Design and geodetic adjustment of levelling network for establishment of unified control points in korea

The unified control points (UCPs), the multi-dimensional geodetic reference points installed in the low elevated area, has been established in Korea for the combination of the horizontal and the vertical geodetic control. While the 1^st-phase UCPs network was completed in 2011 with a spatial density of about 10km, its densification has been underway as the 2^nd-phase project. The UCPs supersedes the legacy geodetic points, such as triangulation points and benchmarks (BMs) once the 2^nd-phase implementation. Although the horizontal network of the UPCs can be readily realised by GNSS technology, a technical challenge of the vertical component remains to be settled due to characteristics of the geodetic levelling technique. To this end, a pilot study was conducted to design a new version of the UCPs-based levelling network and to demonstrate its effectiveness with a comparison of the legacy. In this paper, a concept of the UCPs-based levelling network is briefly addressed with some prominent examples, and details of a pilot network and its measurements is given with the network adjustment procedure. Finally, results of the adjustments are provided with an emphasis on the influence of the newly designed network in terms of accuracy, reliability and estimated heights.