In database development, understanding why is essential to the proper choice of how. Increased use of computers in all phases of development of regional exploration programs and analysis of local prospects has increased the demand for high quality digital maps of surface geology. Large sums of money are being invested by state and federal agencies developing digital geologic map databases. A large part of this investment has focused on new field mapping in areas where published geologic maps were unavailable or deemed inadequate. In these programs, digital databases are usually derived from large scale (1:24,000) base maps developed by the project geologist. The slow pace of database development from new field mapping, combined with budget constraints, requires that more cost-effective methods be used wherever possible to develop statewide or national databases. Where good quality published geologic maps are available, their conversion to digital form has been seen as a solution to the cost problem. Technology and dollars have focused on the precise preservation of geologic patterns printed on these maps. Given the cartographic generalization inherent in the smaller scales (1:63,360 or less) at which most of the maps have been published, the usefulness of the results is seriously limited. A simple but innovative procedure, requiring only modest interpretation of published geologic maps in relation to the topographic model presented on corresponding 1:24,000 scale maps, maximizes the capture of information presented in published geologic maps. The resulting digital databases compare favorably with the results of new field mapping, with significant reductions in development time and labor costs.

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