GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 3.3 519 the areas corresponding to the highest absolute values of ∆ χ , which correspond to the areas where the dominant anomalies are found. These areas are further sampled in smaller cells and a new inversion is performed. The final map selected is the most likely map (MAP model). It is worth noting that the chosen Bayesian approach easily will allow us to extend the developed algorithm for a jointly inversion of data coming from different geophysical methods in an integrated framework. The MAG code has been used to invert the data collected during the magnetic survey in San Pietro Infine (Southern Italy), and the obtained results are compared with the information coming from the multi-methodological geophysical prospection performed in the survey area. Multi-methodological geophysical survey in the archeological site of San Pietro Infine (Southern Italy). Magnetic (MAG), frequency-domain electromagnetic (FDEM) and ground- penetrating radar (GPR) geophysical surveys were carried out in an area of 100×100 m 2 surrounding an outcropping building ( Il Torrione in Fig. 1), which represents an apse belonging to a layered religious complex, identifiable with the medieval building of San Pietro in Flea that was founded on a roman building (probably a statio transformed in a mansio , which was a post office) (Zambardi, 2007). The geophysical prospecting was aimed at identifying anomalies in the distribution of the observed physical parameters related to the presence of remains likely attributable to both the Sancti Petri in Flea church and the surrounding anthropic settlement. In particular, the study area was partitioned into four meshes (Fig. 1b), each 50m×50m in size, in which the data were collected along parallel profiles east-west oriented. Data acquisition parameters were chosen according to the size of the archaeological targets to be detected (i.e., streets, fortification walls, stationes , etc.), whose dimensions are expected to be in the range of a few meters. In particular, as it concerns the MAG survey, a distance of 0.5 m between the profiles was selected. The magnetic data were collected by using the GSM19 Overhauser total field magnetometer (GEM System) in gradiometric configuration with two omnidirectional sensors positioned at 50 cm and 70 cm, respectively, from the surface level. Fig. 2 shows the Fig. 2 - Anomaly map of the vertical magnetic gradient observed in the test area (see Fig. 1b). The black aa’ line represents the inverted MAG profile.