长江三角洲城市群空间结构的分形特征研究

Fractal Dimensions of Spatial Structure of Urban Agglomeration in the Yangtze Delta

城市群是都市连绵区空间结构演变的基础。城市体系的自相似性,使得城市群的空间分布具有明显的无标度特征,可以通过分形维数加以描述。以长江三角洲16个城市下的74个市辖区和县为研究对象,采用国家基础地理信息系统提供的县级以上境界面状数据,使用ArcG IS软件,通过ArcM ap ArcToolbox中的自带工具和VBA编程实现长三角城市群分形维数的计算,分析城市群空间分布的向心性、均衡性和相关性。结果表明:首先,长江三角洲地区已逐步形成以上海、南京和杭州为中心的多中心城市群,城市的分布密度由中心向外围逐渐递减;其次,长三角城市群属于复杂分形,其空间分布逐渐趋向均衡;第三,长三角地区顺畅的交通网络促进了区域内城市群的空间相互作用,有利于区域整体发展。

Urban agglomeration provides the framework for the evolution of spatial structure of urban sprawl.The spatial distribution of urban agglomeration is non-scaling due to the self-similarity of urban system,which could be illucidated by fractal dimensions.In this paper the urban agglomerations in the Yangtze Delta consisting of 16 prefecture-level cities,or 74 municipal districts and counties were chosen as the studying area.The software ArcGIS was employed to calculate 3 kinds of fractal dimensions,namely,aggregation dimension,grid dimension and spatial correlation dimension,with basic data downloaded from National Fundamental Geographic Information System（NFGIS）.The aggregation dimension could be used to describe the spatial aggregan of urban agglomeration,the grid dimension to describe spatial equlibrium and the spatial correlation dimension to describe the spatial interaction between urban agglomerations.The results indicate that the urban agglomerations in the Yangtze Delta are of multi-centers with the regional central cities of Shanghai,Nanjing and Hangzhou.The distribution density of municipal districts and counties gradually decreases from the central cities to the periphery.The urban agglomerations in the Yangtze Delta are relatively evenly distributed and their fractal characteristics are complicated.The convenient transportation infrastructure in the Yangtze Delta promotes spatial interaction between urban agglomerations,which is beneficial for regional integrated development.