The National Spatial Reference System (NSRS)

The National Spatial Reference System (NSRS), maintained by the National Geodetic Survey (NGS), is a consistent National coordinate system that defines latitude, longitude, elevation, scale, gravity, and orientation throughout the Nation, as well as how these values change with time.

There are over 800,000 control survey points in the U.S. Approximately 6,500 of these form the highest accuracy core of the system. They include Federal Based Network (FBN), Cooperative Based Network (CBN), and Continuously Operating Reference Stations (CORS) sites covering the U.S. and its territories.

The NOS MapFinder contains a subset of information on the FBN, CBN, and CORS points. For more information, visit the National Geodetic Survey web site.

An ArcIMS site is also available for viewing and obtaining survey data from NGS.

Continuously Operating Reference Stations

See Also the National Geodedic Survey at

Note: a nifty IMS is also available at This site displays the NGS Survey control Map