城市空间形态离散度指数NDIS构建与应用

中国土地资源有限,需要可持续的、紧凑的城市空间形态与布局,因此,全面度量城市空间形态的紧凑性具有重要意义。通过6个情境分析了离散度指数DIS的优缺点,识别出DIS值在反映城市形态紧凑程度方面的不足,进而提出了一种新的城市空间形态紧凑度指数,即标准化离散度指数NDIS。NDIS不受城市面积规模的影响,且具有唯一性,利于城市紧凑度的横向和纵向比较,能更好地指示城市空间形态。NDIS值越大,城市越离散。进一步将NDIS与成熟使用的标准化紧凑度指数NCI结合,用于分析中国35座城市的空间形态紧凑性,研究结果表明:(1) NDIS最大值是兰州市的1.64,最小值是石家庄市的1.14,均值1.29±0.12(SE); NCI最大值是郑州市0.39,最小值是宁波市的0.1,均值0.24±0.07(SE);(2) NDIS与NCI虽然具有中等程度的相关性(r=-0.44,P0.01),但是NDIS把城市斑块间的距离关系表达得更为准确;(3)将NDIS与NCI结合,能够更加全面地指示城市空间形态的紧凑程度。准确、全面的衡量中国城市的空间形态,则需要与更多的景观格局指数结合使用。

Study on the formulation and application of the urban spatial form dispersion index (NDIS)

Chinese cities need a sustainable, compact spatial layout. Therefore, comprehensive measurement of the urban spatial form is of great significance. This paper introduces the degree of dispersion (DIS), assesses the advantages and disadvantages of DIS through 6 situations, and identifies the deficiency of DIS value in reflecting the compactness of urban morphology, and then put forward a new compact index to assess urban spatial form, that is, the normalized dispersion index NDIS. NDIS is not affected by the size of the urban area, and the city has a unique value, which is conducive to the horizontal and vertical comparison of urban compactness. The greater the NDIS value, the more discrete the city is. Furthermore, NDIS is combined with the normalized compactness index NCI to analyze the compactness of 35 cities in China. The results show that:(1) The maximum NDIS value for the investigated 35 cities is 1.64, the minimum is 1.14, and the average is 1.29 ±0.12 (SE). (2) Values of NCI ranges between 0.1-0.39, with an average of 0.24 ±0.07 (SE). (3) NDIS and NCI have a moderate degree of correlation (r=-0.44, P < 0.01), but NDIS is more accurate in expressing the distance between urban patches. (4) The correlation shows that the two indices have partially overlapping information, but the difference can better highlight the urban morphological characteristics. Of course, NDIS is not a perfect index to measure the urban spatial morphology. A more accurate and comprehensive measurement of the spatial patterns of Chinese cities requires the combination of more landscape metrics. The next step in research would be to focus on combining compactness indices with urban structure and environmental factors to find out the suitable ranges for Chinese cities and provide a guideline for the construction of the compact city, sustainable city, and low carbon city.