Special Column:Celebration of the 70th Anniversary of IGSNRR, CAS
LI Fei-xue, LI Man-chun, LIU Yong-xue, LIANG Jian, CHEN Zhen-jie
The process of urbanization is speeding up along with the development of socio-economy.As a result,urban area grows rapidly.Research on urban growth using RS and GIS has become a focus in recent years by geographers,and it’s meaningful to put more emphases upon urban growth study and lead urban growth by constituting effective policies and measures.Urban boundary information of Nanjing was extracted from aerial photos (1949 and 1976),Landsat MSS (1988),TM(1997,2000 and 2001),and ETM+(2003)images with supervised classification after principal component analysis.Based on the urban growth intensity,the population-urban growth index,the fractal index,the urban growth orientation,the urban gravity transfer model,etc.,this paper analyzes characteristics of urban spatial-temporal change in Nanjing city,Jiangsu province. The driving force of urban growth in Nanjing is discussed form the view points of physical condition,social-economy,etc.,and we concluded that:(1)The urban area expanded by 10 times in Nanjing from 1949-2003.The urban growth process can be divided into three phases: the urban growth maintained slow from 1949 to 1976 with a pattern of quasi-loop expansion and an intensity of 1.85%;then it speeded up from 1976 to 1988,with an intensity of 8.55% and quasi-loop expansion existed together with a leap-forward pattern;subsequently,it kept rapid expansion after 1988,with a pattern of leap-forward and join and an intensity of 18.79%.(2)For the obstruct of the Yangtze River,urban growth presents an“Axis Mode”,and the growth axis is extending along the Yangtze River (viz.from north-east to south-west);meanwhile,the direction of the gravity transfers toward south-east after wavered toward north.(3)As a result of urban growth,morphology of the urban expansion maintained stable after becoming complex,and became more and more reasonable.Urban growth intensity in each district in different periods from 1949 to 2003 is different from each other,and urban growth kept loose in the suburbs and compact in the city proper.(4)The existing urban land border and shape were formed under the joint efforts of many forces,such as socio-economic force,physical condition,and so on.The dominant forces in different phases are different from each other.In the point of quantity of urban growth,development of economy was the leading driving force,and policies were the main factors influencing spatial pattern and spatial morphology.The improvement of infrastructure,especially,transportation extended urban frame, and the adjustment of regionalism provides space for urban growth which is oriented by general urban planning.
