Generalized Geology of the World and Linked Databases, Open File 2915d
The Generalized Geology of the World is a highly simplified
digital geological data set composed of geographically referenced
rock unit patchworks and fault lines which can be combined with
tables of descriptive data. The latter, hereafter referred to as
attribute tables, includes broadly classified age, main rock or
fault type, and name information.
What coordinate system is used to represent geographic features?
Horizontal positions are specified in geographic coordinates, that is, latitude and longitude.
Latitudes are given to the nearest 0.000464.
Longitudes are given to the nearest 0.000464.
Latitude and longitude values are specified in Decimal degrees.
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 6370997 meters.
The flattening of the ellipsoid used is 1/294.98.
The purpose of this data set is threefold: (1) to provide the
basic context for the display of global distribution patterns of
geoscientific data; (2) to allow the preparation of simple,
global-scale, customized thematic maps and page-sized diagrams
using a range of GIS overlay and logical selection techniques on
the currently available data, alone or in combination with other
data; and (3) to provide a basic geological data set which can be
experimented with before designing other regional geological GIS
As a note of caution, displays from this data set are not valid
enlarged to scales much larger than 1:35 million, and should
NOT be used for quantitative analyses of any sort. The
generalization level is extremely high, as discussed in the
generalization section below. GIS overlay of additional data
should be used only with careful consideration of the level of
generalization. Conceptually, overlain data should be as highly
generalized as the age and rock type and fault background layers,
and the product of the overlay envisaged as a global-scale visual
pattern rather than a quantitative correlation.
The preparation of the digital data and the Generalized Geology
of the World hard copy map was accomplished under the auspices of
the Geoscience Information and Communication Division, Geological
Survey of Canada, particularly the Digital Cartography Section,
and the Mineral Resources Division.
The Generalized Geology datasets (ESRI export files) were imported into ArcInfo 8.1 and seven coverages
were created (Rock Unit Polygons), namely: Africa/Arabian, Antarctica, Asia, Australia, Europe, North America, South America.
Using the unique coverage id field (field relate) the coverage attributes were linked to each data table for rock units.
The seven coverages were then combined into a single world geology coverage and this dataset was converted to an
ArcView 3.2 shapefile.
Person who carried out this activity:
The U.S. Geological Survey (USGS) provides this vector data "as is." The USGS makes no
guarantee or warranty concerning the accuracy of information contained in the image 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 this data has been processed successfully on computers at the
USGS, no warranty, expressed or implied, is made by the USGS regarding the use of this
data on any other system, nor does the fact of distribution constitute or imply any such