近40 a来基于低分辨率遥感数据和GIS的全球城市时空变化研究

近几十年来, 全球生态系统、气候和生物多样性已不同程度受到人口快速增长和城市持续扩张带来的负面影响. 使用低分辨率遥感影像数据和GIS技术定量分析了近40 a全球城市时空变化. 世界数字化图(Digital Chart of the World, DCW)城市图层代表1960年至1970年的全球城市面积, 利用MODIS影像数据、稳定夜间光数据和城市格网人口密度数据编制的全球土地覆盖数据城市图(Global Land Cover by National Mapping Organization, GLCNMO)代表2003年时的全球城市面积. 计算了1960年和2003年全球城市的城市用地比重和年城市增长率指数, 从区域尺度、国家尺度和单个城市尺度分析了全球城市扩展的时空变化过程. 结果表明: 在1960年代发达国家城市面积较大, 而发展中国家城市面积小得多; 到2003年发展中国家有相当大的变化, 新增长的城市区域快速扩大. 近40 a来发展中国家城市区域发展速度远快于发达国家, 与欧洲和北美国家相比, 发展中国家城市结构更紧凑和密集.

A Global Comparative Analysis of Urban Spatio-Temporal Variation during Last Four Decades by Using Coarse Resolution Remote Sensing Data and GIS

In recent decades,rapid population growth and urban expansion affects local and regional ecosystems,climate,biogeochemistry,as well as food production.Global urban growth is analyzed during the last four decades by comparing satellite images of urban land area extent at two different times.The Digital Chart of the World(DCW),one of the earliest available global maps,was developed originally by the US Defense Mapping Agency(DMA).DCW populated places layer is a GIS product that was created by digitizing a large collection of maps and navigational charts in the 1960.GLCNMO(Global Land Cover by National Mapping Organization) is the continental scale urban map at 1 km spatial resolution by Gridded Population Density data,nighttime light data and MODIS data with the reference of fine resolution Landsat ETM+ imagery,which shows the urban expansion in 2003.The data processing and analyses were done in geographic information system(GIS),which facilitates the overlaying of multiple themes for analysis.The spatial-temporal changes in world cities during the period from the 1960s to the beginning of 2000s were analyzed by computing the urban percentage,annual urban growth rates and compact ratios.The analysis was carried out on a continent,country and individual urban basis.It is revealed that urban development is achieving momentum in developing countries,expanding more noticeable than that in the previous decades.In developing countries,urban land percentage is lower,but urban growth rate is higher.Urban structure of developing countries is more compact and dense than that in Europe and North America.