Survey and Photogrammetry: Retreiving and Modeling Lost Data

In 2013, an exceptional discovery was made in the Fontainebleau Forest near Paris (France). On a boulder at Vallée au Noirs a never seen before figure representing a human figure framed by two boats with steering oars on one side and a crook-hafted axe with a ring on the other side. The engraving is partially buried which maybe delated its discovery but also protected it from degradation. It is known that this specific boulder is one of the most popular climbing rock of the area and the axe is often used as a fulcrum. The artwork has been totally cleared and recorded then the survey has been refilled. This article focuses on the process to record each step of the survey in order to virtually recreate all elements of the stratigraphy. This allows then to measure, weigh, and precisely locate all discovered artifacts. In this example, the clearing of a site during excavation work is photographed and modelled for each important stage. In addition to the step-by-step monitoring and the archiving possibilities entailed, this method also allows for generating additional data, such as removed cubatures or the precise shape of the studied strata. Those are operations that are carried out on both filled and empty spaces.

Keywords: Photogrammetry, 3D recording, 3D stratigraphy, retro modeling.