Conference Agenda

In the Dragon-5 project SARchaeology, we are working on using satellite SAR data and developing methods to support archaeological prospections and heritage site protection. SAR offers unique advantages, but also several challenges in this field. During Dragon-5, our work focused so far on study sites in China, Russia, Italy, Norway, and Turkey. However, due to the sanctions imposed on Russia, the cooperation on this test area came to a stop, so that the team members who were working on this site (i.e. University of Sydney) are currently focusing their attention on the other areas. In terms of employed methodologies, a strong focus is on the use of long-term multi-baseline SAR interferometry for continuous surface motion stability analysis on cultural heritage sites, as well as change detection methods. In terms of change detection, various approaches are under development, ranging from PSInSAR-based detection of urban developments, automatic coherence and amplitude-based change detection for looting mapping, and coherence change detection for damage assessment. Additionally, multi-sensor / multi-angle image analysis for post-earthquake damage detection in high-resolution SAR images has been undertaken for damage detection after the devastating earthquake that hit Turkey and Syria on 2023-2-6, damaged a vast area and led to immense loss in lives. The area is also well-known for its richness in cultural heritage und unfortunately, widespread damages to cultural heritage has been witnessed. To support the identification of damages at sites of archaeological interest, the team used data from the Dragon-5 project as well as several Third-Party Mission (TPM) data sources. Not all damages to cultural heritage are clearly visible from remote sensing imagery and the situation gets significantly worse when using SAR data. Even using very high-resolution TerraSAR-X staring spotlight datasets, damages are often hard to identify without the availability of similar images acquired before the disaster, which are missing. This proves the importance of continuous observation missions, like Sentinel-1, from which (albeit the very low spatial resolution) damage maps can be derived through coherence change detection analysis, which than can be used as a starting point for visual inspection on high-resolution optical images or very-high resolution SAR images. With optical imagery, the weather conditions play a central role in the detectability of damages, while on SAR images the image configuration, for example orbit direction and looking angles, can determine if a damage is visible or not in a given image.

Looting provides a global threat to cultural heritage, but in the aftermath of natural or man-made disasters, looting unfortunately strives even more. Looting activities are detectable from remote sensing. However, small-scale looting pits/holes are not always identified as such. In an experiment on the detectability of looting activities within SAR data, we conduct an experiment in Wuhan (China), where we create an experimental looting site of two different sizes and monitor the area with SAR data before and after the ‘looting’. Based on the so generated data, we analyse the detectability of looting activity in TerraSAR-X imagery at different resolutions and analyse the influence of polarizations, looking angles, and other SAR acquisition parameters.

Within the experimental area of Wuhan, we are also interested in the threat that the fast urban development of Wuhan poses to cultural heritage sites in and around the city. The fast development of the urban area of Wuhan leads to encroachment of buildings on cultural heritage sites, that, although often protected, are in danger due to the economic pressure with rising property prices. Additionally, the urban development leads to subsidence, which can also threaten the stability of sites. Using long-term SAR interferometry, the subsidence affecting sites of cultural heritage are identified as well as possible endangerment from urban encroachment.

Using a similar approach, threats to cultural heritage assets in the capital city of Rome (Italy) and its surrounding rural landscape are characterised. Sentinel-1 image stacks acquired in 2018-2022 are processed with the SBAS method, and a series of urban sectors affected by ground instability are identified across the wider Province, such as in the area of Fiumicino international airport (representing a relatively young phase of urban development and associated land conversion) and along the Tiber River alluvium, involving monuments and heritage assets. Given the paucity of studies using multi-polarization datasets in InSAR deformation investigations, the performances of the SBAS chain using Sentinel-1 VV and VH cross-polarised channels were also trialled to identify the amount and quality of coherent targets that the method is capable to detect and track using the two polarisations.

So far, the team's work focuses on employing long-term multi-baseline SAR interferometry for continuous surface motion stability analysis on cultural heritage sites, as well as change detection methods. Furthermore, the project has also shown the importance of continuous observation missions, like Sentinel-1, for damage detection and mapping especially in the context of the earthquake in Turkey. The team's experiments on the detectability of looting activities within SAR data will be significant contributions to the field of archaeology and heritage site protection. With further development and collaborations, the SARchaeology project can continue to make significant contributions to the preservation and protection of cultural heritage sites globally.

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