基于地学信息图谱的合肥市城市扩展时空特征及驱动力分析

利用多时相遥感影像，借助ArcGIS平台，采用空间形态分析、等扇分析、等距分析及分形分析等方法，以城市扩展强度、紧凑度、分形维数、重心坐标、扩展弹性系数等为指标，基于地学信息图谱分析了1987~2011年合肥市城市扩展时空特征及其驱动力。结果表明：合肥市在经历了轴向放射状扩展、双核组团扩展及轴间填充后，城市形态由不规则团块状向星楔形、连体双星形转变；24 a间，城市用地面积增长了22415 km2，城市规模扩大了455倍；2000年以前基本保持中、低速扩展，进入21世纪后，开始高速扩展；城市空间主要沿交通线向西南、东南、东、东北等方向非均衡延展，城市扩展最强烈的区域约在距城区中心8 km处，城市重心不断向南偏西方向转移；扩展过程中，城市紧凑度呈“W”型波动，分形维数呈“M”型波动，扩展弹性系数呈“∧”型波动，城市形态最终向着稳定、合理化方向发展；自然环境、经济发展、人口增长、交通建设、政府行为等是合肥市城市扩展的主要驱动力量

ANALYSIS ON SPATIOTEMPORAL CHARACTERISTICS AND DRIVING FORCES OF HEFEI URBAN EXPANSION BASED ON GEO-INFORMATIC MAP

Owing to the regional differences in the nature, society and economy, there are diversities in space expansion in different cities which, accordingly, cause the diversities in social, economic and eco environmental benefits. Therefore, it is beneficial to predict, guide and regulate the future development of the city, analyze and settle the problems in the citys social and economic development by clarifying the changes in urban expansion, revealing the growth process and evolution rule of the city. Since the 1980s, there has been a rapid development in the economy of Hefei City, an increase in its urbanization and obvious changes in the urban space expansion. Based on the geo informatic map, the spatial expansion information of Hefei City was extracted by man machine interactive method from multi temporal satellite images, and the temporal and spatial expansion characteristics of Hefei from 1987 to 2011 as well as their driving forces were analyzed with indices such as urban expansion intensity, compactness, fractal dimension, center coordinates, and elasticity coefficient with the help of ArcGIS software platform and some different research methods, such as spatial form analysis, fans analysis, fractal analysis. The result shows that after the expansion alongside the transportation axes, the dual core group expansion and the filling in the transportation axes, the urban form of Hefei City has transformed from irregular block mass into star wedge complex and conjoined twin star shape. During 24 years, urban land area in Hefei City were increased by 22415 m2，the city size expanded 455 times. Before 2000, the city kept extending mainly at a medium and lower speed, while after entering 21st century, it began extending at a high speed, especially between 2000 to 2006. The urban expansion has showed an obvious spatial heterogeneity, and the urban space has expanded unevenly alongside the external traffic lines towards the southwest, the southeast, the east and the northeast. There are obvious differences among the expansion directions of the urban land in different period. The most obvious expanding area lied in the place which is about 8 km from the city center, and the focus of city shifted to the south. The compactness, fractal dimension and elasticity coefficient of the city were fluctuated just like types of “W”, “M” and “∧” respectively, and the urban spatial form developed towards the stability and rationalization finally. In the future, the focus of city will continue the expansion toward the south while its direction may move to the east a bit, the distance between the north and south will become longer, and the urban form will become more regular and develop into a round shape. Natural environmental conditions, economic development, population growth, traffic infrastructure development, and government behaviors are the main driving forces of the urban expansion in Hefei City. The unbalanced changes in the urban expansion are the results made by the influence of multiple driving forces.