Abstract: Coupled with the basic measurement examples of sea charts, the implementation steps and technical details of water level data preprocessing, datum surface determination, and water level accuracy evaluation are summarized in this paper. The residual water level synchronization curve and the accuracy evaluation result can directly and rigorously determin the residual water level strong correlation tide station. After careful argumentation, the water level correction method based on the residual water level monitoring and tidal model can be applied in the water of Daya Bay to meet the accuracy of water depth measurement and meet the requirements of relevant specifications. It can replace traditional water level correction methods, optimize the layout of tide gauge stations, and reduce the amount of tide stations.

Key words: average sea surface, depth datum, residual water level, accuracy assessment, tide model