TNM Large Scale Shaded Relief is a dynamic service that contains shaded relief elevation layers derived from the National Elevation Dataset (NED). The NED was developed by merging the highest resolution, best-quality elevation data available across the United States into a seamless raster format. Large scale shaded relief represents NED data with horizontal grid spacings of 1/3 arc-second (approximately 10 meters) and 1/9 arc-second (approximately 3 meters) as if it were a surface illuminated by a light source 45 degrees above the northwest horizon. Small scale shaded relief can be viewed at scales of 1:289,000 and larger in The National Map Viewer. Go to http://ned.usgs.gov/ and http://extract.cr.usgs.gov/distmeta/servlet/gov.usgs.edc.MetaBuilder?TYPE=HTML&DATASET=NED13 for more information on 1/3 arc-second NED.