Urban Expansion Analysis of GBA Based on Multi-source Nighttime Light Remote Sensing Images

Nighttime Light (NTL) Remote Sensing Images can effectively reflect urban expansion and spatial pattern changes. In this paper, the DSMP/OLS nighttime light images from 1992-2013 and the "LJ-01" NTL images in 2018 are used to extract urban built-up areas of Guangdong-Hong Kong-Macao greater bay area (GBA), by applying "threshold method based on statistical data". On this basis, in order to reveal the spatial pattern and urban expansion process of each city in GBA, a number of indicators are used, including urban expansion speed, urban expansion intensity, urban expansion morphology index, rank scale index, and primacy index(including the two city index and the eleventh city index). Finally, analyzes the main driving factors of urban expansion in GBA combined with the national economic statistics. The results show that: (1) From 1992 to 2018, the urban built-up area of GBA increased significantly by 3717 km(2), from 3039 km(2) in 1992 to 6756 km(2), and the average annual growth is 142.96 km(2). Guangzhou, Shenzhen and Dongguan were the three cities with the largest growth in the built-up area, while Macao, Hong Kong and Zhuhai were the three cities with the least growth. (2) The urban built-up areas in the GBA are distributed in an inverted "U" shape, concentrated on both sides of the Pearl River Estuary and the southern coastal areas, and the built-up areas in the north, northwest and northeast are relatively scattered and sparse. (3) From 1992 to 2018, the urban built-up areas in GBA have expanded from narrow and scattered to broad and concentrated. The links between cities in the region have gradually changed from weak to strong, and finally formed a pattern of regional integration. (4) From 1992 to 2018, the overall expansion of urban built-up areas in GBA accelerated first and then slowed down. The expansion rate was the fastest in 2002-2007, and the slowest in 2012-2018. (5) From the rank scale analysis, the urban agglomeration structure of GBA was relatively balanced. From the analysis of primacy, the calculated values of the second city index and the eleventh city index were far from the ideal value, which reflects that the first city in GBA was not prominent enough and the agglomeration effect was not obvious enough. (6) Population growth, economic development, improvement of traffic conditions and favorable policies were the main driving forces of urban expansion.