DRG

http://www.google.com/imgres?q=DRG&um=1&hl=en&client=safari&sa=N&rls=en&biw=1205&bih=706&tbm=isch&tbnid=hMCJU9OS73gweM:&imgrefurl=http://egsc.usgs.gov/isb/pubs/factsheets/fs08801.html&docid=ZTPaoJuKsveX7M&imgurl=http://egsc.usgs.gov/isb/pubs/factsheets/fs08801.graphics/drg.jpg&w=386&h=310&ei=KlXIToGSPKPj0QHLmMUv&zoom=1&iact=hc&vpx=464&vpy=190&dur=576&hovh=201&hovw=251&tx=170&ty=87&sig=112690992776489872722&page=1&tbnh=150&tbnw=185&start=0&ndsp=17&ved=1t:429,r:2,s:0

A DRG(digital raster graphic) is a scanned image of a U.S. Geological Survey standard series topographic map giving information of the earths surface. This map obviously illustrates a body of water flowing through the area of space.