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InSAR Time Series Analysis Technique Combined with Sequential Adjustment Method for Monitoring of Surface Deformation
WANG Hui, ZENG Qiming, JIAO Jian, CHEN Jiwei
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (2): 241-249.   DOI: 10.13209/j.0479-8023.2021.002
Abstract944)   HTML    PDF(pc) (10197KB)(254)       Save
Based on the SAR satellite imagery with short revisit periods, this paper proposes a novel SBASInSAR time series analysis technique for efficient and continuous monitoring of surface deformation in the study area. First, standard interferometric processing is carryed out with the existing SAR image set in the study area to obtain the interference map. Then the atmospheric and orbital errors are removed, and the traditional SBAS (small baseline subset) method is used to obtain the surface deformation. On this basis, when a new SAR image is added, the progressive SBAS is adopted to invert the surface deformation at the new moment. The progressive SBAS method integrates the idea of sequential adjustment based on the obtained results derived from existing data set, and combines the newly acquired data to implement incremental calculations, finally achieves the equivalent effect of overall processing. Compared with the traditional SBAS method which needs to resolve all the calculations every time when a new image is added, the progressive SBAS method can reduce redundant operations and improve computing efficiency. The experiment proves that based on the Sentinel-1 satellite SAR data acquired in the Yellow River Delta from May 2018 to August 2016, the surface deformations retrieved by the progressive SBAS method are almost the same as the results of the measured ground level. The correlation coefficient (R) is 0.82, and the difference between the ground deformation rate and the traditional SBAS method is within 1 mm/a. The solution time is shortened by about 40%, and the ground deformation can be efficiently and continuously monitored.
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Research on Moving Target Indication Based on Along Track Interferometry of TerraSAR-X Data
JIAO Jian, TIAN Chongrui, HUANG Jianghui, ZENG Qiming
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (1): 164-172.   DOI: 10.13209/j.0479-8023.2019.112
Abstract692)   HTML    PDF(pc) (6266KB)(49)       Save
The method to combine along track interferometry (ATI) and constant false alarm rate (CFAR) detection, referred to as ATI-CFAR, is considered to be a promising method for ground moving target indication (GMTI). In order to evaluate the ability of the method used for GMTI with TerraSAR-X data, a set of experimental schemes are presented, which include a synchronous in-situ experiment on a section of Beijing’s North Fifth Ring Road, an improved ATI-CFAR method to estimate ATI amplitude and phase, etc. Experimental results suggest that TerraSAR-X data can be used in GMTI, however ATI phase is easily interfered. A published ATI-CFAR method might overestimate the threshold of interferometric phases, and result in missing detection of moving targets. The proposed method based on the priori knowledge of vehicle velocity is able to effectively improve the detection performance, and it improves the detection rate of moving targets in the study area up to 70%, and has an accuracy of 87.5%. The work of this paper validates the availability and potential of TerraSAR-X data in GMTI application.
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A Homogenous Pixel-Weighted Interferometric Phase Filtering Method for Time-series InSAR
HUANG Junsong, ZENG Qiming, JIAO Jian, GAO Sheng
Acta Scientiarum Naturalium Universitatis Pekinensis    2018, 54 (6): 1242-1250.   DOI: 10.13209/j.0479-8023.2018.032
Abstract952)   HTML    PDF(pc) (35224KB)(338)       Save

In order to effectively use the temporal information of multi-temporal InSAR and ensure the homogeneity of pixels in the window, a homogenous pixels-weighted interferometric phase filtering method is proposed. The method firstly uses the goodness-of-fit test to identify the statistically homogenous pixels (SHP) in the multi-temporal SAR images, and then the weighted interferometric phase filtering is performed just within those SHP, which ensures that the central pixels is not affected by the surrounding heterogeneous pixels. The experimental results based on real SAR interferograms show that compared with classic Goldstein filter and Lee filter, the proposed filter has advantages in visual effect, phase residues reduction, and phase derivative standard deviation, and achieves the original intention of the design of this filter.

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A Soil Moisture Co-retrieval Approach Based on AMSR-E and ASAR Data
LI Xin, ZENG Qiming, WANG Xinyi, HUANG Jianghui, JIAO Jian
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (5): 902-910.   DOI: 10.13209/j.0479-8023.2015.142
Abstract1355)   HTML    PDF(pc) (2781KB)(1264)       Save

It is difficult to monitor land surface soil moisture in high temporal and spatial resolution within a wide range for lack of ground observation data when the satellite is passing over. To solve this problem, a new integrated approach termed as “soil moisture retrieval with combined active and passive microwave remote sensing observation” was proposed. AMSR-E soil moisture product is compensated as “high temporal resolution observation control data” and soil moisture benchmark is retrieved together with ASAR alternating polarization mode data. Then both of them are integrated to build up a co-inversion model for soil moisture retrieval. This approach applies to areas where the land surface roughness is small and vegetation index (NDVI) is low. The approach is evaluated in Weibei Upland of Shaanxi Province. According to the regression analysis based on AIEM (advanced integrated equation model), the correlation coefficient between compensated AMSR-E soil moisture and downscaled ASAR backscattering coefficient was approximately 0.81. Verification analysis with the in-situ data of Fengxiang County in the study area shows that the soil moisture retrieved with combined active and passive microwave remote sensing observation displays a correlation coefficient of 0.92, and the root mean square errors (RMSE) of the soil volumetric moisture is 0.025. It indicates that the approach is credible and the soil moisture retrieval results could be used in simulating regional crop growth under water-limited environments.

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InSAR Atmospheric Effects Analysis of ASAR Image Mode Products
CUI Xi’ai,ZENG Qiming,TONG Qingxi,JIAO Jian,LIANG Cunren
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract852)      PDF(pc) (7261KB)(89)       Save
Atmospheric effect represents one of the major limitations of repeat-pass InSAR technique for precise land deformation measurements. To solve this problem, an approach is developed to remove the atmospheric effect on InSAR measurements based on the JPL/Caltech Repeat Orbit Interfeormetric PACkage (ROI_PAC) that performs the InSAR processing. As an example, the Image Mode (IM) mode data covering the Bam of Iran from the Envisat ASAR instrument is chosen to test the approach. The InSAR results without atmospheric correction and that with atmospheric correction are compared from three individual aspects respectively. The results show that the atmospheric phase affects the removal of the residual orbital fringes and the error of the InSAR LOS (line of sight) displacement reduce about 20 mm after the atmospheric effect is removed. It indicates that the removal of the atmospheric effect can improve the accuracy of the InSAR measurement results.
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Construction, Expression, Purification and Characterization of GHRP-scu-PA-32K
JIAO Jianwei,XU Changfa
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract697)            Save
GHRP-scu-PA-32K cDNA was obtained by in vitro site-directed-mutagenesis to insert oligonucleotide sequence (GGTCATAGGCCT) encoding tetrapeptide Gly-His-Arg-Pro into scu-PA-32K gene at site just preceding the amino-terminal residue(Leu1). The mutant cDNA was cloned in pCM-β-neo expression vector and co-transformed CHO-DHFR- cells together with pCM-dhfr. The stable expression cell line was selected. Expression level of the line cultured in serum-free medium was 580IU/106 cell/24h. The product expressed was purified by Zn2+-Sepharose affinity chromatography. The apparent molecular weight of purified GHRP-scu-PA-32K was 33kD by SDS-PAGE and mass spectrometry and its specific activity was 150000IU/mg protein, according to fibrin plate determination. The affinity for fibrin of GHRP-scu-PA-32K was 4.5 times higher than that of scu-PA-32K.
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