Resolution 1 of the 19th CGPM (1991)

Time standards and time comparisons

The 19th Conférence Générale des Poids et Mesures,

noting that the accuracy of clock comparisons has been greatly improved by the use of satellite techniques,

remarks that this accuracy

  • can be further improved by the better use of the satellite techniques already developed,
  • reveals the differences and systematic variations among atomic frequency standards,
  • allows a better synchronization of national time scales,


  • the construction of new primary caesium standards, the improvement of the frequency accuracy of existing primary standards and the study of the systematic differences in frequency which exist between them,
  • that the laboratories participating in International Atomic Time (TAI) stabilize the environmental conditions of each contributing clock, keep careful records of these environmental conditions and report them to the BIPM,
  • that the coordinates adopted for antennas used in single-way time comparison by satellite techniques correspond to their real position in the terrestrial reference system of the International Earth Rotation Service.

DOI : 10.59161/CGPM1991RES1E

The reader should note that the official version of this Resolution is the French text

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