www.lmic.state.mn.us/bmap90/drg/drg.htm
A digital raster graphic (DRG) is a scanned image of a U.S. Geological Survey (USGS) standard series topographic map as a backdrop data layer. The raster image usually includes the original border information, referred to as the "map collar". The image above shows the state capital downtown mall area of St. Paul, Minnesota.
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