Digital Line Graph (DLG)
Digital Line Graph (DLG) : A computer file format for mapping data that provides a topological structure to describe points, lines and polygons. A DLG may contain lists of point coordinates describing boundaries, drainage lines, and other linear or area features, which are organized by USGS quadrangle areas. These data are the digital equivalent of the linear hydrographic and cultural data on a topographic base map. The flood risk thematic layers developed by FEMA will fit the quadrangle as an overlay. The U.S. Geological Survey Digital Line Graph Level 3 Optional format has been adopted by FEMA for the purposes of the National Flood Insurance Program mapping and engineer requirements. Level 3 data files are fully topologically structured and are designed to be integrated into GISs
No records Found