The Model And Method For Monitoring Aspect Deformation Of Landslides By Combining Ascending And Descending InSAR

Satellite synthetic aperture radar interferometry(InSAR)has been widely used in the the identification and monitoring of landslides in recent years,its advantages like large-scale and fine spatial resolution are promising in identifying landslide hazards and monitoring deformation characteristics of landslides.However,InSAR technology based on a single satellite platform or orbit can derive only one-dimensional deformation information of the landslide in the direction of the line of sight(LOS)of the radar satellite but not the deformation along its aspect direction,which cannot meet well the engineering requirements for landslide monitoring.To obtain more direct landslide deformation information of interest,this paper carries out the related researches on extracting the deformation of landslides in the aspect direction by combining ascending and descending InSAR.We conduct a case study of an ancient landslide in Taoping village,Li County in Sichuan province,and develop the the model and algorithm for extracting and analyzing the deformation of the Taoping landslide in the aspect direction.This papre first developes the model and algorithm for extracting the deformation of landslides in the aspect direction by combining ascending and descending InSAR.The method mainly includes:(1)deriving LOS deformation fields of ascending and descending obrit by InSAR technology,(2)defining the slope-based coordinate system,(3)modeling the LOS deformation according to the configuration between the satellites and surface slopes and(4)solving for the displacements of landslides in the aspect and aspect-perpendicular directions with the assumption of no deformation in the slope surface-normal direction.In order to verify the reliability of the model and algorithm,we carry out simulation experiments to extract the deformation velocity fields in the aspect direction by simulating the real deformation velocity fields on the sliding surface combined with the evaluation of root mean square error,including simulation experiment 1 and simulation experiment 2.The results of simulation experiment 1 show that,there are an applicable range and an unapplicable range for the model and algorithm when calculating the deformation in the aspect and aspect-perpendicular directions.In the applicable range,the calculation error of the model and algorithm increases approximately linearly with the noise level.When the noise level reaches10 mm·a^-1,the calculation error is still less than 50 mm·a^-1.In the unapplicable range,regardless of the intensity of the noise,the calculation error exceeds 100 mm·a^-1.Thus,if the sliding surface geometry is located in the unapplicable range,the calculation results are undesirable.The results of simulation experiment 2 show that,the spatial geometric observation intensity formed by the ascending and descending orbit is weak and can obtain the independent two-dimensional LOS observations for calculating the surface deformation.In order to extrct the deformation information in the aspect direction of the ancient landslide in Taoping village,we use the SABS-InSAR technology to derive the LOS deformation velocity fields of ascending and descending obrit with 69 Sentinel-1A satellite ascending inmages and 66 Sentinel-1A satellite descending inmages covering the study area.The results show that,the deformation velocity of ascending obrit changes between-111 and19 mm·a-1 and the deformation velocity of descending obrit changes between-84 and 27mm·a-1.There are big differences in the spatial and temporal distractions of the deformation velocity fields of ascending and descending.Thus,we use the results of the simulation experiments to verify the reliability of extracting the deformation in the aspect direction of the ancient landslide in Taoping village,and combines its LOS deformation velocity fields of ascending and descending obrit to obtain the deformation velocity fields in the aspect and aspect-perpendicular directions.The results show that,in contrast with the LOS deformation,the derived deformation in the aspect and aspect-perpendicular directions can display clearer deformation patterns and high-susceptibility areas.The deformation velocity in the aspect direction changes between 0 and176.82 mm·a-1,and the deformation velocity in the aspect-perpendicular direction changes between-70.1 and 46.5 mm·a-1.There are four significant deformation areas and two deformation patterns in the ancient landslide in Taoping vallige.