A Study on the Spatio - Temporal Changes of Urban Expansion in Shaanxi Province Based on Nighttime Light Remote Sensing Data

With population growth and economic development, timely, accurate information on urban built-up area expansion and in-depth analysis of their spatiotemporal characteristics are crucial for sustainable development. This study utilizes NPP/VIIRS night-time light data from 2013, 2016, 2019, and 2022 to extract Shaanxi's urban built-up areas via the reference comparison method and analyze their expansion's spatiotemporal features. The findings indicate that: (1) From 2013 to 2022, Shaanxi's built-up areas expanded continuously, with an overall "initial increase then gradual decline" trend, and outward growth showed irregular patterns. (2) In terms of compactness and fractal dimension, the city primarily experiences external expansion, with a generally low level of compactness that is decreasing over time. The average fractal dimension showed minimal change, indicating that the urban spatial form in the study area has a regular shape and a simple outline for the urban built-up areas. (3) The standard deviation ellipse area of the built-up area demonstrates a trend of spatial expansion, with a gradual reduction in center movement speed. There are also notable shifts in expansion direction; specifically, there has been an expansion towards the north-south axis and a noticeable contraction along the east-west axis, reflecting the uneven economic development between the north and south of Shaanxi Province. The findings of this study provide insights into the spatiotemporal evolution characteristics of urban expansion in Shaanxi Province and offer theoretical support for the healthy and coordinated development of cities in the region.