Abstract
Photogrammetry has often been the most preferable method for the geometric documentation of monuments, especially in cases of highly complex objects, of high accuracy and quality requirements and, of course, budget, time or accessibility limitations. Such limitations, requirements and complexities are undoubtedly features of the highly challenging task of surveying an underwater archaeological site. This paper is focused on the case of a Hellenistic shipwreck found in Greece at the Southern Euboean gulf, 40-47 meters below the sea surface. Underwater photogrammetry was chosen as the ideal solution for the detailed and accurate mapping of a shipwreck located in an environment with limited accessibility. There are time limitations when diving at these depths so it is essential that the data collection time is kept as short as possible. This makes custom surveying techniques rather impossible to apply. However, with the growing use of consumer cameras and photogrammetric software, this application is becoming easier, thus benefiting a wide variety of underwater sites. Utilizing cameras for underwater photogrammetry though, poses some crucial modeling problems, due to the refraction effect and further additional parameters which have to be co-estimated [1]. The applied method involved an underwater calibration of the camera as well as conventional field survey measurements in order to establish a reference frame. The application of a three-dimensional trilateration using common tape measures was chosen for this reason. Among the software that was used for surveying and photogrammetry processing, were Site Recorder SE, Eos Systems Photomodeler, ZI’s SSK and Rhinoceros. The underwater archaeological research at the Southern Euboean gulf is a continuing project carried out by the Hellenic Institute for Marine Archaeology (H.I.M.A.) in collaboration with the Greek Ephorate of Underwater Antiquities, under the direction of the archaeologist G.Koutsouflakis. The geometric documentation of the shipwreck was the result of the collaboration between H.I.M.A. and the National Technical University of Athens.
Highlights
With 17,000 kilometers of coastline, equivalent to 25% of the total Mediterranean coast, with almost 3,500 islands and at least 1,000 shipwrecks detected in the Greek seas, Greece is a country with one of the largest and perhaps the most important underwater archaeologicalGeoinformatics FCE CTU 11, 2013Diamanti, E. et al.: Geometric documentation of underwater . . .heritage
This paper presents an effort to improve and experiment on the synergy of conventional surveying techniques, such as simple tape measurements and trilateration adjustments, with modern software and digital technology, in order to produce 3 dimensional reconstructions that can assist underwater archaeologists in reaching their scientific conclusions, through a geometrically accurate, documentation of the site and the excavation process, as well as to bring those who do not have the opportunity to access this submerged monument, on a ‘digital trip’ to an ancient shipwreck in deep waters
The Hellenistic shipwreck, whose case is examined in this paper, was found in 2006 in the northwest side of the island Styronisi at Southern Euboean gulf, at a depth range of depth between 39 and 47 meters below the sea surface
Summary
With 17,000 kilometers of coastline, equivalent to 25% of the total Mediterranean coast, with almost 3,500 islands and at least 1,000 shipwrecks detected in the Greek seas, Greece is a country with one of the largest and perhaps the most important underwater archaeological. Practical implication of theoretical and technological developments in the fields of surveying and photogrammetry for the geometric documentation of this underwater heritage is far behind the rapid developments and innovations that are applied when it comes to surveying ‘terrestrial’ monuments. This paper presents an effort to improve and experiment on the synergy of conventional surveying techniques, such as simple tape measurements and trilateration adjustments, with modern software and digital technology, in order to produce 3 dimensional reconstructions that can assist underwater archaeologists in reaching their scientific conclusions, through a geometrically accurate, documentation of the site and the excavation process, as well as to bring those who do not have the opportunity to access this submerged monument, on a ‘digital trip’ to an ancient shipwreck in deep waters
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