The Bureau International des Poids et Mesures (BIPM), Sèvres, France, hosted the 7th International Comparison of Absolute Gravimeters (ICAG) and the associated Relative Gravity Campaign (RGC) from August to September 2005.ICAG 2005 was prepared and performed as a metrological pilot study, which aimed:(1) To determine the gravity comparison reference values;(2) To determine the offsets of the absolute gravimeters; and (3) As a pilot study to accumulate experience for the CIPM Key Comparisons.This document presents a complete and extensive review of the technical protocol and data processing procedures. The 1st ICAG-RGC comparison was held at the BIPM in 1980-1981 and since then meetings have been organized every 4 years.In this paper, we present an overview of how the meeting was organized, the conditions of BIPM gravimetric sites, technical specifications, data processing strategy and an analysis of the final results. This 7th ICAG final report supersedes all previously published reports.Readings were obtained from participating instruments, 19 absolute gravimeters and 15 relative gravimeters. Precise levelling measurements were carried out and all measurements were performed on the BIPM micro-gravity network which was specifically designed for the comparison.

A high-precision laser gravimeter for measuring the absolute value of gravitational acceleration by the free-fall method has been built in the Siberian Branch of the USSR Academy of Sciences (Novosibirsk). The use of a free-fall interferometer illuminated by a He-Ne laser stabilized by an iodine absorption cell ('"I2) together with high-speed electronic counters and a rubidium frequency standard, plus constructive measures aimed at reducing the action of non-gravitational forces, provide an accuracy of measurements better than lo-' m.s-2. In practice, the relative measurement error in g, as determined from convergence of the results of repeated measurements, is below 4 parts in l o 9 (4 xThe gravimeter is used for geophysical experiments and in the investigation of non-tidal variations of the Earth's gravitational field. m.s-').

The fifth in the series of International Comparisons of Absolute Gravimeters (ICAG) was held at the Bureau International des Poids et Measures (BIPM) in November 1997. Fifteen absolute gravimeters participated in the comparison. The mean gravity value obtained at station A (0.9 m) at the BIPM was found to be 980 925 707.8 µGal with a standard uncertainty of 2.8 µGal. This is consistent with the results obtained in previous comparisons at this site. Conclusions based on the analysis of the present results and proposals for future activities are presented.

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