Research On The Atmospheric Delay Correction Of DInSAR Based On Topography

Differential Interferometric Synthetic Aperture Radar is a method of large-scale deformation measuring developing on Interferometric Synthetic Aperture Radar.The deformation phase is extracted by two or more observations to invert the surface deformation.However,atmospheric delay will bring centimeter error to DInSAR result and seriously affect the understanding and analysis of DInSAR deformation monitoring result.Aiming at atmospheric delay correction of DInSAR,there are mainly two methods: atmospheric delay correction based on external meteorological data and atmospheric delay correction based on data itself.The atmospheric delay correction with the aid of external meteorological data is to use GPS or optical satellite remote sensing data(such as MODIS data)to extract atmospheric parameters(mainly water vapor content)to correct InSAR or DInSAR atmospheric delay.This kind of method has some problems because of the differences in the frequency of GPS,optical satellite sensor and SAR,also because of the differences of time and spatial resolution between them.The atmospheric delay correction method based on the data itself is based on the temporal and spatial variation characteristics of atmospheric delay,using the filtering or neighborhood difference method(i.e.,Permanent Scatterer InSAR,PSI)to suppress the atmospheric delay.The filtering method can only restrain the atmospheric delay to a certain extent at the expense of losing low frequency space deformation.The method of PSI can estimate atmospheric delay,but it needs multitemporal observation data and the algorithm is complicated.In view of the shortcomings of the existing atmospheric delay correction methods,considering the atmospheric delay shows low frequency characteristics in horizontal and vertical space and has a linear relationship with elevation,a method of atmospheric delay correction based on elevation data is proposed in this paper.This paper describes the process of atmospheric delay correction based on elevation data and uses the experiments and application examples to prove the effectiveness of this method.What's more,the applicable area type and scale of this method is analyzed.The specific work of this paper is as follows:(1)Analyze the error characteristics of DInSAR,research the changing relation between DInSAR error and baseline error,elevation error,atmospheric delay.Then get the conclusion that the atmospheric delay is the main source of DInSAR error and atmospheric delay changes with the elevation.(2)Based on the characteristic of the changing relation between atmospheric delay and elevation,this paper proposes a atmospheric delay correction method based on elevation.With the help of DEM,select the control points on vertical and horizontal space uniformly.And use the RANSAC algorithm to delete the error points,then build the atmospheric delay correction linear model based on elevation data using the method of least square.(3)Use two areas with different climate circumstance in the western part of Qinghai as example.Make differential interferometry and experiments of atmospheric delay correction combining with 2 Sentinel-1 images and SRTM elevation data.The results of two experiments show that in the case of good correlation(?0.7),the DInSAR atmospheric delay correction based on elevation data can get ideal result.(4)Research applicable area type of atmospheric delay correction method proposed in this paper from the aspects of town area,abnormal atmosphere area and area with strong correlation between atmosphere and elevation.Discover that method proposed in this paper can get best correction result in the area with strong correlation between atmosphere and elevation.(5)By changing the scale of different regions to analyze the correlation between elevation and atmospheric delay and the effect of atmospheric delay correction at different regional scales.Discover that in the area of east-west 100 km,north-south 50 km this method can achieve the best effect in correcting atmospheric delay.(6)Use the atmospheric delay correction method proposed in this paper to correct the atmospheric delay of DInSAR result of landslide area.The result quality of the DInSAR deformation of the landslide is improved,which further proves that the atmospheric delay correction method based on elevation data is effective and practical.