The role of near topography and building effects in vertical gravity gradients approximation

The gravitational effect of the topography and near-building structures and their contribution on the vertical gradient of gravity (VGG) was studied. The strong impact of near topography on the VGG values was found in the case of the mountainous areas – deviations of up to 88% of normal value were obtained by means of relative gravity measurements in selected parts of Slovakia. Newly developed software and a high-quality detailed digital terrain model of Slovakia was used for the evaluation of the topographical effect. The gravitational effect of near-building structures was estimated by means of simple 3D bodies approximation, i.e., rectangular or polygonal prisms. A very specific non-linear behaviour of VGG is demonstrated on model examples. A relatively good agreement between the measured and calculated (predicted) VGG values was achieved for a set of selected 32 real measurement points. The application of estimated (predicted) values of the VGG instead of the normal ones can lead to a quality improvement of global and local gravimetric reference networks, as well as prospecting VGG measurements.