Delineating Functional Metropolitan Areas in China: A Method Based on the Tri-Dimensional PET Coupling Model

Metropolitan areas have become the primary spatial form for China’s new-era urbanization. However, these boundaries have traditionally been delineated based on administrative factors, resulting in a notable discrepancy with the actual functional connections. To tackle this challenge, this study aims to devise and implement an innovative ‘PET’ tri-dimensional coupling model, leveraging the principles of integrated urban subsystems to scientifically delineate functional metropolitan boundaries. The proposed method integrates Population flow (P), Economic density (E), and Transportation accessibility (T) on a fine-grained 1 km raster grid. To enhance accuracy, the crucial population flow component is simulated using a gravity model calibrated with real-world Baidu Migration data. Applying this model to 35 potential metropolitan areas, our findings reveal two key points. First, a comparative analysis with five officially approved plans reveals a significant spatial alignment in core functional zones, which corroborates the model’s accuracy. effectiveness. Secondly, these delineations clearly quantify the notable difference between the ‘functional space’ influenced by socioeconomic factors and the ‘administrative space’ delineated by jurisdictional boundaries. In summary, this research presents a replicable methodology for delineating functional metropolitan areas. It offers vital technical support and policy guidance for optimizing regional planning, enhancing inter-city coordination, and promoting China’s national strategy for regional development.