The NED National Elevation Dataset WMS (Web Mapping Service) is derived mainly from 10 meter to 30 meter high resolution, best quality digital elevation data covering the United States, Puerto Rico, and the Virgin Islands. This is a seamless product updated bimonthly to incorporate the best available Digital Elevation Model (DEM)-a digital representation of cartographic information. NED is available in spatial resolutions of 1 arc-second (roughly 30 meters), 1/3 arc-second (roughly 10 meters), and 1/9 arc-second (roughly 3 meters).