ORTHOPHOTO IMAGING AND GIS FOR SEABED VISUALIZATION AND UNDERWATER ARCHAEOLOGY

Abstract: We present here the first step of an interdisciplinary work dealing with underwater photogrammetry and archaeological data management. In the framework of a phd project we develop a set of tools from underwater data capture to 3D underwater GIS for archaeological excavation. The phd project, managed by Julien Seinturier, is monitored by Odile Papini for the data fusion aspect and Pierre Drap for the underwater photogrammetrical aspect. The project is financed together by the French Region PACA and the COMEX firm, specialized in underwater exploration. In this paper we present the first step experimentation on and underwater archaeological site in Corsica managed by the DRASSM and excavated under the scientific responsibility of Franca Cibecchini. After a brief archaeological presentation of the site we’ll start by a description of the photogrammetric survey phase, made during the excavation, in the same time that a traditional manual survey make thanks to the shallowness site aspect. The first step is an orthophoto production. Buoys and scale bar are present on the site in order to permit orientation an model scale. If the orthophoto produced can’t replace completely the manual survey made in situe, (this kind of survey is, in the same time, an archaeological interpretation made by the expert in the best situation of observation) the archaeologist can have a lot of benefit using this kind of representation. The orthophoto is a photogrammetric product, easy to obtain once the photogrammetric orientation is done and considering a more or less plane seabed, enough accurate for a first site representation. Moreover, due to the small scale photograph the orthophoto generation carry out a lot of very interesting huge quantities of qualitative detail