Sharon Rafferty
19980630
Geohydrologic unit boundaries along the Colorado Front Range
Version 1.0, June 22, 1998
Map
Reston, Virginia
U.S. Geological Survey
http://water.usgs.gov/lookup/getspatial?co_geo_ha742
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).
This data set was created to display the bedrock geologic units along
the Front Range of Colorado as depicted in Robson and others, (1998).
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
<URL:http://rockyweb.cr.usgs.gov/frontrange/>
1998
Current as of publication date.
None Planned
-105.25683629
-104.58906173
40.88668006
39.28197938
none
geology
subcrop
contact
aquifer
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
Water Resources Division
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/geo.jpg
Illustration of the dataset.
jpg
U.S. Geological Survey
dgux, 5.4R3.10, AViiON UNIX
ARC/INFO version 7.0.4
Geologic contacts are from geologic maps published by the
U.S. Geological Survey. Revisions to published mapping are
based on field reconnaissance data. Hydrologic Atlas-746
(Robson and others, 1998)
provides description of geology and references to published
mapping. Procedures used to develop contours are described
in Hydrologic Atlas-742.
Polygon and chain-node topology present.
See supplemental information.
Scanned lines and data points are within
0.01 inch of original line work.
U.S. Geological Survey (comp)
1998
Structure, outcrop, and subcrop of the bedrock aquifers along the western
margin of the Denver Basin, Colorado
Map
Hydrologic Investigations Atlas
HA-742
Denver, CO
USGS
mylar separate
1997
publication date
HA-742
Robson and others (1998).
See Supplemental Information
1998
Vector
Point
153
String
459
GT-polygon composed of chains
137
Universal Transverse Mercator
13
implied
implied
implied
implied
implied
coordinate pair
17.8063663684
17.8063663684
Meters
North American Datum of 1983
GRS1980
6378206.4
294.98
GEO.PAT
Polygon Attribute table of GEO
GIS software
AREA
Area of polygon in coverage units (meters)
Computed
Positive real numbers
n/a
GIS software
PERIMETER
Perimeter of polygon in coverage units (meters)
Computed
Positive real numbers
n/a
GIS software
GEO#
Internal feature number
Computed
Sequential unique positive integer
n/a
GIS software
GEO-ID
User-assigned feature number
User-defined
Integer
n/a
GIS software
GEOLABEL
Labels for selecting, labeling and color-filling,
geohydrologic units.
see, (Robson and others, 1998)
see Entity and Attribute Overview
n/a
see, (Robson and others, 1998)
GEO.AAT
Arc Attribute table of GEO
GIS software
FNODE#
Internal number of from-node
Computed
Sequential unique positive integer
n/a
GIS software
TNODE#
Internal number of to-node
Computed
Sequential unique positive integer
n/a
GIS software
LPOLY#
Internal number of polygon to left of arc
Computed
Sequential unique positive integer
n/a
GIS software
RPOLY#
Internal number of polygon to right of arc
Computed
Sequential unique positive integer
n/a
GIS software
LENGTH
Length of arc in coverage units
Computed
Positive real numbers
n/a
GIS software
GEO#
Internal feature number
Computed
Sequential unique positive integer
n/a
GIS software
GEO-ID
User-assigned feature number
User-defined
Integer
n/a
GIS software
LINE_TYPE
See entity and attribute overview
see (Robson and other, 1998)
character
n/a
User assigned
There are two attribute files associated with this coverage.
A polygon attribute table (.PAT) contains:
Item GEOLABEL contains names for selecting and color filling
polygons representing geohydrologic units. (Please note that
for graphical clarity, some polygons have multiple labels
of the same geolabel.) The labels are defined as follows:
Ka Arapahoe aquifer
Kl Laramie confining layer
Klau Laramie and Arapahoe Formations, undifferentiated
Klf Laramie-Fox Hills aquifer
Kp Pierre confining layer
Ku Pierre undifferentiated confining layer
MPu Mesozoic and Paleozoic rocks, undifferentiated
pE Precambrian rocks
Tdw Dawson aquifer
TKd Denver aquifer
Tu Unsaturated Tertiary rocks
S Subcrop of Laramie-Fox Hills or Arapahoe aquifers under principal
alluvial aquifer
ND No Data
>
>GEO.PAT:
>
>COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
> 1 AREA 8 18 F 5
> 9 PERIMETER 8 18 F 5
> 17 GEO# 4 5 B -
> 21 GEO-ID 4 5 B -
> 25 GEOLABEL 5 5 C -
>
>
An arc attribute table (.AAT) contains:
Item LINE_TYPE is an identifier for the type of graphic symbolic
representation of the polygon outlines. The identifiers represent
the following:
fl = a fault with fault symbol to the left side of the line
fc = facies change line
p = print
np = don't print
s = subcrop
g = geologic
d = dashed
c = cross section
>GEO.AAT:
>
>COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
> 1 FNODE# 4 5 B -
> 5 TNODE# 4 5 B -
> 9 LPOLY# 4 5 B -
> 13 RPOLY# 4 5 B -
> 17 LENGTH 8 18 F 5
> 25 GEO# 4 5 B -
> 29 GEO-ID 4 5 B -
> 33 LINE_TYPE 4 4 C -
>
>
Not available
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/geo_shp.zip
Export
Full coverage
zipped
1
http://water.usgs.gov/GIS/dsdl/geo.e00.gz
Other
Full coverage
zipped
1
http://water.usgs.gov/GIS/dsdl/geo.tar.gz
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_geo_ha742
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998