DESCRIPTION OF DIGITAL FILES FOR PRELIMINARY GEOLOGIC MAP OF THE EL CAJON 30' X 60' QUADRANGLE, SOUTHERN CALIFORNIA, VERSION 1.0

By Rachel Alvarez

INTRODUCTION

Open-File Report 2004-1361 is a digital geologic data set that maps and describes the geology of the El Cajon 30' x 60' quadrangle, southern California.  The El Cajon quadrangle database is one of several 30' x 60' quadrangle databases that are being produced by the Southern California Areal Mapping Project (SCAMP).  These maps and databases are, in turn, part of the nation-wide digital geologic map coverage being developed by the National Cooperative Geologic Map Program of the U.S. Geological Survey (USGS).  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 8.2 coverages and associated tables; Encapsulated Postscript (.eps) files of the geologic map, correlation of map units, and abbreviated description of map units; Portable Document Format (PDF) files of the geologic map and an accompanying geologic pamphlet (which includes a more detailed description of map units); 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 file named el_cajon.zip; see section below titled, SOFTWARE UTILITIES.

ARC/INFO			Coverage		Contains 	
Interchange file

ec1_geo.e00			ec1_geo		Contacts and faults
ec1_str.e00			ec1_str		Folds; attitudes and dip values
ec1_anno.e00			ec1_anno	Annotation subclasses:
							geo(unit labels)
							fault(fault names)
							canyons(canyon names)
							cities(city names)
							mountain(mountain names)
							water(names of water features)
							Leaders					
ec1_arw.e00			ec1_arw		Landslide arrows

ec_hydro.e00			ec_hydro	Water features
ec_hypso.e00			ec_hypso	Topography
ec_trans.e00			ec_trans	Roads
						Cultural information

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		ec1_geo.pat
Arc attribute tables		ec1_geo.aat, ec1_str.aat, ec1_arw, ec1_anno.aat,
				ec_hydro.aat, ec_hypso.aat, ec_trans.aat
Point attribute tables		ec1_str.pat, ec_hydro.pat
Annotation attribute tables	ec1_anno.tatgeo
				ec1_anno.tatfault
				ec1_anno.tatcanyons
				ec1_anno.tatcities
				ec1_anno.tatmountain
				ec1_anno.tatwater

FILES FOR VIEWING AND PLOTTING
       
ec1_map.eps.zip			A zipped Encapsulated Postscript file for viewing and
				plotting the geologic map at full scale.  The
				plot is approximately 40 x 32 inches in size

ec1_map.pdf			A Portable Document Format (PDF) file for viewing
				and plotting the geologic map at full scale.  The
				plot is approximately 40 x 32 inches in size.

ec1_cmu.eps.zip			A zipped Encapsulated Postscript file for viewing and plotting
				the correlation of map units and abbreviated description
				of map units, approximately 26 x 28 inches in size.

ec1_cmu.pdf			A Portable Document Format (PDF) file for viewing and
				plotting the correlation of map units and abbreviated
				description of map units, approximately 26 x 28 inches
				in size.


ec1_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.

For those having access to large-format plotters such as HP650C, HP755C, HP2500c, and HP5000, plots may be made directly from the included plot file.


METADATA

ec1_met.txt			Federal Geographic Data Committee (FGDC) compliant
				metadata file derived from the digital database.

GEOLOGIC SYMBOLS

Files in the plot package have been prepared to produce optimum plots using the shade, line, and marker sets listed below; these symbol sets and supporting fonts are included in a zipped file named symbols.zip (0.18 Mb).

	geoscamp2.lin		Lineset for lines
	geoscamp2.mrk		Markerset for points
	wpgcmykg.shd		Shadeset for colors
	geology2.shd		Shadeset for patterns
	fnt026			Font required for geoscamp2.lin
	fnt037			Font required for geoscamp2.mrk
	fnt035			Font required for geology2.shd
	geoage			folder contains files for Geoage font group

Special geologic characters used in the unit designations are from the Geoage font group and are contained in the geoage folder within the symbols.zip file.  The Geoage fonts are used in conjunction with the geofont.txt textset when using ESRI software.  The geoage folder contains fonts, the geofont.txt textset, and explanatory files.


SOFTWARE UTILITIES

Files that have the .zip file extension were compressed using WinZip, available at http://www.winzip.com.

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/of/2004/1361 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.  This process will create a directory, el_cajon/, 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 Acrobat Reader software, available free from the Adobe website http://www.adobe.com.  Follow instructions at the website to download and install the software.  Acrobat Reader contains an on-line manual and tutorial.

DIGITAL GEOLOGIC MAP SPECIFICATIONS

Digital compilation

Compilation of the El Cajon 30’ x 60’ quadrangle is based upon published mapping at various scales, unpublished mapping at 1:24,000 scale, and reconnaissance mapping.  Even though some of the source geologic data are from significantly larger scale maps, the 1:100,000 scale compilation in this report is intended for use at that scale, digital or plotted enlargements of all or part of the map are not intended and could result in misleading map data.  The lines, points, and polygons were edited using standard ARC/INFO commands.  Digitization and editing artifacts significant enough to display at a scale of 1:100,000 were corrected.

Base map

Hypsography, hydrography, and transportation data were converted from 1:100,000 scale Digital Line Graph (DLG) data (prepared and available from The National Cartographic Information Center) to ARC/INFO coverages.

Spatial resolution

Use of this digital geologic map database 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 edited at a scale of 1:100,000 means that higher resolution information is not generally present in the dataset.  Plotting at scales larger than 1:100,000 will not yield greater real detail, although it may reveal fine-scale irregularities above the intended resolution of the database.  Similarly, although higher resolution data is incorporated at a few places, the resolution of the combined output will be limited by the lower resolution data.

Map accuracy standards

All contacts on the geologic map are shown as solid lines.  Until uniform national geologic map standards are developed and adopted, lines and points on SCAMP 1:100,000 scale geologic maps that are located to within 50 meters, relative to accurately located features on the base map, are considered to meet map accuracy standards.  Published and unpublished mapping by the compiler are known to generally meet this map accuracy standard.  Most, but not all, mapping compiled from other sources is known to generally meet this map accuracy standard.

Faults and landslides

This database is sufficiently detailed to identify and characterize many actual and potential geologic hazards represented by faults and landslides, but is not sufficiently detailed for site-specific determinations.  Faults shown do not take the place of fault rupture hazard zones designated by the California State Geologist (see Hart, 1988).

REFERENCES

Hart, E.W., 1988, Fault-rupture zones in California; Alquist-Priolo Special
         Studies Zones Act of 1972 with index to special studies zones maps:
         California Division of Mines and Geology Special Publication 42
