天山北坡绿洲城市空间形态时空特征分析

Spatial-temporal Changes of Urban Spatial Morphology at the Northern Slope of the Tianshan Mountains

借助GIS软件支持,综合遥感影像、地形图和其它空间数据,提取天山北坡8个绿洲城市1990年和2000年建设用地图形信息,计算1990年和2000年天山北坡8个绿洲城市的平面轮廓形状的分维数、紧凑度以及城市用地扩展类型,讨论紧凑度与分维数的关系。研究结果表明,天山北坡绿洲城市形态总体特征表现为形状规则,结构紧凑。1990￣2000年,城市扩展类型主要为外延型,城市形态分维数增加,紧凑度降低,城市外部形态趋于复杂化和不规则化,而内部结构趋于松散化,与同时期我国大部分城市的用地扩展方式有所不同。同时,天山北坡绿洲城市形态特征描述参数间存在着明显的幂函数关系,并且是一种线性负相关关系,即随着分维数的增加,紧凑度呈递减的趋势。

Urban spatial morphology is an important aspect in the huge and complex urban system. The essential rule of urban development and change cannot be understood via qualitative description, so quantitatively researching urban spatial characteristic has significant practice meaning for urban management and planning. Based on remote sensing, GIS and Landsat TM/ ETM digital images, this paper analyzes the spatial-temporal changes of urban spatial morphology at the northern slope of the Tianshan Mountains in Xinjiang during the period from the late 1980s to the late 1990s by computing compact rations and fractal dimensions of the urban form as well as the types of urban land expansion. The results are as follows： are 0.541 and 0.525, and the mean fractal dimensions are 1.2399 and 1.25 respectively for 1990 and 2000. The type of urban land expansion of 7 cities out of the 8 in the study area is ＇extension＇ from 1990 to 2000. It was found that the to be less compact and more than a less one; so changes shapes of cities in the study area tended fragmentized. Generally, a more compact city has more advantages in the forms of the study area are considered being in a bad way. Shapes of several cities have been drastically changed during the period from 1990 to 2000. Fukang, Miquan and Shihezi are cities with high increment in fractal dimensions and high decrease in compact rations. Urban spatial morphology of them is more compact and regular. However, it is another case in Kelamayi, Kuytun and Urumqi. And （3） Another important finding is that there is a power function relationship between the compact and the fractal dimension of urban spatial morphology, which is only a qualitative deduction before.