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A novel synthetic aperture radar scattering model for sea surface with breaking waves

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Acta Oceanologica Sinica 2022年第4期41卷 138-145页

作者： Xiaochen Wang Yuxin Hu Bing Han Wei Tian Chunhua Zhang Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094China Key Laboratory of Technology in Geo-spatial Information Processing and Application System Chinese Academy of SciencesBeijing 100190China The box51111 Beijing 100190China

In this study a novel synthetic aperture radar(SAR)scattering model for sea surface with breaking waves is proposed.Compared with existing models,the proposed model considers an empirical relationship between wind speed and wave breaking scattering to present the contribution of wave breaking.Moreover,the scattering weight factor p,and wave breaking rate q,are performed to present the contribution of the quasi-specular scattering term,Bragg scattering term,and wave breaking scattering term to the total scattering from the sea surface.To explore the modeling accuracy of sea-surface scattering,a simulated normalized radar cross-section(NRCS)and measured NRCS are compared.The proposed model generated the simulated NRCS and a matching GF-3 dataset was used for the measured NRCS.It was revealed that the performance of the VV polarization of our model was much better than that of HH polarization,with a correlation of 0.91,bias of-0.14 dB,root mean square error(RMSE)of 1.26 dB,and scattering index(SI)of-0.11.In addition,the novel model is explored and compared with the geophysical model of CMODs and satellite-measured NRCS from GF-3 SAR wave mode imagery.For an incidence angle 40°–41°,the relationship between the NRCS and wind speed,relative wind direction is proposed.As with the SAR-measured NRCS,the performance of VV polarization was much better than HH polarization,with a correlation of 0.99,bias of-0.25 dB,RMSE of 0.64 dB,and SI of-0.04.

关键词： synthetic aperture radar scattering model sea surface wave breaking

synthetic aperture radar Raw Signals Simulation of Extended Scenes

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Wuhan University Journal of Natural Sciences 2004年第3期9卷 327-331页

作者： SunJin-yao SunHong SchoolofElectronicInformation WuhanUniversityWuhan430072HubeiChina

A synthetic aperture radar (SAR) raw signal simulation algorithm for extended scenes is presented. This algorithm is based on the SAR two-dimensional system transform function (STF). To cope with range-variant nature of SAR STF and increase the speed of this algorithms, new formulas for range-variant phase corrections in range-Doppler (RD) domain are developed. In this way, many azimuth lines can be simulated with the same SAR STF. It only needs two-dimensional fast Fourier transform code and complex multiplications. Comparing with time-domain simulation algorithm, it is very simple and thus efficient. Simulation results have shown that this algorithm is accurate and efficient. Key words synthetic aperture radar - raw signal simulation - system transform function CLC number TP 751. 1 Foundation item: Supported by the National Natural Science Foundation of China (40376051)Biography: Sun Jin-yao (1967-), female, Ph. D. candidate, research direction: SAR image simulation and 3D recover for SAR image.

关键词： synthetic aperture radar raw signal simulation system transform function

A statistical distribution texton feature for synthetic aperture radar image classification

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Frontiers of Information Technology & Electronic Engineering 2017年第10期18卷 1614-1623页

作者： Chu HE Ya-ping YE Ling TIAN Guo-peng YANG Dong CHEN School of Electronic Information Wuhan University Wuhan 430072 China State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan 430072 China School of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China Hubei P&T Plan-Design Co. Ltd. Wuhan 430023 China

We propose a novel statistical distribution texton(s-texton) feature for synthetic aperture radar(SAR) image classification. Motivated by the traditional texton feature, the framework of texture analysis, and the importance of statistical distribution in SAR images, the s-texton feature is developed based on the idea that parameter estimation of the statistical distribution can replace the filtering operation in the traditional texture analysis of SAR images. In the process of extracting the s-texton feature, several strategies are adopted, including pre-processing, spatial gridding, parameter estimation, texton clustering, and histogram statistics. Experimental results on Terra SAR data demonstrate the effectiveness of the proposed s-texton feature.

关键词： synthetic aperture radar Statistical distribution Parameter estimation Image classification

Detection and suppression of narrow band RFI for synthetic aperture radar imaging

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Chinese Journal of Aeronautics 2015年第4期28卷 1189-1198页

作者： Yang Lin Zheng Huifang Feng Jin Li Ning Chen Jiaqi College of Electronic Science and Engineering National University of Defense Technology Department of Space Microwave Remote Sensing System Institute of Electronics Chinese Academy of Sciences College of Computer and Information Engineering Hohai University

Radio frequency interference（RFI） is becoming more and more frequently, which makes it an important issue in SAR imaging.RFI presented in synthetic aperture radar either on purpose or inadvertent will distort the useful SAR echoes, thus degrade the SAR image quality.To resolve this issue, a long time study was carried out to study the characteristic of the RFI through the RFIaffected spaceborne and airborne SAR data.Based on the narrow band nature of RFI, this paper proposes a new process which contains both RFI detection and RFI suppression.A useful subband spectral kurtosis detector is first used to detect RFI, and then its results are used for RFI suppression.The proposed process has two advantages： one is the economization on the compute time for unnecessary interference suppression when no RFI existed; the other is improving the performance of the suppression method with knowing the exact position where RFI is.Moreover, the previous RFI suppression method––subband spectral cancelation（SSC） is supplemented and perfected.The subband division step is also elaborated detail in this paper.The experiment results show that the subband spectral kurtosis detector exhibits good performance in recognizing both weak and narrow-band RFI.In addition, the validity of the SSC method with subband spectral kurtosis detector is also validated on the real SAR echoes.

关键词： Kurtosis detector Radio frequency interference Subband spectralcancelation synthetic aperture radar

A synthetic aperture radar sea surface distribution estimation by n-order Bézier curve and its application in ship detection

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Acta Oceanologica Sinica 2016年第9期35卷 117-125页

作者： LANG Haitao ZHANG Jie WANG Yiduo ZHANG Xi MENG Junmin School of Science Beijing University of Chemical Technology Jiangsu Key Laboratory of Big Data Analysis Technology/B-DAT Nanjing University of Information Science &Technology The First Institute of Oceanography State Oceanic Administration

To dates,most ship detection approaches for single-pol synthetic aperture radar（SAR） imagery try to ensure a constant false-alarm rate（CFAR）.A high performance ship detector relies on two key components：an accurate estimation to a sea surface distribution and a fine designed CFAR algorithm.First,a novel nonparametric sea surface distribution estimation method is developed based on n-order Bézier curve.To estimate the sea surface distribution using n-order Bézier curve,an explicit analytical solution is derived based on a least square optimization,and the optimal selection also is presented to two essential parameters,the order n of Bézier curve and the number m of sample points.Next,to validate the ship detection performance of the estimated sea surface distribution,the estimated sea surface distribution by n-order Bézier curve is combined with a cell averaging CFAR（CA-CFAR）.To eliminate the possible interfering ship targets in background window,an improved automatic censoring method is applied.Comprehensive experiments prove that in terms of sea surface estimation performance,the proposed method is as good as a traditional nonparametric Parzen window kernel method,and in most cases,outperforms two widely used parametric methods,K and G0 models.In terms of computation speed,a major advantage of the proposed estimation method is the time consuming only depended on the number m of sample points while independent of imagery size,which makes it can achieve a significant speed improvement to the Parzen window kernel method,and in some cases,it is even faster than two parametric methods.In terms of ship detection performance,the experiments show that the ship detector which constructed by the proposed sea surface distribution model and the given CA-CFAR algorithm has wide adaptability to different SAR sensors,resolutions and sea surface homogeneities and obtains a leading performance on the test dataset.

关键词： Bézier curve nonparametric method ship detection sea surface distribution synthetic aperture radar

An Algorithm to Retrieve Precipitation with synthetic aperture radar

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Journal of Meteorological Research 2016年第3期30卷 401-411页

作者：谢亚楠刘志坤安大伟 Key Laboratory of Specialty Fiber Optics and Optical Access Networks Shanghai UniversityShanghai 200072 National Satellite Meteorological Center Beijing 100081

This paper presents a new type of rainfall retrieval algorithm,called the model-oriented statistical and Volterra integration.It is a combination of the model-oriented statistical（MOS） and Volterra integral equation（VIE） approaches.The steps involved in this new algorithm can be briefly illustrated as follows.Firstly,information such as the start point and width of the rain is obtained through pre-analysis of the data received by synthetic aperture radar（SAR）.Secondly,the VIE retrieval algorithm is employed over a short distance to obtain information on the shape of the rain.Finally,the rain rate can be calculated by using the MOS retrieval algorithm.Simulation results show that the proposed algorithm is effective and simple,and can lead to time savings of nearly 50%compared with MOS.An example of application of SAR data is also discussed,involving the retrieval of precipitation information over the South China Sea.

关键词： microwave remote sensing precipitation retrieval algorithm synthetic aperture radar

Speckle suppression in synthetic aperture radar ocean internal solitary wave images with curvelet transform

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Acta Oceanologica Sinica 2016年第9期35卷 13-21页

作者： ZHA Guozhena HE Qingyou GUAN Changlonga SUN Jian HE Mingxia College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China University of Chinese Academy of Sciences Beijing 100049China Physical Oceanography Laboratory Ocean University of ChinaQingdao 266100China Ocean Remote Sensing Institute Ocean University of ChinaQingdao 266100China

This paper proposes a speckle-suppression method for ocean internal solitary wave（ISW） synthetic aperture radar（SAR） images by using the curvelet transform.The band-shaped signatures of ocean ISWs in SAR images show obvious scale and directional characteristics.The curvelet transform possesses a very high scale and directional sensitivity.Therefore,the curvelet transform is very efficient in analyzing wave signals in SAR images.A noisy ocean ISW SAR image can be decomposed at different scales,directions,and positions using the curvelet transform.The information of the ISWs is centralized in the curvelet coefficients of certain directions under certain scales,whereas the speckle noise is distributed in every scale and direction.By manipulating the curvelet coefficients,the signals of the ISWs can be extracted from the noisy SAR image.Finally,the speckle noise is suppressed and the ISW feature is enhanced by adding the signals of the ISWs back to the original SAR image.Experiments demonstrate the effectiveness of this method.

关键词： curvelet transform internal solitary wave remote sensing speckle noise synthetic aperture radar

Observation of Offshore Wind Farm Wakes by Spaceborne synthetic aperture radar

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Journal of Geodesy and Geoinformation Science 2021年第1期4卷 38-48页

作者： Xiaoming LI Susanne LEHNER Key Laboratory of Digital Earth Science Aerospace Information Research InstituteChinese Academy of SciencesBeijing 100094China Hainan Key Laboratory of Earth Observation Sanya 572029China

In this paper,studies on offshore wind farm wakes observed by spaceborne synthetic aperture radar(SAR)are reviewed mainly based on our previous research.Particularly,we focus on investigating wind wakes and tidal current wakes observed by spaceborne SAR of Terra SAR-X,Gaofen-3 and radarsat-2 in high spatial resolution,in two offshores wind farms,i.e.,the Alpha Ventus in the North Sea and the one near Donghai bridge in the East China Sea.Representing examples of wind wakes and tidal current wakes observed by SAR in the two farms are presented and compared.A preliminary statistical analysis on morphology of wind feature downstream Alpha Ventus is presented as well.Besides these studies on wind wakes generated by a single offshore wind farm,we show an example of wakes downstream multiple wind farms in the North Sea to demonstrate"cluster"effect of multiple offshore wind farms on sea wind.

关键词： offshore wind farm wakes synthetic aperture radar

Method of moving target detection based on sub-image cancellation for single-antenna airborne synthetic aperture radar

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Journal of Systems Engineering and Electronics 2007年第3期18卷 448-453页

作者： Liu Shujun Yuan Yunneng Gao Fei Mao Shiyi Dept. of Electronic and Information Engineering Beihang Univ. Beijing 100083 P. R. China

The method of moving target detection based on subimage cancellation for single-antenna airborne SAR is presented. First the subimage is obtained through frequency processing is pointed out. The imaging difference of a stationary objects and moving object in the subimage based on the frequency division is analyzed from the fundamental principle. Then the developed method combines the shear averaging algorithm to focus on the moving target in the subimage, after the clutter suppression and the focusing position in each subimage is obtained. Next the observation model and the relative movement of the moving targets between the subimages estimate the moving targets. The theoretical analysis and simulation results demonstrate that the method is effective and can not only detect the moving targets, but also estimate their motion parameters precisely.

关键词： synthetic aperture radar moving target detection sub-image cancellation parameter estimation.