Abstract: The traditional methods for transferring height between land and sea benchmarking points are affected by factors such as the distance between islands and mainland, and the land-sea environment, leading to measurement inaccuracies. In this article, we propose a method using high-precision quasi-geoid surfaces for height transfer. We investigate error accumulation factors, provide a theoretical model for height transfer, and describe the specific technical process. In the Beibu Gulf area, this method is used to transfer the 1985 national height datum from the mainland to Weizhou Island and Xieyang Island, which are located 40 kilometers away from Beihai city. The elevation differences between GNSS leveling points after the transfer and the independent elevation differences from the second-order leveling measurement on Weizhou Island are all better than ±4.1 cm. This study provides practical reference for height transfer projects in offshore areas nationwide.

Key words: long-distance sea-crossing elevation transmission, error propagation, quasi-geoid, GNSS, leveling