BioEd Online

The most comprehensive and detailed topographic map ever made of Earth has been completed. The elevation data just released cover areas that have never been mapped in three dimensions before, and should be useful in predicting the effects of climate change and sea-level rise.

The Shuttle Radar Topography Mission is a collaboration between NASA, the US National Geospatial-Intelligence Agency and the German and Italian space agencies. It uses a technique called radar interferometry, which combines images taken at slightly different locations to produce a single three-dimensional image.

The method works in the dark, and also penetrates clouds, so it can map the areas persistently covered by clouds that are inaccessible to satellite photography.

The space shuttle Endeavour collected images of 80% of Earth's surface (from 56º S to 60º N) using radar antennas both in the shuttle's main bay and at the end of a 60-metre mast.

"It's probably the most significant scientific mission the shuttle programme has ever done," says Michael Kobrick, mission project scientist of NASA's California-based Jet Propulsion Laboratory.

No stone unturned

It has taken four years to process all the data obtained during the 11 days that the shuttle orbited the planet, but now all of the images are complete. The latest additions cover Australia and New Zealand, and reveal terrain previously unmapped, such as regions of South America and islands in the South Pacific.

The elevation data should help disaster planners on such islands respond to storm surges and rises in sea level, says Kobrick. "Knowing exactly where rising waters will go is vital for mitigating the effects of disasters like the Indian Ocean tsunami."

The images will also be helpful in studying erosion, landslides, ecological zones, and climate change. The elevation data could be used for planning and simulating military missions, determining where to construct communication towers and creating virtual topographic displays in aeroplane cockpits. And they should help to create better maps for backpackers, fire-fighters, geologists and natural resource managers.

"No data set is perfect," says John Townshend, principal investigator for the Global Land Cover Facility at the University of Maryland, College Park. "But in terms of the topography of Earth, this database is an astonishing improvement."