Lee, J.; Kwon, J.H.; Lee, Y., and Lee, H., 2021. Development of the Korean National Geoid Model (KNGeoid18) and applications for the height determination of coastal land points. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 405–409. Coconut Creek (Florida), ISSN 0749-0208.

Since 2008, new land gravity data showing a homogeneous distribution and high precision have been obtained in Korea. In addition, a new version of the global geopotential models which were developed based on observations by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite are available. Thus, a gravimetric geoid was newly developed by the “Remove-Restore” technique using the experimental gravity field model 2016 (XGM2016) and more than 12,000 points of land gravity data. In addition, airborne, shipborne, and Danish Technical University 2010 (DTU10) altimeter gravity data, as well as a terrain model, were applied for geoid modeling. As a final product of the study, the hybrid geoid, Korean National Geoid model 2018 (KNGeoid18), was modeled by fitting the gravimetric geoid to a total of 2,791 points of global navigation satellite system (GNSS)/leveling data located over the entire Korean peninsula. The degree of fit of KNGeoid18 was calculated to be approximately 2.3 cm. One of the necessities of a local geoid model is to efficiently determine the orthometric height in terms of time and cost. Thus, GNSS surveying was conducted at 19 points and GNSS-derived orthometric heights were computed. Among the 19 points, the precision of the official orthometric heights at 12 points located in mountainous areas is known to be larger than 10 cm; hence, the GNSS-derived orthometric heights were calculated using Trimble business center (TBC), Leica geo-office (LGO), and Giodis, and compared with each other. As a result, it was found that the difference in heights at 12 points did not exceed 5 cm. The other 9 points, located in coastal areas, had a difference smaller than 3 cm compared to the official orthometric height. It is expected that orthometric heights with a target precision of 3–5 cm would be determined by GNSS surveying and the local geoid model, but an improvement of the geoid model in mountainous areas is still necessary.