Research On The Key Technologies Of Land Subsidence Monitoring Based On InSAR Time Series With Multi-Track Sentinel-1A SAR Data

The Hebei Plain is one of the most serious and complex areas of land subsidence in the country.For the tens of thousands of square kilometers of Hebei Plain,large coverage land subsidence monitoring is still one of the difficult problems to be solved,mainly as follows:Firstly,how to use InSAR time series technology to perform high-precision deformation inversion based on short time and limited data.Secondly,the deformation monitoring based on single track can't completely cover the Hebei Plain,so how to achieve simultaneous observation of adjacent multi-tracks.Thirdly,how to evaluate the final deformation monitoring results without geodetic data.Therefore,this paper mainly studies how to perform large coverage,high-precision land subsidence monitoring in time series combining multi-track limited Sentinel-1A SAR images.The main research contents and conclusions of this paper are as follows:(1)Analyze and discuss the basic principles and key technologies of NSBAS technique,and it is found that small baseline set generation,phase unwrapping method and PS point extraction method will directly affect the reliability of the subsidence results.An improved seamless mosaic method of multi-track SAR data is proposed to realize large coverage and multi-track land subsidence monitoring.Accuracy assessment is performed using cross-validation of redundant observations in multi-track overlap regions.(2)This paper takes the Hebei Plain as the study area and selects 90 scene SLC data of the Sentinel-1A satellite of two tracks from December 2017 to June 2018.High-precision timing inversion is performed based on single track using NSBAS technique.The multi-track data was successfully merged by using the improved seamless mosaic method of multi-track SAR data.The offset deformation values of two tracks calculated in this paper are 0.08mm,and the mosaiced cumulative deformation map of the Hebei plain is obtained through the unification of the datum.(3)The subsidence of the Hebei Plain is characterized by continuous distribution in the administrative area,and the overall trend is continuous.In this paper,14 main subsidence areas were extracted and their geographic information and subsidence information were statistically analyzed,and the causes of land subsidence were analyzed based on relevant data.Using the cross-validation of redundant observations in the multi-track overlap area to evaluate the accuracy,it is found that the difference of the cumulative subsidence of more than 95%of the two track overlap areas is within 9 mm,and the standard deviation is 6.18 mm,and the subsidence trend of the overlap area is consistent.