Sharon Rafferty 19980630 Version 1.0, June 22, 1998 Map Reston, Virginia U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?co_studyarea_ha742 This digital geospatial data set consists of outlines of the study area in the report "Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along the Western Margin of the Denver Basin, Colorado" (Robson and others, 1998). This data set was created to display the outline of the study area as depicted in (Robson and others, 1998). Procedures_Used: Study area outlines and tic marks were scanned from 1:50,000 maps (Robson and others, 1998) at 200 to 800 dots per inch. These scans then were saved into a TIFF (tagged image file format which is a bit-mapped file format). The TIFF's were converted to unrectified grids (ARC/INFO raster geospatial datasets), by the ARC/INFO command IMAGEGRID. Vector geospatial data sets, known as coverages in ARC/INFO terminology, were created from ascii files containing the latitude and longitude coordinates in degrees, minutes and seconds. These coverages were projected into a State Plane projection that was specific to each county map. From these coverages, link files were then created to help register the grids to the coverages by use of the ARC/INFO command CONTROLPOINTS. Arc: controlpoints fig2_grid fig2_lin fig2_tics nominal identity # point Registration root mean square errors of 0.005 or less were acceptable for the creation of link files. The unrectified grids were georectified with the ARC/INFO command GRIDWARP, which transforms or rubber sheets a grid along a set of links by using a first-order polynomial transformation. The grid-cell size was resampled to a larger cell size to decrease processing time for conversion to coverages. GRID: setcell 20 GRID: fig2_20grid = fig2_rgrid Line coverages were created from the georectified grids with the ARC/INFO command GRIDLINE, using a line thickness of 150 feet, a weed tolerance of 40 feet, and a default dangle of 0.7 times the thickness. GRID: fig2_cov = gridline (fig2_20grid,positive,thin,nofilter, round,noitem,150, #,40) The coverages then were built with line and polygon topology. To improve cartographic display, arcs were smoothed by splining and generalizing in Arcedit with weed tolerances ranging from 30 to 100 units. Individual coverages containing the same thematic data were plotted and checked for line accuracy and attribution. The individual coverages were then appended to form a single thematic coverage. The final coverage represents one thematic layer in maps published in Robson and others (1998). This data set is one of seven digital map data sets being published for this area. The other six data sets are: ARAPBASE - structure contours on base of upper Arapahoe aquifer LFHBASE - structure contours on base of Laramie-Fox Hills and Arapahoe aquifers LFHTOP - structure contours on top of Laramie-Fox Hills aquifer WELLS - location of wells GEOSYMB - point and line geologic structure information GEO - geohydrologic unit boundaries Reviews_Applied_to_Data: March 1998: Colleague review of 1:50,000-scale maps that were generated from the original data set. Manuscript review included validation of method as outlined in map report and inspection for positional accuracy. March 1998: Inspection of copy generated from this data set. April 1998: Colleague review of original digital data set and associated metadata. Metadata review included verification of table and column/item identities and definitions, validation of the reference data sets and citations, verification of consistency between log file and documented procedures, and validation of development method as described in the documentation. References_Cited: Robson, S.G., Van Slyke, George, and Graham, Glenn 1998, Structure, outcrop, and subcrop of the bedrock aquifers along the western margin of the Denver Basin, Colorado: U.S. Geological Survey Hydrologic Investigations Atlas HA-742, 5 sheets, scale 1:50,000. Available through the internet at <URL:http://rockyweb.cr.usgs.gov/frontrange/> 1998 Current as of publication date. Complete None planned. -105.27975774 -104.59333318 40.75322131 39.21441296 None study area inlandWaters none Denver, Colorado Front Range, Colorado None. These data are not to be used at scales greater than 1:50,000. Colorado District Chief U.S. Geological Survey mailing address

Box 25046, MS 415, Denver Federal Center

Denver CO 80225 USA 1-888-275-8747 303-236-4912 (wfhorak@usgs.gov) http://water.usgs.gov/GIS/browse/studyarea.jpg Illustration of the dataset. jpg U.S. Geological Survey dgux, 5.4R3.10, AViiON UNIX ARC/INFO version 7.0.4 n/a Point features present See supplemental information. n/a U.S. Geological Survey 1998 Map Hydrologic Investigations Atlas HA-742 Denver, CO U.S. Geological Survey mylar separate 1997 publication date HA-742 Robson and others, (1998). See Supplemental Information 1998 Point Point 1 String 7 GT-polygon composed of chains 6 Universal Transverse Mercator 13 implied implied implied implied implied coordinate pair 55.93771901438 55.93771901438 Meters North American Datum of 1983 GRS1980 6378206.4 294.98 >STUDYAREA.PAT: > >COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME > 1 AREA 8 18 F 5 > 9 PERIMETER 8 18 F 5 > 17 STUDYAREA# 4 5 B - > 21 STUDYAREA-ID 4 5 B - > > > none U.S. Geological Survey Ask USGS - Water Webserver Team mailing

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://water.usgs.gov/user_feedback_form.html Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. shape file Full coverage zipped 1 http://water.usgs.gov/GIS/dsdl/studyarea_shp.zip Export Full coverage zipped 1 http://water.usgs.gov/GIS/dsdl/studyarea.e00.gz Other Full coverage zipped 1 http://water.usgs.gov/GIS/dsdl/studyarea.tgz None. This dataset is provided by USGS as a public service. 20041108 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+co_studyarea_ha742 FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998