Abstract
The worldwide development of multi-center structures in large cities is a prevailing development trend. In recent years, China’s large cities developed from a predominantly mono-centric to a multi-center urban space structure. However, the definition and identification city centers is complex. Both nighttime light data and point of interest (POI) data are important data sources for urban spatial structure research, but there are few integrated applications for these two kinds of data. In this study, visible infrared imaging radiometer suite (NPP-VIIRS) nighttime imagery and POI data were combined to identify the city centers in Hangzhou, China. First, the optimal parameters of multi-resolution segmentation were determined by experiments. The POI density was then calculated with the segmentation results as the statistical unit. High–high clustering units were then defined as the main centers by calculating the Anselin Local Moran’s I, and a geographically weighted regression model was used to identify the subcenters according to the square root of the POI density and the distances between the units and the city center. Finally, a comparison experiment was conducted between the proposed method and the relative cut-off_threshold method, and the experiment results were compared with the evaluation report of the master plan. The results showed that the optimal segmentation parameters combination was 0.1 shape and 0.5 compactness factors. Two main city centers and ten subcenters were detected. Comparison with the evaluation report of the master plan indicated that the combination of nighttime light data and POI data could identify the urban centers accurately. Combined with the characteristics of the two kinds of data, the spatial structure of the city could be characterized properly. This study provided a new perspective for the study of the spatial structure of polycentric cities.
Highlights
In China, with the acceleration of urbanization and the increasing scale of cities, urban spatial structures have undergone significant changes in many cities over recent decades
Observation units were obtained from the NPP-visible infrared imaging radiometer suite (VIIRS) nighttime light (NTL) data by multi-resolution segmentation
The city centers of Hangzhou were detected using a combination of two types of data, including open-net point of interest (POI) maps and nighttime light images with high spatial resolutions
Summary
In China, with the acceleration of urbanization and the increasing scale of cities, urban spatial structures have undergone significant changes in many cities over recent decades. The primary change has been the transition from a single-center structure to a multi-center or polycentric structure. For the latter case, a city contains multiple urban centers, including one or more main urban center(s) and several sub-urban centers. Urban center is a large and densely populated urban area and may include several independent administrative districts [1]. It shows an urban development pattern with active clustering of the urban population and the economic elements. A polycentric structure is commonly adopted in the master plans of many large cities in China [2]. There has been a lack of effective analysis and evaluation methods, especially relatively objective and rational methods, to evaluate whether the implementation results are consistent with the planning intention
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