Reconstructing planar dimensions and design strategies of the Long Family Ancestral Hall in Zhaotong, Yunnan, China

In contexts involving multicultural interaction, the design logic of high-status architecture in Southwest China has long lacked a reproducible quantitative analytical method. In this research, the Long Family Ancestral Hall in Zhaotong, Yunnan, is taken as a case study, and its Yingzao chi system is reconstructed with the goal of analyzing its proportional logic. A quantitative approach involving historical modular system identification is proposed. Architectural dimensions are decomposed into integer-chi and half-chi modular assumptions. Statistical error analysis is used to evaluate the goodness-of-fit of different modular schemes. By reference to 3D laser scanning point cloud data, a standardized analytical framework for data extraction, modular fitting, and error evaluation is developed. This approach allows the original dimensional system to be reconstructed and the design logic to be identified at both the building and group scales. The results reveal two stable Yingzao chi systems, thus indicating the coexistence of multiple artisan measurement traditions in this context. The design logic reflects the interaction between Han modular architecture and local (Yi) construction practices, which form a composite system. This study provides a reproducible method that can be used to analyze architectural proportional systems and offers novel insights in the field of ethnic architectural studies.