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1.
基于Gabor小波变换的机载SAR海面风向反演方法   总被引:1,自引:0,他引:1       下载免费PDF全文
给出了一种基于Gabor小波变换的机载合成孔径雷达(SAR)海面风向反演的新方法。该方法利用Gabor小波对SAR图像进行二次小波分解,并对小波系数作FFT变换来获取图像谱,其低波数谱连线的垂线方向就是海面风场的风向。利用该方法获得了SAR图像海面风向信息,并与àtrous算法反演结果、浮标测得的海面风向(真值)进行了比较。实验结果表明,采用该方法获得的机载SAR海面风向反演结果与海面浮标实测数据吻合,比àtrous算法有较大改进。  相似文献   

2.
合成孔径雷达(Synthetic Aperture Radar, SAR)因其全天时、全天候、高分辨率对海探测的特点,在海面风场反演方面具有独特优势。分别以合成孔径雷达风向、风速以及风矢量反演为主线,对国内外相关工作进行了详细的总结。  相似文献   

3.
吕尚艳  薄华 《电子设计工程》2012,20(12):169-172
基于合成孔径雷达(SAR)图像的海面风场估计已经得到广泛认可。多数风速反演算法是以估计的风向、校正的δvv为先验条件,应用海风模型计算而得的。在相同风向的情况下,应用不同的海风模型会得到不同的风速反演值,因此选择合适的模型是风场估计的关键。同时,风向数据的精确度也很重要,即使不大的误差也会给风速的反演结果带来明显偏差。为解决上述问题这里提出一种不需要预先已知风向数据的风场估计算法。该算法将基于海洋SAR图像中风浪的条纹信息,以及风浪条纹生成的自相关函数的周期性估计风速数据,同时由风浪条纹的最短周期方向估计风向数据,从而估计出完整的风场矢量。仿真结果显示,该算法对风速和风向数据有较高的估计精度。  相似文献   

4.
李晓峰  张彪  杨晓峰 《雷达学报》2020,9(3):425-443
星载合成孔径雷达(SAR)能够全天时、全天候、高空间分辨率、宽刈幅观测海洋表面,是获取海面风场和波浪场信息的重要微波传感器。该文综述了多极化SAR海面风场遥感原理、地球物理模式函数,以及潜在应用(海气边界层现象、海上风能资源开发、台风监测与预警预报),系统总结了传统星载SAR、新型干涉和极化SAR海浪遥感方法和技术。随着雷达卫星编队飞行技术的逐步成熟,未来海洋卫星组网将成为全球海洋和极地观测新趋势,合成孔径雷达海面风场和波浪场定量遥感将从科学研究向业务化海洋动力环境监测发展。   相似文献   

5.
SAR的海洋动力探测研究及应用浅析   总被引:1,自引:0,他引:1  
朱敏慧 《雷达学报》2012,(4):342-352
该文在深入研究海面微波散射特性及其SAR海面成像机理的基础上,阐述了基于SAR图像的海洋动力探测的探索工作。主要是从内波、水下地形波和船只尾迹产生机理的统计和水动力分析出发、研究了它们的SAR成像特征和相应的物理参数反演,以此拓展SAR的海洋观察应用。  相似文献   

6.
利用分形海面模型、Kirchhoff近似电磁散射模型和基于时序的动态场景回波仿真模型得到星载SAR海面场景回波.给出理想单色波海浪和分形海面回波仿真实例,回波成像结果符合倾斜调制、速度聚束调制和实际海面SAR图像的统计特性,表明该方法有效.仿真得到的回波数据可为星载SAR海面顺轨干涉(ATl-SAR)测洋流、海洋全极化探测、反演海谱等仿真研究提供源数据.  相似文献   

7.
星载全极化微波散射计系统仿真与性能分析   总被引:1,自引:0,他引:1       下载免费PDF全文
宋忠国  董晓龙  林文明  朱迪 《电子学报》2013,41(12):2382-2390
本文对全极化微波散射计遥感海面风场的原理及其特点进行研究,建立了星载全极化微波散射计的系统仿真模型.对比了SeaWinds散射计参数下全极化与同极化的风场反演质量,结果表明全极化微波散射计在星下点以及刈幅远端的区域有良好的风场反演性能,并可提升高风速条件下的风场反演精度.最后分析了极化通道隔离度对全极化散射计系统性能的影响.  相似文献   

8.
顺轨干涉SAR海洋表面流场迭代反演算法   总被引:3,自引:0,他引:3  
该文在分析传统顺轨干涉SAR表面流场速度分离方法不足的基础上,根据海面微波成像仿真模型建立了顺轨干涉SAR海洋表面流场迭代反演算法。利用该迭代反演算法对JPL AIRSAR获得的机载顺轨干涉SAR数据进行流场反演,并将反演流场与普林斯顿海洋模型(POM)的输出流场进行对比,两个流场具有很好的一致性,证实了该迭代反演算法的有效性。  相似文献   

9.
本文以 SeaWinds 散射计为例,针对圆锥扫描散射计星下点附近区域容易产生风向模糊问题,在分析其目标函数分布特征的基础上,对传统的最大似然风矢量反演算法和圆中数滤波算法进行了改进,提出了一种适合于圆锥扫描散射计的海面风场反演方法.该方法通过在目标函数分布较平坦的区域设置风向扩展区间,并使扩展后的更多风向解参与模糊去除来提高风向选择的准确性.利用 200 条轨道的 SeaWinds 散射计 L2A 数据和相应浮标数据,对本文给出的风场反演方法进行了验证.结果表明,该方法在无需外部辅助风场数据作为参考的条件下,能够使星下点附近区域的风向模糊性得到明显改善,从而证明了该方法的可行性.  相似文献   

10.
全极化微波辐射计是进行海面风场测量的新型被动式遥感器。数字极化辐射计通过数字相关器对两个极化通道做相关处理,完成四个Stokes矢量参数的测量,反演海面风场。文中提出辐射计核心器件宽带数字相关器的设计方法。双极化通道通过IQ变换转化为两对正交信号,四片国内自主研制的A/D转换器以2.2Ghz采样率采样四路信号,采样结果通过多路复用DEMUX芯片复用后,传输到新一代现场可编程门阵列(FPGA)-Virtex5芯片中作进一步多路复用和相关运算。文中详细介绍了系统结构,数据处理流程和测试结果。  相似文献   

11.
ERS-1 synthetic aperture radar (SAR) images of atmospheric gravity waves over the ocean are discussed. Several case studies are presented in detail. It is shown that the well-organized long wavelength (1 to 10 km) wave phenomena which often are seen in SAR images over the ocean may be atmospheric gravity waves. The waves appear in the SAR images because they modulate the surface wind speed which in turn modulates the surface roughness and the radar cross section. The wavelength may be measured directly from the SAR image, and the mean wind speed and wind speed modulation near the ocean surface may be estimated from the observed radar cross section modulation using a wind retrieval model. The atmospheric gravity waves usually were generated by the approach or passing of a meteorological front. Atmospheric soundings and a two-layer model for the lower troposphere indicate that, in general, the observed atmospheric wave phenomena could have been supported by accompanying temperature inversion layers and wind shears  相似文献   

12.
Evaluation of JERS-1 SAR images from a coastal wind retrieval point of view   总被引:1,自引:0,他引:1  
Wind retrieval from Japanese Earth Resources Satellite-1 (JERS-1) synthetic aperture radar (SAR) using an L-band model function in coastal regions is evaluated. It is known that JERS-1 SAR has excessive ambiguities. This paper also gives a quantitative evaluation of excessive ambiguities in coastal scenes of JERS-1 SAR. First, focusing on the cases where wind blows from the shore in Sagami Bay, we investigate phenomena of wind speed increase with offshore distance using European Remote sensing Satellite-1 (ERS-1) SAR-derived wind speeds. The relation between wind speed and offshore distance is well formulated, which indicates the transition of the atmospheric boundary layer from land to sea surface. Wind speeds derived from JERS-1 SAR should be overestimated due to the excessive ambiguity. Then, for observation time of each JERS-1 SAR capturing the cases that wind blows from the shore in Sagami Bay, the expected wind speed growth profile is derived from the wind speed growth formula and an in situ wind observation of Hiratsuka Experiment Station. We convert the wind-speed profile into the sigma-0 profile by an L-band model function. Finally, the profiles of JERS-1 SAR-observed and the estimated sigma-0 are compared, and the excessive ambiguity is estimated as the difference between them. As a result, the dynamic range of first azimuth ambiguity is as large as that of the wind-relating signal from the ocean surface. Moreover, higher order azimuth ambiguities and range ambiguity also may have a significant impact on near-shore wind retrieval.  相似文献   

13.
Directional analysis of SAR images aiming at wind direction   总被引:7,自引:0,他引:7  
Currently, the retrieval of wind fields from synthetic aperture radar (SAR) images suffers from inadequate knowledge of the wind direction. State-of-the-art spectral analysis works fine on open seas, but is limited in spatial resolution. The method described here is based on the local gradients computed with standard image processing algorithms. It handles image features not caused by wind and can be applied to irregularly shaped regions. The new method has already been applied to many images from the European Remote sensing Satellite SARs and RADARSAT-1 ScanSAR, usually supplying reasonable wind fields. The spatial sampling most frequently used was 20 /spl times/ 20 and 10/spl times/10 km/sup 2/. In some cases, samplings down to 1/spl times/1 km/sup 2/ were tested. This paper describes the local gradients method including the filtering of nonwind generated image features and gives some application examples.  相似文献   

14.
An L-band geophysical model function is developed using Japanese Earth Resources Satellite-1 (JERS-1) synthetic aperture radar (SAR) data. First, we estimate the SAR system noise, which has been a serious problem peculiar to the JERS-1 SAR. It is found that the system noise has a feature common in all the SAR images and that the azimuth-averaged profile of noise can be expressed as a parabolic function of range. By subtracting the estimated noise from the SAR images, we can extract the relatively calibrated ocean signals. Second, using the noise-removed SAR data and wind vector data from the NASA Scatterometer and buoys operated by the Japan Meteorological Agency, we generate a match-up dataset, which consists of the SAR sigma-0, the incidence angle, the surface wind speed, and wind direction. Third, we investigate the sigma-0 dependence on incidence angle, wind speed, and wind direction. While the incidence angle dependence is negligible in the present results, we can derive distinct sigma-0 dependence on wind speed and direction. For wind speeds below 8 m/s, the wind direction dependence is not significant. However, for higher wind speeds, the upwind-downwind asymmetry becomes very large. Finally, taking into account these characteristics, a new L-band-HH geophysical model function is produced for the SAR wind retrieval using a third-order harmonics formula. Resultant estimates of SAR-derived wind speed have an rms error of 2.09 m/s with a negligible bias against the truth wind speed. This result enables us to convert JERS-1 SAR images into the reliable wind-speed maps.  相似文献   

15.
Wind vector retrieval using ERS-1 synthetic aperture radar imagery   总被引:4,自引:0,他引:4  
An automated algorithm intended for operational use is developed and tested for estimating wind speed and direction using ERS-1 SAR imagery. The wind direction comes from the orientation of low frequency, linear signatures in the SAR imagery that the authors believe are manifestations of roll vortices within the planetary boundary layer. The wind direction thus has inherently a 180° ambiguity since only a single SAR image is used. Wind speed is estimated by using a new algorithm that utilizes both the estimated wind direction and σ 0 values to invert radar cross section models. The authors show that: 1) on average the direction of the roll vortices signatures is approximately 11° to the right of the surface wind direction and can be used to estimate the surface wind direction to within ±19° and 2) utilizing these estimated wind directions from the SAR imagery subsequently improves wind speed estimation, generating errors of approximately ±1.2 m/s, for ERS-1 SAR data collected during the Norwegian Continental Shelf Experiment in 1991  相似文献   

16.
The relative importance of the various motion-related contributions to the SAR imaging mechanism of ocean surface waves is studied by using two-dimensional Monte Carlo simulation techniques. It is shown that for wind waves the often-observed stretching of the peak wavelength and the rotation of the spectral peak toward the range direction is caused by both the degradation in azimuthal resolution and the nonlinearity of the velocity bunching mechanism. The distortion of the SAR image spectrum relative to the ocean wave spectrum due to the degradation in azimuthal resolution is mainly caused by the spread of the radial facet velocities within a SAR resolution cell. The effect of the radial orbital acceleration arising from the long waves of scales larger than a SAR resolution cell on the nonlinearity of the SAR imaging mechanism is small. It is argued that the effect of the wave motions on the SAR imaging mechanism cannot always be reduced to a linear azimuthal low-pass filter acting on the ocean slope spectrum. In those cases where the imaging is nonlinear, the ocean wave spectrum cannot be retrieved from the SAR image spectrum by applying linear inversion techniques. For swell imaging, the nonlinearities are usually less strong because swell spectra have a narrower width than wind spectra. Computer simulations of SAR imaging of fully developed wind seas with different peak wavelengths and propagation directions are presented.  相似文献   

17.
European remote sensing (ERS) satellites synthetic aperture radar (SAR) wind retrievals using CMOD-IFR2 are, for the first time, retrieved in the marginal ice zone (MIZ) and in Arctic coastal areas and compared with in situ observations from reseach vessels (RVs) and output from a high-resolution atmospheric model. The root mean squares (rms) of the comparisons were 1.6 m s/sup -1/ and 2 m s/sup -1/, respectively. The spatial variation of the SAR wind fields established a decrease in wind speed close to the ice edge for the late summer situations where the wind was along the ice edge with the ice to the left. This decrease is believed to be due to changes in atmospheric stability, possibly through development of an internal boundary layer caused by the cold ice cover and melt water. Lower wind speed near the ice edge is confirmed by the atmospheric model and the in situ observations. Furthermore, good results are obtained from SAR wind retrieval in leads when compared with model output during a cold-air outbreak. Routine measurements in the MIZ are useful for estimating the wind stress, and therefore SAR may play an important role in this region. Finally, the identification of a jet out from Hinlopen Strait in the Svalbard region and low wind wakes along the coast in the SAR-retrieved wind field is confirmed by in situ observations as the RV moves through the region. The jet is also confirmed by the atmospheric model, which is able to reproduce the situation.  相似文献   

18.
As part of the Alaska synthetic aperture radar (SAR) Demonstration Project in 1999 and 2000, wide-swath RADARSAT SAR imagery has been acquired on a regular basis in the Gulf of Alaska and the Bering Sea. During 1998 and 1999, similar data were acquired off the East Coast of the United States as part of the StormWatch Project. The radar cross section measurements from these images were combined with wind direction estimates from the Navy Operational Global Atmospheric Prediction System model to produce high-resolution maps of the surface wind speed. For this study, 2862 SAR image frames were collected and examined. Averaged wind estimates from this data base have been systematically compared with corresponding wind speed estimates from buoy measurements and model predictions, and very good agreement has been found. The standard deviation between the buoy wind speed and the SAR estimates is 1.76 m/s. Details of the SAR wind extraction procedure are discussed, along with implications of the comparisons on the C-band polarization ratio  相似文献   

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