README File:                                                      Version: 2/99

This directory contains a Spatial Data Transfer Standard (SDTS), 
Topological Vector Profile (TVP) compliant transfer, produced by the 
National Mapping Division of the United States Geological Survey (USGS).


PURPOSE OF TRANSFER:
        The mission of the U.S. Geological Survey's National Mapping Division
        is to meet the Nation's need for basic geospatial data, ensuring access
        to and advancing the application of these data and other related earth 
        science information for users worldwide. These data are provided in SDTS 
        format as the result of a federal mandate.

        The Digital Line Graphs (DLG's) are the U.S. Geological Survey, 
        National Mapping Division, Vector Program's response to the nation's
        need for accurate and consistent geospatial digital data in
        vector format.

REQUIREMENTS:          
        This transfer requires an external data dictionary from the U.S. 
        Geological Survey, National Mapping Division, with a 4-character
        code of DLG-3, version number 3.00.  These files can be obtained
        from the same web site from which the data was obtained.

STANDARD AUTHORITY:  
        American National Standards Institute (ANSI):
        ANSI-NCITS 320-1998 The Spatial Data Transfer Standard, 
        Part 4: Topological Vector Profile, Version 1, June 9, 1998

ISO 8211 CONFORMANCE:
        All files with extension *.DDF are in the ISO 8211 file transfer
        format. All SDTS spatial addresses are expressed in two 32 bit 
        binary sub-fields defined by the ISO 8211.  Leader and directory 
        information are dropped whenever possible. Files are Level 2 as
        described in ISO 8211.
 
CATALOG DIRECTORY MODULE xxxxCATD.DDF:
        Each transfer will contain this catalog directory module which
        contains a listing of every SDTS ISO 8211 file included in the
        transfer.  (xxxx indicates a four-character transfer base which 
        is common to all files in a transfer.)

IDENTIFICATION MODULE xxxxIDEN.DDF:
        This module contains information that describes the overall
        characteristics of the data in a transfer, including
        its geographical domain.  

REFERENCES:
        "DLG-3 SDTS Transfer Description" This is a  draft document that describes
        SDTS transfers of DLG-3 data, including detailed information on
        each module. Check the SDTS web site at http://mcmcweb.er.usgs.gov/sdts 
        for a copy or contact the USGS.

POINT OF CONTACT:
        SDTS Task Force               
        U.S. Geological Survey        
        1400 Independence Road       
        Rolla, MO 65401              
        E-MAIL: sdts@usgs.gov 
             or mcmcesic@usgs.gov for USGS Product Information.
       
       


