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

USGS DLG Data - product description, prices, sample data, search and order DLG data. 

DLG Standards - site includes links to DLG documentation, selectable by scale at the site; very large documents.

PLSS Documentation - updated document on the attribute codes in WordPerfect 5.1 format, zipped with PKZip; includes detailed definitions for PLSS codes and describes how they were created. This document also includes Appendices A and B.

The SDTS Information Site - includes documentation, FAQ's, and data pointers.

In particular, the Geographic Coordinate Data Base (GCDB) data from the Bureau of Land Management (BLM) for 17 western states may be more accurate as a line coverage. This would be important in determining boundary information for refuges or other applications where line accuracy is an over-riding factor. The GCDB data, however, does not have the attribute information that the PLSS coverages do. There may be times when both coverages are needed. There is an ongoing discussion between USGS and BLM about merging the data; this data standard and the related tools will be updated as needed.

Note: When using the GCDB data, the PLSS data, or any other data source for applications where accuracy is a major issue (such as determining boundary information), you need to carefully check documentation on the source of the data. Quality will vary widely based on the source materials available or used; each state had the option to create the GCDB data differently.  

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.

In the PLSS polygon data that were checked, there was a lack of consistency in how the attribute information was organized. In the sample data used, there were 4 major and minor code sets. As an example of the variation, Code 306, origin of survey, was located in minor1 for one data set, and minor4 for another. Code 301 (section number) varied in the same way. The DBase table, 100plss.dbf, has three fields; major, minor, and description. All the major/minor combinations have the same code values (i.e. Code 301 means the same thing whether it is in the minor1 field or the minor4 field), so lookups can be performed on any of the fields in the DBase table to match fields in the actual DLG data. Also included is a readme.pls 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.

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

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