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 EROS Data Center is the source for 1:100,000-scale data in DLG format. SDTS information for USGS data available in SDTS format. |
| Historical Data | For information on past versions of this standard, contact: Andrey Andreyev, National Data Administrator, Branch of Data and Systems Services, Division of Information Resources and Technology Management |
| Reference(s) |
Part 270, FW 6, Data Management and Standards, dated September 30, 2002 has been superceded by Part 274, FW 2, Establishing Service Data Standards, dated March 4, 2009. USGS DLG Data - product description, prices, sample data, search and order DLG data. DLG Standards - this site includes links to DLG documentation, selectable by scale at the site; very large documents. The SDTS Information 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 |
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. 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 5, 2009 |
| Data Steward |
Chris Lett, National FWS GIS Coordinator, Branch of Data and System Services, Division of Information Resources and Technology Management |