基于多维景观扩张指数的城市紧凑度分析研究

Analysis of Urban Compactness Based on Multi-dimensional Landsc ape Expansion Index

城市紧凑度是反映城市空间形态的重要指标。基于二维平面上建设用地斑块与原有建设用地斑块之间的缓冲区或者共同边分析是现有研究中测度新增建设用地紧凑或者扩散的主要方式,但是这类方法忽视了斑块内部三维建筑物的高度以及斑块之间的距离。为了更加客观准确地评价微观斑块尺度实际紧凑程度,本文提出了多维景观扩张指数(Multi-dimensional Landscape Expansion Index,MDLEI),通过对中国36个主要城市建设用地图斑中的建筑物图斑进行提取,分别使用景观扩张指数(Landscape Expansion Index,LEI)和MDLEI计算建筑物图斑的扩张指数,并对各市两种扩张指数分别占所有城市均值总和的比例进行比较来确定该城市的紧凑度是否被高估。主要结论为:在扩张模式的识别上,MDLEI识别出的飞地式扩张斑块的数量和面积均高于LEI对应结果,表明LEI高估了扩散型增长斑块的紧凑程度;根据MDLEI计算得到的各市扩张斑块紧凑度,发现紧凑度较高的城市均分布在胡焕庸线以东,其中紧凑度最高的厦门、深圳、杭州、上海均为东南沿海城市,总体呈现出东高西低,南高北低的紧凑度分布状态。多维景观扩张指数能较为准确地识别微观层面扩张斑块的紧凑度,为政府因地制宜进行建设用地扩张管理和存量规划提供科学有效信息。

Urban compactness is an important index to reflect the form of urban space.The buffer zone or common edge analysis between new construction land patches and original ones based on two-dimensional plane is the main way to measure the compactness or diffusion of new construction land in existing research.However,this approach ignores the height of the three-dimensional buildingswithin the patch and the distance between the patches.In order to evaluate the actual compactness of micro patch scale more objectively and accurately,a Multi-dimensional Landscape Expansion Index(MDLEI)is proposed in this paper.By extracting building patches from construction land patches of 36 major cities in China,LEI and MDLEI are used to calculate the expansion index of building patches respectively.A comparison of the proportion of the two expansion indexes in the sum of the mean of all cities is conducted to determine whether the compactness of the city is overestimated.The main conclusions are as follows:In the recognition of expansion patterns,the number and area of outlying expansion patches identified by MDLEI are higher than those identified by LEI,indicating that the original results identified by LEI overestimate the compactness of diffusive growth patches.According to the compactness of expansion patches calculated by MDLEI,it is found that the cities with higher compactness are all distributed to the east of Hu Huanyong Line,among which Xiamen,Shenzhen,Hangzhou and Shanghai with the highest compactness are all southeast coastal cities,which shows a compactness distribution state of high in the east and low in the west,high in the south and low in the north.Multi-dimensional landscape expansion index can be utilized to accurately identify the compactness of micro-level expansion patches and provide scientific and effective information for the government to carry out construction land expansion management and stock planning according to local conditions.