In the framework of the regional EURAMET.M.G-K2 comparison of absolute gravimeters, 17 gravimeters were compared in November 2015. Four gravimeters were from different NMIs and DIs, they were used to link the regional comparison to the CCM.G.K2 by means of linking converter. Combined least-squares adjustments with weighted constraint was used to determine KCRV. Several pilot solutions are presented and compared with the official solution to demonstrate influences of different approaches (e.g. definition of weights and the constraint) on results of the adjustment. In case of the official solution, all the gravimeters are in equivalence with declared uncertainties. 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 the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
In order to define gravity datum and gravity scale in the Kingdom of Saudi Arabia (KSA), an absolute gravity network, called KSA Absolute Gravity Network (KSA-AGN), comprising of 25 sites distributed countrywide was observed from January 2013 to February 2013. Two stations were installed at each network site: one inside the building and one outside. Micro-g A10 (#029) portable absolute gravimeter was used for data acquisition of two setups of ten sets each at both inside and outside stations. Set scatters for A10 setups are usually less than ±3 μGal, and the differences between two setups vary in the range of −8 to 5 μGal. The weighted mean of the two setups were calculated as unique absolute gravity value and its uncertainty at the stations. Seven of the stations (five inside and two outside) were collocated by Micro-g FG5 (#111) absolute gravimeter having 24 sets for each setup. Set scatters for FG5 setups are less than ±4 μGal almost like A10 setups. However, we obtained the total uncertainty of FG5 and A10 measurement about ±2 and ±6 μGal, respectively. Furthermore, to reduce measured absolute gravity from the reference height to any height, gravity gradients over both inside and outside stations were measured by using two Scintrex CG5 (#922 and #924) relative gravimeters. Average CG5 gradient at the outside stations is about 3.1 μGal/cm, satisfying the free air gradient in the country. Differences between A10 and FG5 absolute gravities at 72 cm vary between −3.8 and 9.5 μGal at seven stations. Excluding the outside stations, we obtained the differences from −3.8 to 5.5 μGal at inside stations.
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