Ground motion from satellites (EGMS)

The European Ground Motion Service (EGMS) is part of the Copernicus Land Monitoring Service run by the European Environment Agency (EEA). Using radar images from the Sentinel-1 satellites and satellite radar interferometry (InSAR), it measures movements of the ground and buildings across Europe with millimetre precision. The data are updated once a year and are free for any use.

What the data show

• EGMS has three products. Basic and Calibrated show movement along the satellite's line of sight; Ortho splits it into vertical and east-west components on a 100 × 100 m grid.
• The vertical component is the average rate of movement in millimetres per year over the measurement period: a negative number means subsidence, a positive one uplift. Each point has a time series of displacement.
• Measurement points occur mainly where the radar reflects off stable surfaces: buildings, roads and rocks. In forests, fields and on water there are few or none, and in steep terrain they may be missing because of radar shadow.
• The satellites do not measure north-south movement directly.

How to read it

• Values around zero mean stable ground. Small deviations may be just measurement uncertainty, so the Property Check treats movement within ±2 mm per year as stable.
• Long-term subsidence of several millimetres a year may be linked to mining, even historic (undermining), landslides or groundwater pumping.
• If a house moves differently from its surroundings, its foundations may be settling. A viewing and possibly a structural engineer decide; satellite data do not replace an expert assessment.
• The data describe a past period; they are not a forecast.

Where to find the data

Publicly in the EGMS Explorer viewer on the Copernicus website, which always holds the two latest releases.