GNGTS 2016 - Atti del 35° Convegno Nazionale

566 GNGTS 2016 S essione 3.2 For the site in Fondi it could show to a good approximation how the cisterns were “seen” by the single methods; furthermore, the matching of the anomalies confirms the presence of structures. For the Santa Balbina site instead the overlays do not show good matching anomalies, however, it could be useful to discern the differences between the datasets, especially, in this case, in terms of resolution. One disadvantage of this method is that the images might become too confusing if many datasets are overlaid. RGB Colour Composites. In this visualization method, to each of the dataset is assigned Fig. 1 – Results for the Appian Way site (Depth: 1.4 m). a) Normalized GPR and ERT data for a depth of 1.4 m. b) Contour map overlays: GPR data is represented as black contour lines; ERT data is represented as red contour lines. c) RGB colour composite: green indicates the GPR slice and red indicates ERT slice. d) Results for Data Sum. e) Results for Principal Component Analysis (1 st principal component).