城市边缘区是位于城市建成区与乡村地域之间受城市辐射深刻影响的过渡地带。文章采用"断裂点"法的基本原理和Matlab软件编制程序识别图像来运算城市边缘区范围,将西安城市边缘区的扩展划分为五个阶段,分析了各个阶段的扩展情况,以及各个阶段的扩展模式,最后对西安2020年城市边缘区范围进行了展望。

Urban fringe lies between urban area and rural area, and it is a kind of transition belt, which is influenced greatly by the city core. The research on the spatial expansion will be helpful to the harmonizing and management of urban area and rural area in Xi'an, and helpful to the development of Xi'an urban area. The basic theory of Breakpoint method and the Matlab software that is used to program and recognize the image are applied. The spatial expansion in urban fringe of Xi'an is divided into 5 phases:(1)the period before the liberation;(2)the period between 1949 and 1957;(3)the period between 1958 and 1977;(4)the period between 1978 and 1998;(5)the period from 1998 to present since the Strategy of Developing the Western Region was put forward. In each period, the expansion area is calculated to estimate the velocity of spatial expansion. At the same time, two circles are made, and the area of one is equal to the area of urban core area, the other is equal to the area of urban fringe. About the spatial expansion in urban fringe, there are 2 modes: one is Axial Expansion, and the other is Extroverted Expansion. At the same time, three conclusions are get:(1)Before the 1980s, the main expansion mode of urban fringe of Xi'an is Extroverted Expansion, and the distribution of industry is the main driving force; After the 1980s, the main expansion mode is Axial Expansion, and the main driving forces comprise the foundation of the Development Area, the distribution of industry and the development of residential area;(2)The Axial Expansion of the urban fringe of Xi'an extends mostly along some highways, which radiate from urban area;(3)The form of the urban fringe of Xi'an has changed from lumpish shape to asteroidal shape, then to lumpish shape. According to the integrated analysis of the area of Xi'an, the city will develop dispersedly, and the form will be turn into asteroidal shape again. Xi'an city will develop toward Lintong eastward, Chang'an southward, Guodu and Huxian county in the southwestward, Xianyang northwestward, and Jinghe Industry Park northward, and southwest and northwest wouldl be the main developing directions of Xi'an. Based on the analysis above, a prospective map of Xi'an urban fringe in 2020 is made.