DRG (Digital Raster Graphic)

http://www.tceq.texas.gov/gis/drg.html

According to Wikipedia, "A digital raster graphic (DRG) is a digital image resulting from scanning a paper USGS topographic map for use on a computer. DRGs created by USGS are typically scanned at 250 dpi and saved as a TIFF. The raster image usually includes the original border information, referred to as the "map collar". The map file is UTM projected and georeferenced to the surface of the earth. DRG's are regularly used in GIS applications." From the definition, a DRG is simply a paper map that is created into a digital image. More can be done with an image on a computer. In the map above, it features Walter Beach and the surrounding area of Austin, TX. This map is a digital image from a topographic map.