Research On Boundary Extraction And Spatio-temporal Evolution Of Urban Built-up Area

The city is the inevitable product of the development of human society to a certain extent.Urban expansion is an important manifestation of the process of urbanization.Accurately extracting built-up area information is helpful to understand the speed of urbanization process and analyze the driving factors of urbanization process.In the past extraction methods of urban built-up areas(UBA)based on impervious surface area(ISA),the results obtained are often discontinuous due to the discontinuity of impervious surface area.How to maintain the continuity of urban built-up areas is an important research topic,and there are few studies on extracting UBA through thermal infrared methods such as land surface temperature(LST).In the past 20 years,China's cities have expanded rapidly.Current researches mostly focus on the comparison of urban development in large urban agglomerations,the eastern,central and western regions,and the lack of a vertical perspective on the comparison of the temporal and spatial evolution of northern and southern cities.In addition,existing research pays little attention to the long-term functional evolution of urban built-up areas,and lacks agglomeration analysis of different expansion patterns.Qualitative analysis is mostly adopted in the driving force mechanism of urban development,and there is no quantitative test,and the driving mechanism is rarely discussed from the perspectives of time and space.This research proposes an urban built-up area extraction method based on the object impervious surface aggregation density(ISAD).Through the calculation of ISAD and the proposal of the relevant threshold method,and the pervious surface(green space,water body,etc.)surrounded by the urban built-up area is also used as a component of the built-up area,the continuity and integrity of the urban built-up area are guaranteed;In the field of thermal infrared,a ?LST threshold method based on the difference of Land surface emissivity(LSE)is proposed,which is an urban built-up area extraction method.And comprehensively evaluate the extraction effect of these two methods.Taking the main typical cities in the north and south of China as the research area,the impervious surface concentration method of the object is used to extract the urban built-up area from 1995 to 2015.Introduce indicators such as compactness and fractal dimension of urban expansion to analyze the temporal and spatial evolution of urban expansion.Quantitative and qualitative analysis of the driving force factors of urban expansion through GIS spatial analysis and Geo Dectector(GD)and other methods.The process of urbanization is an intuitive manifestation of urban economic development.Through a comparative analysis of the urban expansion of typical cities in the north and south,we hope to find a macro confirmation of the gradual increase in the economic gap between the north and the south in recent years,and provide a scientific reference for the formulation of future development plans for cities in the north and south of China.The main conclusions as follows:(1)The two UBA extraction methods proposed in this thesis have high accuracy and good extraction effect.Among them,the ?LST threshold method based on LSE difference has an overall average accuracy of 86.15% for UBA extraction,and an overall average accuracy of the object impervious surface aggregation density method is 93.12%.The ?LST threshold method based on the LSE difference in the field of thermal infrared remote sensing makes up for the shortcomings of the existing UBA extraction methods based on LST inversion results that are overly dependent on the urban heat island effect.The object impervious surface concentration method is more convenient to operate than the former.Both methods can effectively avoid cloud interference to the UBA extraction process.(2)The 12 cities have different expansion characteristics and temporal and spatial evolution characteristics.The expansion of northern cities is mostly single-core,while the expansion of southern cities is mostly multi-core;the spatial form of most cities tends to be discretized,and the urban expansion process in southern cities is significantly faster than that in the north.(3)The geographic detector reveals that the urban expansion of the study area is mainly related to population and economy,and the north and south are consistent;social factors explain the expansion of cities in the south more strongly than cities in the north,and the natural factors are opposite,and the traffic factors are not significantly different.