Estimation of topographic density by bouguer anomalies and its effect on geoid determination

Gravimetric geoid model is determined by Stokes' formula assuming that there is no topography above the geoid. Then, the approximate geoid height is simply corrected by considering the constant crust density of 2.67 g/cm$^3$ for topographical mass. Indeed, the actual density of topographical mass may vary about 20$\%$ from the constant value. In this study, a local crust density model is derived from complete Bouguer gravity anomalies by using apparent density approximation, then the influence of this approach on the accuracy of gravimetric geoid is investigated in a mountainous region in Turkey. KTH method developed by Sjöberg was exploited to produce geoid models. Moreover, LSMSSOFT was utilized to calculate KTH method effectively and quickly. Numerical results prove that the differences in the geoid height due to the local density model have risen up to several decimetres which should not be ignored in a precise geoid modelling with one cm. Thus, it is offered that since the effect of topographical density variations is significant, a correction or refinement process should be taken into account before the geoid determination, particularly in mountainous regions.