基于遥感数据的中亚五国城市时空扩展变化研究

借助遥感与GIS技术,以1990年LandsatTM和2000年Landsat ETM+遥感影像为数据来源,提取中亚5国首都城市建设用地信息。计算1990年和2000年中亚5国首都城市的城市扩展强度、城市年扩展速率及城市形状紧凑度,对中亚地区五国城市扩展的时空变化进行定量分析。结果表明:1990年和2000年,中亚5国首都城市扩展强度指数和城市扩展速度差距较大,其中阿什哈巴德的扩展强度指数和城市扩展速度最大,分别为0.93、4.6,而最小的是杜尚别,分别只有0.001、2.6,二者相差悬殊。而紧凑度变化幅度不大,2000年,杜尚别、塔什干的紧凑度较大,分别为0.6、0.46,其城市结构更为紧凑,用地集约程度增大,而阿斯塔纳、比什凯克和阿什哈巴德城市结构相对较为松散。同时,中亚五国首都城市空间向外扩张、向内填充的强度、方向各不相同,从而呈现出各自的扩展特点。

STUDY ON SPATIO-TEMPORAL DYNAMICS OF URBAN EXPANSION IN FIVE CENTRAL ASIAN CITIES BASED ON REMOTE SENSING DATA

Central Asia is a core region of the Asian continent from the Caspian Sea in the west,China in the east,Afghanistan in the south,and Russia in the north.It is also sometimes referred to as Middle Asia,and is within the scope of the wider Eurasian continent.For each of the cities,two co-registered Landsat images coincident with years 1990 and 2000 were required to characterize urban change.Since ideal months and years of image acquisition were not always available,some images deviated from the decadal time-points(1990 and 2000),or months of acquisition were offset by one month.In addition to the standardized spatial extent boundary,a core urban area was delineated for each city based on the density of urban land in 1990.Then the spatial-temporal changes in the five Central Asian countries’ capital cities during the period from the beginning of 1990s to the beginning of 2000s were analyzed by computing the intensity of urban expansion,urban growth rates and compact ratios.The results showed that: in the period of 1990-2000,intensity of urban expansion and urban growth rates of in the five Central Asian countries’ capital cities are much different from each other,intensity of urban expansion and urban growth rates of Ashgabat is the largest,respectively 0.93 and 4.6.But intensity of urban expansion and urban growth rates of Dushanbe is the smallest,respectively 0.001 and 2.6.However the compact ratios are not big changes.In 2000,the compact ratios in Dushanbe and in Tashkent are respectively 0.6 and 0.46.The urban spatial morphology of Ashgabat and Dushanbe are more compact,but the urban spatial morphology of Astana,Bishkek and Tashkent are less compact.All these five Central Asian cities are continuously expanded,but the direction and speed of urban expansion are different.