Tellus environment - Cartographier l'invisible pour agir

Discovery of archaeological sites in Picardie

Published in Archaeology

  • Client: SRA de Picardie
  • Domaine: Archéologie
  • Moyens utilisés: le lidar & le traitement Magsalia

Contexte

Forests have a strong archaeological potential, in particular because of remains good preservation in form of micro reliefs, but the forest cover hinders prospecting operations and site study. Airborne scanning, or Lidar, is a recent method of remote sensing which overrides a part of the physical constraints and allows detection and mapping of remains.

In 2011, the Archaeological service of the Picardie region aims at providing new archaeological data in its own database, called Patriache. The data should come from a 50 km2 surface in the Compiègne woods and should be collected with the Lidar technology.

Methods and equipment: Lidar and Magsalia process

Lidar imaging is a technology based on a high-frequency pulsed laser, working like a radar. Whether airborne or land-based, Lidar allows to produce high-definition soil and subsoil maps. For this project, the Lidar technology produces, on average, 20 points for each m2, and the zone has been treated in one day. Once the data has been recorded, we get a raw digital elevation model. In the first instance, the obtained Lidar data is treated and got into shape.

Tellus Environment has outsourced the Lidar measuring campaign.

The Magsalia process, developed by Tellus Environment, consists in mapping underground water circulation, microreliefs, runoff and erosion invisible to the naked eye.

 

Results and customer benefits

A 1 km2 surface equates to 16 million points and represents 2 hours of calculation. What we are searching for is what is real and, nevertheless, that our senses and the current market softwares do not perceive.

The efficiency of the Magsalia process allows an in-depth study of a site, without even degrading the surface. The process’s field experience shows Magsalia increases by a factor of 10 the sensitivity of the sensors and allows to characterise buried objects at depth of 20 cm below the ground surface.

This process has helped to improve knowledge on agrarian structures, parcels of land and the preserved antique habitat to be found in there. The history of human occupation on this forest massif could thus be outlined.

 

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