GEOLOGIC MAP DATA EVOLUTION AT THE ALASKA DIVISION OF GEOLOGIC & GEOPHYSICAL SURVEYS

The Alaska Division of Geological & Geophysical Surveys (ADGGS) has been producing geologic maps with a Geographic Information System (GIS) since 1983. In order to take advantage of emerging GIS technologies and to keep pace with the National Geologic Map Database Project (NGMDB), ADGGS reviewed the geologic map data process and is designing a new data structure that will support ADGGS geologic map production and geologic map data distribution into the future.

Legacy ADGGS map data structure was organized in a GIS file directory system; scripts generate symbols for viewing or printing maps from codes contained in the files. The existing file structures, codes, and scripts have been adapted over time, resulting in inconsistencies. Additionally, geologic attributes and context documentation of the legacy data are limited.

In order to update the agency GIS data structure and methods, ADGGS reviewed the concepts recorded in geologic maps along with the agency geologic map making process. In this review ADGGS examined the definitions and context of geologic maps, their components, and their elements to determine what information makes meaningful geologic maps in geologic maps meaningful. The review considered the existing ADGGS structure as well as existing and ongoing work of the NGMDB and other public agencies.

The result of the review is a new conceptual geologic map database design which recognizes that geologic maps are not a representation of empiric data but represent classification, generalization, and interpretation of observations and empiric data by the mapping geologists. The new design incorporates provisions for documenting data sources, classification methods, and geologic terms used in the database. The ADGGS implementation of this database design will use commercial GIS object-relational database software, and will allow for export of geologically meaningful, well documented, and generic geospatial datasets.