Akademik Veri Yönetim Sistemi
BULLETIN OF GEOPHYSICS AND OCEANOGRAPHY, cilt.63, sa.2, ss.237-248, 2022 (SCI-Expanded)
The theoretical value of the free-air Vertical Gravity Gradient (VGG) is used when the measured or modelled VGG are not available. The errors of using the theoretical VGG become larger in rough topography and propagate into the gravimetric reductions and geoid determination. As measuring the VGG is difficult and time-consuming, the VGG can be modelled. Here, we present a VGG model developed by the 3D least-squares collocation using the remove-compute-restore method. The accuracy of the VGG model is validated over western Turkey by in-situ VGG measurements at 159 ground points. The results show a satisfactory agreement of about 190 E??tv??s between the modelled and the measured VGG values. Moreover, the variability of the modelled VGG with respect to the topographic elevations are also investigated. At higher than 1000 m elevations, the deviation from the theoretical value becomes significant. The accuracy of the measurements improves 30 ??Gal when the modelled VGGs are used for the gravimetric reduction of the absolute gravity value, from the measurement point to the ground as transferred height. To conclude, instead of the theoretical VGG, the use of the VGG model is suggested for reducing the absolute gravity values particularly in rough topography.