A digital raster graphic is a digital version of a USGS or United States Geological Survey. They are topographic maps that are 7.5 min of latitude and 7.5 min of longitude with a scale of 1:24,000. DRG's are georectified which means it has been linked to real world positions using coordinates, datum, and projection. This map came from the Illinois Natural Resources Geospatial Data Clearinghouse.
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