KGEOID12: A new hybrid geoid model in Korea

Abstract:

This study describes in brief the development of a new hybrid geoid model, KGEOID12, which can be used as an accurate vertical datum in Korea. The hybrid geoid model is generally determined by fitting the gravimetric geoid to the geometric geoid undulations from GPS/Levelling data which were presented the local vertical level. For developing the gravimetric geoid model, we performed an optimal remove-restore technique based on the earth gravitaional model 2008 (EGM2008) reference surface. In remove-restore technique, EGM2008 model was analyzed up to harmonic degree and order 2,160, 4-band spherical fast fourier transformation (FFT) with modified stokes kernel and residual terrain model (RTM) reduction method were used for calculating the long, middle and short-frequency part of gravimetric geoid, respectively. A number of land and shipborne gravity data were compiled for modelling the middle-frequency part. A digital elevation model (DEM) gridded by 100m×100m were used for short-frequency part. The accuracy of gravimetric geoid model were evaluated by comparison with geometric geoid ontained from all available GPS/Levelling data in Korea which was about ± 0.107 m with a mean value of -0.360 m. Finally, we developed the hybrid geoid model in Korea, KGEOID12, corrected to gravimetric geoid model with a correction term derived from GPS/leveling data. The correction term is modelled using differences between gravimetric and geometric geoidal undulations at 1,185 GPS/Leveling data. The stochastic model used in the calculation of correction term is a least square collocation method based on second-order Markov covariance function. The post-fit error (mean and std. dev.) of the KGEOID12 was evaluated as 0.001 m ± 0.043 m. This result indicated that KGEOID12 can be used as a vertical datum to determine the height information with a few cm-leveled precision by combining a GNSS positioning technique in Korea.