Abstract
The establishment and continuous improvement of geodetic reference networks are fundamental to ensuring the accuracy, stability, and interoperability of spatial data. This study focuses on the adjustment of the Egyptian Continuously Operating Reference Stations (CORS) network relative to the International Terrestrial Reference Frame 2020 (ITRF2020). Additionally, it aims to readjust the CORS network relative to the High Accuracy Reference Network (HARN–ITRF1994) and derive transformation parameters between the adjusted solutions in ITRF2020 and HARN–ITRF1994. Global Navigation Satellite Systems (GNSS) observations from selected CORS and the neighboring International GNSS Service (IGS) stations are processed to achieve a consistent alignment with ITRF2020. Outlier detection based on standardized residuals and Tau tests is performed to ensure the strength of the network adjustment. The results show that the adjusted Egyptian CORS network achieves horizontal positional accuracies of better than 1 cm and vertical accuracies of better than 4 cm, with error ellipses with semi-major axes of less than 3 mm. The transformation parameters between ITRF2020 and HARN-ITRF1994 are computed using both the Bursa-Wolf and Molodensky-Badekas models, where the latter provides slightly better results.