Monitoring the ecosystem in 3-D
Sending multispectral scanners into space, the National Aeronautics and Space Administration has developed many-layered maps of striking clarity and precision that, in some cases, have replaced the painstaking work of aerial photographers and land surveyors, at a fraction of the time and cost.
The nascent mapping technologies provide a new standard for land classification. The human eye cannot see the detailed nuances of the light spectrum. Across the entire spectrum, however, different objects reflect sunlight in different ways; these differences are said to give each material a "spectral signature."
By designing cameras to record these signatures, mapmakers can plot with precision complex biological mixes on the ground. At the same time, orthographic images, corrected for the topographic distortion created by the geometric angle between the airborne camera and the ground, data compression, geographic information systems and other advances have made for even more detailed mapping information.
But NASA's satellite images are on a grand scale that is not always suited to land-based scientific and government projects. The images typically have insufficient resolution for many applications, their coverage may be limited, they often are obstructed by clouds, and researchers cannot control their timing. At the same time, conventional aerial photography is expensive and requires heavy training.
Under a National Science Foundation Digital Government small business grant, Howard Schultz, senior research scientist at the Computer Vision Laboratory, University of Massachusetts, Amherst, has been developing a general interest commercial instrumentation terrain mapping system.
Potential government customers for the system - developed with a Digital Government grant and an SGER grant, include the USDA Forest Service, the Environmental Protection Agency and the Department of Defense, he said.
The system, under the aegis of Schultz's technology transfer company, Aerial Vision Inc., consists of:
Designed to be cheap, efficient and user friendly, carried by a low-flying plane, the system produces very high-resolution layers, including a multispectral image and a 3-D elevation map of the terrain, Schultz said.
David Hollinger, scientist with the Forest Service's Northeast Research Station in Durham, New Hampshire, is in the woods of Howland, Maine, studying the role of forests in the carbon cycle.
The government has very good figures on the amount of carbon burned by industry and public agencies, Hollinger said. Fairly recently, however, scientists were surprised to learn that only half the carbon dioxide released in the burnoff goes into the atmosphere. The rest is removed by forests and oceans, he said. Some forests, with new, fast-growing trees, are net carbon intakers, while others expel carbon, Hollinger said.
Less well understood is how to best manage the forests to reduce carbon dioxide emissions, thus slowing greenhouse warming and acid rain, he said. Precise data, down to the type and number of trees, and growth figures from year to year, will help, he added.
"Satellite images come in months later (and) the scale is very large," Hollinger said. "This way, we can get data any time in the way we want it."
James Vose works as principal investigator at the Coweeta Hydologic Laboratory in the southern Appalachian Mountains of North Carolina, a working forest in steep hilly country, with lots of rainfall, and mixes of hardwoods, pine and spruce on the ridges, hemlock along the streams.
"It's about as good as it gets here," Vose said of his environment. The focus of the lab is watershed ecology. His chief interest is forest canopies, their spatial and species distribution, and how they influence water and carbon cycling.
His research could help scientists understand the effects of such hot-button issues as tropical deforestation, acid rain and tree disease, he said. But until now, canopy measurements were taken strictly by foot-slogging manual surveys.
"Any disturbance that affects the canopy - tropical deforestation, acid rain, insects and disease - could all be monitored and indexed with this technology," Vose said. "It would be a significant advance. In 30 to 40 years studying the canopy, there never have been any large-scale measurement advances like this."
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