经济欠发达地区中心城市空间拓展分析--以南充市为例

Urban spatial expansion in less developed region of China:A case study of Nanchong

以四川省南充市为例,探讨了西部经济欠发达地区中心城市的空间拓展规律。基于多时相Landsat TM遥感数据和GIS的定量研究方法,以城市分形理论为基础,结合对城市实体地域空间在不同方向上的拓展分析,系统探讨了南充城市空间在不同时期的形态特征。通过人机交互的监督分类方法,提取了1988、1993、1999、2002和2007年5个年份的南充中心城市实体地域数据,在GIS中进行了叠加。采用半径法进行城市分形研究,发现各个时期南充城市总体上存在分形特征,但维数存在两个标度区,而且标度区之间的维数具有跳跃性,以此判断出城市在不同阶段的增长动力存在差异——从自然增长主导的扩张模式向多种增长力量共同作用的综合模式演化。在对南充城市实体地域进行分象限拓展分析后,发现南充城市在演化过程中存在明显的方向性,总体趋势为东北-西南的轴向拓展,并以此为基础建立了城市空间扩展模型。

This paper is an empirical study of the urban expansion of Nanchong by applying the urban fractal theory. Based on multi-temporal Landsat TM remote imaginary data and Geographical Information System, this paper systematically discusses the spatial layouts and patterns of Nanchong city in selected periods since the 1980s through the 2000s via analyzing the response to urban fractal theory and examining the expansion feature in all directions from the city center. As methodology, we extract the geometric data from the remote images of years including 1988, 1993, 1999, 2002, and 2007, and overlap the extracted images by GIS as to conduct comparison over periods. On the one hand, as response to the urban fractal theoretical analysis, the city shows no significance in urban fractal features, but with two sections with evident difference in fractal dimension parameter. In accordance to the findings, we diagnose the distinct share of driving forces of urban expansion in relevant periods--that the natural growth force dominates in early stage of urban expansion, but the comprehensive growth force, combining natural growth and mechanical growth, dominates the period thereafter. On the other hand, Nanchong city has been growing in particular direction since the 1980s--both to the northeast and to the southwest, displaying the stability over time and indicating the potential growth corridor in the future. Based on those findings, a spatial model is established to formulate the expansion patterns.