Mapping Earth's surface in 3D (BBC)
Jonathan Amos
Science correspondent
The German satellite radar twins - TanDEM-X and TerraSAR-X - are a year through their quest to make the most precise, seamless map of varying height on Earth.
They've now acquired data across the entire globe at least once. However, some tricky sampling areas, such as tall mountains and thick forests, will require several passes and so we don't expect to see a fully finished product before 2014.
The Digital Elevation Model, or DEM, has become one of those must-have technical tools.
Planners use them to work out where best to put new buildings, roads and railways; airline pilots need the information to fly planes safely; telecos look at DEMs before siting their transmitters; and generals feed the data into autonomous weapons. Archaeologists, volcanologists, glaciologists, hydrologists, ecologists - they all want to know the shape of the Earth's surface. Even a games developer wanting to produce ever more realistic landscapes will have reason to resort to a DEM.
Space shuttle Endeavour famously made a world DEM in 2000. It hung a radar system out of its payload bay and mapped about 80% of the Earth's land surface.
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more: http://www.bbc.co.uk/news/science-environment-16578176
http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10378/566_read-426/
http://www2.jpl.nasa.gov/srtm/
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