Drap, Pierre 
  
The plotting module dedicated to architecture is based on a formalization of architectural and geometrical knowledge. 
The architectural corpus must be first identified and structured. Then the architectural knowledge is used to guide and 
control the building measuring process. This means that the morphology of the measured object is already known. This 
knowledge is provided by previous analysis of the measured structure, e.g. by the archaeological survey of an historical 
building. Building elements are described as "entities" (elementary elements) providing that they meet two 
requirements: 
> An entity is a unique " object " identified by a single element of the architectural vocabulary. 
> An entity has an obvious and permanent role in the physical structure of the building. 
The object-oriented programming approach enables to gather generic entities into hierarchies of elements sharing 
properties or common behaviors or attributes, each property added giving birth to a new, more specialized (lower in the 
hierarchy), generic element . 
In addition of architectural entities, the system is able to manipulate others concepts present in the architectural 
knowledge corpus used to describe the building, as ashlar block or topological relation between architectural elements. 
1.2 Two different point of view 
This paper focuses about the use of two different point of view on 
the architectural element to be measured : we consider an | Marco Polo describes a bridge, stone by stone. 
architectural entity (for example a wall or an arch) as a structural « But which is the stone that supports the 
element with its own function in the building and also as a set of | bridge? » Kublai Khan asks. 
different ashlar blocks. The goal is to obtain a complete | « The bridge is not supported by one stone or 
geometrical description of both the architectural entity and the set of | another, » Marco answers, « but by the line of the 
ashlar blocks using a partial measurement of the stone and the | CA that they form. » 
information, for each stone, of the architectural entity owner. Rook Khan remains silent, reflecting. Then he 
Each ashlar block morphology is here considered as a polyhedron | « Why do you speak to me of the stones? It is only 
with two parallel faces, in most of the cases only one face is visible, | the arch that matters to me. » 
sometime two, rarely three. The survey process can inform about | Polo answers: « Without stones there is no arch. » 
the dimensions of one face, then the entire polyhedron is computed 
according to the architectural entityS morphology (extrude vector) 
and the data provided by the archaeologist (depth, shape ... ). 
  
Italo Calvino, (Calvino, 93) 
  
  
  
Computing an extrude vector can be easy in the case where the architectural entity morphology is obvious; during a 
wall survey for example an extrude vector can be computed by a least square adjustment of a plane around the survey 
zone. In this case where the entityS geometrical properties are simple, the extrude vector is calculated before the survey 
phase and the block is extruded directly from the measured points. In the case of a round arch the extrude action should 
be radial and needs the geometrical features of the entity (intrados, radius, axis). 
In this case a post process computation is necessary to elaborate the main architectural entity’ features from the ashlar 
block’ measures. In order to achieve to obtain the whole block morphology it is often necessary to compute the 
architectural entity’ features. This can be done by specifying for each type of entity the relevant mathematical 
operation and the way to extract relevant points from the measured ashlar blocks. 
1.3 Using ARPENTEUR : a photogrammetric survey through Internet 
The ARPENTEUR photogrammetric approach is based on the well known routines (Kraus, 1997). The standard steps 
are developed : internal, relative and absolute orientation and since the version 1.4.2 a bundle bloc adjustment is 
available. 
ARPENTEUR is developed in JAVA, using actually JDK 1.1.8 and is operational from any hardware platform 
supporting a web browser using this level of Java. Presently the software is tested with Netscape TM Communicator 4.5 
on PC platform and SUN workstation. 
The ARPENTEUR software is client-server oriented and provides a way to transfer architectural measured objects on 
the server witch is able to generated report files and 3D CAD model survey interpretation. These generated files are 
available on the server thought a FTP transfer. 
2 THE CASE STUDY : “LA PRIORALE NOTRE-DAME DALEYRAC” 
Our case study is dedicated to the Romanesque priory church Notre-Dame d’Aleyrac, in northern Provence (France). 
The choice of this building is motivated as follows: the building, which has been studied recently by the co-author of 
  
188 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 
  
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