Research on Potential Landslide detection method using SBAS Technology——A Case Study of Minjiang River Basin
Key Laboratory of Virtual Geographic Environment,Ministry of Education,Nanjing Normal University
The synthetic aperture radar (SAR) interferometry (In-SAR) technique has already shown its importance in landslide mapping and monitoring applications. However, the usefulness of traditional differential In-SAR applications is limited by disturbing factors such as temporal decorrelation and atmospheric disturbances. And the Persistent Scatters Interferometry (PSI) technique need plenty of scenes, at least 25 scenes. Small Baseline Subsets (SBAS) is recently developed In-SAR approach. And it has a wide range of application prospects in the surface deformation monitoring because it could attain tiny deformation information of the surface and obtain long time series, slow deformation field of the surface. In this paper, we choose the Minjiang river basin as a study area, using SBAS approach obtained the surface deformation, and the deformation points which are unreasonable is removed according to certain conditions. The results show that the surface deformation points are mainly distributed on the right bank of the river, which is related to the low sensitivity of the ENVISAT data whose orbit is descending direction. Analyzed spatial relationship the potential landslide areas extracted using the spatial analysis method in ArcGIS software and the historical landslides. Meanwhile, the potential landslide areas are mainly distributed along the river. The main reason for this rule is the influence of the river erosion on the slope foot so that landslides distributed along the River; What’s more, among 30 historical landslides, 16 points lie in the deformation area, and 11 points lie in the potential landslide area, only 3 points are outside of the deformation area. Which shows that the landslide deformation points can better reflect the spatial distribution of historical landslides. Therefore, in the absence of historical landslide inventories, potential landslides detection by using deformation points provides effective assistance for regional disaster prevention and investigation.
Key words: landslide, SBAS technology, landslide deformation point, Minjiang River Basin.
Fusion of Multi-stack PS Point Clouds over Open Pit Mines
Northeastern University, China, People's Republic of
The surface deformation caused by mining is seriously threatening the safety of Mining area. It is necessary to continuously monitor the surface deformation of mining areas, in order to ensure the safety of production, as well as supporting early warning and risk control. Limited by the side-looking geometry of SAR sensors, only deformation along line-of-sight can be retrieved with time series InSAR technology from a single stack of SAR images. Since the terrain varies greatly in mining areas, it is very difficult to monitor the overall 3D deformation of mining pits and dump sites with a single stack of SAR images. Therefore, fusion of PS point clouds from multi-stack SAR images is necessary.
In this paper, fusion of PS point clouds retrieved by time series InSAR from multi-stack SAR images would be carried out. For the first step, the best PS points are select from the geocoded PS points with a threshold on the variance of estimated heights within a certain window. Then, binary images are generated with the selected PS points. Coarse offsets of the same object between binary images from different stacks are estimated and compensated. After that, point correspondences are created with the compensated PS points, followed by the least squares adjustment to calculate precise offsets between corresponding points. In the final step, offset compensation would be carried out, leading to precisely fused point clouds. the offset between PS points This fusion approach includes several key steps, such as selection of excellent PS points, finding the best PS point matching model between different stacks with iteration, least-squares adjustment without any reference data, PS point cloud re-locating with least squares adjustment, etc.
With this fusion method, three dimensional deformation of an open pit mine in Anshan will be estimated from multi-stack SAR images and presented in the fullpaper. 3D deformation of open pit mines is beneficial to monitoring the mining process. The relationship between mining activity and surface damage can also be analyzed with the assistance of surface deformation pattern, subsidence rate and other possible factors in the mining area.
Key words: Time Series InSAR; Surface Deformation; Multi-stack Fusion; Open Pit Mine