CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey 
tions. A logistical support from the tows St.-Amand-sur-Ornain 
and Naix-aux-Forges helped these meetings. 
The multidisciplinary character of this research put the archae 
ologists in a situation where they could benefit from contribu 
tions of the data processing in their work of reconstitution and 
allowed the researchers to ask themselves about the content and 
the purpose of the computer generated images of the monument 
that they could offer. 
2. THE 3D LASER SCANNER, A MEASURING TOOL 
APPLIED TO ARCHEOLOGY AND VANISHED 
ARCHITECTURE, 
The MAP-CRAI is equipped since 1997 with a laser scanner 
SOISIC designed by the company MENSI . The acquisition 
chain of the laser goes from the sensor to the a posteriori 
software processing of the collected data (3D IPSOS software). 
From the beginning, the main feature of this device was to 
verify measures in industrial environment. Later, other 
applications have been considered: huge shape control 
measurements, large scene capture, plane airframes, ship hulls, 
archaeological and patrimonial cultural heritage, virtual reality, 
models, moulds, etc. 
The MAP-CRAI was more specifically interested in architecture 
and archaeology. This results in multiple adaptations, either at 
data acquisition time, or at data processing time. 
2.1 Laser working principle 
2.1.1 Remote sensing 
The "Soisic" scanner is based on the principle of laser plane 
triangulation. It is made of a sensor (SOISIC), and a 
consolidation and modelling software (3DIPSOS). The sensor 
uses a 2,5 mW power laser beam driven by a mobile mirror. 
The image of the laser spot on the measured object is captured 
by a CCD camera. 
Driven by a PC, this sensor can collect the 3D coordinates of 
the laser spot, at the rate of about 100 points per second. 
The operator defines the data capture area and selects the mesh 
density according to the scale and the measured object nature. 
During the laser measure, a camcorder records views of the 
stage, used then to be mapped on the 3D model. 
This acquisition system presents many advantages among which 
its weight (14 kg), which makes it very handy and its capacity 
to scan surfaces of very diverse aspects (black rubber, stainless 
steel, etc.). In its principle, the measurement by scanner 
increases greatly the precision that one could get with more 
traditional techniques. 
The points clouds (sets of 3D points) are progressively stored in 
files, every point of view on an object being made of the sub- 
points of view corresponding to the reference spheres and the 
different shootings made on this object. The position of the 
scanner in relation to the object, the precision of the points’ 
capture, and the complementarity of the points of view are 
therefore the factors that contribute to a better ulterior 
exploitation of the date file. 
Files results are then transferred to the workstation in order to 
process the data. 
2.1.2 The data processing - funding and modelling: 
The data processing takes place with the help of the 3D Ipsos 
software that allows toimport of the raw Soisic format files. The 
first stage consists in "strengthening" the various clouds of 
points, ie to make all the sub-points of view fit into the same 
general Cartesian mark. Reference sphere placed judiciously 
around the measured object during the phase of acquirement al 
low a partial automation of this stage, allowing to save a great 
amount of time. These spheres form a mark for every sub-point 
of view. Given that every sub-point of view contains a mini 
mum of 3 reference spheres in common with the other sub- 
points of view, the software allows a global reorganization of 
the points clouds. 
The modelling itself constitutes the second stage: based on the 
points clouds data consolidated in the same system of 
reference, the objective is to rebuild a 3D model, with the help 
of simple geometric primitive or of elementary surfaces that 
match the clouds as close as possible. The choice of a global 
reconstruction of the object or a semiautomatic meshing 
depends obviously on the nature of the object to be modelled: 
the statuary is in general well handled by a mesh while some 
architectural or industrial elements should rather be rebuilt 
based on geometric primitives. This conversion of primitive 
shapes and elementary surfaces in DXF standard files format 
allows a further exploitation of the rebuilt model in all other 
software accepting this format. 
2.2 The realizations and their specific problematic 
We performed laser scans and recreated the 3D models in order 
to produce computer generated images, simulate illuminations, 
digitally archive data and to allow the archaeological investiga 
tions : 
■ At the time of the Marmaria site reconstitution in Del- 
phes, several objectives were pursued: test the hypotheses 
concerning the roofing shapes of the buildings according 
to the tiles shapes and valley gutter, determinate the way 
the temples’ doors open according to the door casing 
morphology, virtually analyze some blocks and acroter 
statuary. [CG25] [DD38] [LAR92] [ROU52], 
■ The scan of the Pont Marie bridge in Paris served as ba 
sis for its three-dimensional map-less modelling and as 
support of an illumination simulation. 
■ The capture of the Pont Neuf bridge and the Vert Galant 
park also allowed the representation of an illumination 
project including the statuary and the vegetation of the 
park. 
■ The Capitol of Dougga (Tunisia) reconstruction as it had 
been achieved in 166 b.c. gave place to the setting up of a 
knowledge and information integration method in the re 
construction/modelling/representation chain by leaning on 
photo-modelling techniques. 
■ At the Notre Dame Cathedral in Strasbourg, different 
measured drawings of the statuary and complex architec 
tonic elements (capitals, moulding proportions and profile, 
blocks...) allowed to continue and to complete the restora 
tion chain computerization (computer aided stone cutting 
based on the measure of original blocks) within the work 
shop in charge of this building maintenance. 
2.3 Research developments and problematic 
The functionalities of the 3D IPSOS software not being all 
adapted to the reconstruction / modelling of architectural 
objects, we developed a set of routines permitting to quickly 
generate solids by profile extrusion or by revolution. 
Some researches are in progress concerning the automated 
recognition of architectural objects in point clouds.