These data were collected as part of the National Mapping Program. The DLG files are digital vector representations of cartographic information. Data files of topographic and planimetric map features are derived from either aerial photographs or from cartographic source materials using manual and automated digitizing methods. This is a data-set level implementation of the Federal Geographic Data Committee's Content Standards for Digital Geospatial Metadata.
Nodes define the location of the endpoints of every line.
Lines may not cross over themselves or any other lines except at a node. An area is a continuous unbroken region of a map bounded by lines. There are also two national files. One file contains land grant names and identifiers for the entire United States. Records in these data files can be associated with cartographic features contained in the DLG files.