Impact Estimation and Filtering of Disturbances in FG5 Absolute Gravimeter Observations

Martin Orlob, Alexander Braun

Department of Geosciences, School of Natural Sciences and Mathematics, The University of Texas at Dallas, Richardson, USA.

DOI: 10.4236/ijg.2013.42028                

Abstract

Instrumental and environmental disturbances do affect FG5 absolute gravimeter observations and the estimated gravity values, sometimes to the degree that entire measurement campaigns are discarded. We propose a method which moves towards the re-assessment of previously discarded observations. Once an estimate of the frequency and amplitude of a disturbance in a FG5 data set exists, the proposed method can estimate its impact on the estimated gravity value. This is performed through a Gaussian Bell Summation approach of the functional relationship between disturbance frequency and standard deviation of gravity. The filtering of the identified disturbance is realized through a modification of the functional model of the equation of motion in the least squares adjustment of FG5 observations. The results reveal that the Gaussian Bell Summation approximates the frequency—gravity impact relationship sufficiently well with negligible uncertainties, while the accuracy of the detected disturbance frequency defines a limiting factor for the gravity impact estimation. A realistic disturbance of 15 Hz with an amplitude of 1.5 nm had an impact of ≈48 [μGal] on the gravity estimate. The proposed filter approach reduced the impact to ≈12 [μGal], with the remaining effect being almost entirely associated to the uncertainty in disturbance frequency detection.

Keywords

FG5 Absolute Gravimetry; Gravity; Disturbance Filtering; Gaussian Bell Summation; Least Squares Adjustment

Conflicts of Interest

The authors declare no conflicts of interest.

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