Autonomous Service Drones for Multimodal Detection and Monitoring of Archaeological Sites

Abstract

Constant detection and monitoring of archaeological sites and objects have always been an important national goal for many countries. The early identification of changes is crucial to preventive conservation. Archaeologists have always considered using service drones to automate collecting data on and below the ground surface of archaeological sites, with cost and technical barriers being the main hurdles against the wide-scale deployment. Advances in thermal imaging, depth imaging, drones, and artificial intelligence have driven the cost down and improved the quality and volume of data collected and processed. This paper proposes an end-to-end framework for archaeological sites detection and monitoring using autonomous service drones. We mount RGB, depth, and thermal cameras on an autonomous drone for low-altitude data acquisition. To align and aggregate collected images, we propose two-stage multimodal depth-to-RGB and thermal-to-RGB mosaicking algorithms. We then apply detection algorithms to the stitched images to identify change regions and design a user interface to monitor these regions over time. Our results show we can create overlays of aligned thermal and depth data on RGB mosaics of archaeological sites. We tested our change detection algorithm and found it has a root mean square error of 0.04. To validate the proposed framework, we tested our thermal image stitching pipeline against state-of-the-art commercial software. We cost-effectively replicated its functionality while adding a new depth-based modality and created a user interface for temporally monitoring changes in multimodal views of archaeological sites.

Using QGIS as an Ideal Workspace for Archaeogeography: A Case Study on Castronovo di Sicilia

“…Thermal and multispectral drone photos: During the end of April 2021, targeted flights with drones equipped with thermal and multispectral sensors were carried out in specific areas of the investigated zone. The results of these flights were then integrated into QGIS, which made it possible to extract the thermal orthophoto of the images in four channels (RGB + IR), obtained from the structure from motion process [14,15], and to process the vegetation indices from the multispectral photographs, which were useful for the identification of archaeological elements that were not visible on the surface [16].…”

Geomatic Sensors for Heritage Documentation: A Meta-Analysis of the Scientific Literature

“…Although the camera and drone should be considered as two separate pieces of equipment, each with its own characteristics, vendors dominating the recreational market have introduced combo solutions and have unified characteristics for their products, limiting users' choices. Some drones allow for payload choices, including various RGB cameras, thermal, multispectral, hyperspectral, and LiDAR sensors [52][53][54][55][56][57], but these are aimed at specialized applications/customers.…”

Integration of Thermal and RGB Data Obtained by Means of a Drone for Interdisciplinary Inventory

“…The development of the application of UAV technology to different remote sensing and mapping technologies can also be applied to thermography. Nowadays, UAVs are able to carry different sensors used for thermal acquisition: near-infrared cameras [29], thermal cameras [25,[30][31][32][33][34][35][36], but also multispectral cameras [14,27,37,38] and multimodal platforms with RGB, thermal and depth cameras [39]. In addition, thermal sensing can be executed in complex objects with limited access, thanks to UAV flight flexibility; thermal data can be acquired from the sides without sufficient visibility from the ground view or aircraft operation height.…”

“…In addition, thermal sensing can be executed in complex objects with limited access, thanks to UAV flight flexibility; thermal data can be acquired from the sides without sufficient visibility from the ground view or aircraft operation height. The new applications of UAV thermal sensing are presented in several areas: archaeological sites [25,39], heritage buildings [30,33], and modern buildings [31,34], including photovoltaic inspections [23]. UAV thermography is also applied for thermographic DTM generation [25,32], and crop field sensing [37].…”