A new inquiry into the fundamental module of Sui-Tang Luoyang layout based on compositional proportions

Sui-Tang Luoyang was an international metropolis in the 7th–10th centuries. The 50- zhang unit has long been regarded as the fundamental module for the layout design of this capital. Taking the Danei as the benchmark, this study determines the modular relationships across all precincts by analysing the compositional proportions in the layout of the Palace and Imperial Cities, combined with grid arrangement. Evaluation reveals that the 24- zhang module achieves a mean match rate of 98.68% with the surveyed values, which is 4.63 percentage points higher than that of the 50- zhang module. Moreover, it carries the cultural connotation of ‘Imitating heaven and modelling earth’, making it a more suitable fundamental module for explaining the capital’s layout principles. Revealing the layout principle based on the 24- zhang fundamental module will facilitate future archaeological excavations and enhance the presentation and utilisation of the heritage value of Sui-Tang Luoyang.