Absolute gravity determination with JILAG-3 — improved data evaluation and instrumental technics

In addition to the on-line data evaluation during the measurements with the absolute gravity meter JILAG-3, a subsequently more intensive examination of the measured time/distance data pairs is performed. This allows an additional assessment of the gravity results, the station quality and the measurement conditions. Sinusoidal disturbances in the raw data deteriorate the determination of gravity. Incoming microseisms affect the mean result of the free-fall experiments randomly after a large number of measurements. Instrumental vibrations of the gravity meter during the measurement procedure may influence the gravity result systematically. A station comparison indicates that a 30 Hz frequency is triggered by JILAG-3 itself and influences the measurements depending on the stability of the foundation. Using a mathematical filter it is possible to separate the deteriorations from the gravity acceleration. Up to now an improvement in the absolute accuracy of gravity after filtering could not be proved, but an increase of the precision is indicated.