IDAHO’S GEOLOGIC MAP DATA AND DIGITAL GEOLOGIC MAP DATA MODEL

Since 1992 the Idaho Geological Survey has captured all geologic mapping data with GIS software. Before 2001 each mapping project became a separate, uncontrolled database which resulted in a digital tangle of geologic map data. To organize the data we implemented a standard data framework or digital geologic map data model in which geologic map data, and corollary legend and metadata information related to the map, could be stored, packaged, and distributed. Data customers can better construct derivative maps from geologic map data stored in a data model. The model allows the Idaho Survey to systematically catalog its data and reduce the cost of managing, updating, and migrating data. In addition, geologic map data stored in the Idaho model structure can be translated or exported to the National Geologic Map Database (NGMDB) that is currently under development.

The Idaho Digital Geologic Map Data Model is a variant of the National Digital Geologic Map Data Model (NADM) 4.3. The applied model relies on ArcInfo as its spacial database software and the rest of the map legend and metadata information are stored in related Microsoft Access tables. The Idaho model deviates most radically from NADM 4.3 in the way lithologic descriptions are handled. Map units can have multiple lithologies and each lithology has multiple attributes. Each attribute type is stored in a separate table, including genetic origin, form, minerals, color, grain size, grain distribution, and structures. The source for lithology and attribute terms came mainly from the earth material taxonomies being developed by the Science Language Technical Team working under the supervision of the North American Digital Geologic Map Data Model Steering Committee. Using these taxonomies will insure better translation of Idaho data to the NGMDB.

Geologic map data sets are distributed by the Idaho Survey in 30 x 60 minute edge-matched tiles. Geologic map tiles are compiled from new mapping and the best existing geologic maps. Each data set includes complete data model information: GIS database, legend database, and metadata. When available, geochemistry data is also included. Six Digital Geologic Map data sets are currently published online and on compact disk.