Novarly Parcel
How we measure ground movement from space
The measurement
Radar satellites (like ESA's Sentinel-1) pass over every city every few days and bounce microwave pulses off the ground. By comparing the phase of these pulses across hundreds of passes over multiple years — a technique called InSAR (interferometric synthetic aperture radar) — scientists can measure whether any patch of ground is rising or sinking, with millimetre-per-year precision. This is peer-reviewed, widely used science: the same technique monitors dams, mines, and volcanoes worldwide.
Our data
We build on the published, peer-reviewed vertical-land-motion datasets of the Ohenhen/Shirzaei group (Virginia Tech): the Nature Cities 2025 dataset covering the 28 most populous US metros (VT Figshare doi:10.7294/27606942, CC0 public domain), the denser 2025 New York City–Long Island deposit (5.1M points, Zenodo doi:10.5281/zenodo.17644691, CC-BY-4.0), and the US Atlantic-coast dataset spanning every East-Coast state from New Hampshire to Florida (VT Figshare doi:10.7294/19350959, CC0). In total we aggregate over 45 million InSAR measurement points to a ~100 m screening grid of ~9 million cells. Contains modified Copernicus Sentinel-1 data.
The risk bands
- Green — worst measured motion near the address is slower than 3 mm/yr downward.
- Amber — 3–10 mm/yr downward measured within 150 m.
- Red — faster than 10 mm/yr downward measured within 150 m.
- No data — no reliable measurement at that spot (vegetated lots, new construction, water). This is not a sign the ground is stable.
We assess the worst measured cell within 150 m of the address — ground risk is local, and a fast-moving patch nearby matters. We also show how that value compares with every measured location in the metro (the percentile), because "2 mm/yr" means more with context.
What a screening is — and is not
A screening tells you whether the ground around an address has been measurably moving. It does not tell you whether a specific building is damaged, whether its foundation is sound, or what will happen in the future. Satellite radar measures reflective surfaces (roofs, pavement) — not every parcel has a measurement, and line-of-sight motion is an approximation of pure vertical motion. Treat any amber or red result as a reason to commission a licensed geotechnical engineer — never as a verdict.