Known for unique ultrahigh spatial resolution and timing accuracy, the VLBI global observing system (VGOS) time transfer of ultralong baselines can achieve better long-term stability compared to other techniques. Because of the 1 mm positioning accuracy of the VGOS, comparing high-performance atomic clocks with VGOS time transfer can be used to accurately determine the geopotential difference between two remote stations and unify the world height system in the framework of the theory of general relativity. To investigate its performance in determining geopotential differences, we schedule continuous VGOS sessions with a 7-station network, simulate and estimate the corresponding VGOS observables and determine the geopotential differences of six baselines. Furthermore, the coefficients of the tropospheric turbulence model and clock stability are varied to analyze their influences. The results show that when using atomic clocks with $1.0\times {10}^{-16}$@1 d stability, the accuracy and precision of the weighted averaged geopotential difference remain at the level of 8 m²s⁻² and are sensitive to variations in the troposphere. The improvement by upgrading clock performance is limited by other error sources. In addition, connecting twin telescopes with identical atomic clocks and combining clock parameters in estimation can improve the precision of the estimated geopotential difference by approximately 4%.

VLBI 全球观测系统 (VGOS) 超长基线时间传递以独特的超高空间分辨率和授时精度而著称，与其他技术相比，可以实现更好的长期稳定性。由于VGOS具有1毫米的定位精度，因此可以利用高性能原子钟与VGOS时间传递的对比，在广义相对论的框架内准确确定两个远程站之间的位势差，统一世界高度系统。为了研究其在确定位势差方面的性能，我们使用 7 站网络安排连续的 VGOS 会话，模拟和估计相应的 VGOS 观测值并确定六个基线的位势差。此外，改变对流层湍流模型和时钟稳定性的系数来分析它们的影响。结果表明，当使用原子钟时$1.0\times {10}^{——16}$@1 d稳定性，加权平均位势差的准确度和精度保持在8 m ² s ^-2的水平，并且对对流层的变化很敏感。通过升级时钟性能的改进受到其他错误源的限制。此外，将具有相同原子钟的双望远镜连接起来，并在估计中结合时钟参数可以将估计的位势差精度提高约4%。