Exploring the Spatial-Temporal Dynamics of the Yangtze River Delta Urban Agglomeration Based on Night-Time Light Remote Sensing Technology

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.