Data Layer: HYPSOGRAPHY (DLG)
You are invited to read the definitions of terms used in this data standard.
||Hypsography Data ( DLG)|
||The data consists of digital maps created by the U.S. Geological Survey (USGS) depicting contour lines. 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.|
||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 the National Data Administrator, Branch of Data and Systems Services, Division of Information Resources and Technology Management.|
Part 270, FW 6, Data Management and Standards, has been superceded by Part 274, FW 2, Establishing Service Data Standards.
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.
||The USGS Hypsography 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. Occasionally, data will
be produced to USGS standards by other agencies; in these cases, the data would be the
same as the USGS data.
Hypsography data is contour information. It should match well with Digital Elevation Model (DEM) data for any given area. Generally, this data layer will be used in conjunction with other data layers such as soils (for slope analysis), possibly wetland information for pond sites, etc. The usefulness of the data will likely depend on the intervals between the contours, and the detail needed for analysis.
Some software programs are capable of generating hypsography data from DEM data. If you have newer DEM data in an acceptable scale, this may be a good alternative, as some of the hypsography data is quite old. In areas where there has been little development or other geographic change, however, the date of the data may be irrelevant.
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.
Visit the Public Domain Software for Use with USGS Geographic Data page for notes on all DLG data.
||January 14, 1999|
||January 28, 2011|
||Chris Lett, National FWS GIS Coordinator, Branch of Data and System Services, Division of Information Resources and Technology Management.|