under the needs of specific disciplines related to the modelling process. Only with the specialised 
knowledge in architecture, archeology, conservation or other disciplines a high quality object model can be build up. Because of the 
interaction between geometric and specialised evaluation a geometric documentation of historic objects without this specialised 
knowledge could be without any use for further investigation. 
This conclusion is very important to understand the problems in the co-operation between geodesists and photogrammetrists on the 
one site and architects, archaeologists and historians on the other. This problems shall be illustrated with the following two examples: 
The first one is related to the sometimes from photogrammetrists suggested photogrammetric image archives. Because of the missing 
investigation purpose the precautionary mass documentation of historic buildings by photogrammetric images is not so important for 
the historic disciplines. Photogrammetric mass documentation can only provide a geometric image model of the main object features. 
This information could be relevant for the building classification but surely not for historic investigation purposes. And for the 
historic classification a non metric image is normally sufficient. 
The second one can be observed very often in the daily conservation practise. In many conservation projects only modem surveying 
and documentation methods are isolated used with the result of a regular and high generalised object model. This models may be 
sufficient for the performance of the documentation duty but surely not sufficient under historical aspects. 
For us as surveyors or photogrammetrists it could not be the aim to produce geometric models in a short time with low costs but in a 
poor quality. We should integrate our geometric measurements into the specialised evaluation process to refine the geometric 
measurements to high quality object models. Only with an interdisciplinary understanding of heritage recording the challenge in 
surveying and documentation of historic buildings, monuments and sites will be managed. 
REFERENCES 
Stachowiak, H.: Erkenntnisstufen zum Systematischen Neopragmatismus und zur Allgemeinen Modelltheorie. In: Stachowiak, FI. 
(Ed.): Modelle - Konstruktionen der Wirklichkeit. Miinchen, 1983, pp. 87-146.