Research On Surface Subsidence Monitoring Of Tianjin Based On SBAS-InSAR Technology

Surface subsidence is a geological disaster caused by natural or man-made factors.It’s impact is continuous and irreversible,which is extremely harmful to human production and life.So far,many provinces,cities,and districts in our country are suffering from the effects of surface subsidence disasters,which causes varying degrees of damage.Tianjin is an important hub connecting China ’s domestic and foreign developments.It enjoys a superior geographical location and has a significant effect on regional and inland development.Since the subsidence was discovered in 1923,it has reached a maximum of 3m,which has caused varying degrees of damage.Subsidence monitoring and analysis of Tianjin has important reference significance for the future development of reasonable development planning and settlement prevention.At present,the traditional precision leveling is the main technical means for surface deformation monitoring.This method is mature in technology,accurate in monitoring results,and rich in historical data.However,its shortcomings such as long monitoring period,small monitoring range,sparse monitoring points and costly labor are more prominent.Compared with the leveling method,D-InSAR technology has the great advantages of acquiring large-scale high-precision surface deformation information all-weather,all-weather,low cost,and high efficiency due to its principle characteristics,and is more suitable for monitoring in urban or non-urban areas.In order to explore the difference between DEM extracted based on InSAR technology and sentinel-1 data and other elevation data applied to SBAS time series analysis results and accuracy,this paper first makes a comparative analysis of DEM extraction and SBAS application in the research area.Then,based on the sbas-insar technology,using 29 sentinel-1 orbit drop data,an experimental study on urban surface subsidence monitoring in Tianjin is carried out.The main research results are as follows:1.Based on the principle of space-time baseline optimization,orbit error and atmospheric impact minimization,two suitable SAR images are selected,and the DEM of the sub study area is extracted by InSAR technology.The comparison results with the application of SRTM,GDEM and AW3 D DSM in SBAS time series analysis show that there are great differences in the results of SBAS time series analysis based on different elevation data,while SRTM DEM with 30 m resolution can gain higher accuracy in SBAS time series analysis.2.The SBAS technology was used to obtain the settlement information of the Tianjin area with 29 scenes of Sentinel-1 images and SRTM DEM.The result shows that most areas are in the process of settlement during 2015-2018,with the maximum cumulative settlement of 394 mm and the maximum settlement rate of 170 mm / a,and there forms six settlement centers whose maximum accumulated settlement has exceeded 170 mm.They are respectively located in the southern part of Wuqing District,central and eastern part of Jinghai District,central part of Xiqing District and its junction with southern part of Jinnan District,eastern part of Ninghe District.There is no settlement in the central urban area as a whole,and the four areas around the city,Jinghai District,Ninghe district and Binhai New District all produce slow settlement with the maximum accumulated settlement less than 100 mm.3.The SBAS time series analysis results are consistent with the GNSS observation results.According to the “technical specification for ground subsidence Interferometric Radar Data Measurement” issued by China Geological Survey Bureau,the mean square error indexes of the two are calculated.It is concluded that the mean square error is 12 mm,which meet the requirements of the technical specification.At the same time,they are consistent with the settlement information in the settlement contour map of Tianjin in 2015 It shows that SBAS time series analysis technology is more accurate in the monitoring of urban surface subsidence.