INTRODUCTION
The objectives of the coal resource assessment of the Fort Union Formation and equivalent rock units in the northern Rocky Mountains and Great Plains region are: (1) compile the information needed to assess selected coal beds and zones of the Fort Union Formation and its equivalent formations that are potentially mineable in the next few decades; (2) identify clean and compliant coal that meets standards of the Environmental Protection Agency for sulfur, ash, and trace elements of environmental concern; (3) create a publicly available digital database of this coal that can be rapidly accessed and analyzed to provide information critical to decision-making by government, industry, and the public; and (4) produce widely available digital products accessible in a variety of interpretive and interactive forms. In order to accomplish these objectives, it was necessary to create a computerized database that contains a vast amount of geographic, stratigraphic, and analytical information.   Data were stored, retrieved, manipulated, and analyzed utilizing StratiFact software (GRG Corporation, 1996). This software consists of a relational database manager and a geographic information system (GIS).

The data were acquired through cooperation with the U.S. Bureau of Land Management, State geological surveys, U.S. Office of Surface Mining, and coal companies. The USGS National Coal Resources Data System (NCRDS) also provided digital data. Proprietary and non-proprietary data from these sources consist of drill-hole information and coal quality and coal geochemical analyses provided to the USGS as hard copies or in digital format. The data from hard copies were entered manually using spreadsheet software (for example, Access, QuattroPro, and Excel). The digital files were transformed into processible formats (ASCII) and downloaded into the StratiFact database manager. When all datasets from each drill hole were edited, correlated, and checked for quality control, the completed StratiFact database was queried to retrieve information to generate digital files for processing in other software (for example, ARC/INFO, ArcView, earthVision) for calculation of coal resources.