THE U.S. NATIONAL GEOLOGIC MAP DATABASE

Since the mid-1990's, the U.S. National Geologic Map Database (NGMDB, http://ngmdb.usgs.gov) project has systematically addressed its Congressional mandate to develop scientific and technical standards and to provide a national archive of geoscience map information. Under this mandate in the Geologic Mapping Act of 1992, the U.S. Geological Survey and the Association of American State Geologists (AASG) have made significant advances in the design and development of the NGMDB (see yearly reports of progress at http://ngmdb.usgs.gov/Info/reports/).

The NGMDB's goal is to help users find the information they need to address a variety of societal and research applications. Because our users range in interest and expertise from the general public to the geologic mappers and GIS specialists who prepare maps and databases, the NGMDB project began in 1996 by building a set of fundamental resources and databases that include: 1) a careful and responsive customer service capability; 2) a comprehensive Geoscience Map Catalog of nearly 79,000 products by 350 publishers; 3) the U.S. Geologic Names Lexicon ("GEOLEX"), a standard reference for the nation's stratigraphic nomenclature; and 4) Proceedings from the ten annual Digital Mapping Techniques (DMT) workshops. The DMT workshops have provided a unique venue for discussion of map and database-preparation techniques and web-delivery of geospatial information, and have facilitated convergence toward common practices and toward science and technical standards for the geosciences. These resources receive about 140,000 visits per month from 35,000 users.

Society, businesses, and private citizens commonly are faced with complex, multi-dimensional issues; in order to facilitate the use of geologic information and its integration with other types of information (e.g., soils, engineering, hydrologic, cultural), it must be presented in a form that is readily comprehensible to the non-geologist. In other words, the presentation of geologic information must, to some extent, be standardized. Geological survey agencies produce individual maps, reports, and datasets in a wide variety of formats and layouts, each containing specialized scientific terminology. Without a doubt, these have proven immensely valuable to our users. However, with the advent of GIS and Web services, our users demand access to a more integrated, comprehensive set of geologic maps and reports. With this in mind, the NGMDB project has extensively collaborated with U.S. and Canadian agencies to develop essential standards; these include the NADM geologic map data model and lithologic terminologies, and the FGDC standard for map symbolization and for specifying the locational accuracy of mapped features. NGMDB also participates in development of the emerging international standard for exchange of spatial geoscience information (GeoSciML).

A principal goal for the NGMDB project is to design and build a database of richly-attributed, standardized geospatial information in vector and raster formats. That database is intended to be a distributed system, with nodes hosted by the State geological surveys and the USGS, and integrated with the existing NGMDB databases described above. Because of this project's requirement to build a national archive that can contain geoscience maps from all geological surveys in the U.S., a preparatory period was required in order to: 1) fully discuss among the many participating agencies the technical and scientific options for building such a database, 2) forge a collaboration among these agencies, and 3) agree upon the necessary standards. During this process, essential concepts were prototyped in order to support discussion on how to proceed (see http://pubs.usgs.gov/of/2001/of01-223/soller2.html andhttp://pubs.usgs.gov/of/2002/of02-202/). These concepts included the requirement for the NGMDB system to enable spatial analyses that combined data from the NGMDB and other types of databases; this was viewed as essential to the wider dissemination and use of geologic information by non-geologists who may need, for example, to compare and analyze demographic, hydrologic, engineering, and geologic data. The project is now building a prototype database and portal for this distributed system (see related paper by Percy et al.); we anticipate it will be publicly available in 2007.