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1. 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 Hits2585Downloads1399 Comment 0

2. 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 Hits2343Downloads1255 Comment 0

3. 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 Hits2027Downloads1029 Comment 0

4. 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 Hits1107Downloads551 Comment 0

5. chinaXiv:201701.00021 [pdf]

Random Similarity Between Two Mixed Scatterers

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

Scattering similarity was first proposed by Yang et al. to measure the similarity between two single scatterers. It was extended by Chen et al. to measure the similarity between a mixed scatterer and a single scatterer. This letter develops a random similarity parameter to further measure the similarity between two mixed scatterers. The parameter not only covers Yang's and Chen's similarities by providing a general scattering similarity measurement, but also is useful for scattering randomness description by enabling a fast alternative and a competent complementary to the entropy parameter. A novel model-based characterization scheme of mixed scatterer is then proposed by parallel combining the random similarities between the mixed scatterer and three canonical mixed volume scatterers. By further fusing with the SPAN, the scheme can characterize both the texture and the scattering information regarding a target. Comparative experiment with Chen's approach on L-band ESAR Oberpfaffenhofen data demonstrates its excellent discrimination of radar targets. ?2004-2012 IEEE.

submitted time 2017-01-04 Hits1101Downloads602 Comment 0

6. chinaXiv:201701.00018 [pdf]

The appropriate parameter retrieval algorithm for feature-based SAR image registration

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

This paper is dedicated to investigate the appropriate parameter retrieval algorithm for feature-based synthetic aperture radar (SAR) image registration. The widely-used random sample consensus (RANSAC) is observed to be instable for its inappropriate estimation strategy and loss function for SAR images. In order to enable a stable and robust registration for SAR, an extended fast least trimmed squares (EF-LTS) is proposed which conducts the registration by least squares fitting at least half of the correspondences to minimize the squared polynomial residuals instead of fitting the minimal sampling set to maximize the cardinality of the consensus set as RANSAC. Experiment on interferometric SAR image pair demonstrates that the proposed algorithm behaves very stably and the obtained registration is averagely better than that by RANSAC in terms of cross-correlation and spectral SNR. By this algorithm, a stable estimation for any kind of 2D polynomial warp model with high robustness and accuracy can be efficiently achieved. Thus EF-LTS is more appropriate for SAR image registration. ?2012 SPIE.

submitted time 2017-01-04 Hits1009Downloads443 Comment 0

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