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MULTISCALE ARCHAEOLOGICAL SURVEY BASED ON THE 
INTEGRATION OF 3D SCANNING AND PHOTOGRAMMETRY 
G. Guidi 3 *, 
G. Tucci b , J-A. Beraldin c , S. Ciofi 3 , V. Damato 3 , D. Ostuni d , F. Costantino“ and S. F. El Hakim c 
a Dept, of Electronics and Telecomm., University of Florence, Via S. Marta, 3 - 50139, Florence, Italy 
b Dept, of Scienze e Tecniche per i Processi di Insediamento, Politecnic of Turin, Castello del Valentino Viale Pier Andrea 
Mattioli,39 10125 Turin, Italy 
c NRC Canada, Institute for Information Technology, Bldg. M-50, Montreal Road, Ottawa, ON, K1A 0R6, Canada 
d Dept, of Civil Engineering, University of Florence, Via S. Marta, 3 - 50139, Florence, Italy 
Commission V, WG VI 
KEY WORDS: 3D Scanning, Photogrammetry, Sensor fusion, Multiscale survey 
ABSTRACT: 
The survey intended as non-invasive diagnostic investigation, has reached an significant level of evolution, but in order to be 
effective it should own two fundamental features: rapid acquisition and completeness of data. In such way the status of a particular 
site can be reliably identified, indicating possible pathologies or complex situations, allowing to predict their evolution in time. 
In our case study both aspects had to be respected because the site is inside a religious place, so that all the measurement sessions had 
to be constrained into a well defined time frame, and the diagnostics is simultaneously influenced by an area of soft ground 
influencing the global planarity of the whole roof, and a set of local alterations in the mosaic structure, due to the consequential 
tension. 
1. INTRODUCTION 
Surveying Cultural Heritage involves measurement at different 
possible scale. Wide range measurements as those based on 
Topography or Photogrammetry can be suitable for large 
buildings while for complex surfaces or small objects 3D 
scanning techniques seems more appropriate. In most cases the 
simultaneous presence of different scales in the same survey 
makes useful a possible integration of different levels of detail. 
In an archaeological site where objects with complex surfaces, 
as a piece of mosaic work, have to be accurately measured, it is 
also necessary to measure the structure containing them, where 
it is important to know other information, as the alignment 
between walls, or the planarity of the floor, not needing the 
same level of detail. 
The same aspect emerges in 3D modeling of sculptures, that has 
been explored for application in monitoring, digital moulding, 
multimedia fruition or even rapid prototyping. Also in this case, 
it might be necessary to include the 3D model of a statue in a 
virtual environment as a room or a reproduction of the original 
environment, not needing the high resolution required for the 
sculpture. 
In all these applications a multiscale survey, where the 
information density is correlated with the importance or formal 
complexity of the artwork to be measured, seems to be the ideal 
solution. 
In order to obtain such result a possible approach is represented 
by the fusion of different sensors, as range cameras, based on 
both Triangulation or Time of Flight (TOF) principle, 
Photogrammetry and Topography, each of them capable to 
satisfy complementary survey needs (El-Hakim et al., 1998). 
The study shown in this paper describes the application of the 
aforementioned approach for the study of an archaeological area 
located in the underground of Santa Maria del Fiore Baptistery 
(Florence), containing an ancient mosaic of the roman period, in 
bad conservation conditions. 
2. TECHNICAL BACKGROUND 
Nowadays many instruments for 3D optical scanning are 
available, based on optical triangulation or on time-of-flight 
(TOF). Recent technologies for digital tridimensional 
acquisition have opened innovative applications for the 
conservation, reproduction, study and fruition of sculptural, 
architectural and archeological artworks (Abouaf, 1999; 
Beraldin et al., 1997; Beraldin et al., 1998; Beraldin et al., 2000; 
Bernardini et al., 2002; Guidi et al., 2001; Levoy et al., 2000). 
2.1 Triangulation based 3D scanning 
The most diffused systems for creating a digitized 3D image of 
an object within a limited range (within some meters) are based 
on optical triangulation. A Laser, by means of a rotating mirror, 
forms a light stripe scanning the object, and a camera collects 
the image of the illuminated area. The range information is 
retrieved on the basis of the system geometry. An alternative 
technique is based on the projection of patterns of structured 
light (Sansoni et al., 1994), i.e. a light pattem coded as spots or 
stripes. Both techniques generate a cloud of points that, after 
suitable processing, allow to generate a tridimensional model of 
the object. The systems based on optical triangulation are the 
most accurate, allowing measurement uncertainty lower than 
one tenth of millimeter. Such uncertainty, however, depends 
* Corresponding author. E-mail: g.guidi@ieee.org