Digital line graphs (DLGs) are spatial data products generated by the U.S. Geological Survey that contain vector representations of cartographic map features and attribute codes from standardized large-scale (1:24,000, 1:25,000, 1:30,000, and 1:63,360), medium-scale (1:100,000), and small-scale (1:2,000,000) source materials. DLGs are produced from aerial photos and published USGS topographic maps using manual and automated digitizing methods and are organized by scale and thematic content. DLGs capture and store topologic relationships and utilize a consistent and standardized attribute-coding scheme to describe cartographic features.
Data are organized into separate thematic categories that, depending on scale, include:
1) political boundaries,
2) hydrography,
3) transportation features (roads and trails; railroads; and pipelines, transmission lines, and miscellaneous transportation features),
4) public land survey system (PLSS),
5) other significant manmade structures, including miscellaneous cultural features not in the other major data categories (e.g., schools, churches, hospitals),
6) hypsography,
7) surface cover, including information about vegetative surface cover (e.g., woods, scrub, orchards, and vineyards),
8) nonvegetative surface features, including information about the natural surface of the Earth (e.g., lava and sand), and
9) survey control and markers.
DLGs are distributed by the USGS in several file formats including DLG-standard, DLG-optional, and Spatial Data Transfer Standard.
For more information about DLGs, visit this USGS Web site.
