Research On Elevation Extraction And Atmospheric Correction Algorithm Based On SAR Image

Synthetic Aperture Radar(SAR)is an active earth observation system.Because of its all-day and all-weather characteristics,it is widely used in military,agriculture and other fields.Among them,synthetic aperture radar interferometry(InSAR)was developed at the end of the 20 th century.It has become an important branch in the field of SAR research.The interferometric technology can be used to quickly make large-scale observations of the surface and obtain a digital elevation model(DEM).DEM data is a digital simulation of terrain elevation information,high-precision DEM data It is of great significance to surveying and mapping,meteorology,engineering construction,military and other fields.Differential SAR interferometry(DInSAR)is developed on the basis of InSAR technology.It is used to obtain micro-deformation information on the surface.Its measurement accuracy can reach millimeter level.However,due to differences in the atmospheric conditions of the SAR images imaged at different times,different SARs The interference of the image will cause the atmospheric delay phase to be included in the interferogram,resulting in larger errors in the deformation extraction results.Based on the above two aspects,this paper has done an in-depth study on the elevation extraction and atmospheric correction of SAR images.The main research results are as follows:(1)Based on the principles and characteristics of SAR imaging,this article explains the problems inSAR image interference to obtain elevation models,and introduces the principle of multi-baseline InSAR,analyzes the influence of baselines on InSAR technology,and focuses on interference on decoherence and SAR images.For problems such as shadow overlap and masking,an algorithm combining long and short baseline iterative differential interference and multi-baseline DEM fusion is proposed.A group of multi-baseline SAR images is selected,and the elevation data of the mountainous area near Liangshan is extracted using this algorithm.Comparing the extracted elevation data with the data of Google Earth,the result shows that the root mean square error in the area with large fluctuations is reduced from 9.892 m to 6.150 m.(2)The time-series differential technology can solve the problem of atmospheric effects.By selecting permanent scatterers(PS)that always maintain good scattering characteristics in the time-series SAR images,the atmospheric phase in the differential interference can be removed.This article introduces the most widely used permanent scatterer differential interferometry(PSDInSAR)and small baseline set differential interferometry(SBAS-DInSAR).The selection of the key algorithm high-coherence points is studied,and the atmospheric phase model is carried out.According to the analysis,the atmospheric phase is divided into the vertical stratified delay phase and the turbulence phase,and the characteristics of the two phase models are removed separately.Finally,21 COSMO-Sky Med images in Pu'an County and Qinglong County were selected,and the atmospheric phase was separated using DORIS and Sta MPS software,and the deformation rate before and after atmospheric correction in the area was extracted respectively.The results showed the deformation rate standard before and after atmospheric correction.The differences were 47.74 mm/y and 39.21 mm/y,respectively.