GB-SAR Atmospheric Correction Method Based On Meteorological Data And Its Application In Deformation Monitoring

Deformation is a common phenomenon in nature.Surface deformation will lead to changes in its spatial location,and in some cases even lead to earthquakes,landslides,debris flows and other geological disasters.Deformation monitoring is an effective means of prevention and early warning for such disasters.Common deformation monitoring technologies include conventional ground survey,photogrammetry,ground three-dimensional laser scanning,GPS measurement and so on.Ground-based synthetic aperture radar(GB-SAR)is a new remote sensing deformation monitoring technology developed in recent years.Compared with the commonly used deformation monitoring technology,it has the characteristics of high spatial resolution,high sampling frequency and zero baseline.It can operate all-weather and all-time,and has a wide range of applications.However,the atmospheric effect has a great influence on the electromagnetic wave signals transmitted by GB-SAR,which will lead to the change of its propagation path,thus introducing the atmospheric effect error and reducing the accuracy of monitoring results.How to effectively eliminate the influence of atmospheric effects is still the focus of GB-SAR research.Common atmospheric correction methods include meteorological data correction,fixed point correction and permanent scatterer technology.Based on the meteorological data correction method,this paper mainly conducts relevant research on the atmospheric correction of GB-SAR.The main contents are as follows:(1)Describe three key technologies of GB-SAR,including stepped-frequency continuous-wave,synthetic aperture radar and differential interferometry.The data processing flow of GB-SAR deformation monitoring and IBIS-L system are introduced in detail.(2)The principle of meteorological data correction method and its atmospheric correction model are introduced in detail.IBIS-L was used to carry out a design experiment on Yangtze River Beach in Qingshan,and the meteorological data correction method was applied in this experiment.The results show that the meteorological data correction method can weaken the influence of atmospheric effect to a certain extent.Based on the atmospheric correction model,the influence of the accuracy of experimental meteorological data acquisition on monitoring results is analyzed.It is found that the influence of relative humidity is the greatest,and the influence of atmospheric temperature and pressure is negligible relative to relative humidity.(3)A modified meteorological data correction method is proposed.Its basic principle is to use the stable points of monitoring site to correct relative humidity and to use the modified meteorological data for atmospheric correction.The application of this method in Qingshan River Beach experiment shows that it can effectively eliminate the influence of atmospheric effect and improve the accuracy of GB-SAR deformation monitoring.(4)IBIS-L is used to monitor the Lianziya dangerous rock mass in the Three Gorges Reservoir area,and the modified meteorological data correction method is used for atmospheric correction of the monitoring results,which effectively weakens the impact of the atmospheric effect,but there are extreme points in the atmospheric correction results.Combining with the change of meteorological data,the atmospheric correction results are further analyzed.It is found that the time when extreme point appears corresponds to the time when the trend of relative humidity changes.According to the changing trend of relative humidity,it is modified in different time periods.The modified meteorological data are used for atmospheric correction of the monitoring results,eliminating the extreme point.The monitoring experiment of Lianziya dangerous rock mass further verifies the feasibility and correctness of the modified meteorological data correction method.