This map layer is a 100-meter resolution grayscale shaded relief image of Puerto Rico and the U.S. Virgin Islands, in an Albers Equal-Area Conic projection. Shaded relief was created with the ArcGIS Hillshade command, with 45-degree sun elevation, 315-degree azimuth, and a z-factor of 1.0. Very dark and very light shades both represent steeper terrain. Mid-range grays represent flatter terrain. The grayscale shaded relief data were derived from the National Atlas 100-meter resolution elevation data. The elevation data were derived from 2012 National Elevation Dataset (NED) data and show the terrain of Puerto Rico and the U.S. Virgin Islands at a resolution of 100 meters. The NED is a raster product assembled by the U.S. Geological Survey, designed to provide national elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections made in the NED assembly process minimize artifacts, permit edge matching, and fill sliver areas of missing data. This layer is part of the 1997-2014 edition of the National Atlas of the United States.The 100-meter resolution grayscale shaded relief data were developed to portray the terrain of the United States at 1:1,000,000 scale. They are intended primarily for visual purposes. The original NED data should be used for conducting analysis and determining the most accurate elevation values. No responsibility is assumed by the National Atlas of the United States in the use of these data.