No abstract

In November 2013 an International Key Comparison, CCM.G-K2, was organized in the Underground Laboratory for Geodynamics in Walferdange. The comparison has assembled 25 participants coming from 19 countries and four different continents. The comparison was divided into two parts: the key comparison that included 10 NMIs or DIs, and the pilot study including all participants. The global result given by the pilot study confirms that all instruments are absolutely coherent to each other. The results obtained for the key comparison confirm a good agreement between the NMI instruments. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

19 Lantmäteriet-the Swedish mapping, cadastral and land registration, Sweden

The second international comparison of absolute gravimeters was held in Walferdange, Grand Duchy of Luxembourg, in November 2007, in which twenty absolute gravimeters took part. A short description of the data processing and adjustments will be presented here and will be followed by the presentation of the results. Two different methods were applied to estimate the relative offsets between the gravimeters. We show that the results are equivalent as the uncertainties of both adjustments overlap. The absolute gravity meters agree with one another with a standard deviation of 2 μgal (1 gal = 1 cm/s 2 ). In 1999, a laboratory ( Fig. 5.1) dedicated to the comparison of absolute gravimeters was built within the WULG. The laboratory lies 100 m below the surface at a distance of 300 m from the entrance of the mine. The WULG is environmentally stable (i.e., constant temperature and humidity within the lab), and is extremely well isolated from anthropogenic noise. It has the power and space requirements to be able to accommodate up 16 instruments operating simultaneously. IntroductionMultiple absolute gravimeter comparisons are regularly carried out. Being absolute instruments, these gravimeters cannot really be calibrated. Only some of their components (such as the atomic clock and the laser) can be calibrated by comparison with known standards. The only way one currently has to verify their good working order is via a simultaneous comparison with other absolute gravimeters of the same and/or if possible even of a different model, to detect possible systematic errors.During a comparison, we cannot estimate how accurate the meters are: in fact, as we have no way to know the true value of g, we can only investigate the relative offsets between instruments. This means that all instruments can suffer from the same unknown and undetectable systematic error. However, differences larger than the uncertainty of the measurements, is usually indicative of a possible systematic error.For the second comparison in Walferdange, a few new procedures have been introduced. First, some of the participants accepted to take part in a