Dynamic monitoring of urban expansion based on RS and GIS technology-a case study of Zhengzhou city

Abstract：TM/ETM+ RS images of May 14, 1988 and May 10, 2001 are adopted as main data sources, and three indexes which are normalized difference built-up index (NDBI) , normalized difference water index (NDWI) and soil adjusted vegetation inde (SAVI) to represent three main land cover types (i.e.building, water body and vegetation) are constructed based on data-dimension compression technique.The pseudo-color composite image of the three index-bands is made, and the maximum likelihood supervised classification for the pseudo-color composite image is carried out.Then extract out urban land information from the classification result maps of the pseudo-color composite image by using masking technology of ENVI software.The spatial overlay analysis technique of GIS is used to extract out urban expansion information of Zhengzhou city from 1988 to 2001, which includes urban expansion area, rate and direction, etc.Finally, the urban expansion pattern of Zhengzhou city is analyzed.The results indicate that:the urban expansion area of Zhengzhou city is 109.80km2 from 1988 to 2001, the average annual urban growth rate is 8.98%, the main urban expansion directions are Northeast, West, North, South and Southeast.It is approximately considered that the urban expansion pattern of Zhengzhou city is the concentric circle pattern taking Two-seven Square as its city center.

Keyword：urban expansion;dynamic monitoring;data-dimension compression;RS information extraction;urban land information extraction;