U.S. Geological Survey --------------------------------------------------------------------------- Metadata for DEM250 Table of Contents Identification_Information Abstract Purpose Supplemental Information Data_Quality_Information Spatial_Data_Organization_Information Entity_and_Attribute_Information Detailed Description Overview Distribution_Information Metadata_Reference_Section --------------------------------------------------------------------------- Identification_Information Citation_Information Originator: Musser, Jonathan W. Publication_Date: 1996 Title: Digital Elevation of Georgia, 1:250,000 Scale Edition: 1.0 1.1 Datum change from 1927 to 1983 (North American Datum of 1983) Data Re-projected using North American Datum (NAD83) - September 2000 Series_Information Series_Name: Digital Data Series Publication_Information Publication_Place: Atlanta, GA Publisher: U.S. Geological Survey Online_Linkage: http://csat.er.usgs.gov/statewide/layers/dem250.html Scale_Denominator: 250000 Description Abstract: Digital Elevation Model (DEM) is the terminology adopted by the USGS to describe terrain elevation data sets in a digital raster form. The standard DEM consists of a regular array of elevations cast on a designated coordinate projection system. The DEM data are stored as a series of profiles in which the spacing of the elevations along and between each profile is in regular whole number intervals. The normal orientation of data is by columns and rows. Each column contains a series of elevations ordered from south to north with the order of the columns from west to east. The DEM is formatted as one ASCII header record (A-record), followed by a series of profile records (B-records) each of which include a short B-record header followed by a series of ASCII integer elevations per each profile. The last physical record of the DEM is an accuracy record (C-record). 1-degree DEM (3- by 3-arc second data spacing). Provides coverage in 1- by 1-degree blocks. Two products (three in some regions of Alaska) provide the same coverage as a standard USGS 1- by 2-degree quadrangle. The basic elevation model is produced by or for the Defense Mapping Agency (DMA), but is distributed by the USGS in the DEM data record format. Coverage is for the United States. Purpose: DEMs can be used as source data for digital orthophotos, and, as layers in geographic information systems, for earth science analysis. DEMs can also serve as tools for volumetric analysis, for site location of towers, or for drainage basin delineation. Limitations_of_Data: None Entity_and_Attribute_Overview: COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME INDEXED? 1 VALUE 4 10 B - Indexed 5 COUNT 4 10 B - - Value represents the elevation of the grid cell in meters. Count represents the number of grid cells of each value. Procedures_Used: 1. The data was acquired from NMD over the internet with ftp as 1- by 1-degree blocks. 2. The DEM files were processed with Arc/Info's demlattice to produce elevation grids. 3. The elevation grids were merged together to form one large merged grid. 4. The merged grid was projected into an Albers equal-area projection. 5. A mask grid was created using the 1:100,000 state boundary and the same cell size and orientation as the Albers grid. 6. The mask grid was used to clip the elevation grid to the state boundary. 7. A coastline coverage from the NOAA 1:70,000 coastline was used to create a mask grid of the ocean and inland waterways around the coastal islands. 8. The final elevation grid was created by using this mask grid to clip out the coastline and islands. Revisions: None Reviews_Applied_to_Data: 1. Data checked for complete coverage, no missing data. 2. Visual inspection based on known ground surface elevation features. 3. Colleague review April 30, 1996 by Keith McFadden and Jack Alhadeff. Digital data was reviewed with respect to positional accuracy, contextual accuracy, attribute accuracy, topological consistency, and metadata content. Use of altitude and elevation was fixed to be consistent. Early log file entries could not be recovered due to Arc/Infos record keeping in Grid. County and shoreline data references added to citations. 4. Approved by Georgia District Chief, Tim Hale, on May 3, 1996. Related_Spatial_and_Tabular_Data_Sets: None References_Cited: ------, 1994, Medium Resolution Digital Vector Shoreline, NOAA, NOS, Washington D.C. ______, 1990, TIGER/Line Precensus Files, 1990, U.S. Department of Commerce, Bureau of Census, Washington D.C. ______, 1987, US GeoData Digital Elevation Models Data Users Guide, Department of the Interior, US Geological Survey, Reston, VA. Notes: None Currentness_Reference: Unknown Maintenance_and_Update_Frequency: None planned Access_Constraints: None Data_Set_Credit: US Geological Survey, National Mapping Program Completeness_Report: The DEM is visually inspected for completeness on a DEM view and edit system for the purpose of performing a final quality control and if necessary edit of the DEM. The physical format of each digital elevation model is validated for content completeness and logical consistency during production quality control and prior to archiving in the National Digital Cartographic Data Base. Level 2 DEM: Level 2 DEMs may contain void areas due to interruptions to contours in the source graphic or DLG. Void area elevation grid posts are assigned the value of -32,767. In addition, suspect elevation areas may exist in the DEM but are not specifically identified. Suspect areas can be located on the source graphic as a "disturbed surface" which are symbolized by contours overprinted with photorevised or other surface patterns. Horizontal_Positional_Accuracy_Report: Digital elevation models meet horizontal National Map Accuracy Standards (NMAS) accuracy requirements. NMAS horizontal accuracy requires that at least 90 percent of points tested are within 0.02 inches of the true position. The primary reference from which 1-degree DEM accuracy is derived is source-based, as a minimum, meeting NMAS for 100,000-scale USGS topographic series maps. Vertical_Positional_Accuracy_Report: The vertical root-mean-square error (RMSE) statistic is used to describe the vertical accuracy of a DEM, encompassing both random and systematic errors introduced during production of the data. The RMSE is encoded in element number 5 of record C of the DEM. Accuracy is computed by a comparison of linear interpolated elevations in the DEM with corresponding known elevations. Test points are well distributed, representative of the terrain, and have true elevations with accuracies well within the DEM accuracy criteria. Acceptable test points include, in order of preference: field control, aerotriangulated test points, spot elevations, or points on contours from existing source maps with appropriate contour interval. A minimum of 28 test points per DEM is required to compute the RMSE, which is composed of a single test using 20 interior points and 8 edge points. Edge points are those which are located along, at, or near the quadrangle neatlines and are deemed by the editor to be useful to evaluating the accuracy of the edge of the DEM. Collection of test point data and comparison of the DEM with the quadrangle hypsography are conducted by the quality control units within the USGS. There are three types of DEM vertical error; blunder, systematic and random. These errors are reduced in magnitude by editing but cannot be completely eliminated and may be encountered. Blunder errors are those errors of major proportions and are easily identified and removed during interactive editing. Systematic errors are those errors that follow some fixed pattern and are introduced by data collection procedures and systems. These error artifacts include: vertical elevation shifts, misinterpretation of terrain surface due to trees, buildings and shadows, and fictitious ridges, tops, benches or striations. Random errors result from unknown or accidental causes. DEMs are edited to correctly depict elevation surfaces that correspond to water bodies of specified size. Level 2 DEM: A vertical RMSE of one-half of the contour interval (of 100,000-scale source), determined by the source map, is the maximum permitted. Systematic errors may not exceed one contour interval, determined by the source map, is the maximum permitted. Systematic errors may not exceed one contour interval specified by the source graphic. Level 2 DEMs have been processed or smoothed for consistency and edited to remove identifiable systematic errors. Cloud_Cover: None Abstract Purpose Supplemental_Information Procedures_Used Revisions Reviews_Applied Related_Spatial_and_Tabular_Data_Sets Other_References_Cited Notes Time_Period_of_Content Single_Date/Time Calendar_Date: 1987 Currentness_Reference Status Progress: Approved for release by Tim Hale, Georgia District Chief Maintenance_and_Update_Frequency Spatial_Domain Bounding_Coordinates West_Bounding_Coordinate: -85.60518403 East_Bounding_Coordinate: -80.63815994 North_Bounding_Coordinate: 34.9847311 South_Bounding_Coordinate: 30.33160009 Keywords Theme Theme_Keyword_Thesaurus: None Theme_Keyword: digital elevation model DEM 1-degree DMA Place Place_Keyword_Thesaurus: None Place_Keyword: State of Georgia Stratum Stratum_Keyword_Thesaurus: None Stratum_Keyword: Temporal Temporal_Keyword_Thesaurus: None Temporal_Keyword: Access_Constraints Use_Constraints Point_of_Contact: See Data_Set_Credit Security_Information Security_Classification_System: None Security_Classification: UNCLASSIFIED Security_Handling_Description: None Native_Data_Set_Environment: dgux UNIX, ARC/INFO version 7.0.4 Cross_Reference Originator: U.S. Geological Survey Publication_Date: 1987 Publication_Time: Title: Digital Elevation Models Edition: Geospatial_Data_Presentation_Form: Series_Information Series_Name: Issue_Identification: Publication_Information Publication_Place: Reston, VA Publisher: U.S. Geological Survey Other_Citation_Details: Online_Linkage: http://edcwww.cr.usgs.gov/ Larger_Work_Citation: --------------------------------------------------------------------------- Data_Quality_Information Attribute_Accuracy Attribute_Accuracy_Report: See Logical_Consistency_Report: Not applicable for raster data. Completeness_Report Positional_Accuracy Horizontal_Positional_Accuracy Horizontal_Positional_Accuracy_Report: Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: 60 meters Horizontal_Positional_Accuracy_Explanation: Resolution as reported Vertical_Positional_Accuracy Vertical_Positional_Accuracy_Report: Lineage: See Cloud_Cover --------------------------------------------------------------------------- Spatial_Data_Organization_Information Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Grid Cell Row_Count: 8622 Column_Count: 7495 --------------------------------------------------------------------------- Spatial_Reference_Information Horizontal_Coordinate_System_Definition Planar Map_Projection: Map_Projection_Name: ALBERS Longitude_of_Central_Meridian: -83.5 Latitude_of_Projection_Origin: 23 Latitude_of_First_Standard_Parallel: 29.5 Latitude_of_Second_Standard_Parallel: 45.5 False_Easting: 0.00000 False_Northing: 0.00000 Geodetic Model Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: GRS 80 Semi-major_Axis: 6,378,206.4 Denominator_of_Flattening: 294.98 --------------------------------------------------------------------------- Entity_and_Attribute_Information Detailed_Description Entity_Type Entity_Type_Label: DEM250.VAT Entity_Type_Definition: Elevation in meters relative to mean sea level Entity_Type_Definition_Source: U.S. Geological Survey Attribute: Attribute_Label: - Attribute_Definition: Elevation in meters relative to mean sea level Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: 0-1372 meters Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Attribute: Attribute_Label: VALUE Attribute_Definition: Internal feature number for GRIDs Attribute_Definition_Source: Computed Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: Integer Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Attribute: Attribute_Label: COUNT Attribute_Definition: Number of GRID cells of a VALUE Attribute_Definition_Source: Computed Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: Integer Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Entity_Type Entity_Type_Label: DEM250.STA Entity_Type_Definition: Statistics table Entity_Type_Definition_Source: GRID Attribute: Attribute_Label: - Attribute_Definition: Statistics table Attribute_Definition_Source: GRID Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: - Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Attribute: Attribute_Label: MIN Attribute_Definition: Minimum GRID cell VALUE Attribute_Definition_Source: Computed Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: Real number Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Attribute: Attribute_Label: MAX Attribute_Definition: Maximum GRID cell VALUE Attribute_Definition_Source: Computed Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: Real number Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Attribute: Attribute_Label: MEAN Attribute_Definition: Mean GRID cell VALUE Attribute_Definition_Source: Computed Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: Real number Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Attribute: Attribute_Label: STDV Attribute_Definition: Standard Deviation of GRID cell VALUEs Attribute_Definition_Source: Computed Attribute_Domain_Values Enumerated_Domain Enumerated_Domain_Value: Positive real number Enumerated_Domain_Value_Definition Enumerated_Domain_Value_Definition_Source: Overview_Description Entity_and_Attribute_Overview Entity_and_Attribute_Detail_Citation: Not Available --------------------------------------------------------------------------- Distribution_Information Distributor Contact_Person_Primary Contact_Person: Jonathan W. Musser Contact_Organization: U.S. Geological Survey Contact_Position: Hydrologist Contact_Address Address_Type: mailing address Address: U.S. Geological Survey 3039 Amwiler Road Suite 130 City: Atlanta State_or_Province: GA Postal_Code: 30360-2824 Country: USA Contact_Facsimile_Telephone: 770-903-9199 Contact_Electronic_Mail_Address: jwmusser@usgs.gov Standard_Order_Process Digital_Form Digital_Transfer_Information Format_Name: ARCE ARC/INFO Export format File_Decompression_Technique: gzip Digital_Transfer_Option Online_Option Computer_Contact_Information Network_Address Network_Resource_Name: http://csat.er.usgs.gov/statewide/layers/dem250.html Distributor Contact_Person_Primary Contact_Person: Jonathan W. Musser Contact_Organization: U.S. Geological Survey Contact_Position: Hydrologist Contact_Address Address_Type: mailing address Address: U.S. Geological Survey 3039 Amwiler Road Suite 130 City: Atlanta State_or_Province: GA Postal_Code: 30360-2824 Country: USA Contact_Facsimile_Telephone: 770-903-9199 Contact_Electronic_Mail_Address: jwmusser@usgs.gov Standard_Order_Process Digital_Form Digital_Transfer_Information Format_Name: ARC/INFO GRID Format File_Decompression_Technique: gzip & tar Digital_Transfer_Option Online_Option Computer_Contact_Information Network_Address Network_Resource_Name: http://csat.er.usgs.gov/statewide/layers/zzz.html Distributor Contact_Person_Primary Contact_Person: Jonathan W. Musser Contact_Organization: U.S. Geological Survey Contact_Position: Hydrologist Contact_Address Address_Type: mailing address Address: U.S. Geological Survey 3039 Amwiler Road Suite 130 City: Atlanta State_or_Province: GA Postal_Code: 30360-2824 Country: USA Contact_Facsimile_Telephone: 770-903-9199 Contact_Electronic_Mail_Address: jwmusser@usgs.gov Standard_Order_Process Digital_Form Digital_Transfer_Information Format_Name: BIL Imagery, band interleaved by line File_Decompression_Technique: gzip & tar Digital_Transfer_Option Online_Option Computer_Contact_Information Network_Address Network_Resource_Name: http://csat.er.usgs.gov/statewide/layers/zzz.html --------------------------------------------------------------------------- Metadata_Reference_Section Metadata_Date: 19980323 Metadata_Contact: alhadeff Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: 19940608 Metadata_Time_Convention: Local Time Metadata_Security_Information: Metadata_Security_Classification_System: None Metadata_Security_Classification: UNCLASSIFIED Metadata_Security_Handling_Description: None --------------------------------------------------------------------------- Last modified: 2008-03-20