###### Abstract  
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 \(\pm\) 0.057 mm (north) and 5.1 \(\pm\) 0.056 mm (east), and over 99% of results falling within \(\pm 3\sigma\). 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. e 2025 15 5500 10 May 2025 12 May 2025  
projects: the First Order Geodetic Network Project (1975-1992) and the Second Order Geodetic Network Project (1986-1994) [6]. Since 2008, in response to the increasing use of global navigation satellite systems (GNSSs), triangulation points--especially those located in remote and mountainous areas--have been systematically relocated to urban regions. This nationwide relocation and modernization initiative is referred to as the unified geodetic control point. Between 2008 and 2021, approximately 5500 unified geodetic control points (UGCPs) were established across South Korea. Traditionally, each UGCP was computed using observations from a set of four to five nearby satellite reference stations. However, due to inconsistencies in the selection of reference stations across regions, the existing region-based adjustment strategies have proven insufficient in maintaining positional consistency on a national scale. To overcome this limitation, this study introduces a unified geodetic adjustment strategy that fixes 17 consistent nationwide satellite reference stations as common control points. This approach enables the simultaneous adjustment of all 5500 UGCPs within a single, coherent geodetic network. The proposed strategy is anchored to the International Terrestrial Reference Frame 2014 (ITRF2014) and is designed to enhance spatial coherence, long-term stability, and global compatibility of the national geodetic infrastructure. Moreover, incidents such as the 1995 Daegu gas explosion have underscored the critical importance of accurate geospatial information for disaster preparedness and infrastructure safety. This study aims to contribute to the modernization of Korea's geodetic infrastructure by developing a robust adjustment framework, offering a reproducible model for countries seeking to reform and unify their spatial reference systems [7; 8; 9]. Comparable initiatives have been implemented in countries such as Japan and Germany. Japan's GEONET has adopted a unified adjustment strategy to improve nationwide positional consistency. Similarly, Germany's SAPOS network operates a nationwide system of over 270 GNSS reference stations, where signals are permanently recorded and centrally processed to provide real-time correction data across the country. These international benchmarks further highlight the methodological relevance and global applicability of the proposed Korean framework.