Research On Terrain And Deformation Measurement Technology Using Ground-based Interferometric Rada

Ground based Interferometric Synthetic Aperture Radar(GB-In SAR)is a microwave sensor with the advantages of all-weather observation,high resolution,and high accuracy.SAR interferometry technology plays an important role in terrain surveying and deformation measurement.This article mainly focuses on the key technologies for obtaining high-precision DEM(Digital Elevation Model)and deformation using the GB-In SAR system.The main content and research results are as follows:(1)An optimized GB-In SAR terrain measurement method has been proposed.In the process of extracting DEM by GB-In SAR interference data processing of terrain scenes,the interference phase error is one of the main factors affecting the accuracy of DEM.The conventional interference phase filtering has serious over-filtering and under-filtering phenomena,resulting in interference phase distortion.Especially in the terrain with large field of view and strong fluctuation,the accuracy of interferometric phase unwrapping is low,and the atmospheric change in the data acquisition process is not fully considered,and large interferometric phase error is finally introduced,which seriously affects the accuracy of DEM measurement.Therefore,this paper proposes an improved interference phase error elimination method to ensure the high-precision measurement of DEM.First of all,an adaptive interference phase filtering method is proposed for the serious over-filtering and under-filtering phenomenon of interference phase filtering.This method first suppresses some noise by coherently stacking the radar images under each baseline.Then,by calculating the average coherence coefficient of PS(Permanent Scatterer)in the sliding window,the power exponent of the frequency domain weighting function is adaptively adjusted to replace the value set by the original artificial experience,which significantly reduces the noise of the interference phase and well preserves the edge details of the interference fringe.Secondly,based on the empirical model of atmospheric refractive index,the change of atmospheric refractive index is estimated by using the meteorological data in the scene,and the delay phase error at each slant distance in the observation area is calculated quantitatively to realize the error compensation of interference phase.Finally,the DEM smoothing de-noising is performed by using locally weighted Scatterplot Smoothing(Lowess)to further reduce phase unwrapping error,delay phase error and residual phase of noise.The method proposed in this paper is used to process the measured data of a cliff in Qijiang,Chongqing.Compared with the DEM generated by the terrestrial laser scanner(TLS),this method effectively reduces the interference phase error and improves the measurement accuracy of DEM.(2)An improved GB-In SAR deformation measurement algorithm for complex atmospheric disturbances has been proposed.Atmospheric disturbance is one of the main error sources of ground-based interferometric synthetic aperture radar deformation measurement.Under complex atmospheric conditions,the conventional atmospheric phase compensation method is no longer applicable.In this paper,an improved method based on PS technology is proposed to effectively compensate the atmospheric phase under complex atmospheric conditions,thus improving the deformation measurement accuracy.Firstly,the method establishes the neighboring PS pairs through Delaunay triangulation,analyzes the standard deviation of the differential phase sequence of each neighboring PS pair,and realizes the filtering of noise points or partial deformation points in the PS set;Then,the reference atmospheric phase sequence is estimated according to the meteorological data.By calculating the MIC(maximum information coefficient)of the interference phase sequence of the residual PS and the reference atmospheric phase sequence,combined with the spatial dimensional coherence coefficient,the selection of stable PS is realized by using double thresholds;Finally,Kriging interpolation fitting method is used to realize atmospheric phase estimation under complex atmospheric conditions.The method proposed in this paper is used to process the measured data in the nine corners area.Compared with the conventional method,the atmospheric phase compensation error is effectively reduced,which proves the effectiveness of the improved method.In order to visually verify the accuracy of deformation measurement,this improved method is applied to the measured data of a mountain slope in Beibei District,Chongqing.By comparing with the displacement angle inverse variable,the accuracy of GB-In SAR deformation measurement is guaranteed.