ATHENS, Ga. - A century ago, explorers drew maps so others could follow them into the wilderness. Now, most of us use maps to find the shortest route to Albuquerque. But the function of maps has changed dramatically over the decades, and now many show not only travel routes but geographical features and even vegetation patterns.
The advent of aerial photography made mapping much easier, and satellites have made the job more precise than ever. That's why it may come as a surprise to many that one area of the continental United States has not been thoroughly mapped - the vast swampy river of grass and water called the Everglades. Now, a team from the University of Georgia and the National Park Service is in the final year of mapping the Everglades and other national parks and preserves in south Florida.
"In theory, mapping a place like the Everglades would be easy, but there are huge problems with access and establishing ground control points," said Dr. Roy Welch, director of the University of Georgia's Center for Remote Sensing and Mapping Science. Welch has coordinated the efforts to map the areas with his colleague in the Center, Dr. Marguerite Remillard, along with a team of 10 to 12 graduate students.
Their research was presented at a meeting of the International Society for Photogrammetry and Remote Sensing in Stuttgart, Germany, in September and in Montana last June at a gathering for the Society of Wetland Scientists.
The project actually began with the devastating force of Hurricane Andrew, which hammered south Florida in August 1992. Trees by the thousands were laid flat or splintered, and the National Park Service realized it had no real way to know the extent of damage because no accurate maps existed in the interiors of the Everglades and Biscayne national parks, the Big Cypress National Preserve and the Florida Panther Refuge.
The NPS came to the University of Georgia's experienced team of mapping experts and began plans to construct the modern descendant of the map - a geographic information system database along with detailed vegetation maps.
"While the project started out in response to Hurricane Andrew, the emphasis shifted as we realized we needed to establish a baseline for the area," said Welch. "And a natural disaster like Hurricane Andrew wasn't the only reason it needed to be done."
n truth, threats to the entire area, which extends roughly from Miami on the east to Naples on the west and then south to Florida Bay, are many. Urban expansion, agricultural development, recreation and the sprawling sugar cane industry have all threatened the delicate balance of the area's wetlands. While some areas in the interior of the Everglades are so remote they have few human visitors, other sites in the parks are crisscrossed with miles of off-road vehicle trails that scar the wilderness.
A relatively recent threat is the invasion of exotic species of plants and animals. After natural disasters in decades past, native plants would grow back, re-forming habitat for hundreds of animal species. But interlopers such as the Brazilian pepper and a tree called the melaleuca have taken over, and the disturbances to the ecosystem are only now beginning to be understood.
The project uses aerial photographs from the U.S. Geological Survey, satellite images from the French SPOT satellite program and information derived from the U.S. Department of Defense Global Positioning Satellite (GPS) program and combines them like a multilayer jigsaw puzzle. Field verification has been done with ground checks and by real-time GPS-aided navigation from helicopters.
"A geographic information system is much more than a map," Welch told the magazine Research Reporter in 1995. "A GIS includes a layered `map' database in digital format and a set of computer tools that can combine the layers into a variety of maps that show, for example, projected population distributions, soil erosion patterns and changes in plant cover."
The advantages of using images to map the 6,000 square-mile study area become clear when one considers it takes about 400 aerial photographs and seven or eight satellite pictures to cover the vast wetland area, much of which is accessible only by air boat, helicopter or off-road vehicle. Combining the images into a GIS database gives National Park Service planners an idea of what is here now, so changes -- and their causes -- can be measured as new images become available.
The research team has already started the next phase of the research - mapping areas considered extremely sensitive by the NPS. Some 31 sites throughout all the parks in south Florida are being examined using low-altitude, large-scale aerial photographs. The databases being built from this part of the study will be used for monitoring environmental factors influencing the nesting habits of birds to the impact of exotic plants.
"In Big Cypress, for example, we are mapping off-road vehicle trails," said Remillard. "Since it is a national preserve rather than a national park, it is more openly accessible to the public, and there are fewer vehicle restrictions. The ultimate goal is to find a way to control a lot of people in the area without ruining the environment." This part of the study is about halfway finished, Welch estimated.
A doctoral student participating in the project, Shunfu Hu, has developed a complex multimedia computer presentation that uses the project's GIS databases. The presentation combines text, still and video pictures and sound to present an overview of the area and threats to it. The Center for Remote Sensing and Mapping Science is refining the program, which will likely be used by the National Park Service for visitors to the area, or by schools and other groups.
In addition to public education, the databases will assist park rangers, scientists and law enforcement officials in their jobs.
(Editor/writers: A complete description of the project was published in the November 1995 issue of Photogrammetric Engineering & Remote Sensing, Vol. 61, No. 11. Also, please visit the web site of the University of Georgia Center for Remote Sensing and Mapping Science at www.uga.edu/~crms/.)