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U.S. DEPARTMENT OF COMMERCE | National Oceanic and Atmospheric Administration | National Ocean Service

The GPS precise orbits are derived using 24 hour data segments from the global GPS network coordinated by the International GPS Service (IGS).  The reference frame used in the computation is the International Earth Rotation Service Terrestrial Reference Frame (ITRF). In addition, an informational summary file is provided to document the computation and to convey relevant information about the observed satellites, such as maneuvers or maintenance.

The National Geodetic Survey (NGS) is one of several analysis centers around the globe to contribute its precise orbit. When the orbit is complete it is submitted to the International GPS Service (IGS) for inclusion into its final product, the IGS Precise Orbit.  This precise orbit is considered the International standard and should be used when there is a need for a precise orbit.   It is not made available until a full GPS week has been completed.  For example, Sunday through Friday's orbits will not be made available until Saturday's orbit is ready.  The IGS also supplies the Rapid Orbit available the next day and the Ultra Rapid Orbit which is available every 12 hours.

  1. GPS Naming Convention
  2. Information
  3. Analysis Strategy Summary
  4. NGS Rapid Orbits (1 day latency)
  5. Precise Orbits
    • NGS Precise Orbits
      NOTICE - Beginning Dec. 26, 2004 NGS had begun producing the precise orbits in a new and improved manner. Along with this improvement the orbits no longer have the overlap on each end. Without this overlap the the EF18 binary files should not be joined. To join daily orbits, you should use the program cat_sp3 to join the sp3 files. Also the Sum file is no longer produced.
      The NGS orbit (precise and rapid) is only one of several orbits that is used to create the IGS (precise and rapid) orbit, it is recommended that you use the IGS orbit.
      • constrained 24 hour file - sp3
      • this file was the one uploaded to the USCG Navcen
      • file named by year, month and day
    • IGS Precise Orbits (~ 15 day latency)
      • minimally constrained 24 hour file - sp3
      • file named by GPS Week Number
      • ultra rapid available here
  6. Orbit Utilities
  7. SP3 Format
  8. GPS Calendar
  9. USCG Navigation Center

GPS Links:

GPS Bibliographies
National Geodetic Survey's Continuously Operating Reference Stations (CORS)
Related Geodetic Resources
Transform between height systems with GEOID99

NOAA's Forecast Systems Lab (GPS derived precipitable water vapor)
U.S. Coast Guard's Navigation Center
U.S. Naval Observatory's GPS Data & Information
Univ. of California's Scripps Orbit and Permanent Array Center
Southern California Integrated GPS Network
Jet Propulsion Lab
International GPS Service
Goddard Space Flight Center's Crustal Dynamics Data Information System
Canadian Active Control System
International Earth Rotation Service (IERS)
University NAVSTAR Consortium (UNAVCO)
Geography and Environment Gateway (GEsource)
Physical Sciences Information Gateway (PSIgate)

Orbiteers

Bill Kass
Bob Dulaney

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anim earth National Geodetic Survey - Don Haw
Last modified: June 8, 2005