Abstract
Urban connectivity information is important for regional planning of sustainable development goals. However, there are still challenges in deriving the spatial connectivity relationship among urban areas. The nighttime light data measure anthropogenic phenomenon remotely and can be seen as a unique source for monitoring urban spatial expansion and human activities. This study presents an object-based approach for investigating spatial connectivity among urban patches by incorporating Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite Day/Night Band and land use data collected in 2015. A graph-based method is used to construct connectivity networks and explore spatial patterns considering both quantity and quality of connections in three vibrant urban agglomerations in China, namely, Jing-Jin-Ji (JJJ), Yangtze River Delta (YRD), and Pearl River Delta (PRD) megaregions. Results indicate that networks follow a power law distribution according to cumulative degree distributions. A closer connectivity relationship exists among urban patches in PRD, with a relatively high-intensity connection ratio and a mean degree of 4.5, compared with YRD and JJJ. Block-like connections are observed in core areas of all urban agglomerations (UAs), and single-tree connections are found in peripheral areas. This article implies a significant inequality in the regional development and hub-spoke structures with hubs of provincial capitals and municipalities. Our proposed framework is transferrable for the analysis of connectivity relationship in other regions, and the outcome can contribute to the study of evolution of UAs and bring insights to policymakers for sustainable development at regional level.
Highlights
U RBANIZATION is a global and complicated phenomenon that simultaneously involves the migration of population from rural to urban, the shift of the economy from agriculture to manufacturing and service industries, and the transformation of natural land surfaces into artificial urban landscapes [1]–[3]
This study focuses on the three national-level urban agglomerations (UAs) in China, namely, Jing-Jin-Ji (JJJ, with 13 cities), Yangtze River Delta (YRD, with 42 cities, including Hefei Province), and Pearl River Delta (PRD, with 11 cities, including Hong Kong and Macau) [46], which have experienced the fastest population growth and rapid urbanization over recent decades
The network analysis method based on the graph theory can well express the spatial differences of urban connectivity relationship and the roles of cities that play in UAs, whereas the previous rank-size method can only describe the overall size distribution of urban areas in UAs
Summary
U RBANIZATION is a global and complicated phenomenon that simultaneously involves the migration of population from rural to urban, the shift of the economy from agriculture to manufacturing and service industries, and the transformation of natural land surfaces into artificial urban landscapes [1]–[3]. The ongoing urbanization process has increased the integration of urban landscapes and the continuously aggregated metropolitan areas, and the connections among cities [4]. This process generates urban agglomerations (UAs) worldwide. The internal connections of urban patches belonging to the same city are not shown, and the strongest connections of urban aggregated areas, such as junction urban areas that belong to different divisions, are neglected These studies suffer from the labor-intensive processing of collected data and are prone to
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