NASA, NIMA unveil 3-D mapping

NASA and the National Imagery and Mapping Agency last week unveiled a device the agencies will use during a space shuttle mission next year to gather high-resolution digital images that can support environmental research and improve battlefield accuracy.

The device consists of a 60-meter mast and two radar antennas, which will take images of the Earth's surface. Radar imaging is an improvement over traditional photographic satellite imaging because it can slice through clouds and vegetation. In addition, the two radar antennas will provide 3-D images, which will give researchers a more realistic picture of the Earth's surface.

The two-antenna device also will be an improvement over traditional methods of taking 3-D images, said Craig Lingle, a geophysics professor at the University of Alaska Fairbanks. Satellites typically get 3-D radar images by taking a snapshot of the same spot on Earth during different orbits and from slightly different positions, Lingle said. But the satellites' orbits can vary considerably, diminishing the quality of the images.

With two radar antennas on one spacecraft, the method of gathering images will be simpler because the images will be taken once during one flyover, making the images more accurate, according to those familiar with the project.

For NIMA, the project will yield high-resolution imagery that fulfills a requirement set by a Defense Department committee for NIMA's predecessor, the Defense Mapping Agency, about three years ago. The requirement calls on NIMA officials to digitally map the elevation of the Earth's terrain at 30-meter intervals. NIMA has mapped only about 1 percent of the planet at that level. NIMA has digital information for about 70 percent of the Earth on terrain elevation at 100-meter intervals, which is not detailed enough for military mission planners, who are demanding greater accuracy in the data they use to program cruise missiles or to navigate aircraft.

The shuttle mission next year should yield terrain data for about 80 percent of the planet, said Tom Carson, NIMA's proj-ect manager.

Without the radar project, NIMA would have a difficult time meeting the requirement to map the Earth at 30-meter intervals because of the limitations of traditional photographic satellites. "We'd never get there from here," Carson said.

In addition, the new radar mapping device is "important to us because it's a much denser product," said NIMA spokeswoman Kathleen Neary. "It's a much denser digital terrain model, and it's something our customers are asking for."

For NASA, the digital imagery gathered from the radar array will be used to help the agency, as well as other agencies and organizations, gather data about the Earth. "Radar helps us see things we can't see with our eye, so it's over and above what we see with satellite photographs," NASA spokeswoman Mary Hardin said.

For example, a similar radar project in 1994 yielded imagery of an ancient Cambodian city that was obscured from satellites by a thick jungle canopy.

In addition, the radar data can be used by the airline industry for improved navigation, by the agricultural industry for precision farming, and by conservationists to monitor ground and surface water conditions.