From the BBC: The TanDEM-X satellite has blasted into orbit on a mission to acquire the most precise 3D map of the Earth's surface.
The German radar spacecraft will fly in formation with an identical platform called TerraSAR-X launched in 2007. Together, the pair will measure the variation in height across the globe to an accuracy of better than two metres.
With the TanDEM mission, the intention is to go down to a vertical resolution of two metres, with a spatial resolution of 12m by 12m. Airborne laser instruments (lidars) can do better than this but their DEMs are only regional. To achieve the TanDEM level of detail on all 150 million sq km of the Earth's land surface will require three years of operation.