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NOAA’s National Geodetic Survey

What Is the National Spatial Reference System?

Continuously Operating Reference Stations


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New Study Shows NOAA’s Geodetic Services Worth $2.4 Billion Annually

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Elevating to a New Reference: Positioning Activities Worth $2.4 Billion Annually

GPS antennas

Hundreds of small antennas like this receive radio signals from Global Positioning System satellites, a sort of “flying” reference system. The receivers make up the Continuously Operating Reference System network, a vital part of the National Spatial Reference System.

For over 200 years, NOAA’s National Geodetic Survey (NGS) has defined and managed the National Spatial Reference System (NSRS). This coordinate system defines latitude, longitude, height, scale, gravity, orientation, and shoreline throughout the United States.

A new study now shows that the NSRS is delivering big benefits – a potential $2.4 billion each year – to the U.S. economy.

The Economic Impacts

In this recent study by Leveson Consulting, researchers analyzed the total economic value of all revenue generated from private surveying and mapping as well as from related services in the government and non-profit sectors. They also assessed the potential cost savings from improved accuracy of position and elevation data.

If you’ve ever used a hand-held Global Positioning System (GPS) device or a navigation system on the dashboard of a car to help you find your way, you’ve benefited from the NSRS. But you’ve also benefited in countless other ways as well, probably without even realizing it. The NSRS’s collection of over 1,500,000 positioning points and 1,300 Continuously Operating Reference Stations (CORS) is critical for transportation, navigation, and communication systems; land record systems; mapping and charting efforts; and defense operations.

The Leveson study shows that the CORS network, which provides Global Navigation Satellite System data to support three-dimensional positioning, meteorology, space weather, and geophysical applications, delivers an estimated $758 million per year in benefits. The study also indicates that an additional $522 million in annual economic benefits could be generated by the implementation of a new vertical reference system allowing users to determine more precise elevations using GPS.

A New Vertical Reference

GPS station helps ensure safe navigation

The National Spatial Reference System is essential for a host of activities that require highly accurate location and elevation data such as property surveys, utilities, and other siting public infrastructure such as bridges to ensure safe navigation.

This new vertical reference system will be the outcome of NOAA’s Gravity for the Redefinition of the American Vertical Datum, or “GRAV-D,” initiative. GRAV-D is underway to replace the existing North American Vertical Datum of 1988 (NAVD88). Vertical datums are used as a reference against which to base height measurements in order to know that all measurements start from the same “zero” and can therefore be compared.

NAVD88, the current national vertical datum, is anchored by less accurate, more costly survey monuments, meaning elevation errors ranging from 16 inches to six feet relative to sea level. GRAV-D will allow surveyors and scientists to use GPS to determine more precise and accurate elevations than currently possible, in less time and with less effort. When GRAV-D is successfully completed and the new elevation system is accessed using the CORS network, elevation errors will be reduced to less than one inch.

Improved elevation errors will have broad benefits, including improved floodplain mapping. These improvements could guide the placement of building structures and highways, help establish public safety requirements, and help determine locations of levees and evacuation routes. Approximately $240 million in costs could be saved annually through improved floodplain management.

As NOAA looks to the future, the agency continues to build on the spatial framework of our nation – the framework that provides the foundation for better commerce, a stronger economy, and safer communities.


Measuring the elevation of a hurricane evacuation route

Accurately measuring the elevation of this hurricane evacuation route in low-lying areas of coastal Louisiana is just one of many applications for the National Spatial Reference System.