Urban Spatial Structure Analysis Of Major Cities In China Based On Multi-source Nighttime Light Images

The urban spatial structure has also changed strongly with the urbanization process.In different research scales,it is mainly divided into two parts: urban spatial form and urban internal spatial structure change.Urban spatial form,namely the development and change of built-up areas,is mainly manifested as the gradual increase of the urban area.If scientific planning guidance is not provided in time,blind expansion may lead to a series of consequences such as urban sprawl.Therefore,it is particularly important to grasp the spatial form of urban built-up areas timely and accurately.In addition,the urban residential structure is not only an important part of the urban spatial structure,but also plays a role in promoting the re-development of the urban spatial structure.Therefore,the analysis of the urban residential structure based on the housing vacancy rate can directly reflect the actual occupancy situation and residential structure of the city.Consequently,the estimation of the housing vacancy rate can understand the urban residential structure,which is more conducive to the healthy development of the city in the future.By summarizing and analyzing the existing research at home and abroad,taking the major cities in China as the research area,this paper selected NPP/VIIRS nighttime light data from 2012 to 2019 and the Luojia1-01 nighttime light data from 2018 to discuss urban spatial urban structure.The main research contents and results are as following:(1)In this study,a high-resolution spatial comparison method was used to extract the NPP/VIIRS nighttime light data from 2012 to 2019 time series for major urban built-up areas,and then the Locaspa Viewer 3D digital earth was used to verify the accuracy of the external contour and internal built-up areas of the extracted urban built-up areas.Finally,the urban development and change of major cities in China are analyzed and discussed by using municical expansion forms and directions of urban built-up areas.The analysis founded that from the perspective of urban expansion form,the first-tier cities have the highest compactness,all of which are above 0.28.From the perspective of urban expansion orientation,most of the major cities in China had multi-directional expansion.On the whole,the speed of urban expansion is higher in the West and lower in the East,higher in the South and lower in the north,the urban compactness is "U" shape,and lower in the central region.(2)This study proposed a model to estimation the housing vacancy rate based on the Luojia1-01 image and building data.This model estimates the HVRs of major cities in China by determining the building areas and considering the floor height.It also introduced four driving factors of population,average house price,GDP and the ratio of three industrial structures,as well as two research patterns of geographical division and urban hierarchy to analyze the urban residential space structure with Chinese characteristics.The results reveales that the lowest(15%)and highest(24.3%)HVRs occur in Shenzhen and Nanning,respectively.The urban HVR correlates positively with the three production structures(0.3143)but is significantly negatively correlated with population(0.3841),GDP(0.6139),and urban average housing prices(0.5083).The first-tier,new first-tier,and second-tier cities showed the lowest(16.9%),relatively concentrated(20.5%),and highest(21.3%)average vacancy rates,respectively.The vacancy rateis relatively low in the eastern coastal areas,whereas high in the northeast and western inland areas.