Copernicus reveal: Sinking towers, shifting lands

The European Space Agency’s Sentinel-1 satellites show that the Millennium Tower skyscraper in San Francisco, California, is sinking by a few centimeters a year. Completed in 2009, the 58-story tower has been showing signs of sinking and tilting, possibly because the supporting piles aren’t firmly resting on bedrock.

Studying the city is helping scientists improve monitoring of urban ground movements, particularly for subsidence hotspots in Europe. Scientists combined multiple radar scans from the Copernicus Sentinel-1 twin satellites to detect subtle surface changes down to millimeters. The technique works well with buildings because they better reflect the radar beam. It is also useful for pinpointing displacement hotspots over large areas, thanks to Sentinel-1’s broad coverage and frequent visits.

Working with the European Space Agency, the team from Norut, PPO.labs and Geological Survey of Norway have also mapped areas in the wider San Francisco Bay Area that are moving. European cities experience similar subsidence to the Bay Area. For example, the area around Oslo’s train station in Norway is reclaimed land. Newer buildings, such as the nearby opera house, have proper foundation into bedrock, but the older parts of the station experience severe subsidence.

The open data policy and regular coverage plan of Copernicus promise cost-efficient and reliable deformation data. “The Copernicus Sentinel-1 mission is, for the first time, making it possible to launch operational national deformation mapping services,” said Dag Anders Moldestad, Norwegian Space Centre.

The Sentinel-1 twins provide “radar vision” for Europe’s Copernicus environment monitoring program. In addition to watching land movements, they feed numerous other services for monitoring Arctic sea ice ;routine sea-ice mapping; surveillance of the marine environment; mapping for forest, water and soil management; and mapping to support humanitarian aid and crisis situations.