DESCRIPTION OF DIGITAL FILES FOR PRELIMINARY GEOLOGIC MAP OF THE LOS ANGELES 30' X 60' QUADRANGLE, SOUTHERN CALIFORNIA By Rachel Alvarez INTRODUCTION Open-File Report 2005-1019 is a digital geologic data set that maps and describes the geology of the Los Angeles 30' x 60' quadrangle, southern California. The Los Angeles 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 tar file named los_angeles.tar.gz; see section below titled, SOFTWARE UTILITIES. ARC/INFO Coverage Contains Interchange file la1_geo.e00 la1_geo Contacts and faults la1_str.e00 la1_str Folds; attitudes and dip values la1_anno.e00 la1_anno Annotation subclasses: geo(unit labels) fault(fault names) canyons(canyon names) cities(city names) mountain(mountain names) water(names of water features) Leaders la1_hydro.e00 la1_hydro Hydrography data la1_hypso.e00 la1_hypso Hypsography data la1_trans.e00 la1_trans Transportation data 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 la1_geo.pat Arc attribute tables la1_geo.aat, la1_str.aat, la1_anno.aat, la1_hydro.aat la1_hypso.aat, la1_trans.aat Point attribute tables la1_str.pat Annotation attribute tables la1_anno.tatgeo la1_anno.tatfault la1_anno.tatcanyons la1_anno.tatcities la1_anno.tatmountain la1_anno.tatwater FILES FOR VIEWING AND PLOTTING la1_map.zip An Encapsulated Postscript file for viewing and plotting the geologic map at full scale. The plot is approximately 40 x 32 inches in size la1_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. la1_cmu.zip An Encapsulated Postscript file for viewing and plotting the correlation of map units and abbreviated description of map units, approximately 36 x 30 inches in size. la1_cmu.pdf A Portable Document Format (PDF) file for viewing and plotting the correlation of map units and abbreviated description of map units, approximately 36 x 30 inches in size. la1_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 la1_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 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 .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/2005/1019 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. This process will create a directory, los_angeles/, 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 Los Angeles 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 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