DESCRIPTION OF DIGITAL FILES FOR GEOLOGIC MAP OF THE WEST 
HALF OF THE BLYTHE 30' BY 60'QUADRANGLE, RIVERSIDE COUNTY, 
CALIFORNIA AND LA PAZ COUNTY, ARIZONA (U.S. GEOLOGICAL 
SURVEY SCIENTIFIC INVESTIGATIONS MAP 2922)

By Paul Stone

INTRODUCTION

The results of this map compilation of the geology of the 
west half of the Blythe 30' by 60' quadrangle are presented 
as a digital geologic map database.  This document 
describes the types and contents of files comprising the 
database.  Information on how to extract and plot the map 
also is provided.

This publication includes ARC/INFO (Environmental Systems 
Research Institute, http://www.esri.com) version 8.1.2 
coverages and associated tables; Portable Document Format 
(PDF) files of the geologic map and an accompanying 
geologic pamphlet; and a text file of FGDC-compliant 
metadata for the report.
 
GEOLOGIC MAP DATABASE FILES AND ASSOCIATED FILES

All files listed in this section are in a compressed tar 
file named blw.tar.gz; see section below titled, SOFTWARE 
UTILITIES.

ARC/INFO                 Coverage          Contains
Interchange file

blw_geo.e00               blw_geo          Contacts, 
                                             faults, and 
                                             rock units
blw_str.e00               blw_str          Folds; attitudes 
                                             and dip values
blw_dune.e00              blw_dune          Crests of sand 
                                             dunes
blw_anno.e00              blw_anno          Geologic unit 
                                             labels (with 
                                             leaders) 

The directory, info/, is produced in the process of 
importing interchange files to ARC coverages in ARC/INFO.  
The info/ directory contains:

Polygon attribute table          blw_geo.pat
Arc attribute tables             blw_geo.aat, blw_str.aat, 
                                   blw_dune.aat, 
                                   blw_anno.aat
Point attribute tables           blw_str.pat 


FILES FOR VIEWING AND PLOTTING
       
SIM2922_map.pdf               A Portable Document Format 
                                (PDF) file for viewing and 
                                plotting the geologic map 
                                at full scale.  The plot is 
                                approximately 48 x 36 
                                inches in size.

SIM2922_pamphlet.pdf          A Portable Document Format 
                                (PDF) file for viewing and 
                                printing a pamphlet that 
                                accompanies the map.  The 
                                pamphlet contains a 
                                geologic interpretation and 
                                the description of map 
                                units.

METADATA

blw_met.txt                    Federal Geographic Data 
                                Committee (FGDC) compliant 
                                metadata file derived from 
                                the digital database

SOFTWARE UTILITIES

Files that have the .gz file extension were compressed 
using gzip.  Gzip utilities are available free of charge 
via the Internet at the gzip home page, 
http://www.gzip.org.

The data package is additionally bundled into a single tar 
(tape archive) file.  The individual files must be 
extracted using a tar utility, available free of charge via 
the Internet through links on the Common Internet File 
Formats page, http://www.matisse.net/files/formats.html.  
One such utility is WinZip, available at 
http://www.winzip.com (WinZip can also decompress files).

HOW TO OBTAIN THE DIGITAL FILES

The digital files constituting the geologic map database of 
this report may be obtained via the Internet from the U.S. 
Geological Survey publications website.  Go to the web page 
at http://pubs.usgs.gov/sim/2006/2922/ and follow the 
directions to download the files.

EXTRACTING THE GEOLOGIC MAP DATABASE FROM THE TAR FILE

After downloading the files, they must be uncompressed 
using a gzip utility such as gzip itself or WinZip.  The 
data files must then be extracted using the appropriate tar 
utility.

To do this                         Type this at the Unix 
command prompt

Uncompress blw.tar.gz              gzip -d blw.tar.gz (or 
to blw.tar                           use gzip utility of 
                                     choice)

Go to the directory that will      cd local_directory
hold the directory blw/ (if 
different from local_directory)

Extract the Blythe West            tar -xvof {path to tar 
directory from the tar file          file}/blw.tar
                                     (or use tar utility of 
                                     choice)

This process will create a directory, blw/, that contains 
the ARC/INFO interchange files and supporting files.

CONVERTING THE ARC/INFO EXPORT FILES

ARC interchange (.e00) files are converted to ARC coverages 
using the ARC command IMPORT with the option COVER.  

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

PORTABLE DOCUMENT FORMAT (PDF) FILES

The PDF files are accessed using Adobe Reader software, 
available free from the Adobe website http://www.adobe.com.  
Follow instructions at the website to download and install 
the software.