Delineation of the Shanghai Megacity Region of China from a Commuting Perspective: Study Based on Cell Phone Network Data in the Yangtze River Delta

This study presents a method for delineating a megacity region with functional linkages in a continuous urbanized area. We examine commuting from cellphone network data and delimitate the Shanghai megacity region from 16 cities in the Yangtze River Delta, China. First, we identify places of residence and work based on certain durations of stay in one location from cellphone network data and obtain commuting data in 1 km(2) grids. Second, the core area of the megacity region can be defined as a continuous high-density area by applying incoming employment density as a functional linkage. We use local spatial autocorrelation to define the hotspots of continuous high-density areas and identify a Shanghai-centered continuous high-value area. Third, we choose an algorithm that gradually increases the density threshold based on the results of local spatial autocorrelation to eliminate areas with weak functional connectivity, and delineate the boundary of the core area of the Shanghai megacity region. Results show that the core area exceeds the boundary of Shanghai Municipality and comprises the main urbanized areas of Shanghai and Suzhou. This study provides an effective method for delineating megacity regions by using functional linkages from cellphone network data and for accurately delimitating the boundary of megacity regions.