12 December 2001
Military Wary of Map's
By Mark K. Anderson
wired.com 2:00 a.m. Dec. 12, 2001 PST
NASA is creating the most detailed topographic map of the Earth ever produced -- but its public dissemination has become a point of contention between the space agency and the Department of Defense.
The three-dimensional map derives from a mission of the space shuttle Endeavour in February of last year. A radar interferometer system tethered to the shuttle's cargo bay bounced microwaves off the surface of the planet and read back the results for ten days straight.
The map contains information that researchers can apply to a range of uses -- from predicting floods and mudslides to providing a database of terrain hazards for airplanes, or siting radio and cell phone towers.
But it will also be used for military targeting and reconnaissance -- and the Pentagon wants to ensure other countries or organizations can't use the map for the same purposes.
A week ago the two opposing parties, NASA and the Pentagon, negotiated a compromise that, for now, allows a limited release of the American portion of the map to researchers. The Pentagon keeps the rest to itself. NASA, however, is working to ultimately make the whole world map publicly available.
"We would like to release (the map) as soon as possible," said John LaBrecque of NASA. "But we understand that there are some concerns, and so we're trying to address them. We can't provide a timetable for the release of the data to the general public, but we're working on it."
The subject of a poster session on Tuesday at the annual meeting of the American Geophysical Union in San Francisco, the Shuttle Radar Topography Mission is 12 terabytes of conflicting interests.
The joint mission partners the Pentagon's National Imagery and Mapping Agency (NIMA) with the German and Italian space agencies. The data collected -- a quantity of bits greater than the text of all the books in the Library of Congress -- is now being processed at NASA's Jet Propulsion Labs.
This data generates 3-D maps of the Earth's surface with a level of resolution that rivals the best topographic maps of North America. The global map, still a year or more from completion, can make out details as small as 30 meters horizontally and 10 meters vertically.
The map will eventually cover the entire landmass of the planet between 60 degrees north latitude and 56 degrees south latitude -- 80 percent of the planet, where 95 percent of the population lives.
"We're going to miss Antarctica and a few places like that where there are only penguins," said Mike Kobrick of JPL.
Kobrick is a chief scientist in JPL's map processing team, and his group has already generated virtual fly-overs of the Mojave Desert and the San Andreas Fault, as well as much of the 3-D map of North America.
Since similar data for North America already exist, his team is now comparing their new findings with previous maps to fine-tune their mapmaking algorithms.
JPL is also cranking out individual maps of areas such as Mount Pinatubo in the Philippines and the Amazonian rain forest, for limited release to select geological and geographical researchers. Over the next year, JPL's computers will generate the global map, which will then be turned over to the Pentagon's NIMA.
Because the map is so detailed, NIMA is classifying and retaining the 30-meter resolution maps of the Earth's surface outside of the United States. It is expected, however, to eventually downgrade the resolution by a factor of three and turn over that data to the U.S. Geological Survey for public release.
Douglas Alsdorf of UCLA is a researcher who already has designs on the Shuttle Radar data. He studies the geography of the Amazon basin, and although the kind of microwaves used in the mission do not penetrate the thick rainforest forest canopy, he said he thinks this mission could still provide "amazing" amounts of information.
"The Amazon basin directly affects global climate," Alsdorf said. "What this map really begins to help us do is (develop) the link between the global models and local models."
It also would allow him to study erosion and landscape evolution at an unprecedented level of detail. Previous to the Shuttle Radar Topographic map, the best data available for the Amazon had a resolution of one kilometer -- i.e., one elevation measurement for every thousand meters of terrain.
"But that one has serious errors in it," he said. "In fact, if you try to use that one to make water flow down the Amazon, you'll get water not flowing to the mouth. It'll flow someplace else."
Kobrick said that beyond the new radar map's most immediate application -- "for geologists, hydrologists and lots of other 'ologists," as he put it -- it has many immediate, on-the-ground applications too.
It could provide the database for "ground proximity warning systems" on airplanes, which rely on GPS positioning and topographic maps to alert a pilot when approaching mountains or other hazards.
And in forecasting the path of floods, avalanches or mudslides, of course, the key is to find the steepest slope down a hill -- because that's where the water, mud and rock will go.
"With these digital elevation maps," Kobrick said. "It's easy to tell where downhill is."