U. S. DEPARTMENT OF THE INTERIOR
U. S. GEOLOGICAL SURVEY





A DIGITAL VERSION OF THE 1970 U.S. GEOLOGICAL 
SURVEY TOPOGRAPHIC MAP OF THE SAN FRANCISCO 
BAY REGION, THREE SHEETS, 1:125,000



Digitized by Douglas S. Aitken1 



Open - File Report 97-500








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 its use. 




1997







1U.S. Geological Survey, 345 Middlefield Rd., MS 531, Menlo Park, CA 94025 



INTRODUCTION

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.  These ARC/INFO coverages are in vector format.  The 
vectorization process has distorted characters representing letters and numbers, as well as 
some road and other symbols, making them difficult to read in some instances.  This 
pamphlet serves to introduce and describe the digital data.  There is no paper map included 
in the Open-File report.  The content and character of the database and methods of 
obtaining it are described herein.  

The database was compiled using ARC/INFO versions 5.x and 6.x, a commercial 
Geographic Information System (Environmental Systems Research Institute, Redlands, 
California).   It is stored in uncompressed ARC export format (ARC/INFO version 7.x) in 
a compressed UNIX tar (tape archive) file.  The tar file was compressed with gzip, and 
may be uncompressed with  gzip, which is available free of charge via the Internet from the 
gzip Home Page (http://w3.teaser.fr/~jlgailly/gzip). A tar  utility is required to extract the 
database from  the  tar file.  This utility is included in most  UNIX  systems,  and  can be  
obtained free of  charge  via  the  Internet  from   Internet Literacy's Common Internet File 
Formats Webpage (http://www.matisse.net/files/formats.html).  ARC/INFO export files 
(files with the .e00 extension) can be converted into ARC/INFO coverages in ARC/INFO 
(see below) and can be read by some other Geographic Information Systems, such as 
MapInfo via ArcLink and ESRI's ArcView (version 1.0 for Windows 3.1 to 3.11 is 
available free from ESRI's web site:  http://www.esri.com).


OBTAINING THE DIGITAL DATA

The digital database package can be obtained in any of three ways (Note: The file
sht1.tar.gz is used as an example here, substitute the appropriate database
package anywhere this string appears):

1.  Sending a tape with request
	
A  compressed tar file of the topographic map database and related files can be obtained by 
sending a tape with request and return address to:

		San Francisco Bay Region Topo Sheet
		c/o Database Coordinator
		U.S. Geological Survey
		345 Middlefield Road, M/S 975
		Menlo Park, CA 94025

Please indicate which of the database packages you would like.  Below is a listing of all of 
the available database packages and their sizes.

The compressed tar file will be returned on the tape.  The acceptable tape types are:

	2.3 or 5.0 GB, 8mm Exabyte tape.



2.  Anonymous ftp over the Internet
To obtain the tar file by anonymous ftp do the following:

cd local_directory		go to a directory to receive the tar file
ftp wrgis.wr.usgs.gov		make ftp connection with the USGS computer WRGIS
Name: anonymous			use 'anonymous' as your user name
Password: your email address	use your email address as a password
cd pub/geologic			go  down to the pub/geologic directory
cd ca/of97-500			go down to the open file directory
type binary			change transfer type to binary
get sht1.tar.gz 		copy the compressed tar file across 
   				Internet to the receiving directory
quit				close the ftp connection


3.  From the Western Region Geologic Information Web Page.

To obtain the tar file via the World Wide Web:

The U.S. Geological Survey now supports a set of graphical pages on the World Wide 
Web. Digital geologic publications (including this one) can be accessed via these pages.  
The web page for digital geologic publications from the Western Region is  
Òhttp://wrgis.wr.usgs.govÓ.  Once at the main page, click on 'Geologic Map 
Databases' under the heading 'Data Online'; next click on 'California.'  Scroll down  
to get to the listing for this database.  Set your web browser to save to a local disk and click 
on the link for the database package that you want to download.


	Database Package	Compressed Size (MB)	Uncompressed Size (MB)
	sht1.tar.gz			9				38
	sht2.tar.gz			18.3				86.2
	sht3.tar.gz			24.3				110.4
	sfcu.tar.gz			16.6				63.2
	sfdr.tar.gz			10.8				39.8
	sfrd.tar.gz			8.1				41.5
	sfir.tar.gz			19.2				77.8
	sfix.tar.gz			2.8				9.2
	sftopo.ps			  -				0.872
	sftopo.txt			  -				0.016
	




EXTRACTING THE TOPOGRAPHIC MAP DATABASE FROM THE TAR FILE

These extraction procedures use the Sheet 1 (sht1.tar.gz) database package as an example.  
If you download other packages, simply replace sht1.tar.gz with the appropriate gzip'd tar 
file wherever sht1.tar.gz shows up.

If you obtained the database package on tape:

	put the tape in your tape drive
	cd local_directory		-go to a directory to receive the
					tar file
	tar xvfb /dev/rstn 20		-/dev/rstn is the tape device with
 					n an integer, this puts the tar file 
					in local_directory; 20 is the block
					size of the tar file
	gzip -d sht1.tar.gz		-makes a 38 MB uncompressed 
					tar file sht1.tar
	cd local_directory2		-go to the directory that will hold 
					the directory sht1 (if different 
					from local_directory)
	tar xvfb {path to tar 
	file}/sht1.tar 20		-extract the sht1 directory from 
                                        the tar file; 20 is the block size of
					the tar file.


If you obtained the database package by anonymous ftp or from the web page:

	gzip -d sht1.tar.gz		-makes a 38 MB uncompressed 
					tar file sht1.tar
	cd local_directory2		-go to the directory that will hold 
					the directory sht1 (if different 
					from local_directory)
	tar xvfb {path to tar 
	file}/sht1.tar 20		-extract the sht1 directory from 
					the tar file.

Each of the  processes described above will create a directory "sht1" that contains the ARC 
export  files and  supporting  files as  described below.  The directory structure at this
point will look like this:

	sht1/
		sh1c.e00
		sh1d.e00
		sh1ir.e00
		sh1ix.e00
		sh1r.e00
		sftopo.txt
		sftopo.ps
		import.aml



BASE MAP DATABASE CONTENTS

The San Francisco Bay Region topographic sheets database is available in two formats, by 
sheet (Sheets 1, 2 and 3), which includes all of the layers for each sheet, or by layer 
(culture, drainage, roads, intermediate contours and index contours), which include any 
one of the five layers for all three sheets.  Each of these layers (coverages) has been 
converted to uncompressed ARC/INFO export files.  The ARC export files and the 
associated ARC/INFO coverages, as well as the additional digital material included in the 
database package, are described below:

Sheet 1 (sht1.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh1c.e00		sh1c	      		Culture

sh1d.e00		sh1d			Drainage

sh1ir.e00		sh1ir			Intermediate contours

sh1ix.e00		sh1ix			Index contours

sh1r.e00		sh1r			Roads	


Sheet 2 (sht2.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh2c.e00		sh2c	      		Culture

sh2d.e00		sh2d			Drainage

sh2ir.e00		sh2ir			Intermediate contours

sh2ix.e00		sh2ix			Index contours

sh2r.e00		sh2r			Roads




Sheet 3 (sht3.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh3c.e00		sh3c	      		Culture

sh3d.e00		sh3d			Drainage

sh3ir.e00		sh3ir			Intermediate contours

sh3ix.e00		sh3ix			Index contours

sh3r.e00		sh3r			Roads


Culture (sfcu.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh1c.e00		sh1c			Sheet 1 culture

sh2c.e00		sh2c			Sheet 2 culture

sh3c.e00		sh3c			Sheet 3 culture


Drainage (sfdr.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh1d.e00		sh1d			Sheet 1 drainage

sh2d.e00		sh2d			Sheet 2 drainage

sh3d.e00		sh3d			Sheet 3 drainage


Roads (sfrd.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh1r.e00		sh1r			Sheet 1 roads

sh2r.e00		sh2r			Sheet 2 roads

sh3r.e00		sh3r			Sheet 3 roads




Intermediate contours (sfir.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh1ir.e00		sh1ir			Sheet 1 intermediate contours

sh2ir.e00		sh2ir			Sheet 2 intermediate contours

sh3ir.e00		sh3ir			Sheet 3 intermediate contours



Index contours (sfix.tar.gz)

ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
sh1ix.e00		sh1ix			Sheet 1 index contours

sh2ix.e00		sh2ix			Sheet 2 index contours

sh3ix.e00		sh3ix			Sheet 3 index contours



ASCII text files and PostScript plot files (these 3 files are included with each of the above 
database packages):

	sftopo.txt	This pamphlet.

	sftopo.txt	A formatted version of sftopo.txt

	import.aml	ASCII text file in ARC Macro Language to convert these ARC 
			export files to ARC coverages in ARC/INFO

	utm2lam.prj	A projection file which can be used to reproject these coverages
			into Lambert Conformal Conic projection, which was the 
			projection in which these maps were originally published

The following directory is produced in the process of converting the export files into ARC 
coverages:

	info/		INFO directory containing the database files that accompany each 
			ARC/INFO layer (coverage).




Once the ARC export coverages have been imported (see discussion below), the directory, 
or ARC workspace, will look like this:

	sht1/
		info/
		sh1c/
		sh1d/
		sh1ir/
		sh1ix/
		sh1r/
		sftopo.ps
		sftopo.txt
		import.aml

The sheet 2 and sheet 3  packages will look the same, only the coverages will be those 
associated with each of these 2 sheets.

	sfcu/
		info/
		sh1c/
		sh2c/
		sh3c/
		sftopo.ps
		sftopo.txt
		import.aml

The drainage, road, intermediate contour and index contour packages will look the same 
except they will contain the appropriate thematic layers.
		
The drainage and culture layers for each of the three sheets have been edited in order to 
allow for mosaicing of adjacent sheets.  Marginal material between adjacent sheets was 
removed from each of these six coverages.  If you download any of the three sheets 
(sht1.tar.gz, sht2.tar.gz or sht3.tar.gz), you will get the drainage and culture layers with all 
of the border information.  If you download one of the thematic data packages (sfcu.tar.gz 
or sfdr.tar.gz), you will get the versions prepared for mosaicing.  



CONVERTING ARC EXPORT FILES

ARC export files are converted to ARC coverages using the ARC command IMPORT with 
the option COVER.  In order to ease conversion and to maintain naming conventions, an 
ASCII text file in ARC Macro Language that will convert all of the export files in the 
database into coverages and create the associated INFO directory has been included.  
Change directories to the database package workspace (where the .e00 files are).  From the 
ARC command line type:

Arc:  &run import.aml

Pick the desired .e00 file off of the popup menu and the export file will be converted to an 
ARC/INFO coverage.

ARC export files can also be read by some other Geographic Information Systems.  Please 
consult your GIS documentation to see if you can use ARC export files and the procedure 
to import them. 


DIGITAL COMPILATION

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 
scanned:

	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.


SPATIAL RESOLUTION

Uses of this digital topographic map should not violate the spatial resolution of the data.  
Although the digital form of the data removes the constraint imposed by the scale of a paper 
map, the detail and accuracy inherent in map scale are also present in the digital data.  The 
fact that this database was prepared from 1:125,000 originals means that higher resolution 
information is not present in the dataset.  Plotting at scales larger than 1:125,000 will not 
yield greater real detail, although it may reveal fine-scale irregularities below the intended 
resolution of the database.  Similarly, where this database is used in combination with other 
data of higher resolution, the resolution of the combined output will be limited by the lower 
resolution of these data.  


DATABASE SPECIFICS

The map databases consist of ARC coverages which are stored in UTM projection (Table 
1).  Digital tics are located at the corners of the three map sheets.  The San Francisco Bay 
Region topographic map  sheets were originally published in Lambert Conformal Conic 
projection.  A projection file (utm2lam.prj) has been included with each of the datasets to 
allow for reprojection back to the original coordinate system.


Table 1 - Map Projection
The map is stored in UTM projection

PROJECTION UTM	
UNITS METERS		-on the ground
ZONE 10			-UTM zone 10 
DATUM NAD27
PARAMETERS		-none


The content of the database can be described in terms of the lines that compose the 
map.  Descriptions of the database fields use the terms explained in Table 2.


Table 2 - Field Definition Terms

ITEM NAME	name of the database field (item)
WIDTH		maximum number of digits or characters stored
OUTPUT		output width
TYPE		B-binary integer, F-binary floating point number, 
 		I-ASCII integer, C-ASCII character string
N. DEC. 	number of decimal places maintained for 
		floating point numbers 


LINES  

The lines (arcs) are recorded as strings of vectors and are described in the arc attribute table 
(Table 3).  The arcs in these coverages have not been attributed.



Table 3 - Content of the Arc Attribute Tables  

ITEM NAME	WIDTH	OUTPUT	TYPE	N. DEC	

FNODE#		4	5		B		starting node of arc (from node)   
TNODE#		4	5		B		ending node of arc (to node)
LPOLY#		4	5		B		polygon to the left of the arc
RPOLY#		4	5		B		polygon to the right of the arc
LENGTH		4	12		F	3	length of arc in meters 
<coverage>#	4	5		B		unique internal control number
<coverage>-ID	4	5		B		unique identification number