High-tech map makers create image of coast
by Mary Landers, The Savannah Morning News
March 16, 2014 11:55 PM | 771 views | 0 0 comments | 4 4 recommendations | email to a friend | print
SAVANNAH — From overhead, the outline of Fort Pulaski forms a giant ice cream cone, its edges straight and crisp, its moats brimming with blue-green water.

The beauty of this image and thousands of others along the coast is an incidental benefit of a cooperative effort among Georgia counties and state and federal agencies to acquire high resolution aerial imagery of the entire Peach State coast at low tide.

The resulting orthoimagery data, which combines the photos with accurate horizontal mapping, is a boon for county governments as well as state natural resource researchers and planners.

“If I take a picture, I can’t tell where it is in space,” said Sonny Emmert, coastal resource specialist with the Coastal Resources Division of the Georgia Department of Natural Resources. “I can’t draw county boundary lines. This allows users to have it horizontally accurate, to have parcel lines and boundary lines accurate.”

DNR’s coastal researchers are eager to use the imagery to inventory resources such as the state’s oyster beds and marshes.

And it will come in handy if disaster strikes the coast.

“We wanted a snapshot in time for hurricane preparedness,” Emmert said. “We can document everything on the coast at one point in time. If a dock is being rebuilt, we can say we know exactly what was there.”

The photos were taken in December 2012 and January 2013 at low tide by PhotoScience and delivered to DNR and the multiple partners: county governments of Chatham, Bryan, Effingham, Liberty, McIntosh, Glynn, University of Georgia, Coastal Regional Commission, U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, and the U.S. Geological Survey.

When up-to-date images are needed, DNR will use photography taken from helicopters, which provides an instantaneous image of a small scale area. However, that method is not practical for large areas, nor is it spatially accurate for use in Geographical Information Systems, or GIS.

The project costs about $500,000, but participation by such numerous partners lowered the individual cost contributions, assisted in gaining project support and ensured thorough regional coverage, said Jason Lee, program manager of the nongame conservation section for the Wildlife Resources Division of DNR.

Lee, who used to be a GIS manager at SAGIS — Savannah Area GIS — said counties typically recoup their costs for projects like these with increased tax revenues on the unpermitted property it reveals.

Chatham County has been using this high resolution photography with its orthoimagery since 2008, said SAGIS director Noel Perkins. But this collaborative project brought the cost down by $45,000, making “everybody a winner,” he said.

Because near-infrared images were taken along with true color imagery, researchers can even differentiate among different plant species.

“The near-infrared allows us to see chlorophyll so we can see vegetation and vegetation health,” Lee said.

His office plans to use the data to identify habitats rare species can use, identify clear-cuts and die-offs and to find invasive species, such as tallow or “popcorn” trees.

“We can find individual trees in the canopy before they spread,” he said. “That speaks to the level of detail in the imagery.”

The imagery will be available for download through the NOAA Coastal Services Center Digital Coast website at https://www.csc.noaa.gov/digitalcoast, though it will take some sophistication and computing power to view it.

DNR is working on ways to present it on a more easily accessible Web-based platform and plans to start incorporating the images on existing DNR websites where appropriate.

Even to researchers who work with aerial images all the time, these are something special.

“It blows me away to look at the marsh with all its meandering creeks,” Emmert said. “It looks like a giant puzzle.”

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