Data Set Title / Coverage Name: SAA Topographic Relief Derived from DMA 30 ARC SECOND DEM SAA Version 3.0 Version Date: 3/21/96 ---------------------------------------------------------------- ---------------------------------------------------------------- Identification Information Data Layer Name: topo_30s Description: Topographic Relief in the vicinity of the Southern Appalachian Assessment Study Area Study Area (Derived from DMA 30 ARC SECOND DEM) Keywords: SAA, Southern Appalachian Assessment, elevation, topography, shaded relief, digital elevation model DEM Citation: This data set was initially developed through a series of procedures conducted by the Defense Mapping Agency, Topographic Center (DMATC) and the National Telecommunications and Information Administration (NTIA). Native Data Set Environment: UNIX; ARC/INFO 7.0.3 pathname: Scale: 1:2,000,000 File Format: ARC/INFO 7.0.3 GRID Coverage Use Restrictions: Access Restrictions: ---------------------------------------------------------------- ---------------------------------------------------------------- Spatial Reference Information Datum: North American Datum 1983 (NAD83) Precision: single Projection: Albers Equal Area Units: meters Spheroid: WGS-84 1st Std Parallel: 34 00 00 2nd Std Parallel: 38 00 00 Central Meridian: -82 00 00 Origin: 33 00 00 False Northing: 0.0 False Easting: 0.0 Extent: West Bounding Coord.: -428494.531 East Bounding Coord.: 359505.469 North Bounding Coord.: 739925.824 South Bounding Coord.: 10325.824 Distance Resolution: Vertical Resolution: ---------------------------------------------------------------- ---------------------------------------------------------------- Data Quality Information Thematic Accuracy: unknown Confidence: unknown Accuracy Method: unknown Horizontal Accuracy: unknown Confidence: unknown Accuracy Method: unknown Vertical Accuracy: n/a Logical Consistency: This data set is a 1% (every 10th row and column) subset of the 1-degree Digital Elevation Models produced by DMATC. The 1-degree Digital Elevation Models are reported in USGS Data Users Guide 5 to adequately support computer applications that analyze hypsographic features to a level of detail similar to manual interpretations of information as printed at map scales not larger than 1:250,000. Completeness: ---------------------------------------------------------------- ---------------------------------------------------------------- Source Information Source Material: 30 arc-second digital elevation data. Organization: National Geophysical Data Center, Boulder, CO, USA. Date: 1992 Distance Resolution: 30 arc-seconds Contribution: Elevation values. Source Material: Organization: Date: Distance Resolution: unknown Contribution: --------------------------------------------------------------- --------------------------------------------------------------- Processing History Information The data set is a shaded relief model of the 30 arc second DEM. The history of the DEM follows: 1. The data set distributed by NGDC is described in this section. The 30-second point topography data set was developed through a series of processing procedures conducted by the Defense Mapping Agency, Topographic Center (DMATC) and the National Telecommunications and Information Administration (NTIA). These procedures are briefly outlined in the following paragraphs. The 30-second database was originally derived from a 3-second digital topographic database called Digital Terrain Data. DMATC developed this 3-second file by digitizing topographic contour lines and geographic features from printing plates that were used to produce the 1:250,000 scale U.S. Geological Survey Topographic maps. The digitized elevation contours were then converted into grids of interpolated elevations, with a single value given for every 3" x 3" coordinate cell. These values corresponded to the elevation given for a point situated in the center of each cell. Elevation data were rounded to the nearest 20 foot interval. DMATC developed the 30-second dataset by simply selecting every 10th data point from the completed Digital Terrain Data file. Selecting every 10th data point from the 3-second gridded Digital Terrain Data file has the effect of reducing the resolution by 100%. Although this may seem undesirable, it has resulted in a very compact, manageable and transportable database of U.S. elevation values. Each elevation in the 30-second file corresponded to the elevation at a point situated in the center of a 30" x 30" coordinate cell. The 30-second data set produced by DMATC contained a significant number of format and data errors. To rectify these problems, NTIA checked, updated and reformatted the data generated by DMATC. This final corrected version of 30-second point topography data is the set currently disseminated by NGDC. 2. The following describes the processing steps performed by the USDA, Forest Service in Atlanta, GA. According to the USGS Data Users Guide 5 the 1-degree elevation models from which this data set originated the array of elevations is referenced horizontally on the geographic (latitude/longitude) coordinate system of the World Geodetic System 1972 Datum (WGS 72) or the World Geodetic System of 1984 (WGS 84). Appendix H of the same guide states "All DMA DEM's and DTED's lacking datum descriptors are WGS 72." There being no datum descriptor included in this data set it is assumed the datum is WGS 72. 3. The WGS 72 datum was assumed to be functional equivalent to the NAD83. A point coverage from the original model was provided by the US Forest Service to Karl A. Hermann, NBS Cooperative, University of Tennessee. The point coverage was projected to SAA Albers and POINTGRID was used to convert to a grid with a spacing defined as 800 meters. 4. The shaded relief grid was performed in ARC/INFO GRID with the HILLSHADE function. ---------------------------------------------------------------- ---------------------------------------------------------------- Entity/Attribute Information Entity: TOPO_30S Definition: 800 meter cells for elevation values Attributes: VALUE - elevation (MSL) in feet Entity: Definition: Attributes: Entity: Definition: Attributes: ---------------------------------------------------------------- ---------------------------------------------------------------- Status Information Data Set Status: Available Release Date: 3/21/96 ---------------------------------------------------------------- ---------------------------------------------------------------- Metadata Reference Information Date: 3/20/96 Review Date: Contact: Karl A. Hermann National Biological Service Cooperative University of Tennessee 17 Ridgeway Road Norris, TN 37828 samab@utk.edu (423)-632-1452 ---------------------------------------------------------------- ---------------------------------------------------------------- Distribution Information Distribution Contact: Karl A. Hermann National Biological Service Cooperative University of Tennessee 17 Ridgeway Road Norris, TN 37828 samab@utk.edu (423)-632-1452 Distribution Liability: File Compression Technique: UNIX compress, Arc/Info export format Transfer Size: --------------------------------------------------------------- --------------------------------------------------------------- Contact Information Contact Person: Karl A. Hermann Contact Mail Address: National Biological Service Cooperative University of Tennessee 17 Ridgeway Road Norris, TN 37828 Contact Phone: (423)-632-1452 Contact Fax: (423)-632-1612 Contact email: samab@www.lib.utk Home Page for Updates: http://www.lib.utk.edu/samab ---------------------------------------------------------------- ----------------------------------------------------------------