Mapping Ground Instability in Areas of Geotechnical Infrastructure Using Satellite InSAR and Small UAV Surveying: A Case Study in Northern Ireland

Abstract

Satellite Interferometric Synthetic Aperture Radar (InSAR), geological data and Small Unmanned Aerial Vehicle (SUAV) surveying was used to enhance our understanding of ground movement at five areas of interest in Northern Ireland. In total 68 ERS-1/2 images 1992-2000 were processed with the Small Baseline Subset (SBAS) InSAR technique to derive the baseline ground instability scenario of key areas of interest for five stakeholders: TransportNI, Northern Ireland Railways, Department for the Economy, Arup, and Belfast City Council. These stakeholders require monitoring of ground deformation across either their geotechnical infrastructure (i.e., embankments, cuttings, engineered fills and earth retaining structures) or assessment of subsidence risk as a result of abandoned mine workings, using the most efficient, cost-effective methods, with a view to minimising and managing risk to their businesses. The InSAR results provided an overview of the extent and magnitude of ground deformation for a 3000 km 2 region, including the key sites of the disused salt mines in Carrickfergus, the Belfast-Bangor railway line, Throne Bend and Ligoniel Park in Belfast, Straidkilly and Garron Point along the Antrim Coast Road, plus other urbanised areas in and around Belfast. Tailored SUAV campaigns with a X8 airframe and generation of very high resolution ortho-photographs and a 3D surface model via the Structure from Motion (SfM) approach at Maiden Mount salt mine collapse in Carrickfergus in 2016 and 2017 also demonstrate the benefits of very high resolution surveying technologies to detect localised deformation and indicators of ground instability.

4D Monitoring of Active Sinkholes with a Terrestrial Laser Scanner (TLS): A Case Study in the Evaporite Karst of the Ebro Valley, NE Spain

“…Close-range photogrammetry was applied in a sinkhole site with very rapid subsidence in the Dead Sea, Jordan, to produce 3D digital models of the ground surface (accuracy 10-15 cm) and derive deformation models from them [14]. A similar photogrammetric investigation was conducted in an active salt-mine sinkhole in Northern Ireland using data acquired with an Unmanned Aerial Vehicle (UAV) [15].…”

Observing Geohazards from Space

“…With a similar combination of EO and remote sensing techniques, Cigna et al [8] discuss how to enhance the understanding of historical ground stability and motion in areas of geotechnical infrastructure and abandoned salt mine workings by means of satellite InSAR and tailored small UAV surveying. With a 3000 km 2 study area in Co. Antrim (UK), the authors utilise ERS-1/2 SBAS InSAR to achieve a baseline ground instability scenario over wide areas encompassing several elements at risk and strategic infrastructure.…”

PS-InSAR Analysis of Sentinel-1 Data for Detecting Ground Motion in Temperate Oceanic Climate Zones: A Case Study in the Republic of Ireland

“…Our study is the first (to our knowledge) to do so in Ireland with data from the recently available Sentinel-1 satellites constellation of the European Space Agency's Copernicus Earth Observation program. Previous attempts to apply multi-temporal InSAR to Ireland have been mainly based on using first-generation ERS-1/2 and ENVISAT satellite data and have been limited to urban areas, such as the cities of Dublin, Cork, [19,20] and Belfast [21]. With the recent development of the Sentinel-1 satellites, however, past issues stemming from low resolution in space and time may be surmountable even outside of urban areas.…”

“…Although previous attempts to apply multi-temporal InSAR to Ireland have been based on PS-InSAR but with ERS-1/2 and ENVISAT data [19][20][21], these studies were restricted to urban areas. Here…”