Integration of satellite and aerial images with multichannel GPR surveys in the archaeological area of Augusta Bagiennorum for an improved description of the urban setting

Abstract

The archaeological area of Augusta Bagiennorum (NW Italy) is a well-known archaeological site, extensively investigated since the end of the 19th century. Previous archaeological studies in the area allowed a preliminary definition of the urban setting through several direct soundings. However, the current knowledge of the site needs to be more complete due to the limited extension of previous archaeological surveys. To obtain a more complete description of the urban setting, we analysed aerial and satellite images and multichannel Ground Penetrating Radar (GPR) surveys, which are two remote-sensing technologies often used in this field. Aerial images showed vegetation cropmark patterns in different areas, depending on the time of the day, year, and camera acquisition setup. The GPR surveys locally confirmed the presence of buried structures in correspondence with the cropmarks, and provided a more detailed view of the underground features. The GPR was also helpful in adding Ground Control Points for georeferencing hot-air balloon images. The combined view of aerial and GPR images allowed us to confirm the overall extent of the archaeological area, as reported in past archaeological reports. However, some of the observed structures were located outside the previously known extent of the town. The orientation of some suggests that the streets of Augusta Bagiennorum are not always arranged in a perpendicular pattern, typical of the Roman orthogonal town planning. The adopted methodological approach could be a valuable tool in similar case studies, since it provides multiscale information composed of both overall views and detailed images.