INTEGRATING GIS AND GEOLOGIC METHODOLOGIES TO ACCELERATE MAPPING
Similar to a literary search, the first step to mapping using GIS is to conduct a data search. Pertinent, existing digital data is gathered and organized. Digital data includes soil surveys, water well locations and stratigraphy, aggregate information, geologic maps, digital raster graphics (DRGs) of USGS 7.5' topographical quadrangles, digital orthophotoquads (DOQs: air photos), and digital elevation models (DEMs). Other information is captured digitally including gravel pit locations identified from topographic maps and soil surveys. All data layers are then compiled and analyzed using GIS software to aid in interpretation and identify potential aggregate resources. The next step is to conduct field investigations utilizing aerial photographic interpretations, reconnaissance-level surveying, and drilling. Locations of drill holes and observation sites are recorded using the Global Positioning System (GPS). GPS data points are downloaded into GIS and corresponding geologic observations are entered into a database. Upon completion of field work, mapping units are delineated using on-screen digitizing. Delineations are based on analyses of previously collected data, newly created data, and remotely sensed data. Final point, line, and polygon coverages contain detailed geologic information within associated tables.
The final products exemplify the integration of GIS with geologic information. These products are contained within a comprehensive CD-ROM data set. The CD-ROM includes a four-plate map series available in several digital formats, multiple GIS data layers, and metadata describing these data layers. Data layers have the potential to be linked or joined together, queried, and manipulated for the specific needs of the user. Combined with metadata, GIS data layers are user-friendly and customizable.