A study on the dual-modular system of the central palace in Wudang Mountain’s Yuzhen Palace

Ancient Chinese architectural complexes employed hierarchical modular systems, yet the relationship between planning-scale and construction-scale modules remains insufficiently understood. This study investigates the Central Palace of Yuzhen Palace on Mount Wudang using archaeological and architectural survey data. A datum-point identification and multi-scale grid-fitting workflow was proposed and tested to examine modular relationships across different spatial scales. Results indicate that the Central Palace was planned using a 2 zhang module (1 zhang = 10 chi ), while the Inner Courtyard buildings exhibit a consistent 3 chi module in plan and section. The two systems appear to be spatially integrated through a shared datum point. To assess preliminary applicability, Wulong Palace and Zixiao Palace were analyzed as comparative cases at the planning scale. The results suggest that the workflow can identify coherent planning-scale modular relationships in comparable Wudang palace complexes, providing a preliminary framework for studying historical architectural planning and dimensional control.