This spatial digital database for the geology of the San Pedro River Basin in southeastern Arizona was compiled from three maps by Dickinson (1993, 1998, 2000). Mylar originals of the map sheets were scanned, and the resultant images were rectified to a mathematically-generated set of latitude and longitude registration points. Geologic linework was digitized from the rectified images on screen using ArcView (ver. 3.2), and the resultant shapefiles were converted to ArcInfo (ver. 7.2) coverages. Lines and polygons were then attributed; and the files were merged omtp a single ArcInfo database (quib24k).
This digital spatial database is one of many being created by the U.S. Geological Survey as an ongoing effort to provide geologic information in a geographic information system (GIS) for use in spatial analysis. This database can be queried in many ways to produce a variety of geologic maps. Digital base map data files (topography, roads, towns, rivers and lakes, etc.) are not included: they may be obtained from a variety of commercial and government sources. This database is not meant to be used or displayed at any scale larger than 1:24,000 (for example, 1:12,000).
The map area is located in southeastern Arizona. This report describes the map units, the methods used to convert the geologic map data into a digital format, and the ArcInfo GIS file structures and relationships; and it explains how to download the digital files from the U.S. Geological Survey public access World Wide Web site on the Internet. See figures 2 and 3 for page-size versions of the map compilation.
