Satellite data for ground subsidence and deformation (InSAR)
By Mazdak Ghasemi · Last checked 22 October 2026
How can I measure ground subsidence from space?
With radar interferometry (InSAR), which compares repeat radar images of the same area to detect ground movement. ESA says it can monitor movement down to a few millimetres across wide areas. Sentinel-1 is the free standard, and the European Ground Motion Service measures ground movement across Europe from it.
Which data to use
| Data | Resolution | Revisit | Record | Use |
|---|---|---|---|---|
| Sentinel-1 radar | 10 m pixels; interferometry uses the SLC product | 6 days | From April 2014 | Free, regular repeat images for InSAR |
| ALOS-2 PALSAR-2 Stripmap (commercial) | 3 to 10 m | 14 days | Varies by area | L-band, which keeps coherence over vegetation better than C-band |
| ALOS-2 ScanSAR L2.2 (free) | 25 m pixels | 14 days | From August 2014 | Backscatter only: it cannot measure movement |
How it is done
- Collect a stack of radar images of the area from the same orbit over the period of interest.
- Compare the phase of the radar signal between dates: a change in the distance to the ground shows as a change in phase.
- Turn the changes into displacement over time, correcting for atmospheric effects, and check against ground survey points where they exist.
Limits to know
- Dense vegetation and changing surfaces (crops, water, construction) lose coherence, and movement cannot be measured there.
- InSAR measures movement along the radar's line of sight, not straight up and down.
- It needs many acquisitions from the same orbit, so short periods give weak results.
- The free ALOS-2 L2.2 product is backscatter only; interferometry needs the complex (SLC) products.
Who does this in practice
- The European Ground Motion Service measures ground movement across Europe with millimetre precision from Sentinel-1 InSAR.
- ESA lists land deformation among Sentinel-1's main applications.
What Terrascout returns
The real result for “Detect ground subsidence over the Perth metropolitan area” (Perth, WA), captured on 22 October 2026: the top 4 of 6 sources.
Radar (SAR) sources are listed first: the brief is about ground movement, which radar interferometry (InSAR) can measure to a few millimetres across wide areas.
| # | Source | Type | Resolution | Cost | Fit |
|---|---|---|---|---|---|
| 1 | Sentinel-1 C-SAR | Radar | 10 m | No data fee | 97 |
| 2 | ALOS-2 PALSAR-2 | Radar | 3 m | Commercial (price on request) | 84 |
| 3 | Sentinel-2 MSI | Optical | 10 m | No data fee | 95 |
| 4 | ALOS-2 PALSAR-2 ScanSAR L2.2 | Radar | 25 m | No data fee | 91 |