Nationwide Adjustment of Unified Geodetic Control Points for the Modernization of South Korea’s Spatial Reference Frame

This study presents a nationwide geodetic network adjustment of approximately 5560 unified control points (UCPs) established across South Korea between 2008 and 2021. Addressing the limitations of conventional regional adjustment strategies, the proposed methodology applies a centralized adjustment framework based on the International Terrestrial Reference Frame 2014 (ITRF2014) at epoch 2002.0. Seventeen permanent GNSS stations were rigorously selected and fixed, ensuring spatial uniformity, observational continuity, and metadata consistency. Baseline processing was conducted annually using high-quality GNSS RINEX data, followed by integrated network adjustment with the GAMIT/GLOBK (10.71) software suite. A total of 17,032 observation files were evaluated using an in-house quality control tool (GPS_QC), of which 25.2% failed to meet accuracy thresholds. The final adjustment yielded sub-centimeter precision, with mean residuals of 5.1 ± 0.057 mm (north) and 5.1 ± 0.056 mm (east), and over 99% of results falling within ±3σ. This study confirms the effectiveness of a unified adjustment strategy over conventional region-based approaches and demonstrates its applicability for high-precision national geodetic frameworks. The findings serve as a foundational contribution to the modernization of Korea’s spatial reference system and offer a transferable methodology for other countries pursuing similar geodetic reforms.