Complementarity of acquisition techniques for the documentation of Neolithic engravings: lasergrammetric and photographic recording in Gavrinis passage tomb (Brittany, France)

International audienceThe Neolithic tomb of Gavrinis is famous for its rich and complex engraved art that has inspired a large number of interpretative studies. However, all of these are based on unsatisfactory drawings. This article describes the methodological results of a new project for recording the Gavrinis engravings that combines 3D laser and 2D photographic techniques. Laser scanning not only provides accurate contextual information such as the stone relief and architectural setting in which the art is found. Specially designed processing of point clouds also makes it possible to highlight the contours of the pecked motifs and to record them directly from the 3D model of the decorated stones. This can be further improved by photography using oblique lighting and image processing techniques in order to obtain more detailed recordings of the motifs as well as insights into their chronological relationships. In the unusual case of barely visible engravings made with very slight peckmarks, experimental application of the DStretch colour detection programme has been unexpectedly successful. A comparison of all these results shows that laser and photographic techniques have different strengths and weaknesses that complement each other. Thus, combined use of these techniques within a single methodological process produces innovative and comprehensive documentation of Neolithic tomb art