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Urban fringe is a special area with interaction of urban and rural areas. So far how to identify urban fringe from urban area and rural areas is one of the major fields that urban geography concern. In this paper, remote sensing images of Nanjing district in 2003 is the calculating base. At the same time, the RS and GIS softwares are applied to program and recognize the image. A improved model of message entropy for land use was established based on the theory of information entropy and the feature of land use in city fringe. Through analyzing the distribution characteristics of entropy, the range of city fringe in Nanjing is confirmed with the entropy values of 60 and 68.Then this paper concludes a comparatively boundary between urban area and urban fringe. However, the paper also points out that the boundary of urban fringe is dynamic and in fact, subjective distinguishing with experience is needed in this process, this method has great feasibility in practice.

This paper proposes a research framework for studying urban air pollution. The framework generalizes the comprehensive thinking and process of urban air pollution research from a GIS-based perspective and pays more attention to the spatial distribution of air pollution. It includes three sections in sequence of data acquisition, model running and result applications. The authors utilize spatial data management and analysis that GIS provides to organize the data and implement urban air pollution research methods involved in the framework. Through these GIS-based improvements and implementations, urban air pollution spatial distribution trends are much better represented and learned. The interrelationships between the involved methods are strengthened.

Urban planning is human purposeful, conscious social activity. It is influenced by nature and human society. Research of urban planning and urban space expansion is in the forefront of global urban research, and is one of the hot topics. China is troubled by population growth, lack of resources, ecological and environmental degradation, and rational urban development is closely related to sustainable development of important issues. It is needed and valuable to carry out a comprehensive study on urban space expansion because of multi-cause and problem's complex structure. The simulation of urban planning is a kind of effective way to understand how urban space expands. The aim of this paper is to simulate and study urban space expansion by the realization of USE-CA (Urban Space Expansion-Cellular Automata) model.