The determination of orthometric height based on gravity in Korea

A vertical datum requires an origin, which is a point on the Earth's surface where the height of the point is a defined value(26.6871m). From this origin point, heights (height differences) can be measured to any other point using standard leveling and gravity measurement procedures. However, the leveling network over the Korea has been established by using the normal gravity instead of the actual gravity values, and the heights for the points are published by National Geographic Information Institute (NGU). This may cause height error especially in the area where high-relief mountains are dominant Therefore, the height errors caused by using normal gravity instead of actual gravity values are analyzed in this study. Then, the differences between the orthometric heights and the published heights, i.e., normal orthometric height are analyzed.