New Perspectives for UAV-Based Modelling the Roman Gold Mining Infrastructure in NW Spain

Abstract

This contribution discusses the potential of UAV-assisted (unmanned aerial vehicles) photogrammetry for the study and preservation of mining heritage sites using the example of Roman gold mining infrastructure in northwestern Spain. The study area represents the largest gold area in Roman times and comprises 7 mining elements of interest that characterize the most representative examples of such ancient works. UAV technology provides a non-invasive procedure valuable for the acquisition of digital information in remote, difficult to access areas or under the risk of destruction. The proposed approach is a cost-effective, robust and rapid method for image processing in remote areas were no traditional surveying technologies are available. It is based on a combination of data provided by aerial orthoimage and LiDAR (Light Detection and Ranging) to improve the accuracy of UAV derived data. The results provide high-resolution orthomosaic, DEMs and 3D textured models that aim for the documentation of ancient mining scenarios, providing high-resolution digital information that improves the identification, description and interpretation of mining elements such as the hydraulic infrastructure, the presence of open-cast mines which exemplifies the different exploitation methods, and settlements. However, beyond the scientific and technical information provided by the data, the 3D documentation of ancient mining scenarios is a powerful tool for an effective and wider public diffusion ensuring the visualization, preservation and awareness over the importance and conservation of world mining heritage sites.been also established as a standard of value and currency since the world's first coinage in Lydia (643-630 BC) [5]. However, significant advances in ore deposits prospection and exploitation did not occur until the onset of the New Age. The systematic exploitation of gold ore deposits may have started during the period of Roman domination in the Mediterranean. According to recent archaeological findings in the mining site of Pino del Oro (Zamora), Sánchez-Palencia et al. [6] suggest that the earliest prospection works in northwest Spain started during pre-roman times. The northwest Iberian Peninsula represents the largest Roman gold mining prospect in the world, with the Las Médulas world-class site as one of the most remarkable gold mines due to its important landscape transformation [7][8][9]. In this area, more than 93.5 billion m 3 of Cenozoic sediments were removed by the Romans, recovering upon 5 t of gold [10]. Due to its archaeological and natural values, this site was declared a UNESCO World Heritage Centre in 1997, although recent works based on Airborne Laser Scanning Technology (ALS) suggests that it may not be the largest Roman goldmining site in terms of recovered gold quantities [11,12].Roman gold mining works in northwest Spain were active from the 1st until the 3rd centuries AC. After that period, little gold mining-related information is known, with only minor documented exploitations during the Middle A...

Unraveling the Morphological Constraints on Roman Gold Mining Hydraulic Infrastructure in NW Spain. A UAV-Derived Photogrammetric and Multispectral Approach

“…Besides the different methodologies employed for improving the identification of channels [14,20,21], the analysis of the geometric characteristics is a matter of discussion among researchers [35]. Hitherto, the dimensions and width of the channels were considered to vary according to the availability of water resources.…”

“…This suggests that the width of the channel box was not only conditioned by the availability of water resources but must also be controlled by geological factors, which makes the construction of the channel layout difficult, such as the hardness of the rock, its texture, and the fracture pattern. Besides the different methodologies employed for improving the identification of channels [14,20,21], the analysis of the geometric characteristics is a matter of discussion among researchers [35]. Hitherto, the dimensions and width of the channels were considered to vary according to the availability of water resources.…”

“…Eventually, the combination of high-resolution Digital Terrain Models (DTM) generated from LiDAR and UAV-derived data with image enhancement tools led researchers to improve the visualization of the terrain morphology and mining remains. Undoubtedly, this has had a thoughtful influence on geoarchaeological research by unveiling new findings in the past years [20], highlighting the potential of UAVs for the study of Roman gold mining infrastructure [20,21]. However, the problem of landscape geoarchaeology for identification of ancient structures in areas with dense vegetation cover remains.…”

“…Until now, most scientific attention was paid to the documentation of the hydraulic network using traditional stereoscopic images, LiDAR and UAVs [9,14,[20][21][22][23]. Often, the accuracy of surveying works, and recognition based on aerial images of morphological features strongly depends on subjective factors inherent to the technician experience, technology, and other extrinsic parameters, such as quality of vision [24].…”

A review of UAV monitoring in mining areas: current status and future perspectives

“…They can replace traditional measurements, and complete previously time-consuming and laborintensive tasks rapidly, obtaining periodic data while ensuring much better resolution than satellite images (Agarwal et al 2006). However, the low endurance means that UAVs need more flights in order to cover a large area (Tong et al 2015), which is undoubtedly a challenge in poor regions without continuous power supply (Fernández-Lozano et al 2018). At the same time, the payload is currently too low and is susceptible to environmental factors such as weather and terrain (Martin et al 2015;Salvini et al 2018).…”