The most complete terrain map of the Earth's surface has been published.
The data, comprising 1.3 million images, come from a collaboration between the US space agency Nasa and the Japanese trade ministry.The images were taken by Japan's Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) aboard the Terra satellite. The resulting Global Digital Elevation Map covers 99% of the Earth's surface, and will be free to download and use.
The Terra satellite, dedicated to Earth monitoring missions, has shed light on issues ranging from algal blooms to volcano eruptions.
For the Aster measurements, local elevation was mapped with each point just 30m apart.
"This is the most complete, consistent global digital elevation data yet made available to the world," said Woody Turner, Nasa programme scientist on the Aster mission.
"This unique global set of data will serve users and researchers from a wide array of disciplines that need elevation and terrain information."
Previously, the most complete such topographic map was Nasa's Shuttle Radar Topography Mission, covering 80% of the Earth's surface. However, the mission's results were less accurate in steep terrain and in some deserts.
Nasa is now working to combine those data with the new Aster observations to further improve on the global map.
NASA, Japan Release Most Complete Topographic Map of Earth
Joint Press Release 29 Jun 09;
PASADENA, Calif. – NASA and Japan released a new digital topographic map of Earth Monday that covers more of our planet than ever before. The map was produced with detailed measurements from NASA's Terra spacecraft.
The new global digital elevation model of Earth was created from nearly 1.3 million individual stereo-pair images collected by the Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer, or Aster, instrument aboard Terra. NASA and Japan's Ministry of Economy, Trade and Industry, known as METI, developed the data set. It is available online to users everywhere at no cost.
"This is the most complete, consistent global digital elevation data yet made available to the world," said Woody Turner, Aster program scientist at NASA Headquarters in Washington. "This unique global set of data will serve users and researchers from a wide array of disciplines that need elevation and terrain information."
According to Mike Abrams, Aster science team leader at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the new topographic information will be of value throughout the Earth sciences and has many practical applications. "Aster's accurate topographic data will be used for engineering, energy exploration, conserving natural resources, environmental management, public works design, firefighting, recreation, geology and city planning, to name just a few areas," Abrams said.
Previously, the most complete topographic set of data publicly available was from NASA's Shuttle Radar Topography Mission. That mission mapped 80 percent of Earth's landmass, between 60 degrees north latitude and 57 degrees south. The new Aster data expand coverage to 99 percent, from 83 degrees north latitude and 83 degrees south. Each elevation measurement point in the new data is 30 meters (98 feet) apart.
"The Aster data fill in many of the voids in the shuttle mission's data, such as in very steep terrains and in some deserts," said Michael Kobrick, Shuttle Radar Topography Mission project scientist at JPL. "NASA is working to combine the Aster data with that of the Shuttle Radar Topography Mission and other sources to produce an even better global topographic map."
NASA and METI are jointly contributing the Aster topographic data to the Group on Earth Observations, an international partnership headquartered at the World Meteorological Organization in Geneva, Switzerland, for use in its Global Earth Observation System of Systems. This "system of systems" is a collaborative, international effort to share and integrate Earth observation data from many different instruments and systems to help monitor and forecast global environmental changes.
NASA, METI and the U.S. Geological Survey validated the data, with support from the U.S. National Geospatial-Intelligence Agency and other collaborators. The data will be distributed by NASA's Land Processes Distributed Active Archive Center at the U.S. Geological Survey's Earth Resources Observation and Science Data Center in Sioux Falls, S.D., and by METI's Earth Remote Sensing Data Analysis Center in Tokyo.
Aster is one of five Earth-observing instruments launched on Terra in December 1999. Aster acquires images from the visible to the thermal infrared wavelength region, with spatial resolutions ranging from about 15 to 90 meters (50 to 300 feet). A joint science team from the U.S. and Japan validates and calibrates the instrument and data products. The U.S. science team is located at JPL.
For visualizations of the new Aster topographic data, visit: http://www.nasa.gov/topics/earth/features/20090629.html .
Data users can download the Aster global digital elevation model at: https://wist.echo.nasa.gov/~wist/api/imswelcome and http://www.gdem.aster.ersdac.or.jp .
For more information about NASA and agency programs, visit: http://www.nasa.gov .
JPL is managed for NASA by the California Institute of Technology in Pasadena.
L.A. from space: New view from JPL and NASA [Updated]
LA Times 30 Jun 09;
In collaboration with agencies in Japan, NASA's Jet Propulsion Laboratory has put together a topographical map that covers 99% 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 JPL's Michael Abrams, the U.S. science team leader for the Advanced Spaceborne Thermal Emission Reflection Radiometer project, also known as ASTER. "We're able to cover Alaska, Greenland, northern Asia and Antarctica."
The resolution is so clear that you can plainly see Dodger Stadium and other landmarks in pictures of Los Angeles.
The most complete previous set of topographical data, collected by the Shuttle Radar Topography Mission in 2000, included about 80% of the Earth's landmass. 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 emphasized. The shuttle radar instrument has some pictures ASTER could not get because radar can penetrate clouds, which perpetually obscure some tropical areas from ASTER's sight.
Scientists recently realized they had more than 1 million scenes, enough to create a global topographic map, Abrams said. The data was released Monday, free to the public. 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 already used the satellite instrument to calculate changes in the width and height of glaciers, but Abrams said he could also see a host of commercial uses for the new data. He said cellphone companies could use the new maps to scout sight lines for new transmission towers and Google could probably easily incorporate the new data into its maps.
[Updated at 8:50 a.m.: According to NASA, the cost to produce the instrument was $800,000, with the U.S. space agency contributing half.]
--Jia-Rui Chong