New research perspectives on LiDAR in Central Italy for understanding Final Bronze Age and Early Iron Age highland contexts: an overview of drone LiDAR survey possibilities

The exploration and documentation of archaeological contexts in highland areas of Central Italy have often been neglected due to extensive reforestation campaigns carried out during the last century. Consequently, many of these areas have remained marginal in recent archaeological research, except for some studies conducted by Andrea Cardarelli and Laura Bonomi Ponzi on specific sectors and different chronologies. However, the spread of increasingly advanced remote sensing technologies has opened new opportunities for territorial study and has encouraged the implementation of projects based on the use and subsequent development of these techniques for archaeological purposes. Among these, LiDAR proves fundamental for its ability to distinguish between vegetation and anthropic structures, thanks to the reflection coefficient of objects, allowing for precise reproduction of the environment. Interest in the mountainous areas of the Apennines is fuelled by the availability of LiDAR data that was processed between 2008 and 2009 by the then Ministry of Environment (now Ministry of Environment and Energy Security) for purposes other than archaeological research, but which has enabled new research through the reprocessing of the same point clouds. However, this is not sufficient for conducting in-depth analyses of the area of interest; in fact, the available LiDAR coverage for Central Italy covers only 42% of the territory. To understand the archaeological record during the Final Bronze Age and Early Iron Age in the highland areas of Central Italy, an integrated database was created within a GIS system. It incorporated data derived from bibliographic research aimed at identifying contexts characterized by artificial defense systems. These data were subsequently verified through remote surveys using Italian ministerial LiDAR to identify any visible and recognizable traces. Additionally, a mapping of potential archaeological contexts was carried out, leading to the identification of 1122 new sites with LiDAR anomalies within an area of 26,431 km², corresponding to the portion of territory covered by LiDAR, out of a total of 68,858 km². Of these, bibliographic and chronological information, often generic, was only obtainable for 25% of the sites. However, many fundamental contexts for understanding the dynamics of protohistoric occupation and territorial control fall within the territory without LiDAR coverage, including Monte Croce Guardia (Arcevia -- AN). This already known settlement is the subject of new LiDAR investigations for better understanding of archaeological data through the use of the DJI Matrice 350 RTK drone and LiDAR sensors CHC AlphaAir 10 and DJI Zenmuse L1. The settlement of Monte Croce Guardia (Arcevia, AN) has been the subject of various excavation campaigns in different temporal phases. The first interventions date back to the 1960s, initiated following the discovery of structures during reforestation operations in the area. Subsequently, the site was reinvestigated in the late 1990s and, more recently, in a cycle of excavations conducted from 2015 to 2022 by Sapienza - University of Rome. However, in none of these phases were artificial defense works recognized, which might today be concealed by the dense vegetation present in the area. The current LiDAR analysis aims to verify the presence of any traces of fortifications or other structures of archaeological interest, overcoming limitations related to vegetation coverage. For this investigation, two LiDAR sensors with different characteristics and capabilities are being used: the CHC AlphaAir 10 and the DJI Zenmuse L1, mounted on a DJI Matrice 350 RTK drone. The objective is twofold: on one hand, to identify hidden structures and improve knowledge of the site; on the other, to evaluate the specific potential of each sensor and their applicability in archaeological field. This methodology, which combines the analysis of detected anomalies with a systematic comparison between data collected from the two sensors, is part of a broader research context: it aims to optimize the use of LiDAR technologies for studying highland sites, where vegetation presence and access difficulties represent significant obstacles for traditional archaeological investigation. This work has two main goals: archaeological and technical. The first purpose concerns the identification of new traces of archaeological interest in areas covered by dense vegetation, often inaccessible through traditional investigation methods. In particular, it aims to answer unresolved questions about the presence of artificial defense works in sites like Monte Croce Guardia, where the absence of evidence during previous excavation campaigns might be due to the difficulty of direct ground analysis. The use of LiDAR, with its ability to penetrate vegetation and return detailed surface models, offers a unique opportunity to expand knowledge about fortification systems and other structures of archaeological interest. The second purpose, of a technical nature, focuses on comparing two LiDAR sensors with different characteristics and costs: the CHC AlphaAir 10, a high-end device, and the DJI Zenmuse L1, a more economical solution. Through the analysis of data collected in real operating conditions, the aim is to evaluate the performance of each sensor in terms of archaeological detail detection capability, terrain reconstruction accuracy, and reliability in discriminating between anthropic structures and natural formations. This comparison will not only determine the most suitable solution for specific archaeological contexts but will also contribute to defining new guidelines for the use of LiDAR technologies in future projects, optimizing available resources. This analysis constitutes one of the specific investigations of the author’s ongoing doctoral thesis, aimed at exploring the potential of LiDAR technologies for archaeological documentation and the study of settlement dynamics in protohistoric times.