DRG

Digital Raster Graphics (DRG) are a topographic map image from the U.S. Geological Survey (USGS) that uses the raster data format. Raster data format uses a grid system to place data on a map. These images are scanned and georectified by the USGS. Georectification means that Latitude and Longitude coordinates have been attached to a map.


The map shown is a Digital raster Graphics (DRG) map of Yellowstone. It is a topographic map with contour lines that has been scanned and georectified by the USGS.


http://www.topoquest.com/map-detail.php?usgs_cell_id=48367