Metadata for 7.5-minute Digital Elevation Models (DEMs) - 10 meter resolution These metadata describe the 7.5-minute digital elevation models with a resolution of 10 meters. ------------------------------------------------------------------------ Table of Contents Identification_Information Data_Quality_Information Spatial_Data_Organization_Information Spatial_Reference_Information Entity_and_Attribute_Information Distribution_Information Metadata_Reference_Information ------------------------------------------------------------------------ Identification_Information: Citation: Citation_Information Originator: U.S. Geological Survey Publication_Date: 199807 Title: 7.5 minute Digital Elevation Models Geospatial_Data_Presentation_Form: map Publication_Information: Publication_Place: Menlo Park, CA Publisher: U. S. Geological Survey Description: Abstract: Digitntains 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). 7.5-minute DEM (10- by 10-m data spacing, cast on Universal Transverse Mercator (UTM) projection). Provides coverage in 7.5- by 7.5-minute blocks. Each product provides the same coverage as a standard USGS 7.5-minute quadrangle without over edge. Purpose: DEM's can be used as source data for digital orthophotos, and, as layers in geographic information systems, for earth science analysis. DEM's can also serve as tools for volumetric analysis, for site location of towers, or for drainage basin delineation. These data were collected as part of the National Mapping Program. Supplemental_Information: 7.5-minute DEMs have rows and columns which vary in length and are staggered. The UTM bounding coordinates form a quadrilateral (no two sides are parallel to each other), rather than a rectangle. The user will need to pad out the uneven rows and columns with blanks or flagged data values, if a rectangle is required for the user's application. Some software vendors have incorporated this function into their software for input of standard formatted USGS DEMs. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 197907 Ending_Date: present Currentness_Reference: ground condition Status Progress: In work Maintenance_and_Update_Frequency: Irregular Spatial_Domain Bounding_Coordinates: West_Bounding_Coordinate: -124.7333 East_Bounding_Coordinate: -067.9500 North_Bounding_Coordinate: 49.3833 South_Bounding_Coordinate: 24.5333 Keywords: Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: DEM Theme_Keyword: digital elevation model Theme_Keyword: digital terrain model Theme_Keyword: hypsography Theme_Keyword: altitude Theme_Keyword: height Theme_Keyword: contour line Theme_Keyword: digital contours Place: Place_Keyword_Thesaurus: U.S. Department of Commerce, 1977, Countries, dependencies, areas of special sovereignty, and their principal administrative divisions (Federal Information Processing Standard 10-3):Washington, D.C., National Institute of Standards and Technology. Place_Keyword: US Place_Keyword_Thesaurus: U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of The United States, and associated areas (Federal Information Processing Standard 5-2): Washington, D. C., National Institute of Standards and Technology. Place_Keyword: FIPS code of State or Province Place_Keyword_Thesaurus: U.S. Department of Commerce,1990, Counties and equivalent entities of The United States, its possessions, and associated areas (Federal Information Processing Standard 6-4): Washington, D.C. National Institute of Standards and Technology. Place_Keyword: FIPS code for county or counties. Access_Constraints: None Use_Constraints: None. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from these data. Data_Quality_Information Attribute_Accuracy: Attribute_Accuracy_Report: The accuracy of a DEM is dependent upon the level of detail of the source and the grid spacing used to sample that source. The primary limiting factor for the level of detail of the source is the scale of the source materials. The proper selection of grid spacing determines the level of content that may be extracted from a given source during digitization. Logical_Consistency_Report: The fidelity of the relationships encoded in the data structure of the DEM are automatically verified using a USGS software program upon completion of the data production cycle. The test verifies full compliance to the DEM specification. 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. Due to the variable orientation of the quadrilateral in relation to the Universal Transverse Mercator (UTM) projection grid, profiles that pass within the bounds of the DEM quadrilateral, may be void of elevation grid points, and are not represented in the DEM. This condition occurs infrequently and is always the first or last profile of the dataset. Level 2 DEM: Level 2 DEM's 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, " symbolized by contours overprinted with photorevised or other surface patterns. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: The horizontal accuracy of the DEM is expressed as an estimated root mean square error (RMSE). The estimate of the RMSE is based upon horizontal accuracy tests of the DEM source materials which are selected as equal to or less than intended horizontal RMSE error of the DEM. The testing of horizontal accuracy of the source materials isaccomplished by comparing the planimetric (X and Y) coordinates of well-defined ground points with the coordinates of the same points as determined from a source of higher accuracy. Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: RMSE of the DEM. Horizontal_Positional_Accuracy_Explanation: Digital elevation models meet horizontal National Map Accuracy Standards (NMAS) accuracy requirements. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: The vertical 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 errors; blunder, systematic and random. These errors are reduced in magnitude by editing but cannot be completely eliminated. 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. DEM's 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, 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. Quantitative_Vertical_Positional_Accuracy_Assessment: Vertical_Positional_Accuracy_Value: Vertical_Positional_Accuracy_Explanation: RMSE of the DEM. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: Title: digital contour lines Geospatial_Data_Presentation_Form: map Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Type_of_Source_Media: magnetic tape Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 197907 Ending_Date: present Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: CONTOUR1 Source_Contribution: hypsographic vector information which is interpolated to regular grid posts to form DEM grids in 10- by 10- meter UTM data spacing within the 7.5 minute DEM bounds. Source_Information: Source_Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: Title: photo ID number Geospatial_Data_Presentation_Form: remote-sensing image Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Type_of_Source_Media: transparency Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: various Ending_Date: various Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: PHOTO1 Source_Contribution: elevation values Source_Information: Source_Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: Unpublished material Title: project control Geospatial_Data_Presentation_Form: map Publication_Information Publication_Place: Reston, VA Publisher: U.S. Geological Survey Type_of_Source_Media: magnetic tape Source_Time_Period_of_Content: Time_Period_Information Range_of_Dates/Times: Beginning_Date: various Ending_Date: various Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: CONTROL1 Source_Contribution: ground control points Process_Step: Process_Description: Level 2 DEM: Level 2 DEM's are produced by converting 1:24,000-scale and 1:100,000-scale hypsography digital line graph (DLG) data to DEM format or the DEM's are generated from vector data derived from scanned raster files of USGS 1:24.000-scale or 1:100,000-scale map series contour separates. Level 3 DEM: Level 3 DEM's are created from DLG data that has been vertically integrated with all categories of hypsography, hydrography, ridge line, break line, drain files and all vertical and horizontal control networks. The production of level 3 DEMs requires a system of logic incorporated into the software interpolation algorithms that clearly differentiates and correctly interpolates between the various types of terrain, data densities and data distribution. Water body editing: DEM surface areas corresponding to water bodies are flattened and assigned map specified or estimated surface elevations. Water body areas are defined as ponds, lakes, and reservoirs that exceed 0.5 inches at map scale and double line drainage that exceeds 0.25 inches at map scale. Water body shorelines are derived either from a hypsographic DLG or by interactive delineation from 1:24,000- scale or 1:100,000-scale USGS map series. Edge matching and edge joining: DEM datasets within a project area (consisting of a number of adjacent files) are edge match and edge join edited to assure terrain surface continuity between files. Edge matching is the process of averaging adjacent elevation values along common edges within a zone of approximately 5 row or column grid posts on both edges. When edge values exceed 3 elevation units difference, edge joining is performed. Edge joining is an extensive level of editing and requires editing elevation values internal to the DEM in order to create more accurate terrain representations by correcting the alignment of ridges and drains, and overall topographic shaping within an approximately 25-30 row or column grid post zone on both edges. Quality control: DEM's are viewed on interactive editing systems to identify and correct blunder and systematic errors. DEM's are verified for physical format and logical consistency at the production centers and before archiving in the National Digital Cartographic Data Base (NDCDB) utilizing the Digital Elevation Model Verification System (DVS) software. Source_Used_Citation_Abbreviation: CONTOUR1, PHOTO1, CONTROL1 Process_Date: Spatial_Data_Organization_Information Direct_Spatial_Reference_Method: raster Raster_Object_Information: Raster_Object_Type: grid cell Row_Count: Column_Count: Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 10-19 Transverse_Mercator: Scale_Factor_at_Central_Meridian: .09996 Longitude_of_Central_Meridian: depends on zone Latitude_of_Projection_Origin: 0.0 False_Easting: 500000 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: row and column Coordinate_Representation: Abscissa_Resolution: 10 Ordinate_Resolution: 10 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: North American Datum 1927 Ellipsoid_Name: Clark 1866 Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 294.9787 Vertical_Coordinate_System_Definition: Altitude_System_Definition: Altitude_Datum_Name: National Geodetic Vertical Datum of 1929 Altitude_Resolution: 1 Altitude_Distance_Units: meters Altitude_Encoding_Method: explicit elevation coordinate included with horizontal coordinates Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: The digital elevation model is composed of a 6- character integer raster representing a gridded form of a topographic map hypsography overlay. Each raster entity contains a 6-character integer value between -32,767 to 32,768. Entity_and_Attribute_Detail_Citation: U.S.Department of the Interior, U.S. Geological Survey, 1992, Standards for digital elevation models: Reston, VA, A hypertext version is available at: Softcopy in ASCII format is available at: Softcopy in WordPerfect format is available at: Softcopy in PostScript format is available at: Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: Earth Science Information Center, U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: 507 National Center City: Reston State_or_Province: Virginia Postal_Code: 22092 Contact_Voice_Telephone: 1 800 USA MAPS Hours_of_Service: 0800-1600 Contact_Instructions: In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at: Resource_Description: 7.5-minute digital elevation models Distribution_Liability: Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: DEM Format_Information_Content: USGS standard DEM: The standard USGS DEM can be described as an ASCII formatted elevation file preceded by a metadata header file which consists of one 1024 byte ACSII record. Transfer_Size: 1 Digital_Transfer_Option: Offline_Option: Offline_Media: Recording_Format: Compatibility_Information: none Fees: The online copy of the data set (when available electronically) may be accessed without charge. Metadata_Reference_Information: Metadata_Date: 199807 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: 345 Middlefield Rd. MS 531 City: Menlo Park State_or_Province: CA Postal_Code: 94025 Contact_Voice_Telephone: 650-329-4272 Metadata_Standard_Name: Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: 19940608