Method used to create DEM grid from Hpysography DLG data was based on a process paper from USGS, "Digital Mapping Technicues '98 --Workshop Proceedings, U.S. Geological Survey Open-File Report 98-487, Recipes for Digital Cartography: Cooking with DEMs" by Ralph Haugerud and Harvey M. Greenberg.
URL: <https://pubs.usgs.gov/of/1998/of98-487/haug2.html>
For additional information on steps used, contact South Carolina Geological Survey, South Carolina Department of Natural Resources.