PRESERVING NORTH CAROLINA LEGACY GEOLOGIC AND TOPOGRAPHIC MAPS

Geologic and topographic maps for North Carolina are being collected, scanned, georeferenced, and preserved in a collaboration between the NC Geological Survey (NCGS) and NCSU Libraries. The legacy geologic and topographic maps have no digital counterparts and paper copies are scarcely accessible. Geologic and historic maps are in high demand, and are critical for earth science instruction and research. Digital georeferencing provides new capabilities not possible with paper maps by allowing other data to overlay map images using GIS software. Geologic maps, including collars, are scanned to a 300 dpi TIF file with a large format (42 inch) scanner. Using ArcMap 9.1's georeferencing extension, at least four geographic locations were interactively selected from the TIF based on coordinates and grids printed on the maps. ArcMap creates a table of these selected coordinate values, and with U.S. Army Corps of Engineers Corpscon software, each coordinate pair is converted to NC Stateplane NAD83 meters and then appended to the table. ArcMap then creates a TFW world file and transforms the TIF image so that it is represented in the data view in Stateplane Coordinates. Each image file is rectified with ArcInfo workstation and compressed with MrSID. The TIF images and world files will become part of the North Carolina Geospatial Data Archiving Project, a partnership between NCSU Libraries and the US Library of Congress. As of December 2005, the inventory consists of 113 U.S. Geological Survey geologic maps, 100 North Carolina Geological Survey geologic maps, 36 maps from theses and dissertations, and 165 legacy 15-minute topographic maps, all of which are backed up on multiple secure servers. Data are planned for dissemination through the NC Department of Environment and Natural Resources and NCSU Libraries, and contributed to NCOneMap, the National Geologic Map Database and the National Geologic Map Image Library.