Evaluating Urban Expansion of Nanjing City Based on Remote Sensing and GIS

This paper presents an integrated study of urban expansion in Nanjing City, Jiangsu Province of China, by using Geographical Information Systems (GIS) and remote sensing. Landsat TM/ETM+ images of 2000 and 2007 were used in this study. An improved method was proposed to extract urban built-up areas from the images, which was based on Normalized Difference Built-up Index (NDBI). The proposed method could remove sparse vegetation from the mapped results. Assisted by spatial analysis and statistic techniques of GIS, the spatial distribution of urban land-use was analyzed and the characteristics of urban land-use expansion were studied. The results revealed a notable urban growth from 2000 to 2007 in the study area, and the most active expansion parts were the northeast-southwest axial and the southeast area of the main city zone in Nanjing. Furthermore, the driving forces of urban spatial expansion were also discussed. By analyzing related socio-economic data, it was found that economic development and population growth were the main factors; government decision-making and natural environment also influenced the speed and direction of urban expansion in some degree.