The Underwater site of Qaitbay - CEAlex
The underwater site at the foot of Fort Qaitbay at the eastern extremity of Pharos Island by Alexandria, Egypt, holds the ruins of the Lighthouse of Alexandria, a legendary monument that stood for almost 17 centuries. It was built towards the beginning of the 3rd century BC and was accessible until the end of the14th century. The last mention of the visible presence of its ruins dates to 1420, almost 60 years before the construction of Qaitbay Fort.
The underwater excavations begun in 1994 by the Centre d’Etudes Alexandrines (CEAlex) followed on from the work undertaken by Honor Frost and Kamel Abul Saadat in the 1960s and they have managed to shed new light on the question of the image of the Lighthouse.
Thorough on-site investigations and observations of the physical vestiges, has increased our understanding of this edifice that was, until only a few decades ago, principally known from written sources. The archaeological work has already allowed for a reconstitution of parts of the Pharos and for an understanding of the design process. Nevertheless, the work faced the limits of traditional data recording methods. The abundance of ruins and the unique nature of this sunken site have encouraged innovation in data gathering, both for the ancient elements (more than 3,500 blocks) and for the site itself, whose extent and uneven layout make analysis complicated.
Thus, in 2009-2010, Isabelle Hairy, responsible for the Qaitbay site since 1997, launched a 3D photogrammetry data-gathering programme initially as part of an ANR-SeARCH project. The R&D department of EDF had begun 3D rendering of sunken monuments in 1998 and this work was continued between 2009 and 2012 as part of the ANR-SeARCH programme.
The preliminary work done by SeARCH demonstrated that photogrammetry was the novel solution for rapidly providing quality “digital duplicates” on the scale of the elements, whether sunken or lifted. With around 30 blocks removed from the sea and more than 3000 pieces still underwater, some of which weigh almost 40 tons, this was an important step forward.
Since 2013, this research has been supported by the Honor Frost Foundation, leading to a clear development in data gathering techniques and the consequent improvement in quality of results, visible in the digital imagery produced from the data. We hope that we will be able present an overall digital view of the underwater site of Qaitbay.
More information is also available on the CEAlex website