In collaboration with agencies in Japan, National Aeronautics and Space Administration’s (NASA’s) Jet Propulsion Laboratory has put together a topographical map that covers 99 per cent of the Earth’s land mass, a more complete map than was previously available.
“We’ve got everything except a very small part of the South Pole and the North Pole,” said Michael Abrams, the United States science team leader at the Pasadena, California, lab for the Reflection Radiometre project, also known as ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometre). “We’re able to cover Alaska, Greenland, northern Asia and Antarctica.”
The most complete previous set of topographical data, collected by the Shuttle Radar Topography Mission in 2000, included about 80 per cent of the Earth’s land mass. Because the space shuttle had a limited orbit, the radar-imaging device missed land masses above 60 degrees north and 57 degrees south in latitude.
ASTER, which started collected images in visible and infrared light nine years ago, rides aboard Terra, a satellite that is part of NASA’s Earth Observing System. Its orbit enables it to collect images up to 83 degrees north and 83 degrees south in latitude and also gives it a better angle to collect data in steep mountain areas, Abrams said. The infrared instrument also collects more thermal data than previously available, he said.
The ASTER images are meant to complement the radar images, Abrams emphasised. The shuttle radar instrument has some pictures ASTER could not get because radar can penetrate clouds, which obscure some tropical areas from ASTER’s sight.
Scientists recently realised they had more than one million scenes, enough to create a global topographic map, Abrams said. The data were released on Monday. ASTER’s images have a resolution down to 50 feet, which is enough to detect houses but not so fine as to see the shape of the house or what people are doing in the house, he said.
Scientists have used the satellite instrument to calculate changes in the width and height of glaciers, but Abrams said he could see a host of commercial uses for the new data as well. He said cell-phone companies could use the new maps to scout sight lines for new transmission towers and Google probably could incorporate the new data into its maps.
According to NASA, the cost to produce the instrument was $800,000, with the United States space agency contributing half.