What this tool is and how to read it

🛰️What EGMS is

EGMS (European Ground Motion Service) is a European Union service, part of the Copernicus programme, that uses radar satellites to measure how the ground surface moves across all of Europe — millimetre by millimetre, every few days, since 2015. These aren't photographs: it's a technique called InSAR, which compares radar signals reflected from the same patch of ground at different times to measure its displacement with extreme precision, both vertically (up/down) and horizontally (East-West component) — this tool uses both: a building on a slope or near a slow landslide can move mostly horizontally, a signal the vertical component alone risks missing.

Ground can move for many reasons: natural settlement, groundwater extraction, underground cavities, slow landslides, nearby construction work. A wide or irregular movement in the area around a building can be a territorial signal worth investigating further with geological, geotechnical and structural surveys on site.

📡How up to date this data is

The satellite data currently in use is EGMS release 2020-2024 — it measures ground displacement up to December 2024. The site automatically checks whether EGMS has published a newer release (last check: 2026-08-09); when it does, the site updates itself.

Why isn't it current to today? EGMS doesn't measure in real time: it publishes periodic releases (so far roughly one every 1-2 years), each the result of months of reprocessing and calibration against ground-based GNSS reference stations, to guarantee millimetre-accurate measurements. This isn't a limitation of this tool — it's how the EGMS product itself works, including on the official portal.

What does that mean in practice? The ground motion you see here reflects the situation up to the end of 2024 — since then something may have changed (a new construction site nearby, a geological event, a trend accelerating or slowing down). That's why the score is a priority, not a real-time measurement: the more time has passed since the last release, the more it's worth pairing it with an on-site check rather than trusting the number alone.

🏫Where each school's address and location come from

Every school's name and address come from two Italian Ministry of Education datasets (dati.istruzione.it): the School Buildings Register (street, house number, municipality for every public building) and the School Register (the name). Neither downloadable dataset includes geographic coordinates. But the same Ministry also publishes, building by building, a web page with official latitude/longitude (see below) — it's the first source used to place schools on the map, before falling back to OpenStreetMap or Google.

📍How schools end up on the map

Every school is located by trying several methods, in order, stopping at the first one that works well:

1. Official Ministry coordinate. The "building detail" page of Scuola in Chiaro (the Ministry's public portal, unica.istruzione.gov.it) shows the registered position for every school building — the same data the Ministry itself uses, not an estimate from a name or address. It's the most precise source and currently covers about 95% of schools; where it's missing (the register has no such data for that building), the methods below are tried in order.
2. Real building on OpenStreetMap. Every school building already mapped in the area is queried (via the Overpass API) and matched against the one whose name corresponds to the school. The point is the real building, not a street.
3. Name search on OpenStreetMap. If the building isn't among those already mapped, the school's name is searched for as text instead.
4. Address on OpenStreetMap. Street and house number. Less precise: if that street has no house numbers mapped, the point falls only at street level (a few hundred metres off), not at the building.
5. Google Maps, as a last resort — first by name, then by address. For schools still stuck at street/address precision, the school is first searched for by name (as above: if Google Maps knows it as a place, that's the most reliable match), then falls back to the text address. Only results at "building level" with ROOFTOP or RANGE_INTERPOLATED precision are accepted, and the returned municipality is always checked against the expected one — a common street name (e.g. "Via Cavour") has already turned out ambiguous with a neighbouring municipality once.
6. Approximate street/area, for addresses with no house number. Many schools in small hamlets or rural areas have an address registered as "SNC" (no house number, "senza numero civico" in Italian): without a number to interpolate against, no geocoder — not even Google — can give building-level precision. In these cases the centre of the street or area is accepted automatically, but explicitly labelled as such: it's the most precise position obtainable automatically for that address, not the position of the building itself.

The badge on every school's page shows which method was used, so you know how much to trust the position:

Every geocoded position is checked automatically: if it falls more than a few kilometres from the centre of its municipality, it's discarded rather than kept by mistake — this has already happened during this tool's development (an ambiguous address was matched to a same-named street in an entirely different municipality).

🧮How the score is calculated

For every school, all EGMS measurement points within 200 metres are considered (widening the radius if needed), separately for each component measured by satellite:

The first term captures how much, on average, the ground is moving. The second captures how irregular that movement is from one point to the next within the same area: greater spatial variability in ground motion around a building can point to non-uniform conditions worth a geological or geotechnical follow-up, as opposed to a uniform trend (which a building can more easily "go along with" if it moves as a whole). The satellite data alone cannot diagnose differential settlement of the foundations.

The available components are then combined as the modulus of a vector, not summed — they are the same physical measurement seen from different directions or moments, not independent phenomena:

Schools are then split into four priority bands (based on the statistical distribution of current scores, not fixed thresholds):

🏔️Seismic zone

Every school page also shows the municipality's seismic zone (1-4, where 1 is the highest seismicity), per the official classification of Italy's Civil Protection Department. It's a municipality-level figure, not per building: all schools in the same municipality share the same zone.

It does not enter the EGMS score above, and that's a deliberate choice: summing millimetres of ground motion and a seismic category into a single number would require weighting two very different phenomena, a decision for a structural engineer, not for this tool. They remain two independent indicators, both shown, never merged.

🏗️Year of construction

When available, every school page also shows when the building was constructed (in bands, e.g. "between 1961 and 1975"), from the Ministry of Education's dataset on the origin and construction date of school buildings — the same source as the address, joined on the same building code. It's known for about 87% of the schools covered by this project; for the rest the data simply isn't available in the source, not omitted by this tool.

This too remains an independent piece of information, not a score: knowing whether a building predates or postdates Italy's 1974 anti-seismic regulations (the first organic seismic classification) and its 2003 revision (after the San Giuliano di Puglia earthquake) is relevant information for a structural engineer — this tool does not turn it into a numeric judgement.

🎯How much to trust the measurement

Not every satellite point is equally precise: some have a "cleaner" time series, others a noisier one (due to surrounding vegetation, surface type, or simply how many times the satellite managed to measure them well). When a school's page shows 🟢 reliable measurement or 🟡 less precise measurement, that's exactly what it refers to — not the school's risk level, only how much the number itself can be trusted.

⬇️Downloading the data

The full ranking (Italian-only interface) lists every school, filterable by region, province or municipality, with a "Download data (CSV)" button at each level: it exports everything in scope, not just the final score — one row per satellite measurement point used in the calculation, with its position, velocity, acceleration and reliability. The map (overview or single municipality) has the same button, scoped to whatever you're looking at there. No registration required, no proprietary format.

Every school's page instead has a "Print or save as PDF" button — it uses the browser's own print function (no external service): choosing "Save as PDF" instead of a printer produces a clean PDF of the page, without the interactive map (it doesn't print well) but with the score, indicators and charts.

⚠️Limitations — read before drawing conclusions

📖Essential glossary

Priority index (preliminary)

The number this tool computes for each school. It has no fixed scale — it isn't 0-10, it isn't 0-100 — because it depends on the EGMS data available in that area: an "8" on its own says nothing, it needs to be read together with the coloured band (Low/Moderate/High/Very high) and the school's position relative to other schools, both shown on every school's page. "Preliminary" because the formula is a first version (v1), not yet validated by a structural engineer — see the limitations above. It exists only to rank schools for deciding which to inspect first: it is not a safety assessment of the building, and it does not replace a real technical site visit.

Subsidence

A slow, progressive lowering of the ground level.

InSAR

A satellite radar technique that measures ground displacements of a few millimetres by comparing images taken at different times.

mm/year

Unit of ground motion velocity: a value of -2 mm/year means the point is sinking by 2 millimetres per year, on average.

Differential settlement

When different parts of a building's foundations move differently from one another — one of the most common causes of structural cracking.