LAYERED GEOMETRIC INFORMATION SYSTEM 
Pierre Smars 
Dept of Architecture & Civil Engineering, University of Bath 
Bath BA2 7AY, United Kingdom 
Phone: +44-1225-826654, E-mail: absps@bath.ac.uk 
Koen van Balen, Kris Nuyts 
Raymond Lemaire Centre for Conservation, K.U.Leuven 
Kasteelpark Arenberg 1, B-3001 Heverlee, Belgium 
Phone: +32-16-321687, E-mail: koenraad.vanbalen@bwk.kuleuven.ac.be 
KEYWORDS: Cultural Heritage, Database, Management, Augmented Models, Reconstruction, Visualisation 
ABSTRACT 
Virterf is a software combining recent developments in computer vision and reverse engineering targeted for professionals working in 
the field of architectural conservation. The first part of the software aims at building relatively automatically a 3D model. In this 
article, focus is given to the second part, offering tools to qualify and query it. Information can be added, organised in themes or 
linked to the model. The resulting database with the software’s visualisation capacities facilitates comparison, synthesis and decision. 
Some reference concepts are first presented, the functionalities offered described and - following first applications - some possible 
development are discussed. 
1. INTRODUCTION 
1.1 The Virterf project 
From September 1999 to September 2001, a project called Virterf ran at the University of Leuven. It resulted from a collaboration 
between three departments of the University. The aim was to develop a "three-dimensional digital information system for the 
documentation, representation and conservation of our architectural heritage". 
The department of electrical engineering (ESAT) had experience in 3D reconstruction of scenes and developed a module to acquire 
geometrical data (points) from a set of images and reference points. 
The department of mechanical engineering (PMA) had experience in 'reverse engineering' and developed a module to mesh and 
optimise point clouds coming from the first module. 
The department of architecture (ASRO) had experience in the use of computers in conservation practice (Van Balen) and developed a 
module to visualize, enrich and query the model built with the first two modules. 
This paper will concentrate on this last contribution. The ones of ESAT and PMA are also presented in this symposium: 
J. Schouteden et al., Image-Based 3D Acquisition Tool for Architectural Conservation 
B. Lauwers et al., The Application of Reverse Engineering Technology in Model Reconstruction for Conservation 
1.2 Recording 
Heritage conservation is a complex activity. The study object is very often unique. It is certainly interesting to us for his peculiarities 
(Torsello). The survey (largo sensu) aims to recognize and record them (Feiffer). Every day new dimensions are considered. 
Specialists gather facts. These substantially analytical phases typically leads to some synthesis (interpretations or decisions). All 
aspects are interrelated. It is certainly interesting to organise the information in a common structure, to provide an integration tool. 
Heritage conservation is partly subjective. The differences of attitude according to country or period illustrate very well the cultural 
dimension. A specialist interprets facts. A decision-maker weights contradictory requirements. But it is also true, that every 
respectable school of thought wish to base opinion on objective bases (Torsello). The present interest for cultural heritage strengthens 
this exigency with respect to conservation practice. What is not often clear enough (intentionally or not) is the position of the 
demarcation line between objective and subjective information. It is certainly debatable and conventional, but piece of information 
have admittedly different level of objectivity and a better view on them would contribute to clarify the decision-chain. 
In the recording activity, the question of time is important to discuss. Antagonistic requirements weigh in. On one hand, faster 
surveying is desirable. Apart from the evident financial benefit, it can mean a lot indirectly: underprivileged context can be studied, 
new scale of problems tackled, and objects studied more in depth. The new techniques implied also may extend our vision on the 
reality. On the other hand, timesaving can be dangerous. A 'machine' delivering a complete model at the pressing of a button does not 
fulfil all the requirement of a proper survey. Surveying is a learning process. Time is necessary to understand. The user needs to 
assimilate the features recorded whatever the faithfulness of this recording. It is also clear that every aspect of surveying does not 
Proceedings 18 th International Symposium CIPA2001 
Potsdam (Germany), September 18 - 21, 2001