• Colonna del Tempio di Hera-Lacinia, Crotone (Italy): 
Greek Doric column of the last of 48 columns supporting 
the temple of Hera Lacinia (500-475 BC). Of the whole 
structure, sacked and damaged by the 1683 earthquake, 
there remains a single degraded limestone column with its 
capital halved. The survey results are used for 
documentation purposes and to compare laser range 
scanning with traditional photogrammetric techniques. 
• Nuraghe Iloi, Sardegna (Italy): The nuraghe lloy is a 
complex archaeological building about five metres tall and 
consisting of a tower of conical shape, built with layers of 
enormous boulders without the use of malt cement. The 
survey results are used for documentation purposes, 
structural condition studies and visualization. 
• Hamburg City Centre: This survey was done in the 
context of city modelling and includes 50 scans covering 
several streets in the city centre of Hamburg. It shows that 
laser range scanning allows to quickly acquire detailed 3D 
information of entire streets and even cities. However, it 
also shows that for this kind of application the processing 
software needs to be highly automated and needs to support 
a sophisticated management of the huge amount of acquired 
data. 
Table 1: A list sample objects specifying their type, the 
acquisition hardware used for the survey and the time 
required for acquisition and processing. 
Surveyed 
object 
Sagrestia 
Archivio 
di Stato 
Ex Hotel 
Colombi 
a 
Colonna 
di Hera 
Lacinia 
Nuraghe 
Iloi 
Hambur 
g 
Geometry 
Inside 
Inside 
Outside 
Outside 
Outside 
Laser 
scanner 
Cyrax 
Callidus 
Cyrax 
Riegl 
LPM-HA 
Riegl 
Z360 
N scans 
15 
4 
11 
2 
20 
Type 2D 
camera 
Digital 
Digital 
and 
analog 
Digital 
and 
analog 
Digital 
/ 
N images 
15 
30 
12 
2 
/ 
Time 
acquisition 
(hours) 
8 
12 
8 
8 
8 
Time data 
processing 
(days) 
4 
6 
4 
2 
4 
The diversity of the presented objects shows the versatility of 
lasers scanning in the field of architecture and Cultural 
Heritage. The final 3D models are used for different scopes, 
confirming the importance of this technology for conservation, 
maintenance and presentation of Cultural Heritage 
3. DATA ACQUISITION 
The software described in section 4 allows mapping external 2D 
images on the 3D mesh, which is reconstructed from the raw 3D 
data. Therefore, data acquisition not only refers to object 
scanning but also includes the acquisition of the 2D images. It is 
also possible (although not necessary) to acquire a set of 
external reference points for geo-referencing. Table 1 lists 
details of the data acquisition (i.e. type of scanner, time of 
acquisition) for each of the sample objects. The remainder of 
this section lists some of the lessons we learned during 
acquiring and processing the data and could serve as a small 
guideline for future scanning sessions. 
3.1 3D acquisition 
Usually it requires several scans to cover the entire object and 
resolve all the occlusions and shadows. The main points to 
consider are: 
• Occlusion and shadows: the scanning position should be 
planned carefully to avoid missing data. Holes and 
occlusion become particularly evident if the data will be 
triangulated in a later stage. It is useful if the software 
gives the possibility to register the acquired scans in situ so 
that holes and occlusion can immediately be detected and 
resolved. 
• Angle of acquisition: the precision of the 3D measurement 
acquired with the laser scanner decreases with the 
acquisition angle. A shallow angle also produces a low 
measurement resolution on the object. To increase the 
quality of the final model the acquisition direction should 
be as perpendicular to the object surface as possible. For 
example, the distance between viewpoints along a façade 
should not be too long. 
• Overlap between scans: especially feature-based and 
point-based registration (see section 4.2.2 and 4.2.3) 
require sufficient overlap between scans. For example, the 
ICP registration requires about 30% overlap, which also 
needs to have some geometrical information in all 3 
dimensions (i.e. the overlapping points should not lay on a 
single plane). If possible, it is useful to acquire one or more 
reference scans at low resolution, which cover as much of 
the object as possible and which are then used to register 
the detailed scans. 
• Uniform scan resolution: scanner viewpoints and 
resolution settings should be chosen to yield a fairly 
uniform resolution on the object in order to obtain a final 
3D model with homogeneous geometrical properties. 
• Documenting the acquisition: Especially if the scan are 
not registered on the fly, it is important to take note of the 
data acquisition scheme both for laser scanner viewpoints 
and the acquisition points of the 2D images, otherwise a lot 
time might be spent assigning the different scan and 
images to each other. 
3.2 2D images acquisition 
The 2D data usually is acquired with an uncalibrated standard 
digital camera. However, it is also possible to use calibrated 
photogrammetric cameras to increase accuracy or a different 
wavelength (e.g. infra-red) for special applications. 
• High quality pictures: the images acquired with the 
camera are directly mapped onto the 3D model; therefore 
better images will directly result in a better final result. 
Special care must be taken to avoid reflections and 
shadows and to minimise the difference in exposure 
between images. Even though image balancing is part of 
data processing (see section 4.5.2), most of the balancing 
problems should be avoided during the acquisition phase. 
For inside acquisition the use of artificial light can help to 
avoid shadows. For outside acquisition, the weather during 
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