Documenting ancient anthropogenic signatures by remotely sensing the current vegetation spectral and 3D patterns: A case study at Roman Porolissum archaeological site (Romania)

摘要

The landscape at the Roman Archaeological Site from Moigrad-Porolissum, Romania, is nowadays mostly forested. But how did it look during the Roman period (106-275 AD)? Also, how can multispectral imagery and laser scanning be combined more effectively to detect the signatures of ancient sub-surface archaeological remains? This study employed WorldView2 satellite and LiDAR (Light Detection And Ranging) data to explore current remotely sensed vegetation and terrain proxies. These helped identify past anthropogenic signatures embedded within the landscape for reconstructing the ancient engineered environment. The spectral vegetation and terrain patterns revealed 227 marks (36256.22 m) relevant for the historical landscape, of which 182 correspond to ancient sub-surface features. In open landscapes, the two techniques had equivalent results, while LiDAR provided better detection rates in shrubland patches and forests. Their successive application is an advantageous strategy for optimizing costs. The satellite imagery is employed first, followed by the density analysis of the results, while the more expensive laser-based data collection can be focused on the problematic or promising areas. The vegetation and terrain marks revealed the intricate and extensive ancient defensive system that extended on over 24.5 km(2). Their strategic functions, requiring visibility between and around them, suggest large-scale deforestation (probably over 1 km around the structures). Thus, in contrast to the present forest dominance, it appears that in the 2nd and 3rd centuries AD, at Porolissum there was an anthropogenic open landscape covering over 2158 ha, with urbanization and intense military activity on 198.76 ha.