Relative gravimeter calibration system for high accurate applications

Abstract

A best possible accuracy for the calibration of relative gravimeters is often required to achieve the objectives of state-geodetic and geo-scientific surveys. A scale inaccuracy for relative gravimeters of 1·10-4 is striven for which allows, e. g., to detect small vertical movements of the Earth’s surface or to avoid misinterpretation of observations showing apparent variations due to uncertain calibration of the relative meters. Recently, the Gravity Meter Calibration System Hannover has been improved with respect to its most important parts: the Harz calibration line (3 absolute gravimetric points) and the Vertical Gravimeter Calibration Line Hannover (VGCH, 20-storey building, 20 relative gravimetric points). For this Upgrade 2017, only “state-of-the-art” measurements with gravimeters from Scintrex (Canada) and ZLS Corporation (USA) have been used. For the two calibration lines, the Upgrade 2017 replaces the solution from 2004 which was based on measurements with LaCoste-Romberg instruments only. In the VGCH, the base connection 210-370 (1st to 17th storey, elevator for transportation) has been obtained with a standard deviation of 11 nm/s². The inaccuracy between adjacent points varies between 5 and 10 nm/s² for the points below the 18th storey. The scale inaccuracy of the Harz calibration line as well as of the VGCH is estimated to be 2·10-4 (expanded uncertainty, confidence interval 95%).