Xiaofang Guo

CRInSAR for landslide deformation monitoring: A case in threegorge area

Landslide in threegorge area is a severe geohazard threatening many people. Conventional differential SAR interferometry (DInSAR) and Persistent Scatterers for SAR interferometry (PSInSAR) technique are unsuitable for landslide deformation monitoring in this area due to temporal and lack of natural phase stable point targets. The method of DInSAR using corner reflectors (CRInSAR) is a powerful tool in the vegetation area. The procedure of DInSAR using corner reflectors (CRInSAR) used by this paper is briefly introduced. Using ENVISAT ASAR time series data, the deformation of 12 corner reflectors (CR) in Shuping landslide are analyzed. As to the CR with slow creep deformation, the CRInSAR results are reliable. But as to the CR with nonlinear accelerated deformation, our CRInSAR method still needs to be enhanced.

Land Subsidence Investigation Along Railway Using Permanent Scatterers SAR Interferometry

Land subsidence is a common geohazards in many countries of the world, which cause damages for many urban areas and civil infrastructure. The development of spaceborne SAR interferometry provides an efficient tool for large spatial scale surface deformation monitoring with a high accuracy and precision. This paper presents a case study of land subsidence investigation along railway by using Permanent Scatterers SAR interferometry (PSI). Based upon the conventional InSAR techniques, PS-InSAR overcomes atmospheric delay anomalies and temporal and geometric decorrelation by exploiting the temporal and spatial characteristics of radar interferometric signatures collected from point-wise targets that preserve phase coherent over time. In this work, a linear model is adopted to retrieval land subsidence rate by using the differential phase series of the permanent scatterers. For the subsidence rate derivation along the railway, a buffer with a width of 10 km is set up and those PS within the buffer is interpolated to generate the subsidence map. The results archived using ENVISAT ASAR images acquired from 2003 to 2004 are validated with the precise leveling data and used to investigate the Jing-Jin railway in north china.

Mapping subsidence in Tianjin area using ASAR images based on PS technique

By identifying temporarily stable natural reflectors or persistent scatterers (PS), PSInSAR (Persistent Scatterers for SAR Interferometry) technique can analyze this subset of pixels in SAR images, even with long temporal and space baselines, to get high accuracy deformation measurements. We implement the PSInSAR process that is briefly summarized in this paper and apply this method in Tianjin area to detect the deformation phenomena using ENVISAT ASAR images. Calibration of ASAR images helps us select more PSC and using calibrated backscattering coefficient threshold we can discard the pixels whose amplitude are relatively stable while whose backscattered signals are weak and incoherent. Results obtained by processing 14 images show the distribution and the relative deformation value of the displacement field. The estimated linear velocities of PS are not accurate enough because of the relatively small number of images.

Detection of land subsidence in Beijing, China, using Interferometric Point Target Analysis technique

Land subsidence in Beijing is supposed to be caused by over-exploitation of ground water, which is leading to a rapid decline of water levels, drying out clay layers that finally result in land subsidence.

Monitoring of landslide deformation based on the coherent targets of high resolution InSAR data

Landslides are a kind of typical natural disaster in China, which pose serious threats to civil lives, property and living environment. Therefore, the identification, monitoring and prevention of landslides have been considered as a long-term geological work for the public welfare. In this article, 8 TerraSAR-X high resolution strip-map mode images, acquired in the period from January to March 2012 and covering Fanjinping landslide in Zigui county, Hubei province, were used to test the usability in monitoring the deformation of single landslide. The results of two-pass DInSAR sketched the region and the shape of the deformation field of Fanjiaping landslide. Corner reflectors’ linear deformation rate using CRInSAR method could be approximately validated by the in-situ GPS measurements. From the coherent pixels’ linear deformation rate map, it was inferred that the deformation could be more obvious in the tail of the Muyubao landslide while the lowest frontier of this landslide might prevent the slide. Due to its shorter revisiting period and high bandwidth,,the high resolution TerraSAR-X images can keep better coherence than previous satellite SAR data in the test area and provide basic guarantee to monitor the deformation of single landslides.

Mapping the Deformation of Shuping Landslide Using DInSAR and Offset Tracking Methods

Shuping landslide, belonging to Zigui county, Hubei province, is located on a north-inclined slope at the south bank of Yangtze River and about 50 km away from the Three Gorges Dam. The landslide occupies less than 1 km2 and is covered by densely vegetations. Since the first impoundment of the Three Gorges Reservoir ended on June 15, 2003, the landslide has suffered obvious deformation. The maximum value of Shuping landslide in special month is up to several decimetres.

Monitoring the deformation of a landslide with differential SAR interferometry using corner reflectors

In order to monitor the surface deformation of Shuping landslide in the Yangtze River Three Gorges area, the method of differential SAR interferometry (DInSAR) using corner reflectors (CR) was applied. 12 CR, including 10 pyramidal corner reflectors (PCR) and 2 asymmetrical cubic corner reflectors (ACCR), were designed, made, and deployed on Shuping landslide. Based on the numerical test and the preliminary analyses of 5 ENVISAT ASAR images, we concluded that: 1) ACCR can provide strong response signal even without the best SAR look angle and is especially fit for the multi-angle applications of DInSAR; 2) given a simple phase model, the least square (LS) method can be used to analyze the CRs differential phase and get the accumulative deformation value.

Experimental study of atmospheric correction to interferogram with high-resolution radar images and DEM over shuping landslide

The most important limiting factor of conventional D-InSAR method is strongly atmospheric wet delay during monitoring small landslides located at rainy and mountainous area. The wet delay phase could even cover deformation field of test site sometimes. In this paper, we found the wet delay phase over Shuping landslide was not only closely related with elevation, but also was a function of distance along radar azimuth or range direction. Therefore, based on least-square method, best-fit-polynomial correction models about wet delay filed over Shuping landslide could be established. By removing the wet delay phase field simulated from unwrapping phase, the deformation field of Shuping landslide could appear immediately. The result showed that this correction method could effectively remove the wet delay phase from differential interferograms, and it will have an important significance for monitoring slowly moving landslide in Three Gorges Area.

A study on different PS-like methods for subsidence in Tianjin, China

In this paper, the methods, primary PS-like method and Stanford Method for PS (StaMPS) are both studied and used to monitor the subsidence in Tianjin area.