Identification and characteristics analysis of urban land expansion types in China in the 1990s using DMSP/OLS data

China has been undergoing widespread urbanization process at unprecedented speed since the 1990s. The urban land expansion is an important aspect of urbanization and has diversified types and characteristics, so the identification of urban land expansion types is thought to be crucial for the study of urbanization and urban development management. In view of the insufficiencies in the previous studies, this paper presented a new method for identifying the urban land expansion types based on the temporal change characteristics of light intensity of each cell obtained from the non-radiance calibrated DMSP/OLS nighttime light data of China in 1992, 1996 and 1998. According to the method, the types of urban land expansion were classified into two categories and seven subtypes as accelerated intensifying type, steadily intensifying type, decelerated intensifying type, unchanging type and unsteady type in the infilling category, and 1996 new expansion type, 1998 new expansion type in the sprawling category. In terms of the classification result, this paper analyzed the characteristics of urban land expansion types in composition structure, spatial distribution and developing intensity further, in which some meaningful conclusions were drawn. The new method presented in this paper seems to be useful because it can not only identify the types of urban land expansion on large scale rapidly and simply, but also provide more detailed and realistic information on urban land expansion on the premise of ensuring the comparability of classification result with other researches.