Research On Urban Built-up Area Extraction And Spatial Form Based On GIS And RS

"Urbanization" is an important strategic direction for China's urban development.By the end of 2017,China's urbanization rate will be 58.52%,and it will continue to grow rapidly in the future.The expansion of urban space and the increase of built-up area are one of the manifestations of urbanization.Beijing,as the capital of China,studies the characteristics of the evolution and spatial expansion of built-up areas in Beijing.It is of great significance for the rational use of land resources,avoiding spatial sprawl and expansion,and solving the "big city disease" in the process of urbanization.This paper uses Landsat/OLI remote sensing image data and nighttime light data spanning 27 years and four time periods,and uses ENVI and GIS spatial analysis techniques to obtain the main built-up areas in Beijing.At the same time,a variety of parameters are used to analyze the morphological characteristics of urban built-up areas.Based on the analysis of the spatial patterns of the multi-phase built-up areas,the driving forces for the expansion of the built-up areas were analyzed.The results of this study provide a scientific reference for the planning and management of urbanization development.The main work and research results of the thesis are as follows:First,the city built area information in the study area was extracted.The FLAASH atmospheric correction module of ENVI5.3 software was used to calibrate the remote sensing images of 1990,2000,2010 and 2017 to eliminate the effect of atmospheric on the gray value of pixels.Three types of land cover information such as vegetation,architecture(impervious surface),and water body were extracted through NDVI,NDBI,and MNDWI indices,and overlayed with impervious surface aggregation data in ArcGIS 10.3,We could get the vector boundary of the built-up area,and extract the city boundary of Beijing.The method of determining the built-up area threshold for night light data was used to extract the city border of Beijing.Finally,the weighted fusion method was applied to achieving the integration of Beijing city boundary based on two data sources.Secondly,the urban morphology measurement and analysis of the years in the study area have been carried out.The information of geometric shape and radius of each built-up area is obtained by using ArcGIS software.The shape index,compactness index,urban gravity transfer,fractal dimension expansion direction,expansion speed and expansion strength are analyzed by Fragstats software.In the process of city development in 27 years,Beijing City built-up area compactness decreased year by year,the shape of the city tends to be lax;shape index changes,Beijing city shape tends to be complicated,the diversity of shape index changes that Beijing city tends to form diversified development;in the transfer center,Beijing the city center has moved eastward trend in the past 27 years the whole city expansion speed.In 1990-2017,the average annual expansion rate of increased first and then decreased.From the perspective of expansion intensity,Beijing city in 1990-2000 belonged to a rapid expansion stage.In 2000-2010,Beijing belonged to a rapid expansion stage.In 2010-2017,Beijing was a slow expansion stage.From the aspect of the expansion of the fractal dimension,from 1990 to 2000,the average annual expansion speed and expansion intensity are significantly larger than the SW and ES directions.The average annual expansion strength of the NE orientation from 2000 to 2010 is all orientation years.The average of the expansion strength is the largest,making the center of gravity of the built-up area migrate to the northeast in 2010,showing the phenomenon of "strong eastbound northward expansion";the expansion from 2010 to 2017 is most obvious in the direction of NE and SW,and the average annual expansion speed and expansion intensity both are larger than those of other bearings,but due to the opposite direction of the two bearings,the center of gravity of the built-up area in 2017 will be eastward.