Mapping, digging and documenting using sound - The Cyprus Institute

Mapping, digging and documenting using
sound:
Limitations and perspectives in marine geoarchaeology
Papatheodorou G.,
Geraga M., Ferentinos G.
Αthena Chalari, PhD
Dimitris Christodoulou, MSc
Margarita Iatrou, MSc
Elias Fakiris, MSc
LABORATORY OF MARINE GEOLOGY
AND PHYSICAL OCEANOGRAPHY
DEPARTMENT OF GEOLOGY
UNIVERSITY OF PATRAS

Marine Geoarchaeology
(Archaeological Oceanography)
A recent scientific field that uses:
• a wide range of remote sensing techniques
• in conjunction with the disciplines from Marine Sciences and Ocean
Engineering

There are two approaches regarding the application of marine
geoarchaeological methods to the underwater archaeology:
(i) mapping of submerged sites of archaeological interest (submerged
ancient cities, settlements, ports and man-made structures) –
palaeogeographic reconstruction
NGDC coastal model
(ii) detection and investigation of ancient shipwrecks lying on the
seafloor or partly buried in it
Croatia/UNESCO

Palaeogeographic reconstruction
of Ptolemaic Alexandria
using acoustic remote sensing
techniques*
The survey was planned and carried out by
the Laboratory of Marine Geology and Physical Oceanography of the University
of Patras (Greece)
in co-operation with
the Centres d’É tudes Alexandrines
the Hellenic Institute of Ancient and Medieval Alexandrian Studies
and the Conseil Supreme Des Antiquites Egyptiennes
* Chalari et al., 2009

Alexandria 331 BC

“……entering the Great Port, the lighthouse on the Pharos
island lie to the right while on the left are seen scattered rocks
and the Cape Lochias with a palace standing on it …”
Strabo (XVII)

The Aim
The Method
The reconstruction of the coastal
palaeogeography where the
Hellenistic Alexandria was
developed.
• Sidescan sonar system EG&G
• High-resolution sub-bottom bottom profiling
system (3.5 kHz)
• DGPS (accuracy ±2m)
a simple methodological scheme for the
processing of analogue bathymetrical
and marine geophysical data
developed in a GIS and a MATLAB
computer environment

Methodology – Field work
Subbottom profiler system
(3.5kHz) track lines (90km,
32.5km 2 )
Sidescan Sonar tracklines (186km, 44.3km 2 )

Data Analysis
Seafloor map

Bathymetric map
Ridge (-1): 3km length, SW-NE
direction, with a planar top (-11m
water depth)
Data analysis
(echograms – seismic profiles)

Examination of the 3.5 kHz profiles
on the rocky seafloor surface around
the Eastern Harbour reveals
numerous small scarps which can be
considered as palaeoshorelines

Subsidence rates
Tide Gauge data
Archaeological
evidence
• 1.6-2.9 mm/year (60 years)
(El- Fishawi & Fanos, 1989; Frihy 1992; 2003)
• 6.5 – 8.5 m (Jondet 1912, 1916, 1921)
• 5.5 - 6.5 m (Goddio, 2000)
• 7 m (Tzalas, 2000)
• 2.8-3.4 mm/year relative sea-level change.
Geological data
• 3 mm/year (8000 years) (Stanley & Warne,
1993)
~8 m subsidence (2300)
~ the same rate from 8000 until today

Cape Lochias (an extended part
is now under the m.s.l
(0.721km 2 – 92% submerged
today)
The 8m subsidence scenario
The entrance of Great Port was very narrow (600m)
(today 1700m). The depth of Great Port was 4.5-9m
and covered bigger area than today.
The existence of a small reef above msl.
Existence of small reefs
above m.s.l
and features like «piers»
The rocky ridge (-1) was 3m under
the 2300 BP sea surface
(i) A natural breakwater protecting
the Eastern Harbor from heavy weather
(4m wave height)
(ii) Dangerous reef for ancient mariners
331BC (~2300BP)

Detection of ancient shipwrecks at
the coastal zone of Alexandria
using acoustic remote sensing
techniques
The survey was planned and carried out by
the Laboratory of Marine Geology and Physical Oceanography of the University
of Patras (Greece)
in co-operation with
the Centres d’É tudes Alexandrines
the Hellenic Institute of Ancient and Medieval Alexandrian Studies
and the Conseil Supreme Des Antiquites Egyptiennes

The Aim
The Method
Detection and positioning of targets which
may represent shipwreck or man
made items (Chalari et al., 2003)
• PHASE A
FIELD WORK
• Sidescan sonar system
• DGPS (accuracy ± 2m) & GPS
(accuracy ±10m)
• PHASE B
• Ground-truthing using divers and
R.O.V.

PHASE A
During the side scan sonar survey
a total of 57 targets were detected

PHASE B
Ground Truthing*: Results
Man-made targets
Modern
Historical - Ancient
Total
number
Natural
formations
Didn’t
found
Reexamination
ropes, cables,
tires, fishing
equipment, e.t.c.
Historical anchors,
2 nd World War
torpedo, ship ballast
Ancient shipwreck
57 18 8 11 14 6
100% 32% 14% 19% 25% 10%
* J-Y. Empereur, G. Soukassian, J. Curnier, R. Leffy

TARGAN: A USEFUL TOOL FOR
SIDESCAN SONAR TARGET
CLASSIFICATION
Targan is a MATLAB-based software that
reprocesses analogue side scan sonar records
in order to:
•quantify the nature of the targets on the basis
of shape and backscatter characteristics
•create a database with the characteristics of
each target
•classify the targets into meaningful groups
using multivariate statistical analysis
•minimize the diving time

TARGAN
•Cluster Analysis using the
•Average Linkage algorithm
DATA SET
57 Targets – 9 parameters
•Cluster Analysis using the
•Ward’s Error Sum of Squares
algorithm
•K – means
•Q-Factor Analysis
TARGET CLASSIFICATION

…instead of concluding remarks

References
Chalari, A., G. Papatheodorou, M. Geraga, D. Christodoulou G. Ferentinos (2009). A marine geophysical survey
illustrates Alexandria’s Hellenistic past. Zeitschrift fur Geomorphologie, vol. 53, no.1, pp. 191-212.
Chalari, A., Christodoulou, D., Papatheodorou, G., Geraga, M., Stefatos, A., Ferentinos, G.(2008): Use of remote
sensing and GIS in the reconstruction of coastal palaeogeography of Alexandria, Egypt, In: Y. Facorellis, N.
Zacharias, K. Polikreti (eds), British Archaeological Reports (BAR) International Series 1746, ISBN 978 1
4073 01884, pp. 119-128.
Chalari Α., D. Christodoulou, G. Papatheodorou, M. Geraga, and G. Ferentinos (2003): "Marine Geophysical
Investigation around the Site of the Famous Pharos of Alexandria (Egypt) for the Detection of Ancient
Shipwrecks. (Preliminary Results)". 2nd World Congress. Ancient Greece "The Modern World", Ancient
Olympia (International Olympic Academy), 12-17 July 2002, pp. 62-73.
El Fishawi, N.M., Fanos, A.M., 1989: ‘Prediction of sea level rise by 2100, Nile delta coast’. INQUA, Commission
on Quaternary Shorelines, Newsletter, 11:43–47.
Frihy, O.E., 1992: ‘Sea-level rise and shoreline retreat of the Nile delta promontories, Egypt’. Natural Hazards, 5:
65–81.
Frihy, O.Ε., 2003: ‘The Nile delta-Alexandria coast: vulnerability to Sea-level rise, consequences and adaptation’.
Mitigation and Adaptation Strategies for Global Change, 8: 115–138
Jondet, M.G., 1912: ‘Les Ports antiques de Pharos’. Bulletin de la Socié té Arché ologique d’Alexandrie, 14: 252-
266, Alexandria.
Jondet, M.G., 1916: ‘Les Ports Submergé s de l'ancienne Île de Pharos. Cairo’. Mé moires de l'Institut d'Egypte,
IX: 101.
Jondet, M.G., 1921: Atlas Historique de la Ville et des Ports d’Alexandrie, Imprimerie de l’Institut Français
d’Arché ologie Orientale, Cairo, 54 map plates.
Goddio, F., 2000: ‘Underwater archaeological survey of Alexandria’s Eastern Harbour’. In Mostafa, M.H., Grimal,
N., Nakashima, D., (Eds), Coastal management sourcebooks 2, UNESCO Publishing: 60-63.
Stanley, J-D., Warne, A.G., 1993: ‘Nile Delta: Recent Geological Evolution and Human Impact’. Science, New
Series, 260 (5108): 628-634.
Tzalas, H.E., 2000: ‘The two ports of Alexandria. Plans and maps from the 14th century to the time of Mohamed
Ali’. In Mostafa, M.H., Grimal, N., Nakashima, D., (Eds), Coastal management sourcebooks 2, UNESCO: 22-
32.

We would like to thank:
•Dr. J-Y .Empereur and H. Tzalas for their keen interest and
encouragement
•The members-divers of CEAlex and HIAMAS and especially
Jean Curnier, Robert Leffy and George Soukassian.
Many thanks also go to a lot of people for giving us the
opportunity to participate to amazing projects:
•Dr. K. Baika, University of Peloponnesus
•Dr. J. Pakkanen, Dept of Classics Royal Holloway, University of London
•Dr. S. Demesticha, University of Cyprus and Thetis Foundation
•C. Agouridis, Archaeologist M.A., H.I.M.A
•M. Garras, Physicist, H.I.M.A
•Dr. D. Sakellariou and Dr. V. Lykousis, HCMR
•Greek Ephorate of Underwater Antiquities
•Mr. A. Paleokrassas (Akti Engineering Co.) is thanked for his
assistance in positioning during the first three campaigns in Alexandria