Geomatics

The Vere River basin in Tbilisi, Georgia, experienced a major cascading landslide–flood disaster in June 2015, emphasizing the need to evaluate the present stability of slopes adjacent to the former source area. This study combines small-baseline InSAR (SBAS), RTK-UAV photogrammetry, COSI-Corr image correlation and LS-RAPID numerical modeling to investigate whether the slope remains active and how it responds to changing pore-pressure conditions. Analysis of 109 ascending Sentinel-1 acquisitions acquired between April 2022 and October 2025 revealed persistent positive line-of-sight deformation across the investigated slope. Independent UAV/COSI-Corr analysis identified horizontal displacements of approximately 0.05–0.09 m over 149 days, exceeding the empirical relative displacement detection threshold of 0.0235 m. The measured displacement direction broadly follows the downslope and structural orientation, although its angular offset suggests that the movement is influenced by a combination of topography, bedding, fractures, and heterogeneous slope materials rather than a single planar control. LS-RAPID simulations further showed a nonlinear response to increasing prescribed pore-pressure ratio. Together, the observations indicate that the slope has not fully stabilized after the 2015 event and continues to undergo slow deformation while remaining sensitive to hydrological conditions. This is particularly important for Tbilisi because renewed slope instability in the Vere valley could interact with the confined river corridor and urban infrastructure, increasing the potential for cascading impacts.

Coastal wetlands at urban margins experience interacting thermal, land-surface and hydrological pressures, yet composite remote-sensing assessments require transparent weighting, uncertainty analysis and careful interpretation. This study assessed late-autumn to early-winter environmental conditions across the 6.906 km² Mai Po Marshes–Inner Deep Bay wetland system, Hong Kong, from 2000 to 2025. Landsat Collection 2 Tier 1 Level-2 scenes were harmonized into annual October–December composites to derive land-surface temperature, NDVI, MNDWI, NDBI, water-observation frequency and mapped aquatic area. The Relative Potential Hydrological Connectivity Index combined annual water frequency with proximity to persistent Inner Deep Bay open water, while the Wetland Environmental Stress Index integrated thermal stress, built-up pressure, vegetation deficit, moisture deficit and hydrological isolation using equal weights. Across 22 adequately observed years, NDVI increased significantly and MNDWI declined significantly. Mapped aquatic area also declined significantly, with a primary-threshold Theil–Sen slope of −0.04796 km² per year. Full-series MNDWI sensitivity tests using thresholds of >0.00, >0.10 and >0.20 retained significant aquatic-area declines at all thresholds. In contrast, RPHCI showed no significant monotonic trend under any of the three MNDWI thresholds, and equal-weight WESI likewise showed no significant monotonic trend. Weighting sensitivity indicated stable annual rankings but substantial class changes under hydrology-emphasis weighting. The Landsat–MODIS temperature comparison showed poor agreement and was not treated as validation. Thus, WESI and RPHCI remain season-specific remote-sensing proxies rather than direct measures of annual ecological condition or hydraulic exchange within this wetland system.

Mobile Mapping Systems (MMSs) are increasingly adopted for transport infrastructure inspection, where reliable characterization of global and local geometry is essential. This is critical in GNSS-denied environments such as road tunnels, where trajectory estimation relies on inertial navigation and drift degrades geometric accuracy. This study investigates the influence of acquisition speed and ground control point (GCP) configuration on trajectory accuracy and geometric consistency in a 2.3 km road tunnel. MMS data were acquired at 15, 30, and 50 km/h and processed under progressively denser, uniformly distributed GCP configurations, from unconstrained to fully constrained solutions. Post-processed forward–backward smoothed GNSS/INS trajectories were validated against a topographic control network, and cross-sectional geometry against terrestrial laser scanning (TLS). Without external constraints, planimetric errors at independent check points reached 16.5 m and global deformation reached 0.46% at low speed. Ground control markedly reduced trajectory errors, depending on both control density and acquisition speed. In contrast, locally registered cross-sections showed millimeter-level consistency with TLS in all configurations: median discrepancies of 4–5 mm, with 75–82% of values below 10 mm. Local cross-sectional shape is therefore preserved despite substantial global drift, supporting MMS for shape-based tunnel inspection, while adequate ground control remains necessary for absolute georeferencing.