APPENDIX - THE DIGITAL MAP DATABASE INTRODUCTION This report provides digital data and plottable files that depict the relative susceptibility to certain types of slope failure in the Oakland area, California, at 30-m ground resolution. Although the susceptibility calculations described in the body of the report were derived from digital maps of geology, terrain slope, and landslides, only data for the susceptibility map are included here. The input data on geology, slope, and landslides were compiled and the susceptibility calculations performed in ARC/INFO, a commercial geographic information system (GIS) (Environmental Research Institute [ESRI], Redlands, California), by a program written in Arc Macro Language (AML) for the GRID extension of ARC/INFO. The resulting landslide-susceptibility database consists of a data layer called susgrd_utm, described in table 1 below. The map layer is stored in UTM projection (zone 10; see table 2); projection files are included to convert between UTM and the state plane projection. Digital tics define a 7.5-minute grid of latitude and longitude. Contents of the map database are described as susceptibility values in 30-m grid cells. Terms in table 3 describe the database fields. Table 1. Data layers Data layer name Description susgrd_utm 30-meter raster grid containing the susceptibility values drain Vector coverage of drainage base culture Vector coverage of cultural base roads Vector coverage of road network base hwys Vector coverage of interstate highway base hydro Vector coverage of hydrological base Table 2. Map projection Projection UTM (universal transverse mercator) Units meters Zone 10 Datum NAD 27 Spheroid Clark 1886 Table 3. Field definition terms ITEM NAME Name of database field (item) WIDTH Maximum number of digits or characters stored OUTPUT Output width TYPE B - binary integer, F - binary floating point number, N - ASCII floating point number, I - ASCII integer, C - ASCII character string N.DEC Number of decimal places maintained for floating point numbers Susceptibility values are stored for individual 30-meter grid cells, and are tabulated in the 'count' column (see table 4). Table 4. Content of the value attribute table (SUSGRD_UTM.PAT) Item name Width Output Type N.DEC Description VALUE 4 10 B -- Susceptibility value COUNT 4 10 B -- Number of cells with corresponding value The susceptibility values in table 4 are distributed in the 1:50,000-scale map, which contains 1112 rows and 1394 columns. The number of different susceptibility values is 110; the minimum value is 0.0, the maximum 133.0, the mean 13.2, and the standard deviation 18.1. Because the distribution of susceptibility values is highly skewed (see text figure 7D), the latter two statistics are given for reference only. SPATIAL RESOLUTION Uses of this digital map should not violate the spatial resolution of the data. Although the digital form of the data removes the physical constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. Because this database was extracted from maps at a scale of 1:24,000 and compiled at that same scale, higher-resolution information is not present. Enlargement of the database to scales larger than 1:24,000 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. OVERVIEW OF THE DIGITAL DATABASE This report consists of a 1:24,000-scale digital database, a 1:50,000-scale digital map image derived from it entitled "Map and Map Database of Susceptibility to Slope Failure by Sliding and Earthflow in the Oakland Area, California," and supporting files. The report is stored as several digital files: the spatial data as both ARC export (uncompressed) and ARCVIEW shape formats, and the map image as both Postscript and PDF formats. The exported ARC coverages lie in UTM zone 10 projection and the shape versions are coded in decimal degrees. This pamphlet, which fully describes preparation of the digital map database as well as its content and character, is included as Postscript, PDF, and ASCII text files and is also available on paper as USGS Miscellaneous Field Studies Map MF-2385. A plotted copy of the 1:50,000-scale map can be ordered from a USGS Earth Science Information Center or by telephone at 1-888-ASK-USGS. Any or all of the digital files can be obtained over the Internet or by magnetic tape copy, as described at the end of this section. The full versatility of the 1:24,000-scale spatial database is realized by importing the ARC export files into ARC/INFO or an equivalent GIS. Other GIS packages, including MapInfo and ARCVIEW, can use either the ARC export or shape files. The Postscript map image can be used for viewing or plotting in computer systems with sufficient capacity, and the considerably smaller PDF image files can be viewed or plotted in full or in part from Adobe ACROBAT software running on Macintosh, PC, or UNIX platforms. DATABASE CONTENTS The six sets of digital files comprising the database are encoded in more than one format. Names of the files are unique designators based on the report identifier, MF-2385, followed by part numbers (1 through 6 below) and an extension indicating file type. Some files have been bundled using the tar (UNIX Tape Archive) utility (.tar extension). All larger files have been compressed with the gzip utility, indicated by the .gz extension. The files and their identities are as follows: 1. Revision list: A list of the parts of the report and at what version number of the report each was last revised (if at all) followed by a chronological list that describes any revisions (see REVISIONS, below). MF-2385revs_1a.txt ASCII file 2. Text: The pamphlet (this text), which describes the database and how to obtain it. MF-2385_2a.txt ASCII file MF-2385_2b.ps Postscript file MF-2385_2c.pdf PDF file 3. Database of susceptibility values: ARC GRID containing 30-meter cells. Import.aml will name this grid susgrd_utm. MF-2385_3.e00.gz Arc export grid 4. Supporting files for ARC/INFO use, bundled as one tar file: MF-2385_4a.tar When opened, the tar file yields: sp2utm.prj utm2sp.prj which are projection files to convert between the UTM zone 10 projection of the database and state plane projection, and import.aml which is an ASCII script written in Arc Macro Language for converting the ARC export files into usable coverages and INFO files that are assigned standard names (see IMPORTING THE ARC EXPORT FILES). 5. Quadrangle index database: The data files representing lines and polygons of the quadrangle index (ARC export and ARCVIEW shape format). The ARC version also includes quadrangle names as annotation. MF-2385_5a.e00.gz ARC export files containing MF-2385_5b.e00.gz lines, polygons, and annotation. MF-2385_5c.e00.gz MF-2385_5d.e00.gz MF-2385_5e.e00.gz MF-2385_5.tar.gz Line and polygon ARCVIEW shape files bundled as one tar file. When opened, the tar file yields: Polygon files: MF-2385_5a.dbf MF-2385_5a.shp MF-2385_5a.shx MF-2385_5b.dbf MF-2385_5b.shp MF-2385_5b.shx MF-2385_5c.dbf MF-2385_5c.shp MF-2385_5c.shx MF-2385_5d.dbf MF-2385_5d.shp MF-2385_5d.shx MF-2385_5e.dbf MF-2385_5e.shp MF-2385_5e.shx 6. Plot files for the map: _Map and Map Database of Susceptibility to Slope Failure by Sliding and Earthflow in the Oakland Area, California,_ which measures 30 by 51 inches when plotted. MF-2385_6a.eps Postscript file (39.6 MB) MF-2385_6b.pdf PDF file (4.5 MB) Available on Adobe Acrobat Version 4.0 REVISIONS Any part of the report (the numbered items described above and listed in the revision list MF-2385revs_a.txt) may be changed in the future if needed. Changes could involve, for example, fixing files that don't work, correcting or adding landslide, geology, or slope details, or adding new file formats or other components. Any major revision to the input data or the susceptibility model would result in a new report. The report begins at version 1.00. Any revisions will be noted in the revision list and will result in the recording of a new version number for the report. Small changes will be indicated by decimal increments and larger changes by integer increments in the version number. Revisions will be announced and maintained on the Web page for this report on the Western Region geologic publications server (see next section). OBTAINING THE DATABASE FILES The database may be obtained from: http://pubs.usgs.gov/mf/2002/2385/ or request a CD-R from: Oakland Slope Failure Susceptibility Map Database c/o Database Coordinator U.S. Geological Survey 345 Middlefield Road MS 975 Menlo Park, CA 94025 The specified files bundled in a compressed tar file will be returned to you on the disc. OPENING THE DATABASE FILES Some of the files are packaged as tar files, and the larger files containing the databases and images have been compressed with gzip. Thus, gzip is required to uncompress the files, and a tar utility is required to open the tar files. The necessary utilities are available on-line: Compressed Gzip Files Files compressed with gzip (those with a .gz extension) can be uncompressed with gzip. The gzip utility converts the compressed file name.gz to its uncompressed equivalent name. The compressed file is replaced by the uncompressed file. This utility is free of charge over the Internet at: http://www.gzip.org/ Tar Files (UNIX Tape Archive) To extract the contents of a tar file, first uncompress it with gzip if the extension is .tar.gz. Once the tar extension is exposed, extract the contents with a tar utility. This utility is included in most UNIX systems. Tar utilities for PC and Macintosh can be obtained free of charge via the Internet from Internet Literacy's Common Internet File Formats Web Page: http://www.matisse.net/files/formats.html WinZip This commercial package runs on PCs and can deal with both gzip and tar files. An evaluation copy of WinZip for Windows 3.1, 95 and NT can be downloaded from: http://www.winzip.com/winzip/ IMPORTING THE ARC EXPORT FILES (Note that the export files are ASCII files. Hold down the shift key when you click to download) The ARC export files with the extension .e00 can be converted to ARC/INFO vector maps (coverages) and INFO files by running the import.aml that is included in the database. This will import the export files and assign standard names (see below). Be sure to uncompress the MF-2385_6a.e00.gz file with the gzip utility before running the import.aml. Run import.aml from the ARC prompt in the directory containing the export files: ARC: &run import.aml - run import.aml Note that the ARC coverages and separate INFO files will be given standard names: MF-2385_3.e00 (Susceptibility Database) is named susgrd_utm Arc/Info Readme file found in directory This is a readme file for all of you lucky folks who are interested in landslides in the Oakland area, California. This is basically a directory summary incase other appendices, revision lists, or text confused you along the way. Textfiles, etc. --------------- MF-2385revs_1a.txt Revision list import.aml Import AML to convert .e00 to grid sp2utm.prj Projection file turns stateplane to UTM utm2sp.prj Projection file turns UTM to stateplane Export files ------------ mf-2385_3.e00.gz Susceptibility grid--> exported--> gzipped mf-2385_5a.e00.gz Drainage coverage--> exported--> gzipped mf-2385_5b.e00.gz Culture coverage--> exported--> gzipped mf-2385_5c.e00.gz Roads coverage--> exported--> gzipped mf-2385_5d.e00.gz Interstate Hwy--> exported--> gzipped mf-2385_5e.e00.gz Hydrology--> exported--> gzipped Coverages --------- culture Culture - names, parks, etc. drain Drainage - contours, streams, rivers, etc. hydro Hydrology - bays, lakes, ponds roads Road - network of streets hwys Interstate highways - highways Grids ----- susgrd_utm Final Susceptibility grid Shapefiles, etc. ---------------- mf-2385_5a.dbf Drainage mf-2385_5a.shx mf-2385_5a.shp mf-2385_5b.dbf Culture mf-2385_5b.shx mf-2385_5b.shp mf-2385_5c.dbf Roads mf-2385_5c.shx mf-2385_5c.shp mf-2385_5d.dbf Interstate Highways mf-2385_5d.shx mf-2385_5d.shp mf-2385_5e.dbf Hydrology mf-2385_5e.shx mf-2385_5e.shp ---------------------------------------- mf-2385_5.tar.gz All shape files above tar-ed and gzip-ed.