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8 October 2026/5 min read

Why Switzerland is a blank spot on Europe's ground-motion map

The European Ground Motion Service stops at the Swiss border, and C-band radar goes quiet on snow and ice. What that means for alpine slopes.

By Julian Walder

Open the European Ground Motion Service, the Copernicus product that maps how the ground moves across the continent, and zoom in on the Alps. Austria is covered. Italy, France, Germany and Slovenia are covered. In the middle sits a country-shaped hole. Switzerland is not on the list.

This is not an oversight. The service names the countries it covers, from Austria to the United Kingdom, and Switzerland is absent because it is not a participant in the Copernicus programme for 2021 to 2027. On 5 June 2026 the Federal Council decided against joining for 2028 to 2034 as well, citing the state of federal finances, and said it would re-examine the question in about 2032. On 18 June 2026 the National Council adopted a motion asking the government to reconsider, by 124 votes to 63; the matter now sits with the Council of States.

For anyone working with satellite data in Switzerland, the consequences are precise. The raw Sentinel data remain free and open to any registered user, so the pictures are there. What is missing is the processed, continent-wide motion product, and any Copernicus-funded service contract that would build one.

What the map would show anyway

Even if Switzerland were covered, the European service would be a weak tool for alpine hazards. It is built on Sentinel-1 C-band radar. It is updated once a year on a moving five-year window; the current release runs from January 2020 to December 2024, and the next update is scheduled for the fourth quarter of 2026. An annual product with up to two years of latency cannot catch the onset of acceleration on a slope that changes over months.

There is also a physical problem. ESA's own analysis of Blatten notes that C-band radar struggles in high alpine terrain, in dense vegetation and wherever motion exceeds tens of centimetres per year. The service's own published introduction states that it is weak over perennial snow and ice.

Switzerland does have a national product. A land motion monitoring service built for swisstopo from Sentinel-1 covers about 50,000 square kilometres on five satellite tracks, with data since October 2014, yearly updates and 30 metre velocity grids. It is a real asset. Like the European product it is C-band and annual, its documentation states the snow-cover limitation explicitly, and the point data contain no measurements on snow, ice or vegetation. On a glacier front or a permafrost slope above the tree line, the map is blank where it matters most.

Why flat-land InSAR breaks in the mountains

Interferometric radar, or InSAR, works by comparing the phase of radar echoes from two passes over the same ground. If the ground moved between passes, the phase shifts. Over a city or a lowland dike the method is mature and precise to millimetres. Alpine terrain breaks several of its assumptions at once.

  • Snow. Seasonal snow changes the surface completely between passes. C-band coherence collapses for months each winter and the time series simply has gaps.
  • Fast motion. Above a few tens of centimetres per year, the phase wraps faster than it can be unwrapped. The method saturates, and the fastest, most interesting slopes are the first to drop out.
  • Geometry. Radar looks sideways. Steep slopes facing the sensor fold onto themselves (layover) and slopes facing away fall into shadow. The method also measures only motion along the line of sight, so a slope sliding down a valley wall may be nearly invisible from one orbit direction.
  • Atmosphere. Deep valleys produce strong tropospheric delays that mimic motion unless corrected.
  • Revisit. Even the best cadence is days, not hours.

None of these problems is new to the research community. They are the reason alpine InSAR has stayed a specialist, project-by-project activity.

What changes at longer wavelengths

L-band radar uses a longer wavelength than C-band. It penetrates vegetation and dry snow better and tolerates rougher surfaces and faster motion before coherence is lost. That is why the retrospective analysis of Blatten, using archived L-band data from the ALOS-2 and SAOCOM missions, could see the Kleines Nesthorn moving from 2016 and accelerating to more than 150 centimetres per year by August 2024, while an annual C-band product would have struggled with that rate.

Until 2026 free L-band data over the Alps did not exist; the archives used for Blatten are not open. That changed on 20 July 2026, when calibrated data from NISAR, the NASA and ISRO L-band mission launched on 30 July 2025, became public and free through the Alaska Satellite Facility. From 2028 ESA's ROSE-L mission is planned to add a second L-band source.

A screening system for altitude therefore has to be multi-band by design: L-band for coherence on rough, snowy and fast-moving ground; C-band from Sentinel-1 for its 6-day repeat and its archive back to 2014; and Sentinel-2 optical imagery at 10 metres every five days for tracking features on glaciers that move too fast for any radar phase method.

Filling the blank spot

Watchberg screens Swiss alpine regions with exactly that combination. It fuses Sentinel-1, NISAR and Sentinel-2, builds a motion history for every slope it can see, and uses the European product only where it exists, across the border in Austria, Italy and France, as a calibration and benchmark layer. It reports explicitly where it is blind: which slopes fall into layover or shadow, where winter gaps break the series, and how confident each measurement is.

All of this is projected and to be validated. A pilot programme is planned for 2027, with back-tests on documented Swiss cases and a live weekly service for pilot experts. The point of the design is not to replace the national product or the European one. It is to add the cadence, the altitude and the decision content that neither was built to provide, in the one alpine country that currently has no continent-wide baseline at all.

Sources

  • InSAR
  • EGMS
  • Switzerland
  • Data

Related

Join the 2027 pilot programme.

Watchberg is preparing pilots with hazard offices and operators in three Swiss cantons. If you carry responsibility for alpine slopes, let us show you what a weekly briefing would look like for your region.

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Pilot programme 2027. In discussion with hazard offices in three cantons.