A GEOLOGIC MAP'S ODYSSEY

Bedrock and surficial geologic maps and supporting information provide the foundation for studies of ecosystems, earth history, groundwater, geomorphology, soils, and environmental hazards such as fire history, landslide and rockfall potential, etc. Geologic maps describe the underlying physical conditions of many natural systems and are an integral component of the physical science inventories stipulated by the National Park Service (NPS) in its Natural Resources Inventory and Monitoring Guideline. The NPS has identified GIS and digital cartographic products as fundamental resource management tools.

Digital geologic maps have several advantages over paper geologic maps. Digital geologic maps can be used in a digital GIS environment where they can be integrated with other geospatial data to provide analysis of spatial relationships. A digital GIS provides quick, reproducible, precise analysis results. Digital data are also more easily shared and transferred between users. With digital attribute capability a digital geologic map becomes a powerful database.

One of the unresolved issues facing developers of digital geologic maps models is how to include map unit descriptions, supplemental explanatory text (references and map notes), geologic cross sections, and the variety of other printed information that occur on published maps. In short, the digital product must "look and feel" like its published source.

In accordance with the NPS Geology-GIS Data Model, the spatial and geologic feature types present (i.e. polygon, line, point and fault, fold, unit, etc.) are captured into appropriate GIS coverages and attributed as per the Data Model. These data are then incorporated into the NPS GIS Theme Manager that facilitates (in ArcView 3.2) the presentation of the various map coverages along with any FGDC metadata and accompanying help files that display map notes, unit descriptions and other ancillary data from the original paper source map. Any map graphics (e.g. geologic cross sections) are scanned from the original paper map and hotlinked to a coverage (e.g. in this case the cross section line coverage) on the digital geologic map. These data are then posted on the NPS I&M GIS FTP Website for user access and download.