The sinking Millennium Tower, San Francisco

We often feature imagery from the European Copernicus programme’s Sentinel-2 satellite. The programme has other satellites, including Sentinel-1A and Sentinel-1B, that gather radar data rather than imagery. They seem particularly good at measuring altitude changes over time. For example, we saw a map of surface deformation after a major earthquake in Chile.

A recent story on the European Space Agency (esa) website is about how the satellites have been able to determine that the Millennium Tower, a sky scraper in San Francisco, is sinking by a few centimetres per year relative to other buildings in the vicinity.


Image credit: ESA. The colour scale ranges from 40 mm a year away from radar (red) to 40 mm a year towards radar (blue). Green represents stable targets.

Given the sensitivity of this data it makes us wonder whether or not Google could use it to improve the accuracy of their altitude data. We have noted in the past some fairly major errors in their data, such as the sunken island of Gorgona and significant inaccuracies around Rio de Janeiro.

Timothy has been using Google Earth since 2004 when it was still called Keyhole before it was renamed Google Earth in 2005 and has been a huge fan ever since. He is a programmer working for Red Wing Aerobatx and lives in Cape Town, South Africa.

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