Regional-Scale Systematic Mapping of Archaeological Mounds and Detection of Looting Using COSMO-SkyMed High Resolution DEM and Satellite Imagery

Abstract

“Tells” are archaeological mounds formed by deposition of large amounts of anthropogenic material and sediments over thousands of years and are the most important and prominent features in Near and Middle Eastern archaeological landscapes. In the last decade, archaeologists have exploited free-access global digital elevation model (DEM) datasets at medium resolution (i.e., up to 30 m) to map tells on a supra-regional scale and pinpoint tentative tell sites. Instead, the potential of satellite DEMs at higher resolution for this task was yet to be demonstrated. To this purpose, the 3 m resolution imaging capability allowed by the Italian Space Agency’s COSMO-SkyMed Synthetic Aperture Radar (SAR) constellation in StripMap HIMAGE mode was used in this study to generate DEM products of enhanced resolution to undertake, for the first time, a systematic mapping of tells and archaeological deposits. The demonstration is run at regional scale in the Governorate of Wasit in central Iraq, where the literature suggested a high density of sites, despite knowledge gaps about their location and spatial distribution. Accuracy assessment of the COSMO-SkyMed DEM is provided with respect to the most commonly used SRTM and ALOS World 3D DEMs. Owing to the 10 m posting and the consequent enhanced observation capability, the COSMO-SkyMed DEM proves capable to detect both well preserved and levelled or disturbed tells, standing out for more than 4 m from the surrounding landscape. Through the integration with CORONA KH-4B tiles, 1950s Soviet maps and recent Sentinel-2 multispectral images, the expert-led visual identification and manual mapping in the GIS environment led to localization of tens of sites that were not previously mapped, alongside the computation of a figure as up-to-date as February 2019 of the survived tells, with those affected by looting. Finally, this evidence is used to recognize hot-spot areas of potential concern for the conservation of tells. To this purpose, we upgraded the spatial resolution of the observations up to 1 m by using the Enhanced Spotlight mode to collect a bespoke time series. The change detection tests undertaken on selected clusters of disturbed tells prove how a dedicated monitoring activity may allow a regular observation of the impacts due to anthropogenic disturbance (e.g., road and canal constructions or ploughing).

Satellite-Based Methodology for Purposes of Rescue Archaeology of Cultural Heritage Threatened by Dam Construction

“…Shape is the second variable considered. The distinctive pseudo-circular shape of the majority of the archaeological mounds in the Near East is best appreciated during humid periods as confirmed by both Sentinel-2 (when the near-infrared signal "is more vivid", meaning during highly vegetative periods, Figure 6A) and COSMO-SkyMed imagery (in this case, processed as normalized backscatter images only and not as a derived product such as Digital Elevation Model like in [71]) (Figure 6B). In such agricultural landscapes, the irregular shape of the mound emerging during the humid season is even more pronounced by the regular shape of the cultivated fields located all around.…”

“…Its application has already demonstrated considerable effectiveness in documenting different types of cultural heritage hazards such as flooding [67,68], looting [4,62] and urban sprawl [3,69]. For the scope of the present research, it is worth mentioning that recent research has proved how Sentinel-1 and Sentinel-2 data can be effectively used for detection of archaeological mounds [70,71]. Furthermore, Sentinel image collections are also accessible and can be processed in GEE.…”

Copernicus Program: Artificial Intelligence in Cultural Heritage

“…These spaces, seen with the naked eye by researchers, do not show the social uses of the past, the buried artifacts, and the composition of the cultural landscape itself. The digital elevation model (DEM) is most frequently generated from airborne sensors, drones, terrestrial laser scanners, and satellite remote sensing (with an overview of the semantic categorization of potentials and practicality of such platforms for elevation data acquisition) [5]. With unprecedented data acquired continuously, the Copernicus satellite constellations provide essential information for analyzing and monitoring the Earth's surface and atmosphere [6].…”

Modern Dryland Source-to-Sink System Segments and Coupling Relationships from Digital Elevation Model Analysis: A Case Study from the Mongolian Altai

“…High-quality satellite imagery from various perspectives of the study area was acquired from Google Earth software. To cover all of the Jargalant Nuruu, NASA's (National Aeronautics and Space Administration) 30 m resolution SRTM DEM [51][52][53] was also applied for the S2S analysis. The SRTM GL1 Global 30 m Ellipsoidal (SRTM_GL1_Ellip) DEM data were obtained from OpenTopography, obtained by conversion from the orthometric version using the EGM96 geoid model [54].…”