| With the acceleration of urbanization in China in recent years,problems such as shortage of land resources and urbanization space have become increasingly prominent.Yanan,located in the Loess Plateau,the main city of three mountains encirclement,urban area of less seriously hampered the development of Yanan.One of the ways to solve this problem is Land-creation projects.Yanan New District is built in the Loess Gully area around the city through the development strategy of removing the tops of mountains to fill in valleys to create land on which to build.Besides,the huge amount of construction leads to the inevitable phenomena of subsidence,ground cracks and slope instability.Interferometric Synthetic Aperture Radar(InSAR)technology is a rapidly developed earth observation technology in recent years.It can obtain the large-range and all-day millimeter-level ground deformation information,and can be used to monitor the slow urban ground deformation,which is of great significance for the sustainable and sound development of Yanan New District.In order to monitor the urban expansion and surface deformation fully and accurately,multi-source remote sensing data are used to detect the change and surface deformation of Yanan New District.Firstly,the main principles and steps of the time-series InSAR technique for extracting urban surface deformation,the detection of urban expansion change by optical remote sensing,and the sub-pixel correlation matching are systematically introduced,on this basis,the results of change detection and surface deformation of urban expansion in Yanan New District are obtained.The main research contents and results are as follows:(1)The Gaofen-1 image is used to detect the change of the urban dynamic expansion in Yanan New District.OTSU method is used to process the acquired 9 scens of Gaofen-1 data from November 2013 to September 2021,and the eight-phase change detection results are obtained.The results show that the construction of Yanan New District from 2013 to 2014 is focused on land leveling and slope treatment.From 2014 to 2016,the main road network in the New District is formed,and all kinds of planned land are under construction.Construction of the second stage of the North Area of the Yanan New District on the east side started in 2017,first stage,and there is still in the stage of land leveling until now.(2)Two scenes images of Gaofen-1 obtained in June 2015 and January 2016,and six scenes images of Sentinel-2 from May 2017 to January 2021 is acquired,and eight correlation image pairs were constructed.Based on the sub-pixel correlation matching technology of optical remote sensing,the horizontal deformation information of land surface in Yanan New District is acquired.The results show that from 2015 to 2016,the horizontal deformation is mainly concentrated in the first stage of the north area,and the deformation direction is from southeast to northwest.Some horizontal deformation exists in Yanan New District from 2017 to 2018,which is in good match with the results of InSAR in the same period.(3)Combined with the advantages of small baseline set and permanent scatterer technology,34 sences Sentinel-1 radar images from November 2017 to December 2018 were selected to monitor the land subsidence in the north area of Yanan New District,the annual average subsidence rate and cumulative settlement.Based on the geological conditions,hydrologic structure and other data,the deformation characteristics and the main causes of deformation are analyzed.The results show that there are three main deformation areas in Yanan New District.By analyzing the relationship between the thickness of the fill and the cumulative settlement,the correlation coefficient is calculated to be 0.90,indicating a highly positive correlation between the settlement rate and the thickness of fill.Compared with the measured data of high fill area and high slope area,InSAR monitoring results have better consistency and reliability. |
PDF Full Text Request