Long-term reproducibility, Uncertainty, Popsat opakovana mereni
The repeated absolute gravity measurements are a reliable tool for monitoring geodynamic phenomena.
To get a full benefit from these measurements, it is necessary to have, among others, a good knowledge of the instrumental accuracy and of environmental effects on gravity as the main disturbing effect.
The data of 8 years of AG measurements and 2 years of SG measurements at the Pecný station allowed us to determine the accuracy parameters of the FG5#215 such as repeatability, reproducibility and uncertainty. The important parameter from the geodynamic point of view is mainly the “long-term” reproducibility and uncertainty. The “long-term” reproducibility represents the accuracy of gravity measurements with the same meter at the same site as a typical situation at a geodynamic station. The estimate of this parameter for the FG5#215 is 0.7 mGal (instrumental part). The uncertainty of the FG5 gravimeters of about 2.5 mGal should be considered mainly due to systematic errors between individual gravimeters. For delicate geodynamic studies, such as crustal deformations, it is useful to use only gravimeters for which the variations of systematic errors are well determined from regular participations in international comparison measurements of absolute gravimeters and from regular parallel measurements with a SG at a reference station. It is recommended to perform repeated measurements always with the same absolute gravimeter at the given site.