## 2 Materials and Methods
### Comparison of GNSS Data Processing Strategies and Software  
The analysis is based on coordinate comparison datasets provided for numerous geodetic control points distributed across the Republic of Korea. One dataset contains the coordinates obtained from a GAMIT/GLOBK-integrated network adjustment in the KGD2002 frame, and another contains coordinates from a Bernese software network adjustment in the same frame. Each dataset lists, for each control station, the official \"published\" northing (N) and easting (E) coordinates in KGD2002--often projected in the national Transverse Mercator (TM) grid--alongside the corresponding coordinates computed by the software.  
We processed the dataset independently with two software packages: (1) GAMIT/GLOBK (version 10.71), developed at MIT [16; 17], and (2) Bernese GNSS Software (version 5.2), developed at the University of Bern [19]. Both software were configured to use consistent processing strategies to the extent possible. The precise IGS orbits and Earth rotation parameters for all  
Figure 1: Spatial distribution of common GNSS observation points used in both GAMIT/GLOBK and Bernese solutions across the Republic of Korea. Each red dot represents a control station that was processed using both software packages and included in the comparative analysis. The dataset comprises approximately 3000 geodetic control points, ensuring dense coverage across the mainland, coastal areas, and Jeju Island. Major administrative boundaries and province names are labeled. This visualization highlights the extensive applicability and consistent performance of the two GNSS solutions across the national control network.  
observation days were applied identically in both cases. We used double-differenced GPS L1+L2 observations for baseline processing, applying ionosphere-free linear combinations. Tropospheric delay was estimated with modern mapping functions (e.g., VMF1 in Bernese, GMF in GAMIT) at fixed intervals, and antenna phase center models (IGS14 ANTEX) were applied in both solutions. Integer ambiguities were resolved using the Quasi-Ionosphere-Free (QIF) method in Bernese [19] and the wide-lane then phase-update strategy in GAMIT [16; 17]. The processing of daily baselines in GAMIT was followed by a network adjustment in GLOBK, whereas Bernese used a combined network least-squares adjustment (GPSEST) after baseline processing. The 17 CORS with known KGD2002 coordinates were held fixed, and a 7-parameter transformation was applied to convert all points into the KGD2002 reference frame [20]. This \"fixed stations\" approach yields station coordinates in the KGD2002 datum for all points [13].  
Both GAMIT/GLOBK and Bernese GNSS software packages utilize precise orbit products to enhance the accuracy of satellite positioning. These precise orbits, provided by the International GNSS Service (IGS), are critical for high-precision GNSS processing. However, each software package handles these products differently according to its internal architecture and processing workflow.  
GAMIT/GLOBK directly uses the IGS-provided SP3-format precise ephemerides. The SP3 files contain satellite position and clock information and are widely supported across GNSS software. GAMIT reads the SP3 files natively and integrates the orbital data during baseline and network adjustment processing.  
In contrast, the Bernese GNSS Software requires the SP3 orbits to be converted into its own internal format, known as STD (Standard Orbit Format). This conversion is performed using Bernese's ORBGEN module, which prepares the orbit data for use in subsequent processing steps such as baseline analysis and network adjustment.  
Despite the differences in format and handling, both software packages rely on the same underlying IGS precise orbit data, ensuring consistency in satellite positioning and making the coordinate comparison between the two systems valid and robust.