Bulletin of the Geological Society of Greece Vol. 44, 2011 Remote sensing for underwater archaeology: case stud-ies from Greece and Eastern Mediterranean Papatheodorou G. Geraga M. Chalari A. Christodoulou D. Iatrou M. Fakiris E. Kordella St. Prevenios M. Ferentinos G. https://doi.org/10.12681/bgsg.11440 Copyright © 2017 G. Papatheodorou, M. Geraga, A. Chalari, D. Christodoulou, M. Iatrou, E. Fakiris, St. Kordella, M. Prevenios, G. Ferentinos To cite this article: Papatheodorou, G., Geraga, M., Chalari, A., Christodoulou, D., Iatrou, M., Fakiris, E., Kordella, St., Prevenios, M., & Ferentinos, G. (2011). Remote sensing for underwater archaeology: case stud-ies from Greece and Eastern Mediterranean. Bulletin of the Geological Society of Greece, 44, 100-115. doi:https://doi.org/10.12681/bgsg.11440 http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 26/09/2021 08:19:04 | http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 26/09/2021 08:19:04 | Δελτίο Ελληνικής Γεωλογικής Εταιρίας τομ.XLIV, 2011 100 Bulletin of the Geological Society of Greece vol. XLIV, 2011 Remote sensing for underwater archaeology: case stud- ies from Greece and Eastern Mediterranean sea. PAPATHEODOROU(1) G., GERAGA(1) M., CHALARI(1) A., CHRISTODOULOU(1) D., IATROU(1) M., FAKIRIS(1) E., KORDELLA(1) ST., PREVENIOS(1) M. & FERENTINOS(1) G. ABSTRACT Modern underwater remote sensing technology introduces many advantages that extend the range of conventional diving work providing the means to survey in a detailed and systematic fashion large seafloor area. There are two general approaches regarding the application of these techniques in underwater archaeology; they are being increasingly used to identify, locate and map (i) ancient and historical shipwrecks lying on the seafloor or partly buried in it and (ii) the coastal palaeogeogra- phy and thus submerged sites of archaeological interest (submerged ancient cities, settlements, ports and man-made structures). The underwater remote sensing techniques most commonly applied to underwater archaeology employ: (i) single and multi-beam echosounders (ii) side scan sonar (acousting imaging), (iii) laser line scan (optical imaging) (iv) subbottom profiler, (v) marine magne- tometer and (vi) undersea vehicles. The objectives of this paper are twofold: (i) to present the results of remote sensing surveys that carried out at sites of archaeological and historical interest, in Greece (Dokos Island, ancient harbour of Kyllene and Navarino Bay whereas a historical naval Battle took place) and in Eastern Mediterranean Sea (Alexandria Egypt and Mazotos shipwreck Cyprus), and (ii) to prove the applicability of remote sensing techniques in underwater archaeology showing that a combination of these can be a very effective tool. Keywords: subbottom profiling, side scan sonar, magnetometer, palaeogeography, shipwrecks, Do- kos Isl., Navarino battle,Glarentza, Alexandria, Cyprus. ΠΕΡΙΛΗΨΗ Τις τελευταίες δύο δεκαετίες οι θαλάσσιες γεωφυσικές μέθοδοι έχουν αναδειχθεί σε εξαιρετικά αποτελεσματικό μέσο στη μελέτη της παράκτιας παλαιογεωγραφίας καθώς είναι εφικτό να εντοπί- ζουν και να αναγνωρίζουν καταβυθισμένες παλαιοακτές και γεωμορφές σχετιζόμενες με αυτές. Η επίκληση της θάλασσας και η εμφάνιση καταστροφικών φαινομένων (σεισμοί, παλιρροιακά κύματα) έχουν οδηγήσει στην καταβύθιση αρχαίων πόλεων, οικισμών και λιμενικών εγκαταστάσεων. Επι- πλέον, αυτές χρησιμοποιούνται πλέον συστηματικά για τον εντοπισμό και τη μελέτη κινητών μαρτυ- ριών (ναυάγια) της ανθρώπινης δραστηριότητας στον πυθμένα. Τα όργανα γεωφυσικής διασκόπη- σης του πυθμένα, που χρησιμοποιούνται για τις παραπάνω εφαρμογές είναι : (i) το μονοδεσμι- κό/πολυδεσμικό βυθόμετρο, (ii) o τομογράφος υποδομής πυθμένα υψηλής διακριτικής ικανότητας, (iii) ο ηχοβολιστής πλευρικής σάρωσης, (iv) το θαλάσσιο μαγνητόμετρο, ενώ τα αποτελέσματα της γεωφυσικής διασκόπησης επιβεβαιώνονται με μεθόδους οπτικής παρατήρησης του πυθμένα (δύτες, υποβρύχια οχήματα). Στην εργασία αυτή παρουσιάζονται παραδείγματα εφαρμογής των μεθόδων θαλάσσιας γεωφυσικής διασκόπησης σε περιοχές με μεγάλο αρχαιολογικό ενδιαφέρον από τον Ελληνικό θαλάσσιο χώρο (νησίδα Δοκός, κόλπος Ναβαρίνου, αρχαίο λιμάνι Κυλλήνης) και την Ανα- τολική Μεσόγειο Θάλασσα (Αλεξάνδρεια Αιγύπτου, ναυάγιο Μαζωτού Κύπρου). Λέξεις κλειδιά: Τομογραφος υποδομής πυθμένα, ηχοβολιστής πλευρικής σάρωσης, μαγνητόμετρο, παλαιογεωγραφία, ναυάγια, Αλεξάνδρεια, Δοκός, Ναβαρίνο, Γλαρέντζα, Κύπρος.. (1) Laboratory of Marine Geology and Physical Oceanography, Department of Geology, University of Patras, 26500 Patras, Greece. Email: [email protected], www.oceanus.upatras.gr http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 26/09/2021 08:19:04 | 101 allow archaeologists to detect ancient ship- 1. INTRODUCTION wrecks in the depths of the ocean, far beyond The main research challenge in underwater the 50m depth boundary set by conventional archaeology is to overcome the physical barrier diving. Over the past ten years, several projects of the water coloumn and occasionally of the have proven its scientific merit. A number of loose sediments. Modern underwater remote wrecks were detected at depths of 800 meters sensing technology introduces many ad- off the Skerki Bank in central Mediterranean Sea vantages that extend the range of conventional (Ballard et al., 2000). The “Skerki” wrecks span- diving work providing the means to survey in a ning a period between the 2nd century B.C. to detailed and systematic fashion large seafloor the 4th century A.D., document a previously un- area. The advantages of such surveys are: (i) known open-sea trade route between Carthage high speed of investigation the seafloor which is and Rome. Two 8th century B.C. Phoenician time consuming and therefore can be also prov- cargo vessels were discovered in deep waters en cost-effective, (ii) ability to detect buried tar- on an open water route between Israel and gets, (iii) ability to detect obscure geometrical Egypt. The cargoes of these vessels may be shapes on the macroscopic scale due to the different from those of coastal crafts, providing broader available seabed view than that of the new information about ancient trade and ex- visual field of a diver, (vi) less environmental change (Ballard et al. 2000, 2002). Phaneuf et constrains such as for carrying out the survey al. (2002) used the powerful capabilities of the (low visibility, dirty and polluted waters, strong U.S. Navy’s nuclear research submarine NR1 in currents), (v) precision of seafloor mapping,(vi) an attempt to detect and locate the submarine higher than visual resolution and (vii) reduced shipwrecks along a well-known route trade be- diving hours and unnecessary risks. tween Rome and Greece. NR1’s forward looking The underwater remote sensing techniques sonar discovered a 4th century A.D. wreck rest- most commonly applied to underwater archaeol- ing at about 750m water depth (fig 1) In this ogy employ: (i) single and multi-beam echo- context, two deep-water archaeological surveys sounders (ii) side scan sonar (acousting imag- in the Aegean Sea conducted by Sakellariou et ing), (iii) laser line scan (optical imaging) (iv) al (2007) led to the detection of ancient (Hellen- subbottom profiler, (v) marine magnetometer istic) wrecks; one in the Chios-Oinousses strait and (vi) undersea vehicles. at 70 m water depth, and the second, west of There are two general approaches regarding Kythnos island, at 495 m. the application of these techniques in underwa- Despite the application of the remote sens- ter archaeology: They are being increasingly ing techniques for ancient shipwreck detection, used to identify, locate and map (i) ancient and these methods are often used for the detection historical shipwrecks lying on the seafloor or and recognition of historical shipwrecks. A de- partly buried in it (Ballard et al., 2000; Phaneuf tailed side scan sonar survey has been carried et al., 2002), and (ii) the coastal palaeogeogra- out at the HMHS Britannic shipwreck site almost phy and thus submerged sites of archaeological ninety years after the disaster for the estimation interest (submerged ancient cities, settlements, of the shipwreck condition (Papatheodorou et ports and man-made structures). al., 2008a). HMHS Britannic, the Titanic’s sister ship, sank on just her 6th voyage while serving 1.1. Shipwreck detection as a hospital-ship off the Greek island of Kea in Archaeologists, aided by chance discoveries the Aegean Sea, on November 21, 1916. The by fishermen (mainly otter trawling), divers, wreck was first found and explored by J-Y Cous- dredging operations and marine construction but teau in December 1975 and was relocated and not by remote sensing surveys, have inventoried surveyed in details by Dr. Robert Ballard in and studied several ancient shipwrecks, when 1996. Side scan sonar imagery from the wreck these are located within conventional diving indicates that the Britannic rests on her star- limits. Advanced remote sensing techniques, board side (fig. 2). http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 26/09/2021 08:19:04 | 102 The survey showed that the primarily planned routes of the cables were crossing very close to the shipwreck site. New cable routes were care- fully planned and detailed maps with special notifications of the archaeological site were pro- duced and made available to the engineers. All the necessary precautions were taken so that the safety of the shipwreck would be ensured during the cables lying operations. 1.2. There is increased attention in the