Open Skies

Tools we use

• Sentinel-2 (ESA Copernicus)

  Free, 10 m resolution, ~5-day revisit. Used for base-footprint change detection over time. All imagery is openly licensed under the Copernicus terms.

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• Sentinel-1 (Synthetic Aperture Radar)

  Free C-band SAR imagery, all-weather, cloud-piercing. Used to track structural change at military cantonments where optical imagery is obscured.

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• Planet Labs — Education & Research

  3 m daily PlanetScope imagery available under Planet's research programme for verified academic and human-rights use.

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• Bellingcat — SAR Interference Tracker

  Open Google Earth Engine tool that locates active military radar emissions from public Sentinel-1 data. Used as a leading signal of operational radar sites.

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• Bellingcat — Remote Sensing for OSINT

  The open curriculum that defines our reproducible workflow for satellite analysis.

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Workflow

1. Identify a publicly named site — usually a cantonment whose existence the Sri Lankan MoD itself has acknowledged in press releases or parliamentary statements.
2. Pull a multi-year Sentinel-2 time-series of that site. Generate a true-colour mosaic and an NDVI vegetation index for each window.
3. Compare footprint changes across windows. A reduction in built-up area inside the site boundary may be consistent with land release; an increase is consistent with expansion.
4. Cross-check with Sentinel-1 SAR for the same windows — does coherence drop indicate new construction or demolition?
5. Two-person review. Both investigators must independently agree on what the imagery shows before any publication.
6. Publish only at base-footprint resolution. Faces, vehicles and personnel are never identifiable in our outputs.
7. Hash the exported imagery, store the hash, archive the underlying tile IDs.