The contribution of VNIR and SWIR hyperspectral imaging to rock art studies: example of the Otello schematic rock art site (Saint-Rémy-de-Provence, Bouches-du-Rhône, France)

This paper presents a methodological contribution to rock art archaeology by demonstrating the benefits of hyperspectral imaging, a relatively new method, for the understanding of rock art sites. It illustrates the complementarity of VNIR hyperspectral imaging, applied in rare cases to rock archaeology, and SWIR hyperspectral imaging, implemented here in a unprecedented way to a rock art panel. Applied to a schematic rock art site in southern France, the Otello rock shelter (Saint-Rémy-de-Provence, France), this method allowed the discovery of numerous new figures invisible to the naked eye or unsuspected after image enhancement with the DStretch plug-in of the ImageJ software, the individualisation of figures within complex superpositions, and the discovery of figures covered by weathering products. Moreover, by conferring a spatial dimension to the analysis of pictorial matter, thus allowing a classification of pigments at the scale of the wall, hyperspectral imaging makes it possible to automatically isolate different paintings and to carry out objective groupings of figures on the basis of their composition. Finally, hyperspectral imaging allows us to precisely document, distinguish and characterise weathering products interacting with painted figures. For all of these reasons, this method appears essential to highlight the relative chronology and syntax of iconography, and consequently to understand its cognitive nature.