Annex 1: Description of IERS Conventions Requirements (By Chapter)

The elements of the publication, as outlined in Annex 2, are based on the resolutions of international scientific unions. The publication itself appears both in hard copy published at intervals of several years, or whenever a major change is needed, and in electronic revisions with well-documented revision dates containing upgrades, corrections, introduction of explanatory parts, new software implementations, and possible addition of models that do not affect the principal characteristics.


  • Chapter 1: General definitions and numerical standards
    • Ensure self-consistency and uniformity of IERS definitions and standards with internationally recognized standards provided by the International Astronomical Union (IAU) Division A Working Group on Numerical Standards and the Système International d'Unités (SI).
  • Chapter 2: Conventional celestial reference systems and frames
    • Provide details regarding the definition of the International Celestial Reference System (ICRS) as well as its realization in the International Celestial Reference Frame (ICRF) and the means to access it.
    • Provide information on recently released ephemerides and recommend ephemerides to ensure consistency with definitions of the ICRF.
  • Chapter 3: Terrestrial reference systems and frames
    • Provide details regarding the definition of the International Terrestrial Reference System (ITRS) as well as its current realization in the International Terrestrial Reference Frame (ITRF) and the means to access it.
  • Chapter 4: Transformation between the International Terrestrial Reference System and Geocentric Celestial Reference System
    • Describe, in detail, procedures to transform coordinates between the International Terrestrial Reference and Geocentric Celestial Reference Systems in accord with current practices recommended by the IAU. Descriptions must include references to recommended software to be used as provided by IAU Division A Working Group on Standards of Fundamental Astronomy.
    • Provide test cases for use in validating software.
  • Chapter 5: Geopotential
    • Describe and provide references to the most current geopotential model consistent with the definition of the ITRF.
    • Provide description of the most current tidal models along with references to software to be used to implement the model.
  • Chapter 6: Displacement of reference points
    • Provide detailed description of low-frequency polar motion model to be used in conjunction with Chapter 5.
    • Provide models describing displacement of reference points due to tidal loading and temperature effects in antennas including appropriate software.
    • Provide test cases for use in validating software.
  • Chapter 7: Tidal variations in Earth's orientation
    • Describe and provide software to implement models of the effects of Earth tides on the Earth's rotation and polar motion at all appropriate frequencies.
    • Provide test cases for use in validating software.
  • Chapter 8: Models for atmospheric propagation delays
    • Describe and provide software to implement models of atmospheric and ionospheric delays affecting the treatment of observations used to produce IERS Earth orientation parameters.
    • Provide test cases as appropriate for use in validating software.
  • Chapter 9: General relativistic models for space-time coordinates and equations of motion
    • Review current chapter material to ensure compliance with recommendations of the International Telecommunications Union (ITU) and the IAU regarding relativistic time transfer and the effects of general and special relativity on time comparisons and synchronization.
    • Provide software and test cases as appropriate.
  • Chapter 10: General relativistic models for propagation
    • Review current chapter material to ensure compliance with recommendations of the IAU regarding the effects of general and special relativity.
    • Provide software and test cases as appropriate.