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Object segmentation in cultural heritage 
Leandro Bomaz(*), Fulvio Rinaudo (*), Marco Roggero (*) 
(*) Politecnico di Torino - Dipartimento di Georisorse e Territorio 
C.so Duca degli Abruzzi, 24- 10129 TORINO 
Tel.+39.011.564.7687/7659/ 0161226390 Fax.+39.011.564.7699 
E-mail: bornaz@polito.it; fulvio.rinaudo@polito.it; roggero@atlantic.polito.it: 
KEY WORDS: Remote sensing, Cultural heritage, Analysis, Close Range, Interpretation, Architectural Heritage, Laser scanning, 
Segmentation. 
ABSTRACTS: 
With the introduction of new terrestrial laser scanning technologies it is possible to obtain a “dense DTM” of any cultural heritage 
object in a very quickly and fast way. The 3D model acquired with laser devices represents a dense point cloud of the object. In the 
case of very complex 3D models it is not easy to manually directly derive a correct surface reproduction of the object from the model 
in a simple and correct way. 
A valid aid in the modelling of objects is the segmentation technique. This allows on different layers portions of point clouds that 
have similar geometric ownerships to be organised it. 
The following article shows the results of some segmentation techniques applied to the case of architectural survey. The advantages 
and the disadvantages of every methodology are put in evidence. 
1. INTRODUCTION 
1.1 Introduction 
Recently new instruments have been introduced in the field 
of surveying that are able to survey portions of land and 
objects of various shapes and sizes in a quick and cheap 
manner. These instruments, based on laser technology, are 
commonly known as laser scanners. 
Laser scanners can be considered as highly automated total 
stations. They are usually made up of a laser that has been 
optimised for high velocity surveying and of a set of 
mechanisms that allows the laser radius to be directed in 
space in a range that varies according to the instrument that is 
being used. 
The laser scanner therefore allows millions of points to be 
recorded in a short time. 
Because of their practicality and versatility, these kinds of 
instruments are today widely used in the field of 
archaeological surveying. 
1.2 Why segment? 
The digital models obtained from laser scanners are nothing 
more than dense point clouds (DDEM- Dense Digital 
Elevation Model). These point clouds are often remarkably 
complex. This occurs above all in the case of archaeological 
surveying of monuments and historical buildings in which 
there is a great variability of the structure. 
After having acquired any object with the laser technique, the 
usual aim is that of obtaining the greatest amount of 
geometric information from the model itself in the easiest and 
most automatic way. 
Research today is often dedicated to this new field and many 
treatment and management procedures of laser data have 
been developed. 
One of the stages in which it is necessary to do further 
research is modelling. By modelling we mean passing from a 
point model, as obtained with the laser sensors, to a surface 
model. It is in fact possible to automatically extract sections 
or level curves from the object, carry out numerical analysis 
or even integrate the model with digital images to create a 
coloured 3D model or to produce an orthophoto. 
Figure 1 - A DDEM obtained using a RIEGL LMS Z210 
laser scanner - Piazza San Marco- Venice - Italy 
The solid modelling is easily obtained if the model that has 
been surveyed with a lqser scanner has a simple geometry 
(for example, a bas-relief or a uniform façade without 
balconies or high parts protruding), but can become very