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

Results from geophysical explorations of three deep valleys, selected from different tectonic regimes in the Eastern Alps (Ö tz-, Oichten-, and Drau Valley), are presented and discussed. Ongoing tectonic deformation may use tectonic structures related to these valleys. However, seismic activity is low there. During the Würm ice age, the thickness of the ice cover ranged between 300 and 1,500 m above present ground elevation. The geophysical investigations comprised reflection seismology, gravityand resistivity surveys. The maximum depth down to the erosional base of the valleys varies from *340 to 700 m. Distinct layer packages of the valley-infill at depths greater than 250 m were termed ''old valley-fill''. Geophysical parameters and a comparison with the reflection seismic image of an intermediate layer at the recent Pasterze glacier suggest that the top of the ''old valley-fill'' represents the glacier bed during the decay of the Würm glaciation. Deep erosion is not related to high basal shear stress. The confluence of tributary glaciers is apparently not a significant factor for deep erosion in our examples of deep alpine valleys. We conclude that deep erosion may be related to high water pressure at the glacier bed, supported by specific processes of tectonic weakening.

The International Comparison of Absolute Gravimeters 2009 (ICAG2009) was carried out in September 2009 at the International Bureau of Weights and Measures (BIPM). The ICAG2009 and its data processing were performed in accordance with the agreed Technical Protocol which was approved by the Steering Committee. The pilot laboratory (BIPM) evaluated the final results of the key comparison from the measurements made at the BIPM in the framework of ICAG2009. A pilot study run in parallel allowed evaluation of the offsets for absolute gravimeters from institutes not fulfilling the requirements for participating in the key comparison. The gravity values at the five stations, and the offsets for each absolute gravimeter, were obtained by a weighted least squares fit. The results indicate that all participating gravimeters are consistent within their expanded 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).

The CCM.G-K2.2017 comparison was organised for the purpose of determination of the degree of equivalence of the national standards for free-fall acceleration measurement. The comparison was held in the Changping Campus of National Institute of Metrology China (NIM), from October to November in 2017. This is the first time that such a comparison is organized outside of the Europe continent and establishes a new global comparison sites in China [1, 2]. This comparison is also the largest ever organized with the participation of 13 instruments. Dr. Shuqing Wu, Dr. Jinyang Feng and Mrs. Chunjian Li from the NIM were in charge of the local organization of the comparison and of the elaboration of the results. NIM was the Pilot Laboratory under the leadership of Dr. Shuqing Wu. The comparison steering committee (SC) is composed of Prof. Olivier Francis (LU), Dr. Vojtech Pálinkáš (VÚGTK/RIGTC), Dr. Derek van Westrum (NOAA-NGS), Dr. Reinhard Falk (BKG) and Dr. Shuqing Wu (NIM). The SC is supported and consulted by the CCM-WGG Chair, Prof. Alessandro Germak (INRIM). The comparison was organized in accordance with the CIPM MRA-D-05 of the Consultative Committee on Mass and Related Quantities (CCM).