) 1,60 meters and an
have been supposed,
lia wrecks specimen
ictory stamps haven't
s of the clay refer to
ania and Latium. On
s are visible, used as
or repair these large
ic amphorae small
1 the site too. Only a
finitive results: from
ng to the kind of the
with very big dolia,
ssible to know if the
wards the provinces
roupe wrecks) or the
yusse, Diano Marina
th dolia belong to a
ntury B. C. and the
Dressel 20 fragment,
the date around the
| by eleven blocks of
1 drum rough-hewed
neters from the dolia
oral reef, at a ca. 4-5
the original stowage
e ship. We can't see
? have been crushed
| by a layer of sea
unauthorized fishers
retions and chips do
ments and to read
y.
for all the foundings
v that these specimen
iarble caves (bianco
ninate the original
olute certainty. The
| 9 tons ( block n. 3)
damaged amphorae
] of I century B. C.-
only clue to date the
Id have been carried
| by Mistral, West,
vas sailing along the
Mountains marbles
the middle of the I
age. If it is a Roman
ge ship, because we
ads from 100 to 200
id it connected Luni,
rble, to Rome, where
y were carried along
tisfy the continuous
te architecture.
1.2.4 Traditional survey
The traditional graphic survey of the two sites, particularly the
second, has been made in several following dives, by means of
underwater measurements, hard and tiring (subjected to human
error), from a point zero. The photogrammetry and three-
dimensional modelling program on the two sites has been
started in 2001 by Soprintendenza per i Beni Archeologici della
Toscana (Pamela Gambogi) in cooperation with Marco
Canciani from University of Roma Tre and Pierre Drap from
CNRS in Marseille (France). The purpose is to obtain models
much better and more precise than the traditional relief and
rarely used for underwater sites.
2. PHOTOGRAMMETRIC APPROACH
Underwater surveying is a non-obvious work, not very accurate
and requires a lot of time which is not very convenient in an
underwater context.
Thanks to a new ‘CIPA, Heritage, Documentation’ task group,
dedicated to underwater photogrammetry and created in
September 2001, we take advantage of this multidisciplinary
team, represented by the diversity of the co-authors. [Cipa-uwp,
2002]. The general way to do was inspired from the experience
on the Etruscan wreck surveyed in France, ([Drap, Long,
Durand, Grussenmeyer, 2001-A], [Drap, Bruno, Long, Durand,
Grussenmeyer, 2002]) both for the survey phase and the data
management methodology.
Figure 2. Photograph for the marble survey. On the left side a
buoy with two perforated table tennis balls, on the
right side a ruler for scaling.
2.1 General method
The photogrammetric campaign was done on July 2001 near
Livorno, Italy with the Italian team of Firenze, (Soprintendenza
per i Beni Archeologici della Toscana) Pamela Gambogi,
director of the excavation, in addition we have to thank Rolland
Graille, professional diver from the CNRS “Centre
d'oceanologie de Marseille" who came to help us with his
competence and material.
We decided to use a very simple and cheap way : digital Nikon
Coolpix 990 in a Ikelite housing, *aerial photography" type for
the survey, and Photomodeler software for the orientation and
plotting phase.
2.2 The survey
2.2.1 Shooting photographs
The survey phase was done as an aerial photogrammetry but
without any control points.
Curiously one of the main difficulty was that the piece of
marble which was shallow. The depth was approximately three
meters and the photographer-diver was near the surface which
Figure 3. Refracted and non refracted coordinate of measured
point on three square rims [Kwon, 1998]
is really problematic for the stability. In underwater
photography it's impossible to be far from the object (due to a
lot of suspended particles) .
2.2.2 Orientation
The selected method was to minimize the time of intervention.
A set of rulers to put the model in scale and several buoys for
vertical reference. (The buoys were made with some perforated
table tennis balls).
2.3 The calibration process
The camera calibration in multimedia photogrammetry is a
problem already identified since almost 50 years ([ASP, 1980]
p. 838). You can refer to [Maas, 2000] to have an overview of
the state of art of this field. The problem is not obvious, the
light beam refraction through the different dioptre (water, glass,
air) introduce a refraction error which is impossible to express
as a function of the image plane coordinate alone.
A lot of authors give some solution more or less simple, usually
with iterative process, in order to solve this problem. [Kwon,
Lindley, 2000.] [Maas, 2000]. Even if Hans-Gerd Mass give a
solution simplified it refers always to a ‘standard case’ of
multimedia photogrammetry : only three media, an object in
liquid, a plan-parallel transparent plane making the separation
between the object and the sensor located in air.
[Kwon, 1998] gives a representation of this distortion as a pin-
cushion distortion in a particular case : a set of control points
are marked on a plane, the control plane is parallel to the image
plane and the camera axis passes through the center of the
control plane. In these condition we have a distortion
represented in Figure 3.
To solve this problem in standard condition (normal camera
Figure 4. Photograph for calibration process with Photomo-
deler.
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