EVALUATION OF GLOBAL GEOPOTENTIAL MODELS IN KAZAKHSTAN BASED ON GEOID HEIGHTS AND GRAVITY ANOMALIES

Abstract

Orthometric height is required for all surveying work in civil engineering. The most effective and less labor-intensive method for determining orthometric heights on the ground is the use of GNSS technologies. But to use GNSS technologies, it is necessary to determine the geoid height (the difference between ellipsoidal and orthometric heights). This article reviews and compares the latest high-resolution Global geopotential models (GGM) in order to select the optimal model for creating a model of the geoid of Kazakhstan. The study consists of three stages. In the first stage, the GGMs were evaluated using 112 GNSS/leveling points distributed over the test area. In the second stage, selected GGMs were evaluated based on gravity data. In the third stage, some of the best performing models were further compared using spectral information contained in their spherical harmonic coefficients. The EIGEN-6C4 model demonstrated advantages over other GGMs (XGM2019e_2159, GECO, SGG-UGM-2, EGM2008) that participated in the accuracy assessment, showing a standard deviation of 0.267 m at the first stage. When analyzed to match ground-based gravity data, the EIGEN-6C4 model demonstrated a match with a standard deviation of 5.341 mGal. Based on the evaluation results, it is decided that EIGEN-6C4 is the most suitable model for generating local geoid, which will contribute to the development of geodesy in civil engineering in the future.