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IVS EOP Format

Version 2.1 (last updated: 2009-01-12)

File names ending with .eops contain nutation offsets in dpsi, deps with respect to the IAU1980 nutation model. File names ending with .eoxy contain nutation offsets in dX and dY with respect to the IAU2006 nutation model (the model should exclude free core nutation).

Files are free format with fields separated by at least one blank.


Format Notation



1MJD of the measurement (with at least 5 decimal digits)

Earth Orientation

2x of the pole (arcseconds)
3y of the pole (arcseconds)
4UT1-UTC (seconds)
5dpsi or dX (milliarcseconds)
6deps or dY (milliarcseconds)
Uncertainty of Earth Orientation and Nutation
7uncertainty in x (arcseconds)
8uncertainty in y (arcseconds)
9uncertainty in UT1-UTC (seconds)
10uncertainty in dpsi or dX (milliarcseconds)
11uncertainty in deps or dY (milliarcseconds)
12wrms residual delay of the session in ps (preferably integer)
13correlation coefficient: x, y
14correlation coefficient: x, UT1
15correlation coefficient: y, UT1
16correlation coefficient: dpsi/deps or dX/dY
17number of observables
186 character session code according to the 2nd column of IVS master schedules, e.g for 2017: master17.txt
19span of the observation (in hours)
Rates of Earth Orientation and Nutation
20x rate of the pole (arcseconds/day)
21y rate of the pole (arcseconds/day)
22excess length of day (LOD) (seconds), see comment below
23dpsi rate (milliarcseconds/day)
24deps rate (milliarcseconds/day)
Uncertainty of Rates of Earth Orientation and Nutation
25uncertainty in x rate (arcseconds/day)
26uncertainty in y rate (arcseconds/day)
27uncertainty in LOD (s)
28uncertainty in dpsi rate (milliarcseconds/day)
29uncertainty in deps rate (milliarcseconds/day)
Configuration of network employed for these Results
30sequence of two-character IVS station identifiers as maintained in IVS master control file ns-codes.txt (no blanks between stations) e.g. TsWzWfTcGcFt45Oh, TsWzNy or NyTs N.B.: There may be several lines for an individual session identifying different station configurations


  • For the EOP rates, days are in 86400 SI seconds.
  • The lines starting with characters "! # or *" are considered as comments.
  • Although it is inconsistent to have LOD in the group of rates due to the toggling of the sign, it is maintained here for consistency with other space techniques.
    LOD = UT1(n) - UT1(n+1) with n in days. LOD has the same magnitude but opposite sign of the UT1-UTC rate or the UT1-TAI rate, which are normally determined in VLBI analyses and given in seconds/day.

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