基于多时相Landsat数据的城市扩张及其驱动力分析

AN ANALYSIS OF URBAN EXPANSION AND ITS DYNAMICS BASED ON MULTI-TEMPORAL LANDSAT DATA

以长沙市为例，在多时相Landsat遥感数据支持下，采用监督分类、非监督分类和归一化裸露指数（NDBI）等方法提取城市用地信息。通过对比多期城市用地的熵值变化，定量分析城市扩张的时空特性；运用叠加、缓冲区分析等方法，分析城市扩张和中心城区的关系，绘制城市扩张速度玫瑰图。研究结果表明，长沙市建成区总面积不断扩展，其中，1973～1986年扩张主要表现在东南方向，1987～1993年为西部方向，1994～2001年南和东南方向成为快速扩张方向；对长沙城市扩张驱动力进行分析，认为人口迅速增加是城市扩张的最主要驱动力。

Based on multi -temporal Landsat imageries, the authors extracted the urban builtup areas in Chang sha City, Hunan province on the basis of such methods as supervised classification, unsupervised classification and NDBI index. The spatio - temporal patterns of the urban expansion were analyzed quantitatively by using the entropy value and differential entropy value of sequential urban land use images. Overlay and buffer spatial analysis were used to establish the relationship between the urban expansion and the distance from the city center. On such a basis, the expansion rate map was drawn to show the dominant direction of urban expansion. The results show that the urban builtup areas have continued to increase, and the expansion was directed mostly southeastward from 1973 to 1986, westward from 1987 to 1993, and southward and southeastward from 1994 to 2001. The rapid increase of population is thought to be the most important driving force of urban expansion.