Several different coverages were generated during the construction of each of the three geologic quadrangle maps. Negatives of USGS topographic bases and geologic mylar tracings were scanned at 400 dpi, 1-bit TIFF bi-level compression type 1 (uncompressed) with rows per strip = 12000 on an ANATEK rasterizing scanner, then images were converted to ESRI ARC/INFO grids. The raster grids were converted to vector coverages with ARC/INFO's gridline routine. Alacarte and some custom menus and amls were used to project, transform, edit, tag and build, lines, polygons, and points in each map. A digital layout or map collar was made with Adobe Illustrator. The plot amls run in ARC/INFO and call the coverages, grids, and EPS to make uncompressed PostScript files. All maps are in UTM projection, zone 10, units meters, 1:24,000 scale. The pamphlet that describes the geology is saved to EPS from Microsoft Word.
The source of the base maps used is the U.S. Geological Survey, 1:24,000 scale topographic maps, which have a 10-foot contour intervals (provisional edition, 1987). One base map layer for each of the three 7.5 minute quadrangles was prepared from negatives. Topographic bases for Scotts Mills, Silverton, and Stayton NE quadrangles were scanned on an Ideal rasterizing scanner at 400 dpi as 1-bit TIFF images. Scanned TIFF images of the bases were registered and rectified in ARC/INFO and then made into grids. The images were clipped using ARC/INFO grid to conform to the area of the geologic coverages and merged with the geology grid to give an apparent transparent color image of both combined. These base map-geology layers are digital images but no information other than location is attached to the lines. The base-geology maps are provided for reference only.