OKLAHOMA'S DIGITAL GEOLOGIC MAPPING PROGRAM

Since the mid-1990’s the Oklahoma Geological Survey (OGS), as part of the STATEMAP component of the USGS’s National Cooperative Geologic Mapping Program has been developing a GIS-based digital geologic mapping program for Oklahoma. OGS digital mapping consists of two programs: 1) a series of 1:100,000-scale reconnaissance geologic maps of the entire State that will become the foundation for a new 1:500,000-scale geologic map of Oklahoma; and 2) detailed 1:24,000-scale geologic maps of metropolitan areas, which help identify potential engineering and environmental hazards in rapidly growing urban areas.

Although both projects entail differing geological mapping procedures, cartographic methodology for the 1:100,000- and 1:24,000-scale maps are virtually identical. Procedures in converting the geologists’ field maps into digital format that can be viewed as both GIS data files or as hard-copy color maps are as follows: 1) the original USGS topographic base is subdivided into three component film positives consisting of culture, hypsography and hydrography, and each is scanned at 400 dpi producing a TIFF image; 2) the hydrography and hypsography layers are vectorized using ASC R2V software, which allows for better line work and color manipulation of these components; 3) all three layers are then incorporated and georeferenced as shapefiles in ESRI ArcInfo 8.1, forming the final, digital base; 4) the geologists’ field sheets are carefully georeferenced with ESRI ArcView 3.2 and digitized into individual layers representing each geologic formation; and 5) this compilation is then incorporated into ESRI ArcInfo 8.1 and placed underneath the base layers for final layout. For hard-copy reproduction of finalized geologic maps, the coloration of units, unit labels, map explanation, and any other information are manipulated and standardized using CorelDraw 8.

Once the geology has been adequately georeferenced, the shapefiles can be incorporated onto any number of specialized USGS bases (DOQ’s or DEM’s) with little additional manipulation.