关键词: DMSP/OLS, 建成区, 重心, 分离度

Abstract:

In April 2016, Chengdu-Chongqing Urban Agglomeration Development Plan firstly officially confirmed the connotation and specific boundary of Chengdu-Chongqing urban agglomeration. It's conducive to optimize and adjust the trend of development in future and help understanding the spatial patterns and dynamic changes of Chengdu-Chongqing urban agglomeration. Firstly, during the pretreatment process of DMSP/OLS night-time light data, the traditional methods calibrated images by a representative invariant region and those frequently selected regions were far away from the study area, causing uncertainties and errors. We calibrated all pixels of the DMSP/OLS night-time light data within the boundaries of urban-district in 2013. Next, we designed a rule to calibrate the statistical data. On the basis of these two kinds of data, we calculated out the best thresholds of the urban built-up areas in 5 stages of Chengdu-Chongqing urban agglomeration from 1997 to 2013. Comparing extractive areas with statistical areas, the total average relative error is only -0.38%. The result was more stable and accurate than other methods. We tested the extracted built-up polygons (2013) with the certain built-up polygons that sketched on Google Earth historical images. The results showed that the accuracy of extraction had reached 98.29%. Furthermore, we selected the barycenter index and landscape isolation index to analyze the extraction results. We studied the shifting processes of barycenter and the integrating processes of cities and found that: (1) the level of integration was highly consistent with planning and Chengdu-Chongqing urban agglomeration had entered a stage of rapid development; (2) Chongqing metropolitan and Chengdu metropolitan gradually formed and the former achieved greater developments and it also deteriorated regional imbalance. Overall, our research results can be used to optimize the development of Chengdu-Chongqing urban agglomeration, and we provided a template for the study on the space forming processes of urban agglomeration.

Key words: DMSP/OLS, built-up area, barycenter, landscape isolation