Study on the Evolution of Urban Spatial and Temporal Patterns in Sichuan Province from the Perspective of Nighttime Light Data

A timely and accurate understanding of spatial-temporal evolution patterns and the development status of cities is essential for effective urban planning. This study utilized NPP/VIIRS nighttime light (NTL) data from 2012 to 2021 to extract the built-up areas of 34 prefecture-level and county-level cities in Sichuan Province. Key indicators, including the urban center of gravity, standard deviation ellipse, expansion speed, expansion intensity, fractal dimension, and compactness, were employed to analyze urban spatial patterns across three stages. The findings reveal that the urban center of gravity in Sichuan Province shifted from northeast to southeast, with cities dispersed in the northwest-southeast direction and clustered in the northeast-southwest direction. Prefecture-level cities generally exhibited high or medium speed to lower development levels, evolving towards relatively low and low intensity expansion, while county-level cities expanded more slowly at low intensity. Furthermore, better-developed cities are primarily located in the eastern region of Sichuan. Throughout the study period, outlying expansion was the predominant urban expansion model, and the spatial evolution of cities demonstrated considerable diversification. This research offers valuable insights into the sustainable development and planning of cities in Sichuan Province.