Abstract:
This digital geospatial data set consists of geohydrologic
unit boundaries shown in the report "Structure, outcrop, and
subcrop of the bedrock aquifers along the western margin of
the Denver Basin, Colorado" (Robson and others, 1998).
Supplemental_Information:
Procedures_Used:
Geohydrologic boundaries, fault lines, and tic marks were scanned
from the 1:50,000 maps (Robson and others, 1998) at 200-800 dots per inch
into a tagged image file format (TIFF, a bit-mapped file format). The TIFFs
were converted to unrectified grids, (ARC/INFO raster geospatial data sets),
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 State Plane projection
specific to each county map. Link files then were created to help
register the grids to the tic 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 then 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 reduce processing
time for conversion to vector format 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)
To improve cartographic display, arcs were
splined and generalized in ARCEDIT with weed tolerances ranging from 30
to 100 feet. All individual coverages of geohydrologic unit data were
plotted and checked for line accuracy. The individual coverages with the
same thematic data were then appended to form a single thematic coverage.
The appended coverage then was built as line coverage to add topology and then
attributed with the item "LINE_TYPE". Outlines of the study area were
added to the coverage so it could be cleaned and built as a polygon coverage.
Polygon item "GEOLABEL" was added to the polygon attribute table to represent
geohydrologic unit. The lines then were generalized and splined
in ARCEDIT with a grain tolerance range from 10-200
Drafts of these coverages then were plotted at a scale of 1:50,000, checked
against the original sheets, and corrected for omissions.
The coverages were appended and built into a single coverage that was then
cleaned with a dangle tolerance of 0 feet and a fuzzy tolerance
of 55.938 feet.
The final coverage is intended to be used as one thematic layer in
maps in Robson and others (1998).
This data set is one of seven digital map data sets being published
together for this area. The other six data sets are:
ARAPBASE - structure contours on base of upper Arapahoe aquifer
LFHTOP - structure contours on top of Laramie-Fox Hills aquifer
LFHBASE - structure contours on base of Laramie-Fox Hills and Arapahoe
aquifers
WELLS - location of wells
GEOSYMB - point and line geologic structure information
STUDYAREA - outline of study area
The following is an AML to generate a graphic of this coverage.
>display 9999
>map geo.map
>mape geo
>pageunits inches
>mapunits meters
>mappos cen cen
>mapinfo
>
>/*Color filling geologic areas
>resel geo poly geolabel cn 'Kl' and geolabel nc 'Klf'
>shadesymbol 63
>shadecolor cmyk 55 -1 40 -1
>shadeput 63
>polygonshades geo 63
>clearsel
>resel geo poly geolabel cn 'Klf'
>shadesymbol 66
>shadecolor cmyk 18 -1 100 -1
>shadeput 66
>polygonshades geo 66
>clearsel
>resel geo poly geolabel cn 'Kp'
>shadesymbol 74
>shadecolor cmyk 35 -1 100 9
>shadeput 74
>polygonshades geo 74
>clearsel
>resel geo poly geolabel cn 'S'
>shadesymbol 39
>shadecolor cmyk 4 30 65 -1
>shadeput 39
>polygonshades geo 39
>clearsel
>resel geo poly geolabel cn 'Klau'
>shadesymbol 60
>shadecolor cmyk 18 -1 65 4
>shadeput 60
>polygonshades geo 60
>clearsel
>resel geo poly geolabel cn 'Ka'
>shadesymbol 25
>shadecolor cmyk 20 -1 20 -1
>shadeput 25
>polygonshade geo 25
>clearsel
>resel geo poly geolabel cn 'Ku'
>shadesymbol 48
>shadecolor cmyk 26 -1 40 15
>shadeput 48
>polygonshades geo 48
>clearsel
>resel geo poly geolabel cn 'Tu'
>shadesymbol 20
>shadecolor cmyk -1 45 55 6
>shadeput 20
>polygonshades geo 20
>clearsel
>resel geo poly geolabel cn 'Tdw'
>shadesymbol 21
>shadecolor cmyk -1 8 36 6
>shadeput 21
>polygonshades geo 21
>clearsel
>resel geo poly geolabel cn 'TKd'
>shadesymbol 22
>shadecolor cmyk -1 22 40 12
>shadeput 22
>polygonshades geo 22
>clearsel
>resel geo poly geolabel cn 'pE'
>shadesymbol 23
>shadecolor cmyk -1 66 70 6
>shadeput 23
>polygonshades geo 23
>clearsel
>resel geo poly geolabel cn 'MPu'
>shadesymbol 24
>shadecolor cmyk 60 7 15 -1
>shadeput 24
>polygonshades geo 24
>clearsel
>
>/*Labelling geologic areas. To avoid overprinting, use
>/*the ARC/INFO commands OVERPOST and LEADERS
>textset font.txt
>textsymbol 3
>textsize 4 pt
>textcolor black
>polygontext geo geolabel
>
>/*Outlining geologic areas. This also defines the
>/*original study area boundaries.
>lineset plotter
>linesymbol 1
>linecolor black
>linepen .001
>lineput 1
>arcs geo
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, 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
http://rockyweb.cr.usgs.gov/frontrange/