Revisiting Cosa (Ansedonia, Italy): contributions of SAR-X images from the PAZ satellite to non-invasive archaeological prospecting

 Highlights: Some archaeological results obtained using SAR-X images received through the PAZ satellite and applied to a part of what was called Ager Cosanus are shown in this article. The study has been completed with the analysis of multispectral images TripleSAT and Sentinel-2A and the historical aerial photos from 1944 and 1954. The possibilities of using PAZ images treated multi-temporally as a high-resolution panchromatic image applicable to multispectral optical images of the type Sentinel-2 were tested. Abstract: Some archaeological results are shown in this article, which have been generated from the use of Synthetic Aperture Radar (SAR)-X images obtained from the PAZ satellite and applied to part of what was called Ager Cosanus, that is, the territory of the city of Cosa, which was one of the first maritime colonies of Rome in the heart of Etruscan territory. Our study has been carried out mainly based on previous works in which a set of images was used to improve the quality of the resulting image, reducing the noise caused by the speckle of the radar images and maintaining the quality of the spatial resolution that can be obtained from these images (1.25 m/pixel). More specifically, a set of images obtained between 2019 and 2021 was used. The study has been completed with the analysis of multispectral images TripleSAT and Sentinel-2A, the historical aerial photos taken from 1944 and 1954, and the use of the historical cadastre of Tuscany, prepared at the beginning of the 19th century. As an addition, the Digital Terrain Model (DTM) Light Detection And Ranging (LiDAR) of the Region of Tuscany was used, on which various functions of the Relief Visualization Tool (RVT) programme have been applied, complementing or contrasting the results. It can be confirmed that the multi-temporal treatment of SAR PAZ images provides better results than an individualised analysis of the image. Finally, it is of great interest to verify the results of studies using new technologies, where it was previously possible to resort only to prospecting on the ground and to analogical aerial photography in black and white. In this case, the Sinistra Decumano I (SDI) structure was seen, which Castagnoli observed in the aerial photography, but of which he only located materials on the ground and it was visualised both in individualised PAZ images and in Sentinel-2.