Prediction of vertical gravity gradients using gravity and elevation data

Abstract

The vertical gravity gradients play an important role in the reduction of absolute gravity measurements and in the geoid determination, too. In order to enhance the precision of the gravity reductions and the geoid computations, the difference between the vertical gravity gradient of the real and the normal gravity fields should be taken into account. In this paper the vertical gravity gradients are computed by prism integration using constant density for the crustal masses and a high-resolution (gridsize 10m) digital elevation model to represent the topography in the Sóskút test area. On the other hand, gravity gradients are also predicted from point gravity data using spectral techniques. The calculated gradient values are compared to each other, and are validated using terrestrial measurements at 6 points in the Sóskút test area. The measurements of the vertical gravity gradients were carried out by the Loránd Eötvös Geophysical Institute and have an accuracy better than 80E, and are within the interval of 3189-3805E. The vertical gradient values calculated from the DEM range from 2926 to 3330E, and the values fitted the measured values with the standard deviation of ±244E, and the maximal residual of 547E. The vertical gravity gradient has been investigated by Csapó-Papp (2000) in the study area, using the lithospheric model developed by Papp. Their results fitted to the observed values with the standard deviation of ±561E, with a maximal residual of –1298E.