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AUTOMATIC DEM GENERATION USING DIGITAL SYSTEM InduSCAN: 
AN APPLICATION TO THE ARTWORKS OF MILANO CATHEDRAL 
FINALIZED TO REALIZE PHYSICAL MARBLE COPIES 
Marco Scaioni 
Politecnico di Milano, Dip. I.I.A.R. sez. Rilevamento 
p.za Leonardo da Vinci 32, 20133 MILANO (ITALY) 
Giorgio Vassena 
Università degli Studi di Brescia, Dip. di Ingegneria Civile 
v. Branze 38, 25123 BRESCIA (ITALY) 
Torsten Kludas, Jens-Uwe Pfeil 
Carl Zeiss Jena GmbH, D-07740 JENA (GERMANY) 
Commission V, Working Group 4 
KEY WORDS: Digital Object Reconstruction, Surface Statue Survey, Architecture, Reconstruction, 
DEM/DTM, Close-Range Photogrammetry, Cultural-Heritage, Automation 
ABSTRACT 
In this paper is presented a method to realize copies of sculptures using numerical control milling machines. 
The carving is obtained from the survey and D.E.M. reconstruction of their surfaces. The starting point for 
this study has been the need of the "Fabbrica del Duomo di Milano" to realize automatically copies of 
marble artworks which are decaying for the pollution. The most complex technical problems to realize such 
an automatic process are the precise object survey and its physical reproduction driving the tool of a 
numerical control machine. The first item has been carried on using the “photogrammetric industrial 
measurement system InduSCAN" by Zeiss Jena. The second problem has been solved transforming the 
D.E.M., from InduSCAN, in the path-tools of the milling machine. The physical execution of the copy has 
been made by BOVERE GRANITI (Italy). To verify the feasibility of the whole process, a survey of two 
sculptoral marble elements of the Cathedral has been realized and copies of some elements of these have 
been made. 
This study has defined a process able to reproduce in a semi-automatic way the statues of the Duomo. The 
work of the sculptors is so reduced to an indispensable finishing touch only. 
1. INTRODUCTION 
This paper deals with a project that is trying to save 
one of the most important monuments of the 
Northern part of Italy: the "Duomo di Milano". Due to 
the high value of the pollution present in the air of 
Milan, the marble decorations of the Cathedral are 
under a quick process of decay. At the moment, 
under the supervision of the chief-engineer of the 
"Fabbrica del Duomo", some sculptors spend their 
working-days making physical copies of the most 
damaged decorations and statues of the “Duomo”. 
The costs of this process are always higher and the 
number of elements that can be copied is very 
small. 
It is important to underline that the connotation of 
this copy-making are somewhat different from those 
of past ages, when they preeminently satisfied the 
interest of private collectors. Today the copy- 
making is mainly due to the acceleration of decay 
by environmental agents and to a more heedful 
attitude towards the conservation of the cultural 
heritage. 
581 
The aim of this paper is to present an innovative 
methodology to make marble copies of the main 
artworks present in the Cathedral. The innovation 
consists on an effort to create an almost completely 
automatic surveying and reproduction process. A 
description of the surveying and reproduction 
process are here presented. 
2. THE REPRODUCTION PROCESS 
A complete system suitable for the sculptures 
reproduction has to be composed by two moments: 
the survey, defining the objects surfaces D.E.M. 
and the physical reproduction using numerical 
control (N.C.) milling machines. 
A two steps process can permit to survey the 
artworks in their own position in the monument, 
while the marble copy can be made later in a 
suitable milling-workroom, so to avoid damaging the 
sculpture during the removing-works and before its 
survey. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996