further 
nts them 
y image 
velength, 
ontaining 
mage. 
r simple 
jects and 
ration of 
nsor into 
data, and 
lying all 
inversion 
sensor's 
? System. 
em based 
tion and 
ints with 
ition and 
ct to the 
) models 
out any 
least 4 
d. LPM- 
jentation 
zes. 
with the 
ved the 
1e and is 
by pairs 
ilcareous 
ave held 
g stumps 
normous 
ach one 
s with a 
| named 
trimonio 
tettonica 
1 by one 
ut 48 m 
h of 20 
think of 
“hurch is 
lding was 
caused by 
' different 
rnished it 
Jeside the 
icade was 
1775, it 
urned out 
lete it. In 
numental 
financial 
representation. As a matter of fact, since we had a previous 
survey of the facade realized with the photogrammetric method, 
it has been useful to verify and test their accuracy. 
  
Fig. 1 - Main facade of S. Nicoló's Church in Catania. 
The same procedure has been followed to scan the inner circular 
courtyard of Convitto Cutelli in Catania. Till recent years it was 
attributed to G. B. Vaccarini but nowadays ultimate studies 
have pointed out F. Battaglia's authorship. The courtyard is 
made up of three floors: downstairs, some tuscan columns, 
flanked by round arches, support the architrave; upstairs, the 
different rooms, pillars and crowning parts are connected by a 
continuous balcony; finally the attic crowns the whole 
courtyard and presents geometrical and classical patterns. The 
openings are framed by pilaster strips ending with geometric 
capitals. 
  
Fig. 2 - Inner circular courtyard of Convitto Cutelli in Catania. 
The possibility of surveying the above-mentioned architectural 
organism by scanning it has become the ideal solution to a 
problem that, as architectural surveyors, we had been facing for 
a long time. This is what it was about: the representation of 
buildings with central plan, whose elevation outline is strictly 
3D and is not representable by the traditional orthogonal views, 
such as facades and cross-sections. 
As a matter of fact, the traditional drawing that represents an 
architectural object is a plan configuration, that risks to be 
confused and extremely complicated if the object parts are not 
plane, so that it is necessary to reproduce it in a 3D perspective. 
  
Fig. 3 - Point clouds of Cutelli's courtyard. 
To acquire the whole geometry of the courtyard, we needed to 
perform two scansions. We used some reflecting marks (4), 
putting them in very visible points In order to connect this 
scansions. 
The two load stations were at a distance of about 15 mt. In one 
hour work we have surveyed about 3781 95 points: scanner has 
been placed at about 20 m from the facade and we have set up 
an angular stepwidth of 8 Mgon, so that we have obtained a step 
of 2.5 cm. This result is better than the previous one and is 
suitable for the accuracy of the representations to a scale of 
1:50. 
At first point clouds have been converted in a DXF format and 
after in a DWG one, in order to be processed successively. The 
aim was to extract profiles, plans, cross-sections so that we 
could reconstruct the 3D geometry and the texture of the 
circular courtyard. 
After some months, we had the chance to use a new 3D laser 
scanner type: LPM 25HA. It provides unprecedented flexibility 
for 3D measurement, inspection and modeling. Options include 
hemispheric scanning, automated or manual operation, 
reflectorless ranges to 60 metres, accuracy in the millimetres 
and a comprehensive 3D data acquisition software package 
operable from a laptop PC. 
Without the use of a retroreflector, the LPM-25HA calculates 
the distance to the surface in question, based upon the time-of- 
flight measurement of a short laser pulse. The point of impact of 
the measuring infrared laser beam can be observed, if desired, 
by the red beampointer laser. The pan & tilt mount serves to 
position the measuring beam automatically by integrated 
stepper motors with an accuracy of 0.009 degrees. Handwheels 
for manual operation are provided, too. 
=291