DRG stands for Digital Raster Graphic. The term "raster" means that pixels are used to create the image. It is simply a high resolution scan of a USGS physical topographic map, and each scan is referenced to the datum of the source map and adheres to the Universal Transverse Mercator projection. These maps are heavily used in GIS applications. This is a DRG of the western part of Washington D.C.
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