基于电子地图兴趣点的城市建成区边界识别方法

A novel method for identifying the boundary of urban built-up areas with POI data

城市建成区边界是认识和研究城市的重要基础性信息,也是落实城市功能空间布局、实施界限管控的前提。但是,以往通过夜间灯光的强度、土地覆被或建筑覆盖率等信息获取城市空间范围的方法,由于受到数据精度和尺度限制,对城市社会经济活动的解释性不强,因而存在较大局限性。电子地图兴趣点(POI)作为城市空间分析的基础数据之一,直观且有效地反映了各类城市要素的集聚状况。本文基于POI与城市空间结构和城市要素空间分布的关联性,提出了一种新的通过POI密度分布来判别城市建成区边界的技术方法。为此,开发了DensiGraph分析方法,用来分析POI密度等值线的变化趋势,在此基础上对城乡过渡地带的阈值识别的方法进行了理论分析,并讨论了单中心圆结构、双中心"鱼眼型"结构、双中心"子母型"结构等各类城市POI密度等值线的生长规律,证明了Densi-Graph分析方法的适用性。较之以往的城市建成区边界识别方法,这种方法的基础数据更加直观可信,分析结果也更加客观。运用这种方法,本文对全国地级以上城市的建成区边界进行了实证分析,探索了城市建成区边界的阈值及其与城市人口规模、城市所在区域之间的关系。

The boundary of urban built-up areas provides foundational information for urban studies and meets the requirements for urban pattern and urban spatial structure research. However, commonly used methods for identifying the boundary of urban built-up areas such as using remote sensing data of night-light and land use, cadastral data, and building coverage data, are limited in accuracy. To remedy this, this paper proposes to use POI （Point of Interest） data obtained from web maps, assuming that it well reflects the agglomeration of urban activities at higher precision. Based on the underlying connection between POI and the spatial distribution of urban activities, a new method called ＇Densi-Graph＇ is proposed to identify the actual boundary of urban built-up areas with the contour map of the kernel density of POI, where the threshold value for the contour lines to make significant change from densely to loosely placed is picked, giving the boundary of urban and rural areas. Different contour structures for mono-centric, poly-centric and linear cities are discussed, whereby the Densi- Graph method using POI data is validated. The method is also used to study the boundaries of urban built-up areas in China＇s prefecture level cities. The relationships between the Density- Graph thresholds and the population and location of different cities are discussed. This study advances previous studies in presenting more reliable and objective data on the boundary of urban built-up areas.