Integration of Digital Photogrammetry and Caad: Constraint-based Modelling and Semi-automatic Measurement

The integration of state-of-the-art photogrammetric methods with the capabilities of CAAD has great potential for a variety of architectural applications. This paper describes the current status of an ongoing research project which aims to develop an easy to use tool for the photogrammetric generation of accurate, reliable and well structured 3D CAAD models of architectural objects. The system essentially consists of a standard CAAD package to which additional functionality was added and a Digital Photogrammetry Station (DIPS), providing semi-automatic computer measurement. The paper concentrates on two main issues in the design of the system: the data-integration and the caad-based 3D feature extraction. The data-integration is achieved using a knowledge-base. On top of an adequate data-transfer between the two systems this knowledge-base enables constraint-based modelling in CAAD and qualitatively controlled measurement in DIPS. In the section about Digital Photogrammetry we describe the 3D feature extraction procedure in detail and point out how the qualitative control can be achieved. A practical example is used to illustrate the performance of the system.