Abstract:

Taking the Landsat TM/ETM+images of Wuxi City in 1991，1996，2001 and 2005 as the data source，this paper used the improved band combination threshold extraction to 〖JP2〗extract the spatial information of urban builtup in Wuxi City.Then the result was corrected referring〖JP〗 to the land use classification map in drainage area of Lake Taihu.By overlaying of four classified images，the law of spatial distribution of urban expansion in Wuxi City from 1991 to 2005 were researched.Result indicates that the overall expansion of Wuxi has increased continually since 1991.In particularly，after 2000，urban expansion had a rapid development.At the same time，Wuxi showed an uneven development of spatial expansion.The spatial expansion mainly included two typical expansion modes which were centralized flaky development and axial expansion.The mostly direction of urban expansion in Wuxi was along the centerline of ChangzhouWuxiSuzhou and encircle the Lake Taihu.Meanwhile，the speed of expansion in southeast and east was the fastest.Combining with the data of socioeconomic and humanities，the impact of urban expansion by population and economic development was analyzed too.The results show that population growth and economic developments are two important factors which impact on the urban expansion of Wuxi City.

Key words: urban expansion/ urban builtup/ remote sensing information extraction/ feature space/ driving forces