Evolution of an Object-Oriented, NADM-based Data Model Prototype for the USGS National Geologic Map Database Project

Geologic maps are complex scientific documents that provide considerably more than cartographic representations of geologic information. Modeling these documents in sufficient detail that they can be recorded and manipulated in computer database form, not simply as raster graphics, is essential to continued progress in geologic science. This paper discusses the principal challenges in geologic map data modeling, presents a novel, object-oriented data modeling approach to some of these challenges, and reports on a prototype implementation of that approach. This work forms part of ongoing efforts by U.S. and Canadian government data providers to create national geologic map databases, and standard geologic map data models, in conjunction with the North American Digital Geologic Map Data Model (NADM) initiative. Specifically, this object-oriented evolution of NADM is demonstrated in the GESmallworld GIS; it is tested with 1:24,000 and 1:100,000-scale geological map data provided by the Kentucky Geological Survey. Reported are both practical results and lessons learned from the prototyping exercise. Overall, the new object-oriented data model appears tenable and well suited to fundamental geologic map information; however, some additional refinements are required, and tradeoffs between model sophistication and operational efficiency also must be considered.