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The importance of data quality assessment has significantly increased with the boom of information technology and the growing demand for remote sensing (RS) data. The Remote Sensing Data Quality Wo...

As an advanced form of differential interferometric synthetic aperture radar (DInSAR), small baseline subset (SBAS)-interferometric synthetic aperture radar (InSAR) boasts large space coverage and high precision and provides an effective monitoring technique for ground deformations. Maintaining high coherence through the monitoring process is a common method for SBAS-InSAR to select ground stable points. Usually, such points are obtained with small temporal and spatial baselines. However, it is unlikely to maintain high coherence in non-urban and non-rock landscapes, due to the change of surface cover or vegetation growth. This change is common in long-term surface deformation. Even with a high average coherence, an interferogram still contains many low coherence areas, where it is difficult to implement phase unwrapping or collect sufficient deformation information. This often results in an incomplete spatial image of the deformation pattern, which hinders the interpretation and research of surface deformation. What is worse, surface deformation might not be detected at all in incoherence areas. To solve these problems, this paper proposes a low-rank matrix completion method to complete the low coherence areas, making the interferograms complete. Then, the general SBAS method was followed to extract the deformed time series. The proposed strategy was applied to the time series monitoring of surface deformation of a 250-km2 area in southern Zibo, China, from January 2, 2016, to March 22, 2018. Compared with the traditional SBAS method, the proposed method can obtain more information of surface deformation. The complete deformation information of the area is obtained.

In recent years, the land subsidence of Liupanshui has begun to attract people’s attention. In order to grasp the current situation of land subsidence in Liupanshui city, ALOS-2 data and NSBAS-InSAR technology were selected to monitor the surface deformation of Liupanshui city. The L-band ALOS-2 SAR data is very suitable for land subsidence monitoring based on InSAR technology due to its high ground resolution, long wavelength, and short revisit period. The results show that the surface cumulative deformation ranged from −72 to 12 mm in most regions of study area. The maximum settlement is −553 mm, which is near the Shangjia Town. The areas where the settlement is obvious include Shuangdong Village, South of Muqiao Village, Dahe Town, and Junlong Mountain.

Towards spaceborne spotlight SAR, the antenna is regulated by the SAR system with specific regularity, so the shaking of the internal mechanism is inevitable. Moreover, external environment also has an effect on the stability of SAR platform. Both of them will cause the jitter of the SAR platform attitude. The platform attitude instability will introduce antenna pointing error on both the azimuth and range directions, and influence the acquisition of SAR original data and ultimate imaging quality. In this paper, the relations between the antenna pointing errors and the three-axis attitude errors are deduced, then the relations between spaceborne spotlight SAR imaging of the point target and antenna pointing errors are analysed based on the paired echo theory, meanwhile, the change of the azimuth antenna gain is considered as the spotlight SAR platform moves ahead. The simulation experiments manifest the effects on spotlight SAR imaging caused by antenna pointing errors are related to the target location, that is, the pointing errors of the antenna beam will severely influence the area far away from the scene centre of azimuth direction in the illuminated scene.

The impact of underground coal mining on the surface is not only manifested in the period of coal mining, but also after the coal mining stops and after the coal mine closes down, there will still be residual settlement, or the opposite movement - surface uplift. With the continuous development of microwave earth observation technology, time series InSAR technology has become one of the important means of surface deformation observation in mining areas. In this paper, SBAS-InSAR technology is applied to study the surface deformation movement in Lingzi coal mine, Shandong Province. The time series observations of Sentinel-1A/B data acquired from March 2015 to August 2019 were analyzed, it is found that the seasonal variation of atmosphere is more obvious under the short revisit period and long time series of satellite data, especially in mountainous areas. Considering this effect, the polynomial method is used to fit the observed results. The results show that the surface deformation in Lingzi coal mine is diverse. Some areas continue to uplift, with the maximum uplift of 69mm. Others first subsidence and then uplift, with the maximum subsidence of - 80mm. The process of subsidence and uplift is based on different mechanisms. The subsidence is the residual subsidence of underground caving caused by coal mining, and the process of uplift is related to the recharge of groundwater.

Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) is a new trend of SAR remote sensing technology which combined polarized multichannel information and Interferometric information. It is of great significance for extracting DEM in some regions with low precision of DEM such as vegetation coverage area and building concentrated area. In this paper we describe our experiments with high-resolution X-band full Polarimetric SAR data acquired by a dual-baseline interferometric airborne SAR system over an area of Danling in southern China. Pauli algorithm is used to generate the double polarimetric interferometry data, Singular Value Decomposition (SVD), Numerical Radius (NR) and Phase diversity (PD) methods are used to generate the full polarimetric interferometry data. Then we can make use of the polarimetric interferometric information to extract DEM with processing of pre filtering , image registration, image resampling, coherence optimization, multilook processing, flat-earth removal, interferogram filtering, phase unwrapping, parameter calibration, height derivation and geo-coding. The processing system named SARPlore has been exploited based on VC++ led by Chinese Academy of Surveying and Mapping. Finally compared optimization results with the single polarimetric interferometry, it has been observed that optimization ways can reduce the interferometric noise and the phase unwrapping residuals, and improve the precision of DEM. The result of full polarimetric interferometry is better than double polarimetric interferometry. Meanwhile, in different terrain, the result of full polarimetric interferometry will have a different degree of increase.

In this letter, a uniform scale-invariant feature transform (SIFT)-like algorithm is proposed for synthetic aperture radar (SAR) image registration, which can extract enough robust, reliable, and uniformly distributed features by the strategies of optimal feature selection based on a Voronoi diagram and feature scale-space proportional extraction. SAR images, taken from different viewpoints by an airborne sensor and at different times by spaceborne sensors, were used as test data to validate the effectiveness of the proposed algorithm. The indexes of local density and global coverage were used to assess the spatial distribution of matches. Compared with the traditional SIFT-like algorithm for SAR images (SAR-SIFT), the results show that the proposed algorithm can increase the number of matches and optimize their spatial distribution.

In this paper, we describe our land cover classification and height extraction experiments with high-resolution X-band polarimetric interferometric synthetic aperture radar (PolInSAR) data acquired by Chinese airborne PolInSAR system over Linshui in southern China. The experimental area contains plenty of natural and artificial objects. We present two polarimetric synthetic aperture radar (PolSAR) classification schemes for different land cover types. An Oriented-Object classification scheme based on hierarchical segmentation is employed to the regular land cover classification experiment. The Entropy–PSD unsupervised classification method based on pixel is employed to the low backscattering targets classification experiment. Fully taking advantage of the characteristics of the multi-baseline data set, a dual-baseline polarimetric interferometry method is applied to the PolInSAR experiment of height extraction. Our PolSAR and PolInSAR experiment results demonstrate that high-resolution X-band PolInSAR ima...

Mapping and monitoring of woodland resources is necessary, since woodland is vital for the natural environment and human survival. The intent of this paper is to propose a fusion scheme for woodland extraction with different frequency (P- and X-band) polarimetric synthetic aperture radar (PolSAR) and interferometric SAR (InSAR) data. In the study area of Hanjietou, China, a supervised complex Wishart classifier based on the initial polarimetric feature analysis was first applied to the PolSAR data and achieved an overall accuracy of 88%. An unsupervised classification based on elevation threshold segmentation was then applied to the InSAR data, with an overall accuracy of 90%. After Dempster-Shafer (D-S) evidence theory fusion processing for the PolSAR and InSAR classification results, the overall accuracy of fusion result reached 95%. It was found the proposed fusion method facilitates the reduction of polarimetric and interferometric SAR classification errors, and is suitable for the extraction of large areas of land cover with a uniform texture and height. The woodland extraction accuracy of the study area was sufficiently high (producer’s accuracy of 96% and user’s accuracy of 96%) enough that the woodland map generated from the fusion result can meet the demands of forest resource mapping and monitoring.

The intent of this paper is to propose the method of dual-aspect radiometric and geometric terrain correction to solve the two problems, radiometric variation and radiometric information loss. Firstly, the radiometric terrain correction method which considered gamma naught based image plane as measure of backscattering coefficient, which can correct radiometric variation of PolSAR images at the facing slope and back slope areas. Secondly, two color PolSAR images with dual opposite viewing angle are mutually fused by replacing invalid radiometric value with valid radiometric value from the opposite viewing image, which can generate integral radiometric information for orthophoto creation.

In this paper, we describe our polarimetric interferometric synthetic aperture radar (PolInSAR) experiments with high-resolution X-band data acquired by a multi-mode airborne SAR system over an area of Linshui in southern China. First, we introduce our latest multi-mode X-band airborne imaging radar system (Multi-Mode-XSAR), which integrates three operation modes of bistatic, ping-pong, and mixed. Then, the Multi-Mode-XSAR data set and the corresponding ground measurements in test areas are briefly described. Considering the characteristics of the Multi-Mode-XSAR imagery, a dual-baseline polarimetric interferometry (DPI) method is proposed in this article. The proposed method guarantees a high coherence on the full polarimetric data and combines the benefits of short and long baselines to facilitate the phase unwrapping and promote height sensitivity. Our PolInSAR experiment results demonstrate that the DPI method is capable of generating DSM with higher accuracy than other multi-baseline (MB) methods and...

Synthetic Aperture Radar Interferometry (InSAR) techniques are increasingly applied for monitoring land subsidence. The advantages of InSAR include high accuracy and the ability to cover large areas; nevertheless, research validating the use of InSAR on building deformation is limited. In this paper, we test the monitoring capability of the InSAR in experiments using two landmark buildings; the Bohai Building and the China Theater, located in Tianjin, China. They were selected as real examples to compare InSAR and leveling approaches for building deformation. Ten TerraSAR-X images spanning half a year were used in Permanent Scatterer InSAR processing. These extracted InSAR results were processed considering the diversity in both direction and spatial distribution, and were compared with true leveling values in both Ordinary Least Squares (OLS) regression and measurement of error analyses. The detailed experimental results for the Bohai Building and the China Theater showed a high correlation between InSAR results and the leveling values. At the same time, the two Root Mean Square Error (RMSE) indexes had values of approximately 1 mm. These analyses show that a millimeter level of accuracy can be achieved by means of InSAR technique when measuring building deformation. We discuss the differences in accuracy between OLS regression and measurement of error analyses, and compare the accuracy index of leveling in order to propose InSAR accuracy levels appropriate for monitoring buildings deformation. After assessing the advantages and limitations of InSAR techniques in monitoring buildings, further applications are evaluated.

This paper makes man-made objects detection experiment with the high-resolution X-band PolInSAR data acquired by Multi-mode airborne SAR system over an area around Linshui. Polarimetric and PolInSAR analysis for manmade objects are presented, some polarimetric and PolInSAR descriptors sensitive to man-made objects are selected. Experimental result of man-made objects detection demonstrates that multi-mode-XSAR dataset have intuitive capabilities for application of man-made objects detection.

Synthetic Aperture Radar (SAR) ship detection is an important maritime application. However, azimuth ambiguities caused by the finite sampling of the Doppler spectrum are often visible in SAR images and are always mistaken as ships by classic detection techniques, like the Constant False Alarm Rate (CFAR). It is known that radar targets and azimuth ambiguities have different characteristics in polarimetric SAR (PolSAR) data, i.e., first ambiguities usually have strong odd- or double-bounce scattering and the maximum amplitude of the first ambiguity in SHV is always considerably smaller than that of the corresponding target for zero or high velocity. On the basis of this characteristics, this paper finds that first ambiguities usually have low volume scattering power relative to ships and almost have no helix scattering by Yamaguchi decomposition. But some residual ambiguities still exit in the volume scattering power and have similar scattering intensity to small ships, and some parts of a ship also have zero helix scattering owing to some physical factors (e.g., ship structure, radar incidence angle, etc.). Thus, for high-precision ship detection, a new ship detection method based on cross-correlation between the volume and helix scattering mechanisms derived from Yamaguchi decomposition is proposed to avoid false alarms caused by azimuth ambiguities and enhance Target-to-Clutter Ratio (TCR) for improving the miss detection rate of small ships. By experiments, it is proved that our method can work effectively and has high detection accuracy.

Aiming for steep terrain relief and complex geomorphic types, the practical airborne SAR mapping system (SARMapper) of China developed by a group led by CASM was constructed. SARMapper consists of hardware and software mapping system. In this paper, some new methods and mapping technical flow were proposed aiming for difficult terrain area in the process of developing mapping software system. Several key technologies and solutions were studies, such as DEM extraction through refined interferometry, stereogrammetry, and DEM fusion, Digital Orthophoto Map (DOM) generation with single/multi-polarization SAR images acquired from multi-direction, Digital Line Graphic map (DLG) generation under stereo-environment. Then SAR mapping workstation is used to map in such a large area. And then the comprehensive experiment in Qinling Mountain Area was carried on including interferometric parameters calibration, different resolution of airborne SAR data acquisition and mapping production generation. Experimental results have proved that these productions could satisfy the mapping accuracy of 1:10000 and 1:50000.

Because of the influences of imaging characteristic and the terrain of survey area, SAR images acquired have server geometric and radiometric distortion, particularly evident in mountain areas. In addition, SAR images have heavy speckle noise usually. Therefore, traditional image matching methods have some limitations for SAR image matching. The paper proposed an improved SIFT matching algorithm. The paper used TerraSAR-X and Radarsat-2 images from the same survey area in Hengduan Mountain in western China as experimental data. This survey area has complex landform types, high altitude, and big elevation difference. We carried out feature points extraction and automatically matching experiments with the homologous and heterologous SAR images. For homologous SAR images, the accuracy of matching could be up to 99%. While for heterologous SAR images, it was about 86%. Experiments show that the improved SIFT algorithm is stable and reliable, has good robustness, effectiveness and suitability.

Due to the urgent requirement on SAR image interpretation, a method to extract building footprints from PolSAR image based on polarimetric scattering features and texture features was proposed. Firstly, polarimetric scattering features are extracted by Freeman decomposition and H/A/α decomposition method. Texture features are extracted based on gray level co-occurrence matrix (GLCM). Then, support vector machine (SVM) with Gaussian kernel function is trained to detect building regions by different features sets selected. At last, building polygons extraction is implemented: Line segments are extracted from obtained building regions by radon transform; cycles corresponding to the profiles of buildings in the graph are searched after determining line segment endpoints graph; building footprints are created by eliminating false cycles and connecting component cycles. The approach was demonstrated using airborne PolSAR image. Different features sets selected from experiment data were used to extract building footprints. Comparing the extraction results, the optimum features sets fitting for building footprints were extracted. Results show that the method provides a reliable way to extract building footprints comprehensively using multi-features and edge information. complex scattering characteristics of buildings, accuracy of SAR building extraction is low. In order to monitor the city buildings in all day, all weather and improve the accuracy of building extraction with SAR image, a new building extraction method was put forward in the paper, based on the polarimetric scattering features, texture features and edge information of the airborne PolSAR image. With comprehensive use of polarimetric scattering features, texture features and edge information, a good building extraction effect can be got. A case was studied in the paper to test the method and perfect results were achieved. The research provides a new method to extract the city buildings automatically with PolSAR image. II. ANALYSIS OF BUILDING FEATURES OF POLSAR IMAGE

Interferometric parameters calibration of InSAR system can acquire both baseline parameters and inter- ferometric phase bias. It is significant to calibrate interferometric parameters of dual-antenna airborne InSAR systems for deriving accurate DEM. First of all, the error model based on sensitivity equations was educed by differentiating InSAR imaging equations, then the least square control point calculating slant range difference, and phase information of reconciliation through the interferometric phase information and unwrapped phase difference to the essence of the slant range, and to obtain high precision inclined to participate in the interferometric para- meters calibration from the phase difference calculation. The experiment confirmed that the interferometric parameters obtained by means of high precision. Keywords- interferometric synthetic aperture radar; sensitivity equations; calibration; slant phase difference

Due to steep terrain relief and complex geomorphic types in Hengduan Mountain area, COSMO tandem with short temporal separation and the interferometric baseline revealed high potential for large area topographic mapping. Topography is mostly serious with steep slopes and covered by permanent snow. Furthermore, the quality of the InSAR DEM may vary significantly depending on the local topography. Interferometric processing consisted of coregistration of COSMO image pairs, multi-looking, range and azimuth direction filtering, interferogram generation and coherence map calculation, phase unwrapping; in areas of low coherence larger windows were used to reduce the uncertainty and bias of the estimation. For the geocoding of the COSMO DEM, Range-Doppler model based on few control points was used to build the relationship between ground point geodetic coordinates and image coordinates. Maps have been produced for a 15 000km 2 large area in China in western mapping project. At present, the proposed method, technical flow and software module has been widely used in the 1:50000 Scale Topographic Mapping Project in Western China. The experiment result proves that it is effective and practical.