MODAGSPACE · The management of agrarian areas from Protohistory to modern times: modeling time-space dynamics from archaeological sources, written and environmental data

The management of agrarian areas from Protohistory to modern times: modeling time-space dynamics from archaeological sources, written and environmental data

The MODAGSPACE project focused on the study of time-space dynamics of agrarian areas in the long term (from Protohistory to the 19th century), mainly from the analysis of ceramic material collected 'off-site' during fieldwalking operations, coupled with various other sources and especially light detection and ranging (LIDAR) derived digital terrain models (DTM). The main study area of this project is located in the South of France along the plain bordering the Mediterranean Sea (Languedoc). It is situated around the coastal lagoon between the towns of Mauguio and Lunel, in a very flat area, a marshy zone heavily managed during the past and currently occupied by scrubland, vineyards and arable land. A LIDAR survey was carried out in 2006 and the group has produced a DTM with a resolution of 0.5 m. This data was used for archaeological interpretation, with the aim to detect and then compare the location of the paleofeatures identified with the knowledge acquired about the land use of this region from Protohistory to Modern times. The high resolution of the LIDAR DTM is well adapted to the detection of micro-relief. But this precision is also problematic in the context of fields, which are still under cultivation, because the plough lines and other modern developments produce a lot of noise. Thus, we tried to use existing tools like edge detection and Fourier analysis from image processing software. The recognition of paleofeatures on LIDAR digital elevation models depends on the way this data is displayed. Particularly, the hillshading model chosen is very important in our capability of identifying remains of human activity. We tested two different hillshading models: the Swiss hillshade model and the multi-directional oblique weighting hillshade model (MDOW). Our conclusion would be not to choose a single method, but to combine and test several ones and use advanced methods, such as sky view factor developed by the group. The advantage of LIDAR DTM, comparing to other sources, is that it allows the detection of small changes in relief, which are invisible on the field. The digitising of these anomalies allowed the detection of 85 features within the extent of the lidar coverage. The comparison of the location of these features with a recent orthophoto coverage showed that 80 % of them were not visible in the current landscape and 75 % of them were not visible on the 19th century cadastral maps. Most of the detected anomalies are linear features that we can interpret as former field boundaries, channelling or drainage ditches. We compared the directions of these features with several other known field systems first planned in the Roman times or drawn in the 19th century. Secondly, we compared the location of lidar features with the location of agrarian manurings and settlements identified during the fieldwalking campaigns, in order to build a hypothesis on the chronology of these paleofeatures. The results show a slight, but statistically relevant, difference between the minimum distances observed for LIDAR paleofeatures and that for random points. The average minimum distance for random points is much higher than LIDAR features, indicating a possible link between the location of features detected by LIDAR and by fieldwalking. The second study area was located near Vaunage in the northern part of the Languedoc area. The data of the agrarian manurings for the area were already available, but the semantic data regarding medieval and modern ceramics were not recorded. A corpus of texts documenting the Languedoc comprises thirty groups of texts dated from the mid-twelfth century. These will be studied in two main directions: the identification of changes in land uses and assessment of land quality. The integration of these data is still largely to be done, as soon as the chronology of the agrarian manurings will be precise. Then the challenge will be to map as much information taken from the medieval texts as possible.

Data: CORDIS, © European Union