A digital version of the 1970 US Geological Survey topographic map of the San Francisco Bay region, three sheets, 1:125,000
This Open-File report is a digital topographic map database. It
contains a digital version of the 1970 U.S. Geological Survey
topographic map of the San Francisco Bay Region (3 sheets), at a
scale of 1:125,000.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest unknown
Ordinates (y-coordinates) are specified to the nearest unknown
Planar coordinates are specified in meters
The topographic map information was digitized from stable
originals (cronaflex mylar blackline positives) of the map
separates at 1:125,000 scale. The following separates were
1. Composite of the culture, culture-names, land net and primary roads
2. Composite of the drainage and drainage names
3. Composite of intermediate and index contours
4. Secondary roads
Scanning was done on a Scitex R280 at a resolution of 20
points/millimeter (508 dpi). The Scitex R280 was used to edit
the raster scans and to separate the index and intermediate
contours into separate coverages. The raster scans were then
vectorized on the Scitex R280 with a curvetype of 1 and a
tolerance of 1. The vectorization process distorts characters
representing letters and numbers, as well as some other symbols,
rendering them unreadable in some instances. The vectorized
scans were imported into ARC/INFO using the SCITEXLINE command.
ARC/INFO was used to modify edge joins, and to remove duplicate
names (in adjacent sheets) and marginal information (to allow for
mosaicing of adjacent sheets). Each file was converted from
digitizer inches to UTM meters using latitude/longitude
intersections on the scanned separates as reference points.
Date: 08-Jun-2009 (process 2 of 2)
Creation of original metadata record
Person who carried out this activity:
This report is preliminary and has not been reviewed for conformity
with U. S. Geological Survey editorial standards or with the North
American Stratigraphic Code. Any use of trade, product, or firm names
is for descriptive purposes only and does not imply endorsement by
the U. S. Government.
This database, identified as "A digital version of the 1970 U.S.
Geological Survey topographic map of the San Francisco Bay Region,
three sheets, 1:125,000," has been approved for release and
publication by the Director of the USGS. Although this database has
been reviewed and is substantially complete, the USGS reserves the
right to revise the data pursuant to further analysis and review.
This database is released on condition that neither the USGS nor the
U. S. Government may be held liable for any damages resulting from