USING GIS TO INTEGRATE DIVERSE DATASETS TO SUPPORT GEOLOGIC MAPPING

The Wisconsin Geological and Natural History Survey (WGNHS) is developing a geographic information system (GIS) database structure to support geologic mapping projects. This database enables management of a variety of data, tracking of interpretations, and easy creation and maintenance of map elements.

Geologic mapping in Wisconsin involves field work focused on outcrops and supplemented with various collections of subsurface data. The subsurface data are compiled from a variety of sources and are of variable quality. For a current bedrock-mapping project in St. Croix and Pierce Counties, WGNHS project personnel began to develop a database in ESRI® geodatabase format, accessed primarily through the ArcMap™ desktop application. The goal was to enable management not only of the traditional geologic map features, but also the raw data from which interpretations are made. Key geologic logs were imported from our enterprise database, WGNHS GEOBASE, and supplemented with the various subsurface data. As field work proceeds, other data are added, including field notes, outcrop photographs, and laboratory analyses. Geologists can then track the source of data, make assessments of data quality, and record interpretations. Geologic map features are digitized either directly on-screen or through a digitizing tablet.

This approach enables the use of multiple data types (outcrops, core samples, well logs) and sources (residential well logs from one agency, photographs of core from another), and the ability to qualify, filter, and query data. Because data are readily edited and queried, this approach facilitates experimentation with interpretations, permitting more flexibility and efficiency in the mapping workflow. Maintaining project data in a digital environment enables data sharing and portability and facilitates preparation of final map products and text figures.

Our plans include refining the database structure, enhancing the user interface, and migrating project data into WGNHS GEOBASE. We have begun testing map-server technology to enable Internet publication of geologic maps.