EarthData International fast tracks aerial data

Mar. 2, 2007
By JOSEPH M. DELEON News-Post Staff
jdeleon@fredericknewspost.com

FREDERICK — A digital mapping approach will give engineering, construction and economic development firms the tools to help Mississippi recover as part of the state's post-Katrina redevelopment process.
     Frederick-based EarthData International Inc., a company that produces aerial maps, is using a digital process to speed delivery of high-resolution aerial data collected from six counties in Southern Mississippi.
     The maps show damage, topography, infrastructure and other details that the public and private companies need to rebuild the area.
     Louis Demargne, marketing director, said EarthData imaged roughly 3,000 square miles in less than four weeks. While digital imaging saved time during the collection process, the company will save more time during image processing.
     “Digital is quicker because you can cover the area in a short er time than with film because of the higher altitude,” he said. “And with digital you eliminate one very time-consuming step — you don't have to develop and then scan.”
     The data, part of the Gulf Region Base Mapping Program, will be delivered to Mississippi officials later this year.
     The first lower-resolution maps should be ready this spring, with higher-resolution maps expected in the fall.
     Rural areas were imaged at a 1-foot-to-pixel resolution, which would allow viewers to make out details as small as a car.
     Urban areas and counties that sustained extensive damage were imaged at a 6-inch-to-pixel resolution — twice the quality, enough to see the make and model of a car.
The company uses color orthoimagery, which combines the image characteristics of an aerial photograph with the geometric qualities of a map.
Camera lenses used in photography warp the images, making them inaccurate.
The curvature of the earth and distance between points on the ground at different elevations further deform the image.
     EarthData removes the distortion so topographic features are shown in their true position. The resulting map can be used to make direct measurements of locations, mark distances and check angles.
     “What we do as the picture is taken is correct it so it essentially becomes a map,” Demargne said. “But instead of a bunch of lines to represent a road or green stuff to represent a forest, you have a photograph.”
     The mapping program is funded by the Mississippi Development Authority with a grant from the United States Department of Housing and Urban Development. The Mississippi Coordinating Council for Remote Sensing and GIS will make final maps available to state and local government agencies and institutes of higher learning.
     EarthData imaged the coastal counties of Hancock, Harrison and Jackson, as well as the inland counties of Pearl River, Stone, and George.