Detection of funerary monuments in the northern necropolis of Segobriga using multispectral and georadar imaging

The existence of an extensive Gräberstraße-type necropolis in the Roman city of Segobriga is confirmed by the funerary-type structures located 2,400 m from the city and by the excavation of five funerary monuments located along its main entrance/exit road. The inscriptions, sculptures and architectural remains of funerary character exhumed prove, in addition, its use by members of the higher social classes, including wealthy freedmen. Until now we did not know the spatial structuring of the monumenta and their relationship with each other and with the road. This information is vital to know the internal topographic organisation and the constructive density of the necropolis. Geophysical surveys with ground penetrating radar (GPR) and multispectral images captured with unmanned aerial vehicles (UAV) have recently been carried out in order to improve our knowledge in this field. They have been developed within the framework of an ongoing research project to study the northern suburb. The objective of these surveys was to identify new funerary monuments not visible on the surface along the route of the road. This paper analyses the methodology and processing of the two techniques used. It also evaluates their comparative applicability to detect buried remains in calcareous soils. The data obtained indicate the presence of mausoleums on both sides of the roadway according to the Italic model of funerary viae. Those located in the first line form two continuous rows, while isolated monuments are located at the rear. This model prevailed in the cemetery areas of the Western Roman Empire from the end of the 1st century BC onwards.