###### Abstract
Second, the KNGeoid14 model was developed using the same method utilized for developing the KNGeoid13 model, by adding the gravity data obtained in 2014 and shipborne gravity data from the Korea Hydrographic and Oceanographic Agency (KHOA, [[http://www.khoa.go.kr](http://www.khoa.go.kr)]([http://www.khoa.go.kr](http://www.khoa.go.kr))) to the gravity data constructed on KNGeoid13, and its standard deviation of residuals was evaluated as approximately 3.3 cm [14]. Finally, the KNGeoid18 model was developed using Experimental Gravity Field Model 2016 (XGM2016) based on the GOCE gravity data [15] generated as the initial version of Earth Gravitation Model 2020 (EGM2020), and its standard deviation of residuals is 2.33 cm [16]. The development of geoid model based on the longer wavelength part of the geoid derived from the EGM2008 has been performed. Several studies have implemented accuracy evaluation of geoid heights derived from GGMs by comparing them with the GNSS/leveling geoid height data obtained in the national control points (BM and UCP) of South Korea [5; 6; 7; 8; 9]. The EGM2008 is a spherical harmonic model of the Earth's gravitational potential developed through a least-squares combination of the ITG-GRACE03S gravitational model and its associated error covariance matrix, with the gravitational information obtained from a global set of area-mean free-air gravity anomalies defined on a 5' equiangular grid [4]. The EGM2008 is complete to degree and order 2159 and contains additional coefficients up to degree 2190 and order 2159. The EIGEN-6C4 [17], the newest ultra-high-degree global gravity field model, is the latest release in the EIGEN-6C series, containing the complete satellite gravity gradiometry (SGG) data of the GOCE mission. The GOCE-EGM2008 combined model (GECO) [18] is a global gravity model which is computed by incorporating the GOCE-only TIM-R5 solution, which is the fifth release (R5) of the time-wise (TIM) model, into the EGM2008. The EGM2008 geoid undulations are computed on a global spherical grid with a 0.5\({}^{\circ}\) resolution by synthesizing the EGM2008 coefficients up to degree 359. The GOCE geoid on the same grid is computed by synthesizing the TIM-R5 coefficients, up to degree 250. Finally, the GECO spherical harmonic coefficients are computed by analyzing the combined global geoid grid up to degree 359 (consistently with the 0.5\({}^{\circ}\) resolution). From degrees 360 to 2190, the GECO coefficients are the same as those of EGM2008. The GECO coefficient errors are computed as the weighted average of the coefficient errors of EGM2008 and the TIM-R5 solution [18]. Once the latest high-degree global gravitational field model has been developed and published, precision analysis is performed to determine its utility. The International Center for Global Earth Models (ICGEM, [[http://icgem.gfz-potsdam.de/home](http://icgem.gfz-potsdam.de/home)]([http://icgem.gfz-potsdam.de/home](http://icgem.gfz-potsdam.de/home))), operated by GFZ in Germany, receives the GNSS/leveling data from Australia, Brazil, Canada, Europe, Japan, and USA, and performs a local precision analysis. Table 1 represents the precision levels of the three GGMs that were used in this study. The precision levels are root-mean-square-error of the mean differences between the GNSS/levelling-derived geoid heights and the model-computed geoid heights. It is open to the public. The aim of this study was to evaluate the accuracy of the geoid heights derived from the latest high-degree GGMs developed based on satellite gravity data such as those from GRACE and GOCE as compared with the GNSS/leveling-derived geoid heights of the 1182 UCPs that have been installed by NGII in South Korea since 2008, as shown in Figure 1. In addition, the geoid heights derived from the KNGeoid models were compared with the GNSS/leveling-derived geoid heights of the 1182 UCPs to assess the accuracy of the gravimetric geoid models in terms of relative geoid heights to GNSS/leveling data for further gravimetric geoid determination studies in South Korea.