Evaluation of the Topographic Effect using the Various Gravity Reduction Methods for Precise Geoid Model in Korea

Abstract

The topographic effect is a most important component in the solution of the geodetic boundary value problem (geodetic BVP) and should be considered properly for developing a precise geoid model. It is necessary to select a proper gravity reduction method in order to calculate the topographic effect precisely, especially in mountainous area. The selection of the gravity reduction method in context of precise geoid determination depends on the magnitude of its indirect effect, the smoothness and magnitude of the reduced gravity anomalies, and their related geophysical interpretation. In this paper, we studied gravimetric geoid solutions using various gravity reduction methods such as Helmert's second method of condensation, RTM method and Airy topographic-isostatic method and evaluated the usefulness of each method. In Korea, the gravimetric geoid model was determined by restoring the gravity anomalies (included TC) and the indirect effects was computed from various reduction methods on the EIGEN-CG03C reference field and the results were compared to geoid undulations at 503 GPS/levelling points after LSC fitting. According to the results, the RTM method is the most suitable for calculating topographic effect in the precise geoid determination in Korea.