Satellite maps offer sprawl insight

Mid-Atlantic Regional Earth Science Applications Center

State agencies and local government planners now have ready access to inexpensive

satellite-based maps for monitoring water quality, as the result of a NASA-sponsored

program that provides detailed and accurate maps of impervious surfaces

such as buildings and paved areas.

Maps of such surfaces show planners where large storm water runoffs

can occur, and therefore, where they can expect major erosion and large

levels of soil and chemical discharge into rivers, streams and ground water.

Urban sprawl significantly increases these problems.

The trouble, according to Andrew Smith, a faculty research assistant

who is developing the maps at the University of Maryland's Mid-Atlantic

Regional Earth Science Applications Center (RESAC), is that local governments

have been able to generate such detailed maps only by using aerial photography,

a process that can cost tens of thousands of dollars. That cost makes the

process too expensive for many governments.

"By contrast, satellite maps can be provided much more regularly, since

the satellites are always up there, and they cost only several hundred dollars,"

Smith said. "Ancillary data is needed, which can boost the cost some, but

even so it's far less than what aerial photography costs."

The Landsat 7 images that are used now are lower-resolution maps than

those produced from aerial photography, Smith said, but he expects that

images from satellites that will be launched over the next few years will

produce maps accurate to four-meter and, eventually, one-meter resolutions.

The RESAC team already has provided maps to the Chesapeake Bay from

Space project, the Maryland departments of Planning and Natural Resources

and the Montgomery County Department of Environmental Protection, among

others. It is working with planning departments to see how to add the data

from the maps into future urban planning models.

Smith said the technique should be made available to governments across

the rest of the country in the next several years. He also is hopeful that

it can be applied to other natural features that might be affected by sprawl,

such as tree and plant cover.

Robinson is a freelance journalist based in Portland, Ore.