Benefits of an accurate 3D Documentation in Understanding the Status of the Bronze Age Heritage Cave 'Les Fraux' (France)

摘要

An interdisciplinary team of archaeologists, surveyors, environmentalists and archaeometrists has jointly carried out the study of the Bronze Age "Les Fraux" (Saint-Martin-de-Fressengeas, Dordogne, France) since 2007. This archaeological decorated cave, registered as a French Historical Monument, forms a wide network of galleries, characterized by the exceptional richness of its archaeological remains such as ceramic and metal deposits, parietal representation and domestic fireplaces. This cave is the only protohistorical site in Europe wherein testimonies of domestic, spiritual and artistic activities are gathered. This project 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. Accurate 3D models of the cave constitute the common framework for the different partners. We present in this paper an overview of methods of data recording based on contact-free measurement techniques in order to acquire a full 3D-documentation of the site. Different techniques based on Terrestrial Laser Scanning, Digital Photogrammetry and Spatial Imaging have been used in order to generate geometric and photorealistic 3D models 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, e.g. global volume of the cave, parietal representations, and deposits. Measurements from an original method of 3D indoor magnetic field recording are combined with the 3D models in order to locate magnetic anomalies in the cave. All the surveys are conducted in compliance with the integrity of the site.