Multimethodological Geophysical investigations to study the archaeological site of Norba (Norma, Central Italy)

To enhance the knowledge of the unexcavated portions of the archaeological site and to locate the position of the unknown buried structures, geophysical prospections employing the Ground Penetrating Radar method were performed between September and November 2017. For the measurements, a GPR system SIR3000 (GSSI), equipped with a 400 MHz bistatic antenna with constant offset was employed to survey 18 different sectors closing to few excavated area. Taking into account the environmental conditions of the site and the nature of the hypothesized structures, some areas have been surveyed with a spacing interval between parallel profiles of 0.25 m while other areas have been investigated with a spatial interval between closed parallel profiles of 0.50 m. Furthermore, differential magnetic surveys were carried out using the Geoscan FM256 in two areas, overlapping the GPR areas. With the aim to have a better understanding of the subsurface, a qualitative and quantitative integration of the results, have been employed. For the integration process the following techniques: maps overlays and RGB colour composites (graphical integration), binary data analysis and cluster analysis (discrete data integration) and data sum, data product and principal component analysis (continuous data integration) have been used. The results obtained from the geophysical surveys were interpreted together with the archaeologists to define the meaning of the individuated structures and to enhance the knowledge of the ancient town's layout and mapping.