Geologic map of the Stillwater Complex, Montana: a digital database
This report provides a digital version of the Geologic map of the
Stillwater Complex, Montana originally published by N. Page and
W. Nokleberg (1974). Paper copies of the four geologic map
sheets from the original report were scanned and initially
attributed by Optronics Specialty Company (Northridge, CA) and
remitted to the U.S. Geological Survey for further attribution
and publication of the geospatial digital files. The resulting
digital geologic dataset can be queried in a geographic
information system (GIS) in many ways to produce a variety of
This GIS dataset consists of two Arc/Info datasets. The first is
a line and polygon file (i797) containing geologic contacts and
structures (lines) and geologic map rock units (polygons). A
second file contains structural point data (i797p). Since the
topographic base map for the original publication is no longer
readily available, a georeferenced image (tiff) of the original
basemap is also included.
Page, Norman J, Nokleberg, Warren J., and Miller, Robert J., 2002, Geologic map of the Stillwater Complex, Montana: a digital database: U.S. Geological Survey Miscellaneous Investigations Series Map I-797, U.S. Geological Survey, Menlo Park, CA.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.001195
Ordinates (y-coordinates) are specified to the nearest 0.001195
Planar coordinates are specified in survey feet
The horizontal datum used is North American Datum of 1927.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378206.4.
The flattening of the ellipsoid used is 1/294.978698.
The i797geo dataset includes:
1) A geologic linework arc attribute table, i797geo.aat, that
relates to the i797geo.con contact look-up table, i797geo.con;
a structure look-up table, i797geo.st2, and a source reference
look-up table i797geo.ref
2) A rock unit polygon attribute table, i797geo.pat, that
relates to the rock unit look-up table i797geo.ru and
source reference look-up table i797geo.ref.
The i797p dataset includes a structural point data attribute
table, i797p.pat, that relates to the symbol look-up table
i797p.lut and source reference look-up table i797geo.ref.
Optronics Specialty Company scanned the four geologic map sheets of
Page and Nokleberg (1974) and provided minimally attributed
ArcInfo interchange-format files to the USGS.
Helen Z. Kayser (contractor) registered and transformed to the
datasets to the Montana state plane coordinate system.
Robert Miller combined the 8 individual sheet files into the two
theme (geology and structural data) datasets, attached and
attributed an interim geologic map data model; and visually
compared the hard copy plots with the source documents.
This dataset was developed to provide a spatial database of the
1:12,000 scale geologic map of the Stillwater Complex for use in
future spatial analysis. These data can be printed in a variety
of ways to display various geologic features or used for digital
analysis and modeling. This database is not meant to be used or
displayed at any scale larger than 1:12000. The digital geologic
map graphics and plot files (i797.gra/ps and i797-map.pdf) that
are provided in the digital package are representations of the
digital database. They are not designed to be cartographic
Optronics Specialty Company scanned the published paper geologic map sheets
Date: 2001 (process 2 of 4)
The digital files were registered and transformed to state plane coordinate system by Helen Z. Kayser (contractor) at the USGS Spokane Field Office. R Miller combined the datasets and applied an interim geologic map data model. The data were then checked for position and attribute accuracy by comparing plots of the digital data to the source maps.
(process 3 of 4)
Low resolution scans (100 dpi) of portions of the basemap were georeferenced and converted to Arc/Info grids. The grids were clipped and merged into a single file then saved in a TIFF format.
Person who carried out this activity:
Robert J Miller
U.S. Geological Survey, GEO-WRG-MRS
Mail Stop 901
345 Middlefield Rd
Menlo Park, CA
Date: 21-Feb-2002 (process 4 of 4)
Creation of original metadata record
Person who carried out this activity:
How well have the observations been checked?
The attribute accuracy was verified by manual comparison of the
source with hard copy printouts, plots, and on-screen
evaluation. Further digital review was performed as part of the
USGS publication process. This included automated searching for
missing or incorrect attributes.
How accurate are the geographic locations?
The horizontal position accuracy for the digital data is no
better than +/- 18 feet for the east half of map (sheet 1 and 2
of original publication) and +/- 8 feet for western half (
sheets 3 and 4 of the original) based on the digitizing root
mean square (RMS) error. The geologic mapping was compiled on
a topographic basemap map made for the project. This basemap
locally differs from modern 1:24,000 topographic maps of the
area, and thus geologic linework may locally appear mislocated
when viewed with other than the original publication basemap.
The individual scanned images of parts of the basemap typically
had an RMS error of approximately 3 meters. However, where
parts of the georeferenced scans overlap, local shifts of up 15
meters were noted..
How consistent are the relationships among the observations, including topology?
Polygon and chain-node topology present. Segments making up the
outer and inner boundaries of a polygon tie end-to-end to
completely enclose the area. Line segments are a set of
sequentially numbered coordinate pairs. No duplicate features
exist nor duplicate points in a data string. Intersecting lines
are separated into individual line segments at the point of
intersection. All nodes are represented by a single coordinate
pair, which indicates the beginning or end of a line segment.
This digital database is not meant to be used or displayed at any
scale larger than 1:12,000 (e.g. 1:6,000).
Any hardcopies utilizing these data * shall clearly indicate their
source. If the user has modified the data in any way they are
obligated to describe the types of modifications they have
performed on the hardcopy map. User specifically agrees not to
misrepresent this data set, nor to imply the U.S. Geological Survey
approved changes the user has made.
The U.S. Geological Survey (USGS) provides these geographic data "
as is". The USGS makes no guarantee or warranty concerning the
accuracy of information contained in the geographic data. The USGS
further makes no warranties, either expressed or implied as to any
other matter whatsoever, including, without limitation, the
condition of the product, or its fitness for any particular
purpose. The burden for determining fitness for use lies entirely
with the user. Although these data have been processed
successfully on computers at the USGS, no warranty, expressed or
implied, is made by the USGS regarding the use of these data on any
other system, nor does the fact of distribution constitute or
imply any such warranty.
In no event shall the USGS have any liability whatsoever for
payment of any consequential, incidental, indirect, special, or
tort damages of any kind, including, but not limited to, any loss
of profits arising out of use of or reliance on the geographic
data or arising out of the delivery, installation, operation, or
support by USGS.
This digital geologic map GIS of the Stillwater Complex, Montana,
is not meant to be used or displayed at any scale larger than