A study on urban spatial structure changes based on spatiotemporal big data coupling analysis

Urban spatial structure is a core topic in urban geography and planning, with significant practical implications for sustainable urban development. This study adopts a refined spatial coupling framework that integrates Black Marble nighttime light (NTL) data and points of interest (POI) data to examine the coupling patterns between nighttime economic activity and urban functional facilities of Xi’an in 2012 and 2022, as well as their changes over the intervening decade. We also analyze the influencing factors and underlying interaction mechanisms shaping these patterns. While methods such as kernel density estimation, coupling coordination modeling and bivariate mapping are well-established, the contribution of this study lies in data refinement, spatial grid optimization and systematic interpretation, rather than the development of new analytical models. The findings reveal the following: (1) The coupling analysis of NTL and POI data offers an effective proxy for characterizing urban spatial structure. (2) Xi’an remains predominantly monocentric around its historic core, though notable expansion has occurred over the past decade, particularly northward, driven by rapid construction. Several spatially distinct high-coupling coordination agglomerations have emerged in suburban districts to the north (Gaoling, Yanliang and northern Weiyang), indicating an incipient pattern of sub-center formation rather than a fully mature polycentric configuration. (3) Coupling coordination exhibits a clear gradient decline from the urban core outward. (4) The observed coupling patterns are closely linked to regional economic conditions. Zones with high-high, high-medium, and medium-high coupling are concentrated in the city center and extend toward peri-urban fringes; high-low coupling zones tend to occur in transitional urban-rural interfaces, whereas low-medium zones are sporadically scattered across economically less developed suburban counties. (5) The evolution of Xi’an’s spatial structure is shaped by a tightly coupled interplay among policy orientation, socio-economic development, and spatial-industrial structure. These forces operate through sequential feedback loops, continuously adjusting the spatial alignment between nighttime economic activity and urban supporting facilities, steering the city from a strictly monocentric model toward a more functionally coordinated configuration.