National Geospatial Data Asset (NGDA) Continuously Operating Reference Stations (CORS)

The National Geodetic Survey (NGS), an office of NOAA's National Ocean Service, manages a network of Continuously Operating Reference Stations (CORS) that provide Global Navigation Satellite System (GNSS) data consisting of carrier phase and code range measurements in support of three dimensional positioning, meteorology, space weather, and geophysical applications throughout the United States, its territories, and a few foreign countries.

Surveyors, GIS users, engineers, scientists, and the public at large that collect GPS or GNSS data can use CORS data to improve the precision of their positions. CORS enhanced post-processed coordinates approach a few centimeters relative to the National Spatial Reference System, both horizontally and vertically.

The CORS network is a multi-purpose cooperative endeavor involving government, academic, and private organizations. The sites are independently owned and operated. Each agency shares their data with NGS, and NGS in turn analyzes and distributes the data free of charge. As of August 2018, the CORS network provides data from more than 2,000 active sites. CORS data holdings to include decommissioned stations, comes to a total of 2,718 sites. These sites are contributed by over 230 different organizations, and the network continues to expand.

The CORS data set enables users to attain centimeter-level positioning for points of interest and can be used to measure crustal motion, moisture content for the lower atmosphere, and total electron content (TEC) in the upper atmosphere.

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The data includes daily GPS or GNSS observables along with computed geometric coordinates (Latitude, Longitude, Ellipsoid Height) for each station.

Information on the details of the data sets is available at: https://www.ngs.noaa.gov/CORS/

Use at your own risk

While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

https://www.ngs.noaa.gov/CORS/

https://geodesy.noaa.gov/CORS/

ftp://geodesy.noaa.gov/cors/

https://alt.ngs.noaa.gov/CORS

ftp://alt.ngs.noaa.gov/cors/

https://geodesy.noaa.gov/UFCORS/

https://www.ngs.noaa.gov/CORS/standard1.shtml

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While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

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The GPS or GNSS data collected at these stations are made available to the public by NGS in Receiver INdependent EXchange (RINEX) format. The data include observation, meteorological (where available), navigation/ephemeris, station logs and NGS coordinate files for the stations. Most data are available within 1 hour from when they were recorded at the remote site, and the rest have a delay of 24 hours.

Receiver and Antenna is at least dual frequency, receiving L1 and L2 signals.

Receiver tracks at least ten satellites above 0 degrees.

Receiver provides L1 and L2 full wavelength carrier phase.

Receiver must have be accepted as suitable for inclusion into International GNSS Service or IGS network

Antenna code, antenna model + radome, must be permitted by NGS for inclusion into the CORS network.

The carrier phase observations are accurate to a few centimeters, once biases have been removed.

For further information, see https://geodesy.noaa.gov/CORS//coords.shtml

+/- 2.0 cm

+/- 4.0 cm

The carrier phase observations are accurate to a few centimeters, once biases have been removed.

For further information, see https://www.ngs.noaa.gov/CORS//coords.shtml

The National Geodetic Survey, or NGS, publishes coordinates for CORS in several reference frames. This includes the current global reference frame from the International GNSS Service, or IGS, and with respect to the National Spatial Reference System, NSRS, realizations of the North American Datum of 1983, NAD 83, as defined by NGS. Reference frames are updated periodically as according to policy: http://geodesy.noaa.gov/INFO/Policy/files/042011_CORS_Coordinate_Policy.pdf

To become part of the NOAA CORS Network, each station must meet NGS' station criteria standards and maintain its integrity. See https://geodesy.noaa.gov/CORS/Establish_Operate_CORS.shtml document. Data is quality controlled by NGS before it is distributed to the public. In addition, NGS publishes position and velocity values for each CORS in both the global reference frame and in the National Spatial Reference System. More information about the NOAA CORS Network is available at: https://geodesy.noaa.gov/CORS/

NGS defines thresholds during processing.

NGS makes every effort to archive missing data.

NGS CORS dataset is ingested at two geographically separate and independent facilities, providing Continuity of OPerations (COOP). RINEX data is held and staged at the National Centers for Environmental Information (NCEI) for 30 days. NGS is allowed to make changes to that data holding at NCEI within the 30 day window. NCEI transfers data for archive to NOAA's Comprehensive Large Array-data Stewardship System (CLASS) after the 30 day period. NGS is the authority on the CORS data set, and can replace or remove archived files at its discretion.

CORS data is processed at an hourly or daily cadence, dependent a particular stations' retrieval frequency. Hourly data is deleted one day after daily file is created.