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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 Hits18536Downloads1600 Comment 0

2. chinaXiv:201703.00301 [pdf]

A novel deorientation method in PolSAR data processing

Zhu, F.Y.; Zhang, Y.H.; Li, D.
Subjects: Geosciences >> Space Physics

Deorientation plays an important role in polarimetric synthetic aperture radar (PolSAR) target decomposition, terrain classification, and geophysical parameters retrieval. The existing deorientation method roughly rotates the target by an average/mixed orientation angle (OA) about the line of radar sight. However, regarding the complex high-entropy mixed scatterer, which usually comprises several comparable sub-scatterers with different OAs, the average/mixed OA is obviously insufficient to account for the diverse OAs’ reality. To address this, a novel PolSAR data deorientation method is proposed in this letter. The proposed method deorients a mixed scatterer by reconstructing the underlying sub-scatterers using the eigenvalue-based Cloude–Pottier decomposition first, and then compensates the OA of each reconstructed sub-scatterer using Huynen’s desying operation, respectively. One important feature of the proposed method is that it is consistent with Huynen’s desying operation that the real part of the (1, 3) element of the deoriented coherency matrix should be zero. The proposed method provides a fine deorientation for mixed targets, and is especially suitable for the extraction of oriented urban regions. Comparative experiments with the existing method on RADARSAT-2 PolSAR data demonstrate the excellent deorientation performance of the proposed method. ? 2016 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

submitted time 2017-03-10 Hits2801Downloads1120 Comment 0

3. 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 Hits3557Downloads1256 Comment 0

4. 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 Hits2259Downloads1274 Comment 0

5. 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 Hits2665Downloads1450 Comment 0

6. 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 Hits2427Downloads1312 Comment 0

7. 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 Hits1782Downloads971 Comment 0

8. 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 Hits2092Downloads1067 Comment 0

9. chinaXiv:201701.00023 [pdf]

Fast PolSAR data visualization and classification based on Huynen canonical decomposition

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

A scattering degree of preference parameter is developed from Huynen canonical dichotomy which displays superior classification ability over the scattering similarity parameter. A scattering hue parameter is then proposed and demonstrated to be of superiority compared with scattering alpha on description of scattering mechanism. A scattering saturation parameter is further defined and shows comparable to scattering entropy on description of scattering randomness. A Huynen dichotomy-based PolSAR data visualization scheme is finally obtained which not only works more efficient but also makes the results look better than that from H/alpha. ?2014 VDE VERLAG GMBH.

submitted time 2017-01-04 Hits913Downloads458 Comment 0

10. chinaXiv:201701.00022 [pdf]

On the appropriate feature for general SAR image registration

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

An investigation to the appropriate feature for SAR image registration is conducted. The commonly-used features such as tie points, Harris corner, the scale invariant feature transform (SIFT), and the speeded up robust feature (SURF) are comprehensively evaluated in terms of several criteria such as the geometrical invariance of feature, the extraction speed, the localization accuracy, the geometrical invariance of descriptor, the matching speed, the robustness to decorrelation, and the flexibility to image speckling. It is shown that SURF outperforms others. It is particularly indicated that SURF has good flexibility to image speckling because the Fast-Hessian detector of SURF has a potential relation with the refined Lee filter. It is recommended to perform SURF on the oversampled image with unaltered sampling step so as to improve the subpixel registration accuracy and speckle immunity. Thus SURF is more appropriate and competent for general SAR image registration. ?2012 SPIE.

submitted time 2017-01-04 Hits1154Downloads575 Comment 0

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