D-SITE 2022 International Conference – 16-18 juin 2022
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Second Session: Aerial, Ground and Underwater Robotics for Cultural Heritage
University of Pavia – Department of Civil Engineering and Architecture
– Fabienne Dugast, Isabelle Le Tellier – «Detection of buried archaeological remains in large areas. Methodological review and feedback on the use of combined UAV technologies: LiDAR, Infrared and Magnetic measurement. Case study of the Eure Valley (France)»
Our communication will present the outcomes and findings following two years of fieldwork as part of the research project, namely ValEuRT (Eure Valley: One River, Several Territories), initiated by the CNRS Laboratory Orient & Méditerranée (UMR 8167, Paris). The aim of this project is to study the land-use and settlement dynamics over the ages (from the Neolithic period to the present day) of the Eure catchment, little-studied part of the western Paris Basin, France. Located at the crossroads of several culture areas, the Eure valley has a rich archaeological and historical past, but no obvious traces are visible on the ground.
As it represents more than 3,000 square km in area, extending between Chartres in the South and the confluence with the Seine in the North, it cannot fit easily within a fieldwalking survey or traditional ground geophysical prospecting.
In addition to conventional archaeological exploration technologies, airborne geophysical campaigns by drone have been programmed to serve as a test before implementation on a larger scale. Four distinct zones with slight traces of ancient or medieval remains, were selected from the analysis of aerial photos taken by plane in the past decade. Each of these zones are 20 to 110 ha in area and from different type of soil: silty alluvial plain, stony alluvial plain (outcrops of flint), the third one, limestone table. The last zone, unlike the first three that are agricultural fields, is wooded.
The technical solutions that have in the first place been selected are LiDAR, Infrared and Magnetic measurement. Theoretically, these technologies allow us to obtain surface information under ground cover and sub-surface information to locate and describe archaeological remains.
- LiDAR provides complete microtopographic coverage with an accuracy of 5 to 20 cm. In addition to providing an accurate, up-to-date topographic map, that serves as a support document for any survey, the interpretation of microtopography classically reveals archaeological traces on the ground, that are not visible to the naked eye (Figure 1).
- Thermal mapping, by measuring the Infra-Red radiation of the ground, can reveal weakly buried structures made up of materials that have a different thermal conductivity from their surroundings. This technology has shown good results for low walls or old buildings that do not come out in microtopography (Figure 2).
- The magnetic measurement technology has been widely tested in ground geophysical survey, to locate weakly buried structures with a conductivity that contrasts with the surrounding rock. The aim of this project is to validate the use of this technology in airborne by drone.
While LiDAR by drone is a well-established technology, thermal and magnetic measurements are tricky because of their implementation and the influence of the environmental measurements (ground, nearby activity, weather, etc.).
The paper focuses as much on the field methodology as on the post-processing of the data and their interpretation. This being an exploratory project, the results are leading to new insights about UAV sensors implementation in the field of cultural heritage.