MANAGING 3D GEOLOGIC MAP INFORMATION IN THE NATIONAL GEOLOGIC MAP DATABASE

Conventional geologic maps can provide sufficient subsurface data and inferences about the spatial relation of geologic units to allow a three-dimensional model of the geologic framework to be attempted. However, many geologic maps do not include subsurface information, and such modeling is feasible only by expert geologists. Non-geologists are, therefore, unable to adequately visualize the geology in three dimensions, and so cannot apply to their public or private decisionmaking a complete understanding of the geologic framework.

Over the past few decades, many high-quality 3D geologic maps have been created. More recently, some have been adapted into databases, in GIS format. This, however, is not widely done, owing both to the variable nature of subsurface information and to the complexities of integrating that information with conventional geologic maps. Venues including a series of 3D mapping workshops (http://www.isgs.uiuc.edu/3DWorkshop/nu_3d_welcome.html) and the Digital Mapping Techniques workshops (http://ngmdb.usgs.gov/Info/dmt/) bring together experts on this subject, and help to converge our approaches to managing 3D information in map databases.

The U.S. National Geologic Map Database (NGMDB) is charged with creating a system that will manage, in a distributed computer network, a national archive of geologic map information produced by Federal and State geological surveys (http://ngmdb.usgs.gov/info). We strongly feel that this system must be capable of managing not just conventional geologic maps, but also must integrate geologic maps, subsurface information, and 3D geologic models. To this end, the NGMDB has worked with various agencies, in international forums, to develop a data model for geologic map databases. We are in the process of adapting this data model to accommodate 3D information in both vector and raster formats. This work involves database design, and testing with 3D datasets; given the limited number of geologists involved in both 3D geology and database design, progress is slow. We invite interested parties to work with us.