DLG

https://www.e-education.psu.edu/natureofgeoinfo/c7_p7.html

Digital Line Graphs (DLGs) are vector representations of most of the features and attributes shown on USGS topographic maps. DLGs exist at three scales: small (1:2,000,000), intermediate (1:100,000) and large (1:24,000). This picture is of a portion of a three Digital Line Graph (DLG) layers for USGS Bushkill, PA quadrangle