The tests of logical consistency were performed by the USGS PROSYS program. The neatline was generated by connecting the four corners of the digital file, as established during initialization of the digital file. All data outside the enclosed region were ignored and all data crossing these geographically straight lines were clipped at the neatline. Data within a specified tolerance of the neatline were snapped to the neatline. Neatline straightening aligned the digitized edges of the digital data with the generated neatline, that is, with the longitude/latitude lines in geographic coordinates. All internal areas were tested for closure using PROSYS.
For Digital Revision Status = Limited Update This file has undergone limited update digital revision. The file contains only (1) those features that are photoidentifiable on monoscopic source, supplemented with limited ancillary source, and (2) those features, present on the original source quadrangle, that can not be reliably photoidentified but that are not considered particularly prone to change.
For Digital Revision Status = Standard Update This file has undergone standard update digital revision. The data completeness of this file meets NMD standards for feature content.
- scanning a stable-based copy of the graphic materials. The scanning process captured the digital data at a scanning resolution of at least 0.001 inches; the resulting raster data were vectorized and then attributed on an interactive editing station.
- scanning the paper map. The scanning process captured the digital data at a scanning resolution of at least 0.001 inches; the resulting raster data were vectorized and then attributed on an interactive editing station.
- scanning a stable-based copy of the graphic materials. The resulting raster data were then manually digitized and attributed on an interactive editing station. The resolution of the digital data is at least 0.001 inches.
- scanning the paper map. The resulting raster data were then manually digitized and attributed on an interactive editing station. The resolution of the digital data is at least 0.001 inches.
- manually digitizing from a stable-based copy of the graphic material using a digitizing table to capture the digital data at a resolution of at least 0.001 inches; attribution was performed either as the data were digitized, or on an interactive edit station after the digitizing was completed.
- manually digitizing from the paper map using a digitizing table to capture the digital data at a resolution of at least 0.001 inches; attribution was performed either as the data were digitized, or on an interactive edit station after the digitizing was completed.
The determination of the DLG production method was based on various criteria, including feature density, feature symbology, and availability of production systems. Four control points corresponding to the four corners of the quadrangle were used for registration during data collection. An eight parameter projective transformation was performed on the coordinates used in the data collection and editing systems to register the digital data to the internal coordinates used in PROSYS, and a four parameter linear transformation was performed from the PROSYS internal coordinates to Universal Transverse Mercator (UTM) grid coordinates. The DLG data were checked for position by one or more of the following processes: - comparing plots of the digital data to the graphic source. - comparing the digital data to the digital raster scan.
DLG data classification was checked by at least one of the following processes. - comparing plots of the digital data to the graphic source - comparing the digital data to the digital raster scan.
For Boundaries: 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.
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.
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.
A hypertext extract is available at: <URL:http://edcwww.cr.usgs.gov/glis/hyper/guide/usgs_dlg>
Softcopies in ASCII, WordPerfect, and PostScript format are available at: <URL:ftp://mapping.usgs.gov/pub/ti/DLG/>
U.S.Department of the Interior, U.S.Geological Survey, 1990, Standards for Digital Line Graphs; Reston, Virginia
Softcopies in ASCII, WordPerfect, and PostScript format are available at: <URL:ftp://mapping.usgs.gov/pub/ti/DLG/>
<URL:http://mapping.usgs.gov/esic/esic_index.html>
<URL:http://edcwww.cr.usgs.gov/glis/hyper/order_info/prices#100KDLG>
Dataset searching and ordering capabilities are available through the Global Land Information System (GLIS) at:
<URL:http://edcwww.cr.usgs.gov/webglis>