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OBJECT-ORIENTED DATA-INTEGRATION BETWEEN DIGITAL ARCHITECTURAL 
PHOTOGRAMMETRY AND CAAD 
Urs Hirschberg, Dipl. Arch. ETH 
Architecture and CAAD, 
Swiss Federal Institute of Technology, ETH Zürich, 
Switzerland 
KEYWORDS: Architecture, Automation, Knowledge-Base, CAD, Modeling 
ABSTRACT 
The integration of digital architectural photogrammetry with computer aided architectural design (CAAD) has 
great potential for a variety of architectural applications. While both, digital photogrammetry systems (DIPS) 
as well as CAAD programs essentially rely on point-coordinates in three Dimensions, their datastructures still 
differ significantly. So the data-integration becomes non-trivial, as soon as more than the most basic geometric 
information needs to be shared between the systems. This is necessary in semi-automated photogrammetry 
systems, where an object-oriented structure, similar (but not identical!) to the one found in todays CAAD 
systems, can provide qualitative guidance in the computer measurement. 
In this paper an approach to an object-oriented data-integration between a standard CAAD program and a 
DIPS is described. It was developed in the framework of an ongoing research project for which this 
integration is essential. The data-integration relies on the concept of a knowledge base, which enables an 
object-oriented structuring of geometric data suitable for photogrammetric evaluation. The knowledge-base 
can be shared between the CAAD system and the DIPS, thus enabling a very efficient run-time transfer of 
data. This run-time transfer between the systems, which is necessary for the modelling of approximations, is 
done by means of a specially developed transfer protocol. It could theoretically be used by any 3D-CAD 
package, not just the one used in the prototype implementation. 
1. THE PROJECT DIPAD mentioned commercial packages do). Most 
importantly it takes advantage of the digital format 
of the data to increasingly automatize the time- 
consuming measurement process. 
The Integration of Computer Aided Architectural In this paper the main focus will be on the 
Design (CAAD) and digital photogrammetry has long integration of the datastructures of the employed 
been recognized as a powerful technology. Its digital photogrammetry system (DIPS) and a standard 
possible applications range from the documentation CAAD-system. For the semi-automatic measurement 
of historical monuments to the generation of digital techniques employed in our DIPS, the point and 
town models and virtual reality environments. line-based data-structures traditionally found in 
The commercial programs for architectural digital photogrammetry systems are inadequate. 
photogrammetry available on the market today are We will argue in this paper, that the data-integration 
restricted to manual measurement [1][2]. Therefore with CAAD, or in fact the introduction of any object- 
the accuracy of the delivered data largely depends structure with semantic implications in the DIPS, is 
on the dexterity of the operator. On top of that the the prerequisit for a qualitative control and for an 
application of these programs is usually quite time- increasing automation of the photogrammetric 
intensive and requires special training. These processing. 
shortcomings may account for the fact that these 
programs are still rather rarely made use of in the 1.2 Principles of DIPAD 
architectural practice. 
The system for digital photogrammetry and The research environment DIPAD aims to develop 
architectural design (DIPAD) currently under an easy to use tool for the photogrammetric 
1.1 Introduction 
development at the Swiss Federal Institute of generation of accurate, reliable and well structured 
Technology aims to overcome these shortcomings. 3D CAAD models of architectural objects. 
The system not only transfers traditional The system essentially consists of a DIPS and a 
photogrammetric techniques which usually involved standard CAAD program with a true programming 
very expensive mechanical equipment to a interface (AutoCAD). With the combination of these 
computer-terminal (which is, essentially, what the two systems, a model-based approach is pursued. The 
237 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996