Abstract
Abstract. Underwater photogrammetry in archaeology in Egypt is a completely new experience applied for the first time on the submerged archaeological site of the lighthouse of Alexandria situated on the eastern extremity of the ancient island of Pharos at the foot of Qaitbay Fort at a depth of 2 to 9 metres. In 2009/2010, the CEAlex launched a 3D photogrammetry data-gathering programme for the virtual reassembly of broken artefacts. In 2013 and the beginning of 2014, with the support of the Honor Frost Foundation, methods were developed and refined to acquire manual photographic data of the entire underwater site of Qaitbay using a DSLR camera, simple and low cost materials to obtain a digital surface model (DSM) of the submerged site of the lighthouse, and also to create 3D models of the objects themselves, such as statues, bases of statues and architectural elements. In this paper we present the methodology used for underwater data acquisition, data processing and modelling in order to generate a DSM of the submerged site of Alexandria’s ancient lighthouse. Until 2016, only about 7200 m2 of the submerged site, which exceeds more than 13000 m2, was covered. One of our main objectives in this project is to georeference the site since this would allow for a very precise 3D model and for correcting the orientation of the site as regards the real-world space.
Highlights
In 1994, the Centre d’Etudes Alexandrines (CEAlex, USR 3134, CNRS) launched the first scientific excavation in the field of underwater archaeology in Egypt on the submerged site of the lighthouse of Alexandria situated on the eastern extremity of the ancient island of Pharos at the foot of Qaitbay Fort, which was constructed at the end of 15th century by the Mamluke Sultan Qaitbay
The submerged site was discovered in 1960 thanks to the pioneering work of Kamel Abou Elsaadat, and in 1968 Honor Frost undertook a UNESCO mission on the site which led to the publication of a preliminary report revealing the importance of the site (Empereur, 2000) The underwater site of Qaitbay Fort holds the ruins of the lighthouse of Alexandria, a legendary monument that stood for almost 17 centuries
Manual photographic data acquisition methods were applied, using a DSLR camera and low cost materials to develop a digital surface model (DSM) of the entirety of Qaitbay underwater site, which exceeds more than 13000 m2
Summary
In 1994, the Centre d’Etudes Alexandrines (CEAlex, USR 3134, CNRS) launched the first scientific excavation in the field of underwater archaeology in Egypt on the submerged site of the lighthouse of Alexandria situated on the eastern extremity of the ancient island of Pharos at the foot of Qaitbay Fort, which was constructed at the end of 15th century by the Mamluke Sultan Qaitbay. Underwater excavations began in 1994 under the direction of Dr Jean Yves Empereur, director of CEAlex, in the hope of shedding new light on the question of the image of the lighthouse. These excavations led to the reconstitution of certain parts of the lighthouse and to an understanding of the design process. The extent and unique nature of this sunken site have encouraged innovation in data gathering, both as regards the ancient material — more than 3525 blocks — (fig. 1) and the overall site itself, whose size and uneven contours make any analysis complicated. (Hairy, 2009)
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