Continuously Operating Reference Station (CORS)
Entry ID:
gov.noaa.ngdc.G10019
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Summary
ABSTRACT: The National Geodetic Survey (NGS), an office of NOAA's National Ocean Service (NOS), coordinates a network of geodetic-quality continuously operating reference stations (CORS) that provide Global Positioning System (GPS) carrier phase and code range measurements in support of 3-dimensional positioning activities throughout the United States and its territories. The positions of ... these CORS sites help define the National Spatial Reference System (NSRS). The NSRS provides a consistent national coordinate system to support mapping, charting, navigation, boundary determination, property delineation, infrastructure development, resource evaluation surveys, and scientific applications. The CORS system enables positional accuracies that approach a few centimeters relative to the NSRS, both horizontally and vertically.
PURPOSE: The CORS program primary objective is to allow users to improve their positional coordinates in post-processing activities by providing access to the CORS data set and software tools such as OPUS. In other applications, CORS data is used for modeling the water vapor content in the troposphere and for modeling total electron content in the ionosphere.
SUPPLEMENTAL INFORMATION: NGS has two facilities: the main facility in Silver Spring, MD and the parallel facility in Boulder, CO. Both CORS facilities provide geodetic-quality GPS data on a continuous basis from sites operated by: 1. Federal Aviation Administration's Wide Area Augmentation System (referred to as "WAAS" sites) 2. U.S. Coast Guard Maritime and Nationwide Differential GPS (M/NDGPS) Service (referred to as "USCG" sites) 3. other government, state, or private agencies (referred to as "Internet" sites) NGS also provides services to users that allow them to apply their data to the National Spatial Reference System frame (NSRS) using tools such as the Online Positioning User Service (OPUS) at http://www.ngs.noaa.gov/OPUS/ site. Note: The term Global Navigation Satellite Systems (GNSS) has been created to reference all navigation satellite systems. GNSS encompasses the United States' GPS system, the Russian Federation GLONASS system, and any future systems such as Europe's Galileo or China's Compass.
CURRENTNESS REFERENCE: ground condition
SPATIAL DATA ORGANIZATION INFORMATION
Indirect Spatial Reference: CORS data reference the U.S. and its territories, with selected areas in the Caribbean, Central America, Iraq, and Africa.
Geographic Coverage
Spatial coordinates
| N: 90.0 |
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S: -90.0 |
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E: 180.0 |
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W: -180.0 |
Data Set Citation
Dataset Creator:
DOC/NOAA/NOS/NGS > National Geodetic Survey, National Ocean Service, NOAA, U.S. Department of CommerceDOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce (comp.)
Dataset Title:
Continuously Operating Reference Station (CORS)
Dataset Release Date:
1994-02-09
Dataset Release Place:
Silver Spring, MD
Dataset Publisher:
National Geodetic Survey (NGS)
Online Resource:
http://www.ngs.noaa.gov/CORS/
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Temporal Coverage
Location Keywords
Science Keywords
ISO Topic Category
Project
Quality
ATTRIBUTE ACCURACY REPORT: The carrier phase observations are accurate to a few centimeters, once biases have been removed.
LOGICAL CONSISTENCY REPORT: To become part of the CORS network, the GPS site must meet or exceed the NGS site criteria. Further detail is found at the http://www.ngs.noaa.gov/CORS/Establish_Operate_CORS.html website. Once a site is established, the output ... is passed through NGS' validation process. Data is only made available if the site successfully completes this validation. Metadata, such as site log information for each site, is recorded and added into the NGS database and made available online. Data is ingested into the CORS system at an various rates (instantly, hourly, daily) and processed with the UNAVCO software program 'teqc' to input the official NGS coordinates and output a daily RINEX file. NGS monitors through daily solutions of the GPS CORS network (24h of observed data) the quality of the computed coordinates. As a byproduct, NGS compiles time series plots of the variation of the CORS ITRF00 coordinates with respect to the published values in the local horizon reference frame (n, e, u), spanning a period of 60 days. It should be emphasized that all plots were corrected for the effect of station velocity. The 60-day plots are found at the ftp://www.ngs.noaa.gov/cors/Plots/plots.html site
COMPLETENESS REPORT: Data is reviewed for completeness. Automated routines perform daily checks of missing hours. Monitoring tools allow easy visualization of missing hours and days, and data can also be fetched manually. In the event that a site position deviates beyond expected values, for example: a jump is found on the 60-day plot, then the site operator is contacted. If a site does not output data for 30 consecutive days, NGS policy is to suspend the site by flagging it as a 'non-operational' state. These sites are reincorporated into CORS once repairs are done. In the event that the site is inoperable, it is flagged as 'decommissioned'. Any faulty data is removed from online servers. Coordinates and velocities are periodically updated to be consistent with the most current reference frames, or to update sites after an event such as a large earthquake. More information can be found at the http://www.ngs.noaa.gov/CORS/coordinates/ website.
HORIZONTAL POSITIONAL ACCURACY REPORT: The horizontal coordinates of the GPS site, specifically the GPS antenna location, are accurate to about a centimeter once biases are removed.
VERTICAL POSITIONAL ACCURACY REPORT: The vertical coordinates of the GPS site, specifically the GPS antenna location, are accurate to about 2 centimeters.
LINEAGE/PROCESS STEP:
PROCESS DESCRIPTION: WAAS and USCG sites are ingested as hourly files. Any raw receiver data are converted by NGS into RINEX via the software program 'teqc'. Hourly files are processed to create a single daily file and NGS coordinates are input via the 'rtconfig' application. Internet sites are ingested in either hourly or daily files. Any raw receiver data are converted by the user either software provided by the manufacturer or by applying the UNAVCO software 'teqc' to output a RINEX formatted file. Hourly files are processed to create a single daily file and NGS coordinates are input via the 'rtconfig' application. NGS keeps two versions of the RINEX format files available on the CORS online servers. The first version is the original RINEX observation file recorded at the original sampling rate, and is gzip-compressed. The second version is a Hatanaka-compacted RINEX file, at a 30-second sampling rate, and is UNIX-compressed. The Hatanaka-compaction is a common compression scheme designed for GPS use. Each version has a different file type according to the age of the file. The information below shows the chronological transition of the version types. VERSION 1: RINEX original form *Day 0 (current day) consists of Type H1: Hourly files at original sampling rate. *Days 1-30 consists of Type D1: Daily file at original sampling rate. *Days > 30 consists of Type D2: Daily file decimated to a sampling rate of 30-seconds. VERSION 2: RINEX Hatanaka-compacted form *Day 0 (current day) consists of Type H2: Hourly files decimated to a sampling rate of 30-seconds. *Day 1-30 consists of Type D2: Daily file decimated to a sampling rate of 30-seconds. *Day > 30 consists of Type D2: Daily file decimated to a sampling rate of 30-seconds.
PROCESS DATE: 19940209
Access Constraints
ACCESS CONSTRAINTS: None
DISTRIBUTION LIABILITY: 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.
Use Constraints
None
Ancillary Keywords
Data Set Progress
Data Center
Distribution
Distribution Format:
ASCII 2.10
Fees:
None
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Personnel
FRANCINE
COLOMA
Role:
TECHNICAL CONTACT
Role:
DIF AUTHOR
Phone:
303-497-3692
Fax:
303-497-6513
Email:
Francine.Coloma at noaa.gov
Contact Address:
325 Broadway
City:
Boulder
Province or State:
CO
Postal Code:
80305
Country:
USA
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Related URL
Link:
GET DATA
Description:
FTP site from CORS parallel facility in Boulder, CO
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Creation and Review Dates
DIF Creation Date:
2008-01-11
Last DIF Revision Date:
2008-02-26
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Links
