Effect of the Generation of Bouguer Anomalies on the Geoid Determination: A Case Study in a High-Mountainous Area

Abstract

Different types of gravity anomalies are engaged in geophysical and geodetic tasks. Whether they are used for regional or global applications, they require efficient calculations. All variants are based on the so-called free-air gravity anomalies. Mean free-air gravity anomalies on an equidistant grid are needed for gravity field modeling. Three possible ways of compiling mean free-air gravity anomalies are discussed in detail. One method is via simple Bouguer gravity anomalies, the second, more time-consuming method is via complete Bouguer gravity anomalies, and the third method is via topographic-isostatic reductions, which is a tedious task. In flat areas, the differences between using any of the three methods should not be significant. However, in mountainous regions, each dependency can negatively affect the interpolation process of gravity anomalies. The reduced gravity anomalies should be as smooth as possible in order to minimize the interpolation error which is inherent in the interpolation of the information in the arbitrarily distributed gravity observation points to obtain block average signals. This study investigates the effects of Bouguer and topographic-isostatic reductions on the accuracy of the mean gravity anomalies and the resulting gravimetric geoid model. The numerical results indicate that complete Bouguer approximations improve the accuracy of the geoid model by a few millimeters. Therefore, this method should be used to predict mean gravity anomalies, especially in mountainous regions, in few of the 1 cm geoid determination.