Moreover, scanning speed allows you to survey a quite large 
object in a few minutes: it results in a “cloud of points”, whose 
spatial co-ordinates are stored into files. From this cloud, we 
can extract the polygonal model and subsequently the poly- 
mesh one, which the virtual model of the object derives from. 
According to the object’s shape — projections, overhangs, 
columns, bases, pilaster strips, not supporting pilaster strips 
concerning buildings; conformation of faces, body position, 
drapes, etc. regarding statues — we can't conjecture the survey 
of all points, by a single scan. Laser ray notes the distance 
among the points that it recognizes during its rectilinear course. 
Therefore, with respect to not plane objects, we need multiple 
scans taken from different points so as to load all the surveying 
parts. 
To assemble two or more scans, we use some fiducial marks 
placed so that they may be seen in the next scan. Thanks to 
these marks, we can connect the first scan to the following one 
so as to unify the co-ordinate system. 
What we obtain is a 3D survey representing a digital space 
model that the scholar can “manage” as he wishes. Straight 
after, he can analyze the model and watch it from each 
perspective; he will be able to *go deeply" into the smallest 
morphologic details and virtually work at the object before 
settling the operations (i.e. restoration). 
Laser scanners can be divided into two typologies: the first one 
which is used for short distances, and the second one which 
works at a distance of several ten metres. The former centainly 
gives a better definition than the latter, even if its sphere of 
action is fairly small. 
However, survey quality is always at the highest point. The 
precision of these scanners varies between 3 and 20 millimetres 
for a “wide” surveying mesh (which is used for big architectural 
works) , whereas it varies of about some millimetres for more 
exact scans. Scanning times can’t be compared to the traditional 
and photogrammetric survey ones. We need only a few minutes 
to survey bigger objects, instead of traditional methods’ days or 
months. Lastly, if we link together images (photographic ones 
or images in RGB format) and colorimetrical analysis which are 
leaded through computer instruments, we can reach the whole 
digital “representation”. Thanks to the latter and to subsequent 
researches, it is possible respectively to recognize and schedule 
the restoration parts and cycles. 
Scanning system utilisation is more and more urged by research 
agencies, Universities, CNR (National Research Council), local 
agencies, so that producers compete with each other to 
introduce solutions of different typology. 
1. PRACTICAL APPLICATIONS 
Here in Catania we are working on a large scale project that 
aims at the acquisition of 3D data to create virtual architectural 
models. Various scanning experiences with Laser Scanner 3D 
are part of this framework. 
At first, we used the Laser Scanner LMS-Z210, whose range 
finder electronics is optimized in order to meet the requirements 
of high speed scanning performance. 
The fast angular deflection ("line scan") of the laser beam is 
realized by a rotating polygon which provides an unidirectional 
scan within an angle of e — 80?. The slow scan ("frame scan") is 
provided by rotating the complete optical head up to 333?. 
The acquired data through laser scanner are discharged into a 
laptop by means of the LPM-SCAN software, provided with 
laser scanner. 
This software allows the operator of the 3D imaging sensor to 
perform a large number of tasks including sensor configuration, 
data acquisition, visualization, manipulation, and archiving. 
During on-line data acquisition LPM-SCAN stores data 
intermediately in memory, optionally logs to file and extracts 
images for immediate on-line visualization and further 
processing from the data stream. 
Extracted from the binary data LPM-SCAN represents them 
primarily as color-encoded range image, as intensity image 
showing the reflectivity of the objects at the laser wavelength, 
and as combined range and intensity image. Data containing 
true colour information can also be visualised as colour image. 
These images provide an easy-to-use interface for simple 
measurement tasks as, e.g, distance between two objeds and 
allow data selection for further processing or configuration of 
the 3D sensor in the on-line mode. 
LPM-SCAN converts binary data of the 3D imaging sensor into 
polar co-ordinates, Cartesian co-ordinates, reflectivity data, and 
true colour data (if they are provided by sensor) by applying all 
required decoding procedures and transformations. Conversion 
into Cartesian co-ordinates takes into account the sensor's 
position and its orientation in a pre-defined co-ordinate system. 
The 3D data can be registered into this co-ordinate system based 
on various methods, e.g. by determining the position and 
orientation of the sensor from identified reference points with 
known co-ordinates. Thus it is not necessary to position and 
align the 3D sensor before data acquisition with respect to the 
desired co-ordinate system. 
Merging of several 3D data sets allow generating 3D models 
which can be virtually viewed from all sides without any 
occlusions. Data merging is based on identifying at least 4 
points/objects in two 3D images which are to be merged. LPM- 
SCAN then automatically calculates the position and orientation 
data of the sensor during acquisition for the two 3D images. 
«kk 
In May 2001, different scanning tests were performed with the 
collaboration of Nikon Instruments: the first one involved the 
main facade of S. Nicoló's Church in Catania. 
It is a grand monument which is covered with limestone and is 
made up of two levels enclosed by a giant order formed by pairs 
of pilaster strips. These ones are hidden behind four calcareous 
columns that, according to the original design, should have held 
up a pediment populated by some statues, only some big stumps 
of which have been built, that are placed on enormous 
basemerts . 
At the first level, we can see three portals 
corresponding to the nave and the two aisles. 
The upper level is characterised by three big windows with a 
stone balustrate. 
This scanning work is part of a research project named 
CLUSTER 29, “Il recupero e la valorizzazione del patrimonio 
architettonico della Sicilia orientale: l'emergenza architettonica 
urbana e l'edilizia rurale", WP1 — A2. 
In one hour work, about 52600 points have been taken by one 
scansion. Scanner has been placed at a distance of about 48 m 
from the fagade and, setting up an angular stepwidth of 20 
Mgon, we have obtained a step of 15 cm. We cannot think of 
this result as a suitable one in the architectural scale. 
each one 
  
Thanks to its remarkable size, S. Nicold l'Arena's Church is 
considered the largest religious monument in Sidly. The building was 
begun in 1687 by Contini who designed it. After the damages caused by 
1669 eruption, it has been rearranged and accomplished by diffèrent 
architects among whom F. Battaglia and S. Ittar. The latter furnished it 
with a dome, 62 m high. The church inside is 105 m long. Beside the 
aisles, we find six semicircular chapels with balustrade. The façade was 
begun by the Amato's, but the building was interrupted. In 1775, it 
became the object of a competition far a new design that turned out 
badly. Finally, C. Battaglia Santangelo was charged to complete it. In 
1796 he signed, on the central window, this ambitious and monumental 
work that has never been realized, because of technical and financial 
difficulties. 
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