Manuscript Information Authors

[1]	Frédéric Surmely, DRAC Auvergne-Rhône-Alpes and GEOLAB/UMR 6042 CNRS, Clermont, Ferrand, France.
[2]	Jean-Baptiste Chalin, Association Terre Ancienne, Clermont-Ferrand, France.

Abstract

The estimated number of medieval tunnels is in ten of thousand in France, and almost 500 have been recorded in the Auvergne region. Principal uses include secure storage spaces for crops and keeping goods and possessions from thieves and parasites. Their length is variable, rarely exceeding 100m. Various additions and modifications include: storage (alcoves, silo), ventilation (holes linking the galleries to the surface), security (doors, bottlenecks, S bends, return bends), removal of the infiltrated water (drains, channels), lighting (small alcoves to house lamps), and of course access (stairs, trap doors, etc. ….) were added to the structures. Traditionally the surveys were carried out following methods similar to the ones used in potholing, using measuring tapes, topofils (topography laser), compasses, and clinometers. Using modern topographical instruments such as theodolites or GPS, is impossible due to the minimal space in the tunnels and lack of satellite access. Therefore we tried a new measuring instrument, a 3D laser scanner. Its capacity to render high precision surveys, by associating stations and combining inside and outside measures, allows for connecting structures with their external environments. Its small size renders it effective in confined spaces. It is a pioneer experiment. Two tunnels of the south Cantal (Mourjou and Montvert) were our experimental sites. By crossing internal and external views, the tunnel can be positioned in reference to the surface, offering useful data aiding in the preservation and understanding of these widely known but poorly researched structures.

Keywords

Middle Ages, Tunnels, Laser-Scanner, Archaeometry

Reference

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