This map layer is a 100-meter resolution grayscale shaded relief image of Alaska, 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 Alaska 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 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. National Atlas of the United States. (2013). 100-Meter Resolution Grayscale Shaded Relief of Alaska. National Atlas of the United States. Available at: http://purl.stanford.edu/qz033pg4379. The Grayscale Shaded Relief data set was derived from 100-meter resolution elevation data that are also distributed by the National Atlas of the United States. Characteristics and development of the elevation data are described in the metadata for that data set. Included with the GeoTIFF are an information file (.xml), an auxiliary information file (.aux.xml), an image overview file (.ovr), a value attribute database file (.vat.dbf), a .tfw file (more information included below), and a .prj file (more information included below.) The contents of the associated world file (.tfw) are: >100.0 >0.0 >0.0 >-100.0 >-3326950.0 >2437950.0 The projection (.prj) file contains the following information: > PROJCS["Albers_NAD83_Alaska", >GEOGCS["GCS_North_American_1983", >DATUM["D_North_American_1983", >SPHEROID["GRS_1980",6378137.0,298.257222101]], >PRIMEM["Greenwich",0.0], >UNIT["Degree",0.0174532925199433]], >PROJECTION["Albers"], >PARAMETER["False_Easting",0.0], >PARAMETER["False_Northing",0.0], >PARAMETER["Central_Meridian",-154.0], >PARAMETER["Standard_Parallel_1",55.0], >PARAMETER["Standard_Parallel_2",65.0], >PARAMETER["Latitude_Of_Origin",50.0], >UNIT["Meter",1.0]] Data set extent in meters (Albers Equal-Area Conic projection) >North 2438000 >West -3327000 >East 1654000 >South 346000 There are no NULL or NODATA values in the GeoTIFF. Instead, all elevation values in oceans have been set to zero as part of the masking process. Information about National Atlas Web services can be found on the Web Map and Web Feature Services page; see <http://nationalatlas.gov/infodocs/webservices.html>. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.