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1. chinaXiv:201703.00305 [pdf]

Model-based decomposition with adaptive selection of unitary transformations

Zhu, Feiya; Zhang, Yunhua; Li, Dong; Gu, Xiang
Subjects: Geosciences >> Space Physics

In this paper a three component model-based decomposition with adaptive selection of unitary transformations for polarimetric synthetic aperture radar (POLSAR) data processing is proposed. Singh et al implemented two unitary transformations on the coherency matrix to minimize the power of cross-polarization, and as a result the T23element of the coherency matrix becomes zero. Another two unitary transformations are proposed by us to carry out on the coherency matrix also to minimize the power of crosspolarization, and the T13element of the coherency matrix becomes zero. Here, we first implement Singh's two unitary transformations and the proposed two unitary transformations on the coherency matrix separately. Then we select the one which leads to the smaller T33. At last, we carry out the three component model-based decomposition proposed by Freeman and Durden based on the obtained coherency matrix. The smaller T33is obtained, the better the over-estimation of volume scattering in model-based decomposition can be suppressed. The RADARSAT-2 POLSAR data of San Francisco area is used to validate the improvement of the proposed method over the three component decomposition only with Singh's two unitary transformations.

submitted time 2017-03-10 Hits17750Downloads1166 Comment 0

2. chinaXiv:201703.00299 [pdf]

A novel deorientation method for PolSAR data processing

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

In PolSAR data processing, deorientation operation is often necessary. The existing deorientation method uniformly deorients all the sub-scatterers of a resolution cell with one orientation angle. For high entropy situation, the sub-scatterers have diverse OAs, and the effect of the existing method is unsatisfactory. A novel deorientation method is proposed to well treat the high entropy situation. Cloude's eigen-decomposition to the coherency matrix is first carried out. The three eigenvectors are then separately deoriented with their own orientation angles. Experiments demonstrate that the proposed method is suitable for extraction of urban regions, especially for extraction of oriented urban regions. ?VDE VERLAG GMBH ?Berlin ?Offenbach.

submitted time 2017-03-10 Hits2938Downloads872 Comment 0

3. chinaXiv:201703.00297 [pdf]

A novel polarimetric interferometric SAR coherence parameter and its application in buildings detection

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

Man-made buildings detection is important in land use supervision and land control applications. Generally, polarimetric synthetic aperture radar (PolSAR) data are processed to detect buildings well. But for some buildings which are not aligned with the radar track, these buildings are usually incorrectly recognized as forest, because the oriented buildings produce additional cross-polarization. Polarimetric interferometric SAR (PolINSAR) acquires two measurements with a spatial baseline or a temporal baseline. For the PolINSAR with a temporal baseline i.e., the repeat pass PolInSAR, the two polarimetric measurements are sensitive to targets' temporal variations during the time. The buildings, regardless of the orientations, have high coherence, while some natural targets have low coherence. A novel parameter is proposed here, which represents the mean PolINSAR coherence and can be utilized to distinguish between buildings and some natural targets. The parameter is based on the coherence optimization theory of Cloude and Papathanassiou, and is the mean of the three optimal coherences with three pseudo-probabilities. Based on this new parameter and the SPAN, a method to detect buildings is further proposed. The excellent performance of the proposed method on buildings extraction is demonstrated by processing German Aerospace Center (DLR) L-band E-SAR repeat pass PolINSAR data of Oberpfaffenhofen area.

submitted time 2017-03-10 Hits3112Downloads981 Comment 0

4. chinaXiv:201703.00292 [pdf]

A novel interpretation of the PolSAR coherency matrix data

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

Cloude-Pottier incoherent target decomposition (ICTD) and Touzi ICTD has been widely applied as a popular approach to interpret the scattering characteristics of a target in polarimetric synthetic aperture radar (PolSAR) data processing. However, they have a common drawback, i.e. proliferation of parameters (PoP) is unavoidable. Paladini et al. solved this problem by developing an orientation-invariant ICTD based on the coherency matrix under circular polarization basis. As an alternative to Paladini decomposition, we proposed a novel ICTD based on the frequently used coherency matrix under linear polarization basis. The proposed method can also avoid the problem of PoP, and avoid the ambiguity of alpha angle of Paladini decomposition as well. Real PolSAR data is processed to validate the proposed decomposition.

submitted time 2017-03-10 Hits2303Downloads892 Comment 0

5. chinaXiv:201703.00248 [pdf]

An Extension of a Complete Model-Based Decomposition of Polarimetric SAR Data

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

The model-based decomposition that originated from Freeman-Durden three-component decomposition (FDD) has been widely applied in polarimetric synthetic aperture radar (PolSAR) data processing for its clear physical interpretation and easy implementation. Numerous improvements have been proposed to settle the twomain drawbacks of FDD, i.e., the incomplete utilization of the polarimetric information in the coherency matrix and the negative scattering power problem. Recently, Cui et al. proposed a complete model-based three-component decomposition which successfully settled the two aforementioned drawbacks. However, the three scattering components' powers are not totally derived using scattering models, and the remaining coherency matrix (RCM) obtained by subtracting the volume scattering component from the coherency matrix is not consistent with the models of surface and double-bounce scattering components. As an extension of Cui's method, this letter is dedicated to develop a novel method to discriminate the surface and double-bounce scattering components both using scattering models. With the orientation angle (OA) variation and helix angle (HA) variation compensated for the RCM, the RCM is automatically consistent with the models of surface and double-scattering components. The OA variation and HA variation compensation for the RCMis done by unitary transformations of the eigenvectors of the RCM. The powers of surface and double-bounce scattering components are positive. The effectiveness of the proposedmethod is demonstrated by processing the real PolSAR data.

submitted time 2017-03-10 Hits1613Downloads874 Comment 0

6. chinaXiv:201701.00028 [pdf]

A fast offset estimation approach for InSAR image subpixel registration

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

A fast offset estimation approach for interferometric synthetic aperture radar (InSAR) image pair subpixel registration is proposed for cases of relatively gentle topography and/or short baseline. A coarse-to-fine registration strategy is taken. The pixel-level offset is estimated in the coarse registration step by a fast feature-based estimation, which uses the speeded up robust feature operator and fast least trimmed squares (Fast-LTS) estimator to accelerate the feature extraction and parameter estimation. A fine registration is performed subsequently. The conventional normalized cross-correlation algorithm (NCCA) searches for the optimal subpixel offset by oversampling either the coarse cross correlation or the InSAR image patch pair. The offset estimation accuracy is restricted by the oversampling rate, and the computational burden is heavy when high accuracy is demanded. In this letter, we transform the oversampling and correlation searching process of NCCA into a nonlinear optimization problem, which takes the maximization of the coherent cross correlation as the objective function; by solving it, the subpixel offset can be fast and exactly obtained without any image oversampling. The final registration parameters are inverted by Fast-LTS fitting of a series of subpixel tie point correspondences which can be constructed after applying the approach to several image patch pairs. RadarSat-2 data are used to test the approach, and the results show that it performs very well not only on the speed but also on the accuracy. ?2006 IEEE.

submitted time 2017-01-04 Hits1957Downloads1008 Comment 0

7. chinaXiv:201701.00027 [pdf]

Fast least trimmed squares (Fast-LTS); Image registration; Parameter estimation; Random sample consensus (RANSAC); Weak affine transformation

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

A novel image registration scheme is devised in view of the weak affine transformation, which is a kind of similarity transformation with anisotropic scales or affine transformation without shearing. Two robust algorithms are proposed to retrieve the registration parameters from the error-prone initial correspondences based on the fast least trimmed squares (Fast-LTS) and the random sample consensus (RANSAC). In terms of several criteria, the algorithms are evaluated on three carefully selected datasets from different sensors and the experimental results demonstrate that the proposed scheme and algorithms perform robustly and accurately. Our findings also indicate that the Fast-LTS-based algorithm is more stable and appropriate for image registration than the RANSAC-based algorithm although the speed is slower. ?2012 Elsevier B.V. All rights reserved.

submitted time 2017-01-04 Hits1581Downloads810 Comment 0

8. chinaXiv:201701.00026 [pdf]

A rigorous SAR epipolar geometry modeling and application to 3D target reconstruction

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

A rigorous epipolar geometry modeling for synthetic aperture radar (SAR) is developed from a concise imaging model proposed in the paper. The imaging model and epipolar model not only geometrically unify the SAR imaging and the optical camera imaging, but also motivate a 3D target reconstruction which is theoretically validated to be consistent with the radargrammetry and experimentally demonstrated to be accurate. ?2008-2012 IEEE.

submitted time 2017-01-04 Hits1795Downloads926 Comment 0

9. chinaXiv:201701.00025 [pdf]

Canonical Huynen decomposition of radar targets

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

Huynen decomposition prefers the world of basic symmetry and regularity (SR) in which we live. However, this preference restricts its applicability to ideal SR scatterer only. As for the complex non-symmetric (NS) and irregular (IR) scatterers such as forest and building, Huynen decomposition fails to analyze their scattering. The canonical Huynen dichotomy is devised to extend Huynen decomposition to the preferences for IR and NS. From the physical realizability conditions of polarimetric scattering description, two other dichotomies of polarimetric radar target are developed, which prefer scattering IR, and NS, respectively, and provide two competent supplements to Huynen decomposition. The canonical Huynen dichotomy is the combination of the two dichotomies and Huynen decomposition. In virtue of an Adaptive selection, the canonical Huynen dichotomy is used in target extraction, and the experiments on AIRSAR San Francisco data demonstrate its high efficiency and excellent discrimination of radar targets. ?2015 SPIE.

submitted time 2017-01-04 Hits1242Downloads671 Comment 0

10. chinaXiv:201701.00024 [pdf]

Epipolar geometry comparison of SAR and optical camera

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

In computer vision, optical camera is often used as the eyes of computer. If we replace camera with synthetic aperture radar (SAR), we will then enter a microwave vision of the world. This paper gives a comparison of SAR imaging and camera imaging from the viewpoint of epipolar geometry. The imaging model and epipolar geometry of the two sensors are analyzed in detail. Their difference is illustrated, and their unification is particularly demonstrated. We hope these may benefit researchers in field of computer vision or SAR image processing to construct a computer SAR vision, which is dedicated to compensate and improve human vision by electromagnetically perceiving and understanding the images.

submitted time 2017-01-04 Hits1467Downloads722 Comment 0

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