Digital geologic map of Lawton quadrangle, southwestern Oklahoma

                           (diskette 1 of 3)



        U.S. Geological Survey Open-File Report 96-376



Directory   / (root) a_readme.1st  file:





                                ABSTRACT



   This diskette contains a digital data set and accompanying

documentation for surficial geology of the 1:250,000-scale Lawton

quadrangle, Oklahoma.  The original data are from the Geologic Map,

sheet 1 of 4, included in the Oklahoma Geological Survey publication,

Reconnaissance of the water resources of the Lawton quadrangle,

southwestern Oklahoma, Hydrologic Atlas 6, Havens, 1977.  The geology

on sheet 1 was compiled by R.O. Fay, 1967-68 and J.S. Havens, 1973.

                                         

                                INTRODUCTION



   This diskette contains a digital data set and accompanying

documentation for surficial geology of the 1:250,000-scale Lawton

quadrangle, Oklahoma.  The original data are from the Geologic Map,

sheet 1 of 4, included in the Oklahoma Geological Survey publication,

Reconnaissance of the water resources of the Lawton quadrangle,

southwestern Oklahoma, Hydrologic Atlas 6, Havens, 1977.  The geology

on sheet 1 was compiled by R.O. Fay, 1967-68 and J.S. Havens, 1973.

                                         

   The data are provided in a nonproprietary file format.  ARC/INFO

software was used in the development of this data set (ESRI, 1995).

The use of trade names is for descriptive purposes only, and does not

imply endorsement by the U.S. Government.  



   All references to file names, directories, and pathnames in this

document are enclosed in quotation marks.  Pathnames use MS-DOS-style

naming conventions, with the "\" character indicating the highest-

level directory of the diskette.  



   Compilation of the data set on this diskette was funded under a

cooperative Joint Funding Agreement between the U.S. Geological Survey

and the State of Oklahoma, Office of the Secretary of Environment.



                            FILE FORMATS



   The data set files with ".gz" extensions were compressed for

distribution on the diskette.  The data are stored in the generic,

nonproprietary Digital Line Graph (DLG-3) Version 3, Optional

Format. Designed for data interchange, the DLG-3 format allows the

simple creation of a vector polygon or line data structure.  The

topological linkages are explicitly encoded for node, area, and line

elements.  The files are composed of 8-bit ASCII characters organized

into fixed logical records of 80 bytes.  A detailed description of the

DLG-3 Optional format may be found in Data Users Guide 3, Digital Line

Graphs from 1:2,000,000-Scale Maps (U.S. Geological Survey, 1990).

These files need to be uncompressed to access the digital data. The

file "\gzip\gunzip.exe" is an MS-DOS executable program included on

diskette 3 of 3 that will uncompress the data files. To uncompress a

file, type "gunzip -a" and the file name. For example:



gunzip -a geology.gz



Table 1 shows the uncompressed file characteristics.



Table 1.  Uncompressed file characteristics.

---------------------------------------------------------------------- 

File name       Original     Uncompressed    Uncompressed  

                file name    DOS file size   UNIX file size

                             in bytes        in bytes

----------------------------------------------------------------------

geology.gz      geology      3,353,940       3,303,454



   A graphic image of the data sets on both diskettes is provided in a

Graphics Interchange Format (GIF) file and has a file extension of

".gif".  The GIF file is easily displayed on a variety of computer

systems using readily available display software.  This image provides

a simplified view of the data sets, and may be used for browsing purposes.

The GIF file portrays significantly less spatial resolution and

information content than the actual data sets.



                        DISKETTE ORGANIZATION



   This diskette is compatible with the MS-DOS operating system.  File

names with extensions of ".gz" and ".gif" are binary-format files.

Other files are ASCII format files.  All ASCII files use MS-DOS record

delimiters (carriage return, line feed) to indicate the end of lines.

Conversion of record delimiters in these ASCII files may be necessary

for use with operating systems other than MS-DOS.  A utility such as

DOS2UNIX, the FTP file transfer utility, or a text editor may be used

to convert the record delimiters.  Unix users may use the following

perl script to convert the record delimiters:



#!/usr/bin/perl -pi.dosbak

s/\r\n$/\n/;





   This diskette is organized into six files:



\-------|-a_readme.1st  - This file

        |-a_notice.txt  - Liability disclaimer

        |-geology.lut   - Attribute table of geologic formations

        |-geology.gz    - Geology data set in DLG-3 Optional format

        |-geology.fgd   - Complete documentation of the sources

        |                 and procedures used to create the geology

        |                 data set

        |-browse.gif    - Browse image of the data sets in GIF format

        



                         DATA-SET DOCUMENTATION

     

   A documentation file (known as metadata) for the data set has a

file extension of ".fgd".  The documentation file complies with the

Federal Geographic Data Committee (FGDC) Content Standards for Digital

Geospatial Metadata (Federal Geographic Data Committee, 1994).  The

FGDC-compliant metadata file contains detailed descriptions of the

data set, and includes a narrative section describing the procedures

used to produce the data set in digital form.



                           GEOMETRIC REGISTRATION



   The Albers Equal Area map projection (Snyder, 1987) is used for the

data set.  This projection is appropriate for maps of the conterminous

United States because of the visual presentation and equal-area

characteristic, which facilitates areal analysis.  This projection

frequently is used for nationwide digital map data sets.  The

projection is cast on the North American Datum of 1983. Table 2

provides map projection information.



This projection slightly distorts shapes and distances (scale) in

order to maintain equal-area properties.  Scale is true along the

standard parallels, which are to the north and south of Oklahoma.

Scale distortion in Oklahoma reaches a maximum of slightly less than

one percent at the northern border of the state (Snyder, 1987.)



------------------------------------------------------------------------------

Table 2.  Albers Equal Area projection parameters



[GRS80, Geodetic Reference System 1980; NAD83, North American Datum 1983]

______________________________________________________________________________



Projection parameters:



   Spheroid                            GRS80

   Datum                               NAD83

   First standard parallel             29 30 00 North

   Second standard parallel            45 30 00 North

   Central meridian                    96 00 00 West

   Latitude of projection origin       23 00 00 North



Coordinate system parameters:



   False easting                       0

   False northing                      0

   Planimetric units of measure        meters

______________________________________________________________________________



                             REFERENCES CITED



Environmental Systems Research Institute, Inc. (ESRI), 1995,

     ARC/INFO Command References, ARC/INFO Version 7.0.3 ArcDoc:

     Redlands, CA.  [online documentation].



Federal Geographic Data Committee, 1994, Content standards for digital

     geospatial metadata (June 8): Federal Geographic Data Committee,

     Washington, D.C., 78 p.



Havens, J.S., 1977, Reconnaissance of the water resources of the             

     Lawton quadrangle, southwestern Oklahoma: Oklahoma Geological

     Survey, Hydrologic Atlas 6, scale 1:250,000, 4 sheets.  (Geology

     on sheet 1 compiled by R.O. Fay, 1967-68 and J.S. Havens, 1973.)



Snyder, J.P., 1987, Map projections--A working manual: U.S. Geological

     Survey Professional Paper 1395, 383 p.



U.S. Geological Survey, 1990, Digital line graphs from 1:2,000,000-

     scale maps, data users guide 3: U.S. Geological Survey National

     Mapping Program Technical Instruction, 70 p.

