Abstract
Studying the generation and development of urban areas is of great significance to improve our understanding of urbanization. However, it is still difficult to explore the spatial-temporal dynamic characteristics of urban agglomeration in the global scope. The easily accessible night-time light (NTL) data provide a window to observe the progress of human urban development from space. This study proposes a method based on NTL-Internet data. By combining the NTL center of gravity and the interregional link index model, it is used to detect the spatial expansion characteristics of the Yangtze river delta urban agglomeration (YRDUA), thus completing the comprehensive exploration of the urbanization in YRDUA. Results demonstrate that YRDUA, compared with the five major urban agglomerations in Europe, North America, and Asia, maintains the greatest urbanization potential. Further analysis shows that the urban area of Hefei has a huge development momentum. In addition, the urbanization level of YRDUA is easily affected by national planning, which conforms to the model of urban expansion, including infilling, edge expansion, and leapfrogging in different metropolitan areas. Finally, the link index model based on Internet data is utilized to quantitatively calculate the relevance of various cities in YRDUA. The results not only confirm the findings based on the NTL data but also explain that those metropolitan areas play a complementary and indivisible role in the urbanization process of YRDUA. This study will provide a framework for other research works to assess the spatial-temporal changes in urban characteristics, which is beyond the scope of a single city.
Highlights
A S A RAPID and historic transformation of human social roots on the global scale, urbanization is a complex process, which involves land-use change, rural–urban shift, and urban expansion [1]–[3]
The classification results based on grow slope of NTL (GSON) images and the night-time light (NTL) center of gravity analysis reveal the urbanization evolution on both urban agglomerations (UAs) and city scale
The areas with the low NTL and low GSON accounts for 10.95%, 10.73%, 17.60%, and 33.90% in Atlantic Coast urban agglomeration (ACUA), Great Lakes urban agglomeration (GLUA), South-Central England urban agglomeration (SEUA), and Northwest European urban agglomeration (NEUA), respectively, which reflects the higher cessation level of urbanization of ACUA and GLUA because the areas that are easy to expand the urban areas are small and limited in them
Summary
A S A RAPID and historic transformation of human social roots on the global scale, urbanization is a complex process, which involves land-use change, rural–urban shift, and urban expansion [1]–[3]. This process has caused a series of urban problems, including urban heat islands [4]–[6], air pollution [4], [7], [8], climate change [9]–[11], and ecological degradation [12]–[15], etc. Due to the advantages of easy access, long time series, and large spatial span [19], NTL data have been widely used in the extraction and expansion of urban spatial information [20], [21], urban system evolution analysis [22], [23], and the impact of urbanization on the ecological environment [24]–[28]
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