January 24, 1996
Technical Announcement National Mapping Division
U.S. Geological Survey

Improved computerized maps are now available on compact disc-read only memory (CD-ROM) from the U.S. Geological Survey (USGS). These high-quality files, known as digital line graph (DLG) data, depict boundaries, transportation systems, and many natural and man-made features.

The DLG data were collected at a scale of 1:2,000,000 (one inch equals nearly 32 miles). No data source more than five years old was used in updating the DLGs, which were originally collected in 1979 and 1980.

Besides the popular DLG optional distribution format, these data are also now available on CD-ROM in the Topological Vector Profile (TVP) of the Spatial Data Transfer Standard (SDTS). The SDTS is an effective mechanism for the transfer of spatial data between dissimilar computer systems.

"These data provide an accurate and up-to-date framework for statewide, regional, and national mapping projects, planning efforts, Earth science investigations, and many other applications," according to Eric Anderson, chief of the USGS Mapping Applications Center in Reston, Virginia, which produced the latest DLG data.

"Users of our older DLG files have provided us with many good suggestions for improving these small-scale data, and we have responded by incorporating the best recommendations in our latest CD-ROM products," said Anderson. "Among many others, the Bureau of the Census and the National Park Service made major contributions to this effort," said Dick Witmer, acting chief of the USGS National Mapping Division. "We are pleased with the high level of cooperation from the many agencies that were involved."

"This project is a good example of how federal mapping and natural resource management organizations work together to reduce duplication of effort. The USGS will maintain this national data set, but we depend on our cooperators to update the map features, such as National Park boundaries, that are not the responsibility of the USGS."

The DLG data have been released in two formats on CD-ROM. One disc contains data in the popular "DLG Optional" format. The other CD-ROM disc contains data in the SDTS TVP format. Each CD-ROM is available for $32 plus a $3.50 handling fee, and is available from USGS-Information Services, Box 25286, Denver, Colorado 80225.

The USGS stock number for the CD-ROM containing data in the optional format is 01-DLG-02M. The stock number for the CD-ROM containing data in SDTS TVP format is 01-DLG-02M-S.

The USGS is promoting the use of the STDS and is providing 1:2,000,000-scale digital cartographic data in SDTS format to the public at no cost via the Internet. World Wide Web users can retrieve these data at the following Universal Resource Locator (URL): http://sun1.cr.usgs. gov/glis/hyper/guide/2mil/.

SDTS transfers can also be retrieved from the Internet by direct file transfer protocol (anonymous FTP) at the following address:

edcftp.cr.usgs.gov
username: anonymous
password: enter your e-mail address

For World Wide Web users the URL is: ftp://edcftp.cr.usgs.gov/pub/data/DLG/2M/.

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