Context
Many cities sit on compressible soils, reclaimed land, historical mining zones, or aquifers under abstraction pressure. Ground movement in such settings is rarely uniform: one district may be stable while a neighbouring one settles steadily. Asset owners and insurers with urban exposure need to understand these spatial patterns without inspecting every building.
Challenge
Traditional approaches — levelling campaigns, GNSS stations, inspection visits — provide accurate point measurements but cannot economically cover thousands of buildings, and they rarely extend back in time. The challenge is to reconstruct multi-year movement histories across an entire urban area at the scale of individual blocks.
Data
Sentinel-1 SAR imagery acquired every 6–12 days over a multi-year period, in ascending and descending geometries. Dense urban fabric provides abundant persistent scatterers — building corners, roofs, and hard surfaces that reflect radar consistently over time.
Method
Persistent Scatterer InSAR (PSInSAR): stable reflective points are identified across the full image stack, atmospheric and orbital errors are estimated and mitigated, and a displacement time series is computed for each point relative to a reference area. Results are quality-checked and aggregated to building-block level.
Findings
In a typical demonstration processing of this kind, the majority of measurement points show velocities within a stable band, while localised clusters exhibit sustained movement of several millimetres per year, spatially coherent across adjacent structures. Time-series plots distinguish steady linear trends from seasonal signals and from step-like changes. (Demonstration description — replace with figures from a specific processed dataset.)
Business relevance
The output is a ranked spatial picture: which blocks moved, how fast, since when, and how that compares to their surroundings. For an insurer this supports portfolio review and underwriting context; for a municipality or asset owner it identifies where inspection budgets are best spent.
Limitations
PSInSAR measures movement of radar-reflective points, mostly on structures — not the ground beneath vegetation or water. Velocities are line-of-sight and relative to a reference. Cause attribution (groundwater, consolidation, mining, construction) requires supporting geotechnical and hydrogeological context.