Geopotential Difference Determination via BDS and Galileo Multi-Frequency Time-Frequency Signals

Traditional methods for determining geopotential and height require successive transfers of leveling and gravity measurements, which are prone to error accumulation, face challenges in transoceanic applications, and are generally time-consuming, labor-intensive, and inefficient. Based on the principles of general relativity, an alternative approach using high-precision time-frequency signals to determine geopotential can overcome these limitations. In this study, simulation experiments were conducted to determine geopotential differences using BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer technology. The simulations employed clocks with different performance characteristics, utilizing precise clock offsets and multi-frequency observation data from both systems. The results show that the frequency stability achieved by BDS and Galileo five-frequency undifferenced carrier phase time-frequency transfer can reach approximately 3×10⁻¹⁷. The root mean square of the determined geopotential differences corresponds to centimeter-level equivalent height accuracy, and the convergence accuracy of the geopotential difference by the final epoch can reach better than 3.0 m²·s⁻². Given the rapid development of GNSS multi-frequency signals and ongoing improvements in the precision of products such as code and phase biases, geopotential determination based on Galileo and BDS multi-frequency signals is expected to have broader application prospects in the future. This study was supported by the National Natural Science Foundation of China project (No. 42304095), the Key Project of Natural Science Research in Universities of Anhui Province (No. 2023AH051634), the Chuzhou University Research Initiation Fund Project (No. 2023qd07).