July 31, 1995 By Bill McGarigle
The prime contractor for the freshwater wetlands mapping project was Markhurd of Minneapolis. The company was responsible for developing digital ortho quarter-quad (DOQQ)2 basemaps and delineation overlays in ArcInfo format, and conventional photo basemaps on Mylar with superimposed wetlands delineations. To date, New Jersey is only one of two states to have complete DOQQ coverage of the entire state.
The subcontractor, Greenhorne & O'Mara, of Greenbelt, Md., provided photo analysis and interpretation, field verification, and a signature key to identify and classify ground features.
The 1:58,000-scale aerial photography, taken by the National Aerial Photographic Program was shot in March and April of 1986 and 1992, during the wettest ground conditions and before the spring leaf out. Color infrared (CIR) imagery was chosen specifically for its ability to discriminate vegetation types and various levels of soil saturation.
The aerial photos provided the images from which DOQQ basemaps were developed. Each quarter quad covers an area of roughly 12.5 square miles and has a minimum mapping unit of one acre, enabling analysts to delineate all wetland features down to 10 feet in width.
NJDEP's contract manager for the project, Bob Cubberly, said that since the quarter-quad basemaps were digitized for GIS applications, they had to fit together like puzzle pieces. "We had to have a cartographic base that produced a seamless edge match. That's where the prime contractor, Markhurd, came in. They considered the whole state in the solution, instead of in blocks or strips, so all the map edges match; the corner coordinates of all the quarter quads are shared between adjacent maps." A total of 624 quarter quads were required to cover the entire state.
Following extensive quality-control processes, digitized composites of the basemaps with wetland delineations were delivered to the NJDEP in ArcInfo format, along with a database of all field information, including post-processed GPS data recorded by field verification teams. Other deliverables included hard copies of basemaps, Mylar composites of the basemaps and delineations, and acetate copies of only wetlands delineations.
The wetlands GIS maps and database are proving effective and versatile resource-management tools for the NJDEP, enabling state officials and scientists to make informed decisions about present applications, and to rapidly assess the impact of developments on wetland resources. Wildlife biologists are also using the maps to identify and monitor locations of threatened and endangered species habitats and to protect rare plant communities.
Under data-sharing agreements, most counties in New Jersey with GIS now have overlays of the wetlands delineations. The databases are also being used in emergency preparedness; officials can model the probable extent of an oil spill in a waterway, identify areas that will be affected, and determine appropriate responses. As for the overall cost of the mapping project, some of that will be recovered through map sales to developers, local Realtors and property owners.
Ernest Hahn stresses that the GIS is not a regulatory tool. "There are some people who would like to see us going into a GIS terminal, bringing up a map and regulate from the computer. While the GIS has valuable applications in resource management, the bottom line is that most of the calls we make just can't be made off the computer screen. You're looking at things like endangered and threatened species habitats, whether or not they are connected to surface-water features," he said. "Those are really the things that need to be looked at in the field." The reason, he said, is that connections between habitats are analyzed. "You can only get to a certain level of detail with remote sensing," he said.
Comparing the present program with previous federal and state efforts, Hahn said "we have a much more comprehensive program. We've thrown a lot more people at it than the Army Corps of Engineers did. They didn't have the resources to adequately enforce the program. We believe that we do.
"As a result, other [state] resource agencies will get a better handle on what's going on because we do a more thorough investigation of all the permits that come in front of us," Hahn said. "So the advantage is twofold: one, it streamlines the process, and two, we're more effective in protecting the resources of the state."
Bill McGarigle is a freelance writer residing in Santa Cruz, Calif.
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