U.S. Fish & Wildlife Service

Data Layer: POLITICAL BOUNDARY (DLG)

You are invited to read the definitions of terms used in this data standard.

Name
 Political Boundary Data (DLG)
Description
 The data consists of digital maps created by the U.S. Geological Survey (USGS) that depict political boundaries such as park, towns, counties or states. Although these data now exist in Spatial Data Transfer Standard (SDTS), as well as Digital Line Graph (DLG) format, they are still called DLG data. The data are available on the Internet, free-of-charge, or on inexpensive CD's. The CD's contain 1:100,000- and 1:2,000,000-scale data in DLG format, available nationally. The 1:24,000-scale data on the Internet  is available only in SDTS format. While it is not yet completed nationally, work is in progress.
Source
 USGS EOS Data Center at http://edc.usgs.gov/geodata/ is the source for 1:100,000- scale data in DLG format.
SDTS information is at http://mcmcweb.er.usgs.gov/sdts/data.html for USGS data available in SDTS format.
Reference(s)

Part 270, FW 6, Data Management and Standards, dated September 30, 2002.

USGS DLG Data information is found at http://edc.usgs.gov/products/map/dlg.html. This includes a section on SDTS data, as well as DLG optional data.
The Data User's Guide is available from http://geography.usgs.gov/standards/. This is complete DLG documentation, selectable by scale at the site; very large documents.
Political Boundary Documentation is found at http://www.fws.gov/data/gisconv/bd.zip. This updated document on the attribute codes gives a detailed definition of each code and describes how they were created. It is in WordPerfect 5.1 format, zipped with PKZip. A complete set of this updated documentation for DLG data is also available at the Data User's Guide site referenced above, in the dlgstnds subdirectory.
The SDTS Information Site is at http://mcmcweb.er.usgs.gov/sdts/. This site includes documentation, FAQ's, and data pointers.

Use Instructions
 The USGS Political Boundary data layer in DLG format should be used wherever it is available in an appropriate scale and with current information. Other supplementary data may be needed if the USGS data is old or not in the large scale format. In some parts of the country, TIGER data may be a good alternative.

Service personnel can use the tools referenced below to convert the data to other formats and relate the associated tabular data. Political boundaries data is usually used as a reference GIS layer, but may be used in analysis as well, particularly with tabular data and report creation.

Limitations: Data should always be used at the scale appropriate to the application. The USGS makes every effort to achieve a high level of accuracy in all of its published products. An important aim of its accuracy control program is to meet the U.S. National Map Accuracy Standards. These standards vary with scale; for example, 1:24,000-scale data will be much more spatially accurate than data at the 1:100,000-scale. If the degree of precision is very important to the application, check the above reference to make sure the data being used are appropriate.

Tools
 Political Boundary attribute data are available at http://www.fws.gov/data/gisconv/100bndry.zip. These files contain a list of the attribute codes in Dbase III file (dbf) and WordPerfect 5.1 (textual) format, zipped with PKZip. The codes have the same descriptions in both files when they are present in both files. The dbf file contains only current codes. The WordPerfect document also contains older or deleted codes displayed in italics within parentheses.

The columns in the DBase table are Major3, Minor3, and Description, matching the columns in the actual DLG data. Also included is a readme.bd file, with specific notes on the other two files. Although these files were originally created for the 1:100,000-scale data, the attribute information has been edited so that it should work for all scales of data in DLG format.

The Federal Information Processing Standards (FIPS) Codes can be found at http://www.fws.gov/data/gisconv/fips.zip. These are the codes for states and counties in Dbase III format, zipped with PKZip. The format for these files is similar to the Dbase table above; the states file has columns Minor1, statcode, and statname; the counties file has Major1, Minor1, Major2, Minor2, postal (the same as statcode), and county. These also correspond to the columns in the DLG data file.

Tools for using the SDTS format data will be referenced here when available.

Visit the Documentation and Tools for Utilizing USGS DLG Data page for notes on all DLG data.

Phase
 Adopted
Approval Date
 January 14, 1999
Validation Date
 January 3, 2005
Data Steward
 Deb Southworth Green, National FWS GIS Coordinator, Branch of Data and System Services, Division of Information Technology Management

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These pages are maintained by the U.S. Fish and Wildlife Service, Division of Information Technology Management. Please feel free to contact Deb Southworth Green with any questions and comments.

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