Assessing the potential of multispectral and thermal UAV imagery from archaeological sites. A case study from the Iron Age hillfort of Villasviejas del Tamuja (Caceres, Spain)

In recent years, the miniaturization of remote sensing equipment and the striking improvement of UAV technology has provided a new, high-resolution view of archaeological sites beyond the visible spectrum. This work explores the potential of low altitude remote sensing (multispectral and thermal infrared imaging) for the study of complex archaeological zones through the study case of an Iron Age hillfort in the southwest of the Iberian Peninsula. We describe the methodology developed in order to maximize and objectively quantify the detection of buried structures. On the one hand, we evaluate the capacity to categorize the response to varying depths of the overlying sediments, exploring the limits of the statistically significant separability between noise and signal. On the other hand, thermal IR images taken at different times of the day are compared to assess the optimal conditions for the identification of archaeological features. The results reveal that although we can only approach meaningful separability values, it was possible to identify a large number of buried structures. These results were finally validated by comparison with the data obtained by geophysical survey and excavation.