Apports de la numérisation 3D multi-échelle à l’étude intégrée de la grotte ornée des Fraux (Dordogne)

For six years, an interdisciplinary team carried out the study of a Bronze Age underground network. This program has been labelled by the Institute of Ecology and Environment of the French Research Council (CNRS), who wants to promote new methodologies and experimental studies in Global Ecology. It takes advantage of the support of the French Ministry of Culture. The archaeological cave of Les Fraux (Saint-Martin-de-Fressengeas, Dordogne) is the only protohistorical site in Europe wherein are gathered testimonies of domestic, spiritual and artistic activities. Fortunately, the cave was closed at the end of the Bronze Age, following to the collapse of its entrance. The site is currently registered in the French Historical Monuments. The cave forms a wide network of galleries, characterized by the exceptional richness of its archaeological remains such as ceramic and metal deposits, numerous parietal representations (engravings or fingerings incised in the clay-walls and paintings sometimes in association with deposits) and about sixty domestic fireplaces. In that framework, 3D models of the cave constitute the common work support and the best way for scientific communication for the various studies conducted on the site by nearly forty researchers. In this specific context, a partnership among archaeologists and surveyors from INSA Strasbourg allows the team to develop, in an interdisciplinary way, new methods of data acquiring based on contact-free measurements techniques in order to acquire a full 3D-documentation. All the surveys are conducted in compliance with the integrity of the site. Different techniques based on Terrestrial Laser Scanning, Digital Photogrammetry and Spatial Imaging System have been used in order to generate a geometric and photorealistic 3D model from the combination of point clouds and photogrammetric images, for both visualization and accurate documentation purposes. Various scales of acquiring and diverse resolutions have been applied according to the subject: global volume cave, parietal representations, deposits… The aim of this paper is firstly to issue a statement of 6 years of 3D-recording in the cave and secondly to display recent methodological developments as for the integration of heterogeneous data in 3D models (i.e. magnetic field recording combined with the 3D models in order to locate magnetic anomalies in the cave). Another purpose is to give an overview of methodological and technological limitations we experienced since 2008. Finally, we attempt to present work in progress as to 3D-modelling and simulating and thinking on the way we should use 3D in archaeological caves.