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Title
New perspectives to save cultural heritage
Author
Altan, M. Orhan

CIP A 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
518
In applications which require recording of large objects, usually
the integrated or combined use of laser scanning with
photogrammetric methods can give better results than the sole
implementation of each one technique. This paper discusses the
combined use of photogrammetric and laser scanning methods
for the creation of an accurate 3D solid model of a complex
large statue. The ancient statue made by Praxiteles presents the
mythical god Hermes and is housed in the archaeological
museum in Ancient Olympia in Greece (Figure 1). Data
collection and processing aspects for each methodology are
described and results are given to highlight the advantages that
are available to end users through the combined use of the two
technologies.
2. THE HERMES OF PRAXITELES PROJECT
The main objective of the “Hermes Project”, which was funded
by the Hellenic Ministry of Culture, was the construction of a
seismic isolation retrofitting assembly for the statue. This is
because the region whereby the archaeological museum of
Ancient Olympia is located and houses the statue, is subject to
high seismic activity. The assembly is designed to minimize the
ground accelerations and to nullify the possibility of causing
damage to the statue due to any possible earthquakes. For this
purpose, an accurate 3D model of the statue was required. The
project was commissioned to a team of researchers from the
Schools of Civil Engineering and Rural and Surveying
Engineering of the National Technical University of Athens, in
Greece.
The Hermes statue is considered a masterpiece of sculpture art
of the classic antiquity era. It is dated circa 343 BC and is made
of Parian marble. It is believed to be the only original work still
existing by the famous sculpture Praxiteles. The statue was
dedicated to the sacred Altis from the Eleians and the Arcadians
to commemorate their peace treaty. The statue shows Hermes
holding in his left arm the infant Dionysos while in his raised
right hand he probably held a bunch of grapes. Hermes looks
sluggish but manly, resting in the trunk of a tree. His hair are
mixed up and come in contrast with his skin, which looks
tender and smooth (Figure 1). The statue’s height is 2.13m, and
is standing on a marble base of dimensions 1.25 in height and
1.26 m by 0.84m horizontally.
For the creation of the statue’s 3D model, it was decided to
perform a complete close range stereoscopic photographic
documentation as well as an independent scanning using a
terrestrial triangulation laser scanner. The use of two
independent techniques allows evaluation of the reliability of
each and the attained precision in restitution of the object’s size
and shape.
3. DATA COLLECTION
The data acquisition from both methods, due to the size of the
sculpture and the fact that the object was impossible to move,
required the use of scaffolding with appropriate levels, so that
access to all parts of the statue could be facilitated. The width
of the scaffolding was broad enough to enable unobstructed
movement of the instruments and operators within necessary
distances between the camera or scanner and the object.
Special attention was paid to the stability of the construction, so
that vibrations during data capturing mainly caused by the
operator would be minimised. This is important, because
motions during data capture may introduce noise to scanned
images and displacements of the control points at the photo
images. Figure 2 depicts the wooden construction specifically
built for this project.
Figure 2. Special scaffolding was constructed for the data
collection
The scaffolding had basically two levels:
• A first level of 1.25m height from the ground, which
surrounded the sculpture with a width of 1.20m and at
distance of 0.30m from the perimeter of the sculpture’s base.
This level was used during the photo acquisition of the whole
body of the sculpture and the scanning of the lower body
part.
• A second level of 3.90m height from the ground, which was
effectively above the sculpture with a width of 1.00m. In
addition, a gap of dimensions 0.80x0.50m was purposely
constructed to enable access for the photo acquisition of the
upper parts of the sculpture, heads and hands of Hermes and
infant Dionysos (Figure 3).
• An alternative location of the second level at height of 2.70m
from the ground, which encircled the statue’s upper body in
order to allow details of the upper parts of the object being
captured (Figure 4).
Figure 3. The central photo of the strip taken from the top
Data acquisition for the base of the sculpture was performed
last in sequence, from the ground level when all levels of
scaffolding were removed.