The contribution of geophysical prospecting to the reconstruction of the ancient topography of the Messapian necropoleis in Lecce

Extensive urbanization cover important archaeological structures that are still buried in the urban areas. Ground Penetrating Radar method is the most promising alternative for resolving buried archaeological structures in urban territories. In this paper a case study that involves a geophysical survey employing the surface three-dimensional (3D) GPR techniques, in order to archaeologically characterize the investigated areas. GPR measurements, integrated with archaeological and topographical research aimed at the production of a digital archaeological map integrated in a webGIS platform, were carried out in some areas in the historical centre of Lecce (Apulia, Italy). The investigate areas are related to some sectors of the Messapian necropolises (dated mainly in 4th-3rd century BC), characterized by different types of graves (pits dug in the bedrock or built with slabs, sarcophagi and hypogea) that lied also inside the settlement surrounded by city walls. Geophysical survey was carried out using the IDS Hi Mod georadar system, incorporating the dual band 200-600 MHz centre frequency antennae. The GPR time slices were constructed from closely spaced parallel profiles. The time slices, computed from averaging radar reflections over vertical time windows several nanoseconds thick, are used to map subsoil features associated with the structures, probably of anthropogenic origin. The time slices were georeferenced in the archaeological map of Lecce in order to acquire new data on the distribution and the ancient topography of the funerary areas inside the settlements. Moreover, to facilitate the interpretation of the results, a three-dimensional image was constructed using closely spaced parallel profiles, which are interpolated.