Earth Orientation Parameters Data Documentation

• Data used:

  1. Files:

     ftp://ftp.nga.mil/pub2/gps/eopp36/yyyyeopp/EOPPyddd.TXT

     Contains: NGA coefficients for the upcoming week (see Documentation)

     Updated: Daily
     Each day a file of the form EOPPyddd.TXT is produced where y is the last digit of the year and ddd is the day of the year.

  2. Files:

     ftp://hpiers.obspm.fr/iers/series/opa/eopc04
     ftp://hpiers.obspm.fr/iers/series/opa/eopc04_IAU2000

     Contains: Observed data (x, y, UT1-UTC, LOD, δΔψ, δΔε), (δX, δY)

     Updated: Daily

  3. Files:

     http://maia.usno.navy.mil/ser7/tai-utc.dat

     Contains: TAI-UTC data

     Updated: With new leap seconds

• Data documentation can be found at:

  • Earth Orientation Parameter Prediction Description (NGA Coefficients)

    http://earth-info.nga.mil/GandG/sathtml/eoppdoc36.html

  • EOP C04 Series
    

    http://hpiers.obspm.fr/eoppc/eop/eopc04/C04.guide.pdf

  • Explanatory Supplement to IERS Bulletins A and B
    

    http://hpiers.obspm.fr/iers/bul/bulb/explanatory.html

  • Note to IERS C04 and Bulletin A users
    

    ftp://ftp.iers.org/products/publications/messages/message_198.txt

• Process:

  1. NGA coefficients for the coming week are obtained from Source 1.

  2. Observed data is obtained from Source 2.

  3. Predicted data is also obtained from Source 2 and goes out 180 days.

  4. Delta Atomic Time (TAI-UTC)/leap second data is obtained from Source 3.

• Keywords:

  • VERSION major.minor
    Provides major and minor version of current data format.

  • UPDATED yyyy Mon dd hh:mm:ss UTC
    Provides UTC date and time of current update.

  • BEGIN NGA_COEFFICIENTS
    END NGA_COEFFICIENTS
    Marks beginning and end of NGA coefficients.

  • NUM_OBSERVED_POINTS number
    Indicates number of records of data in the Observed Data section.

  • BEGIN OBSERVED
    END OBSERVED
    Marks beginning and end of the Observed Data section.

  • NUM_PREDICTED_POINTS number
    Indicates number of records of data in the Predicted Data section.

  • BEGIN PREDICTED
    END PREDICTED
    Marks beginning and end of the Predicted Data section.

• Observed and Predicted Data Format:

  ------------------------------------------------------------------------------------------------------
  FORMAT(I4,I3,I3,I6,2F10.6,2F11.7,4F10.6,I4)
  ------------------------------------------------------------------------------------------------------
  Column
  000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000111
  000000000111111111122222222223333333333444444444455555555556666666666777777777788888888889999999999000
  123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012
  ------------------------------------------------------------------------------------------------------
  yyyy dd mm MJD      x         y        UT1-UTC     LOD        dPsi    dEpsilon    dX        dY     DAT
  ------------------------------------------------------------------------------------------------------
  yyyy dd mm nnnnn +n.nnnnnn +n.nnnnnn +n.nnnnnnn +n.nnnnnnn +n.nnnnnn +n.nnnnnn +n.nnnnnn +n.nnnnnn nnn
  ------------------------------------------------------------------------------------------------------
  2000 01 01 51544  0.043251  0.377681  0.3555151  0.0009068 -0.050825 -0.002257 -0.000222  0.000124  32
  ------------------------------------------------------------------------------------------------------
  

  Columns	Description
  001-004	Year
  006-007	Month (01-12)
  009-010	Day
  012-016	Modified Julian Date (Julian Date at 0h UT minus 2400000.5)
  018-026	x (arc seconds)
  028-036	y (arc seconds)
  038-047	UT1-UTC (seconds)
  049-058	Length of Day (seconds)
  060-068	δΔψ (arc seconds)
  070-078	δΔε (arc seconds)
  080-088	δX (arc seconds)
  090-098	δY (arc seconds)
  100-102	Delta Atomic Time, TAI-UTC (seconds)