Update of Korea National Geoid Model and Accuracy Analysis of Network RTK based Orthometric Height

As GNSS (Global Navigation Satellite System) surveying became widely used, the use of modern surveying method that determines the orthometric height at an unknown point using a geoid model is growing in the surveying field. Considering the precision of the current geoid model, which is about 2-3 cm, it is expected that orthometric height with an accuracy of approximately ±10 cm can be achieved based on network RTK (Real Time Kinematic) surveying, especially for the reconnaissance survey among public surveys. Therefore, a total of 6,499 data with ellipsoidal heights on the NCPs (National Control Points) were collected through network RTK surveying for the public survey, and orthometric heights were calculated. At this point, a new hybrid geoid model called KNGeoid24 (Korea National Geoid 2024) was developed and applied as the current official geoid model, KNGeoid18, has regional bias due to reannouncement of orthometric heights for NCPs in 2023. The degree of fit of KNGeoid24 was evaluated at approximately 2.3 cm. When comparing the orthometric heights determined using KNGeoid24 with the official orthometric heights of NCPs, it was found that 95.3% of the 6,499 data points (6,196 points) showed differences within ±10 cm. Therefore, it is necessary to revise public survey regulations to utilize the latest KNGeoid when determining orthometric height based on network RTK surveying for reconnaissance survey.