According to the agreement between the City of Duluth and the Natural Resources Research Institute, and funded by the DNR Coastal Program, 1:24,000 color infrared photos, taken in September 1997 and acquired from Minnesota DNR, were digitally scanned at high resolution (800 DPI), geo-referenced (rectified) to the USGS Digital Ortho Quads (DOQ's) using an Arcview image warping routine. Each photo needed between 20 and 40 points to achieve the required degree of accuracy. These digitally rectified aerial photos served as the base for identifying both upland forest and wetlands. Wetland classification followed U.S. Fish and Wildlife Service conventions for the National Wetlands Inventory. The completed GIS wetlands layer is available in ESRI's shapefile format which can be downloaded from this page.
The D.A.W.I. wetlands maps available on this site were created using a module of ESRI's Arc/Info software called ArcPlot. An AML (Automated Macro Language) batch routine was run which draws all the elements of the maps on screen at high resolution. This screen is then captured, and resized into one of the available sizes for viewing here.
Aren't current wetlands maps good enough?
National Wetlands Inventory (NWI) maps prepared for the City of Duluth are outdated, and contain numerous errors. The photos used to do the NWI air photo interpretation were 1:80,000 black and white photos taken in November 1978. Forested and shrub wetlands were often mis-interpreted because of Duluth’s red clay soils, and in several cases, forested ravines were mis-identified as wetlands. Wetland boundary placement is imprecise because of the high-altitude photography used. Extensive areas of emergent wetlands in the St. Louis River were not mapped because of the November photo date.
Here is an example of the difference between the National Wetlands Inventory
(NWI) wetlands and NRRI's D.A.W.I.
GIS layer created for this project:
(click on the image for a closer look)