How was this data gathered?....Technical details.
Color infra-red photos (1:24,000 scale), taken in September 1997 by, and acquired from Minnesota DNR, were digitally scanned at 800 dots per inch. These digital scans were then 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. An experienced forester and GIS technician then digitized the forest polygons on screen. According to the contract agreement, ten percent of the delineated polygons were field checked to ensure accuracy. This completed GIS layer, called the Duluth Forest Inventory is available in ESRI's shapefile format which can be downloaded from this page.
The D.F.I. forest 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.
On the left you can see the original image ready to be delineated. On the right we see the image after delineation with the highlighted polygon shown in the database...click on either of the images for a closer look.
