基于最佳尺度的城市扩张特征研究——以苏州中心城区为例

为深入、准确揭示城市扩张特征，采用国土部门1996年、2005年、2014年3个年份1∶5000土地利用变更数据，基于ArcGIS10.2平台提取相应年份中心城区的城市用地，以50 m为步长，分析了 50～1 000 m 尺度范围内城市扩张规模、分形特征和扩张模式差异，得出最佳分析尺度为350 m。基于最佳尺度，分析了1996～2014年苏州城市扩张特征，结果表明：（1）1996～2005年扩张速度明显高于2005～2014年，其规模与工业化、城市化阶段密切相关；（2）扩张类型具有明显的周期性与规律性，早期以蔓延式扩张和飞地式扩张为主，后期出现明显的填充式扩张，在各个方向上存在梯度推移现象；（3）近20a来，城市分形维数D逐渐提高，基于城市用地生成的凸包图形愈加复杂，表明城区进一步扩张趋势突出。最后提出了城市扩张管理的对策建议，以期为工业化中后期城市的研究及扩张管理提供可能的借鉴参考。

Characteristics of Urban Land Expansion Based on the Optimal Scale:A Case Study of Suzhou

This paper collects the sustained land data from the Department of Homeland, for studying the influence of scale change on urban expansion. We extract urban land for the corresponding annual central city by using ArcGIS10.2 software, and then change the data scale from 50m to 1000m and take 50m for the step size. The urban expansion scale, fractal characteristics and expansion model are analyzed in different scales. It shows that 350 m is the optimal study scale. Based on optimal scale, the characteristics of urban land expansion from 1996 to 2014 are studied. The results show that: (1) Expansion rate of 1996-2005 is obviously higher than 2005-2014. Its scale is in accordance with industrialization and urbanization period.(2) The type of expansion acts as obvious periodicity and regularity. Early expansion mainly includes spread expansion and enclave expansion, and then significant filling expansion emerges. There are gradient moves in all directions. (3) In the past 20 years, the urban fractal dimension has been growing. Convex graphics indicates that the city center would expand again in the future and has been becoming more complex. In the last part of this paper, we provide some suggestions for the management of urban expansion, and expected to make references for the similar regions or studies.