Network scale monitoring of transportation infrastructure in Ireland using full resolution EGMS InSAR data

Aging earthworks pose significant challenges that are being exacerbated by climate change and associated extreme weather events, which has led to numerous failures to critical Irish, UK and International transportation infrastructure. However, slope failure is not the only concern. Serviceability associated with seasonal (shrink-swell) movements is also a big problem, particularly in the UK (soft clays in the SE of England in particular) and in Ireland (peatlands). Extreme wet weather and unusually hot and dry conditions can lead to shrinkage and swelling of earthwork fill materials, resulting in considerable service disruption. Transportation line closures and service disruptions can significantly impact quality of life, for instance by increasing commuting times for road and rail passengers. Therefore, accurate and timely monitoring of transportation networks is important to enable proactive intervention strategies and to avoid failures. These networks are many thousands of kilometres in length, which, given the heterogeneous nature of the infrastructure, makes it extremely challenging to identify problem areas and monitor their condition using existing approaches, which rely heavily on infrequent, in-person visual assessments. The European Ground Motion Service (EGMS) provides free and accessible Europe-wide ground motion products for ground displacement analysis. This service offers a valuable opportunity for nationwide ground motion monitoring across transportation networks. But it has not yet been fully leveraged at nationwide scale. In this study, full-resolution calibrated Level 2B EGMS products (2019–2024) are used to monitor transport networks in Ireland. Ascending and descending Line-of-Sight (LOS) observations are extracted within a 25 m buffer along the networks. A nearest-point search strategy is applied to combine the ascending and descending observations to derive vertical and horizontal displacements at full resolution. This strategy identifies matching pixels within 5 m in predefined groups (middle, left shoulder, right shoulder) along transport networks. Matching points are then used to compute vertical and horizontal displacements at each location, maintaining high spatial detail. The analysis first evaluates EGMS's potential and limitations for transport infrastructure monitoring, including spatial coverage of ascending, descending, vertical, and horizontal products, as well as data quality and density along linear features. Problematic sections of the transport networks with high rates of ground motion (i.e., ascending, descending, vertical, horizontal, and seasonal) are identified. Example problematic sites with significant ground motion are then analysed in detail. Sentinel-1 images from 2016 to 2026 are applied to monitor the long-term ground motion of these sites using the open-source SARvey software. Cross-validation is performed against available supplementary datasets, such as hydrological, geological, geotechnical, and meteorological records, at selected locations to contextualise observed motions.