Articles by Serge Cassen

Gavrinis, on the estuary of the river Vannes, is known for the extraordinary abundance of engravings preserved on the monolithic wall pillars. These engravings have of course contributed to the reputation of the site, to such an extent that the terms “temple” or “sanctuary” have spontaneously added themselves to the notion of sepulchral space which is generally applied to this family of Neolithic architecture. Our objective is to re-qualify these representations using a new frame of reference, based on a new corpus of engraved signs, including their architectural context and position in the volume of the rock. Recording of the topographical, archaeological, petrographic and acoustic data of the cairn and the passage grave provides a representation of both architecture and engraved (or painted) signs. Our survey involved re¬cording geolocational data (108 million points), with different scales of acquisition. Thus the whole cairn and surrounding ground were scanned using a time-of-flight camera. Then the walls of the tomb and the upper face of the cover slab were recorded with a second scanner with infra-millimetric resolution. Dif¬ferent software treating point clouds were tested to find the best tool for rendering the engravings using a graphic tablet. For the engraved signs on granite, a comparison of methods is proposed, showing the advantages and disadvantages of old techniques (stamping, tracing paper, polyethylene cellophane) in relation to new techniques (digital photographs, scanner 3D). There is no doubt that the scanner enables engravings to be reproduced with the exact relief of the rock, as well as in the architectural sequence of the monument. However, the precision of scanner recordings of surface lines on hard rock (sandstone) is no greater than that of digital photography with oblique lighting or digital image process revealing colors. The two methods are thus complementary.