DLG

 

http://www.dnr.sc.gov/GIS/descdlg.html 

Digital Line Graph (DLG) is digital vector data. Data about map features are stored as lines (arcs), points, and areas (polygons) and can contain information for topography, hydrography, boundaries,etc. The map above shows information for hydrography (which is useful for the navigation of shipping) while also having information of municipal boundaries, which could be important for identifying who would be responsible for problems with those establishments (structures in navigating rivers).