一种改进的SAR图像聚焦算法     

倪崇  王岩飞  徐向辉  周长义  崔鹏飞 《测绘学报》2012,41(3):449-453

针对现有的相位梯度自聚焦(phase gradient autofocus,PGA)算法的加窗方法和特显点选取所存在的问题,提出一种改进的PGA算法。该算法提出一种新的确定相位误差点扩展函数支撑域的方法,此方法计算方位向上能量分布的平均值作为支撑域外的平均能量,以此来确定加窗的宽度。基于这种自适应加窗方法,还提出一种改进的特显点选取方法,该方法能够选择信杂比大的特显点,去掉信杂比小的特显点。试验结果表明,与传统的加窗方法和特显点选取方法相比,该方法能够得到更好的聚焦效果。  相似文献   

统计假设检验方法在全极化SAR变化检测中的应用   总被引：1，自引：1，他引：0  

郝洪美  张永红  石海燕  黄金波 《遥感学报》2012,16(3):520-532

本文以全极化SAR数据为研究对象。由于全极化数据相干矩阵T3或协方差矩阵C3服从复wishart分布,所以首先在此分布的基础上利用统计假设检验方法构建似然比参数,用以表征地表地物的变化程度,然后利用基于广义高斯分布模型的EM迭代算法(GGM-EM)对变化信息进行初提取,最后充分考虑上下文信息,利用概率松弛迭代算法对初检测信息进行优化。该方法不仅全自动提取变化信息,而且经过非相干平均、初始分类、分类结果优化3次降斑去噪处理,因此检测精度较高。通过与传统对数比值法的比较,证明该方法的有效性。  相似文献   

“凤凰”台风期间海面风、浪的高频地波雷达OSMAR071遥感   总被引：1，自引：0，他引：1  

李伦  吴雄斌  李炎  龙超  刘斌  徐兴安  陈珉  薛超英 《遥感学报》2012,16(1):154-165

介绍了OSMAR071高频地波雷达系统“凤凰”台风期间海面风、浪遥测结果。文中给出高频地波雷达OSMAR071 风、浪反演算法：利用SBM模型结合多波束采样法反演风向;利用改进的Barrick模型进行有效波高的反演;利用SMB关系式进行风速反演。将雷达定点观测结果与浮标数据进行对比,表现出很好的一致性,其中有效波高相关系数为0.72,均方根误差为0.48 m,风向相关系数为0.97,均方根误差为27.7°,风速的相关系数为0.6,均方根误差为 3.5 m/s。文中还对影响探测精度的因素进行了分析。  相似文献   

机载激光雷达技术的数据处理与4D产品制作     

李淑琴 《全球定位系统》2012,37(2):43-47

主要介绍了机载激光雷达的点云数据的获取、处理流程及其关键技术,并结合自己的工作经验详细阐述了运用点云数据制作4D产品的过程,预测未来遥感与GIS技术在数据获取方面的发展趋势,即借助机载激光雷达,再现真实三维场景。  相似文献   

Ionospheric corrections of MARSIS subsurface sounding signals with filters including collision frequency     

Zhenfei Zhang  Erling Nielsen  Roberto Orosei 《Planetary and Space Science》2009,57(3):393-403

Ionospheric corrections of Mars advanced radar for subsurface and ionosphere sounding (MARSIS) subsurface sounding signals are necessary before they can be further analyzed. Usually the ionosphere correction only considers the phase dispersion owing to the electron densities. In this paper we show that if the electron-neutral collision frequency is included in the correction filter, the signal-to-noise ratio of the processed signal can be further maximized and the spatial resolution of the signal be improved. Three different models of the ionosphere profile have been studied, and it is shown that a uniform slab model, of both densities and collisions, is feasible and probably the best choice when implementing the correction filter including collisions. The physical significance of the parameters obtained with the uniform model (equivalent parameters) is discussed, and it is shown that they are useful for the estimation of the real physical parameters of the ionosphere. We developed a recursive, random search algorithm to facilitate the realization of the correction process with the filter including collision frequency.  相似文献   

基于PS-VF-TBD的地波雷达船只目标航迹起始方法     

高昆鹏  纪永刚  王祎鸣  孟俊敏 《海洋科学》2022,46(4):13-24

针对地波雷达低信噪比目标信号"闪烁"导致的航迹起始困难问题,本文提出了一种基于PS-VF-TBD的航迹起始方法.该方法综合利用了地波雷达回波谱中目标信号的展宽特征和运动特性,利用PS-VF-TBD方法对运动目标能量有效积累的特点,提高对疑似目标多帧信号间的关联概率,进而提高对真实目标的搜索概率和航迹起始成功率.通过地波...  相似文献   

Statistical assessment of shapes and magnetic field orientations in molecular clouds through polarization observations     

K. Tassis  C. D. Dowell  R. H. Hildebrand  L. Kirby  J. E. Vaillancourt 《Monthly notices of the Royal Astronomical Society》2009,399(4):1681-1693

We present a novel statistical analysis aimed at deriving the intrinsic shapes and magnetic field orientations of molecular clouds using dust emission and polarization observations by the Hertz polarimeter. Our observables are the aspect ratio of the projected plane-of-the-sky cloud image and the angle between the mean direction of the plane-of-the-sky component of the magnetic field and the short axis of the cloud image. To overcome projection effects due to the unknown orientation of the line-of-sight, we combine observations from 24 clouds, assuming that line-of-sight orientations are random and all are equally probable. Through a weighted least-squares analysis, we find that the best-fitting intrinsic cloud shape describing our sample is an oblate disc with only small degrees of triaxiality. The best-fitting intrinsic magnetic field orientation is close to the direction of the shortest cloud axis, with small  (∼24°)  deviations towards the long/middle cloud axes. However, due to the small number of observed clouds, the power of our analysis to reject alternative configurations is limited.  相似文献   

A comparison of the midlevel kinematic characteristics of a pair of supercell thunderstorms observed by airborne Doppler radar   总被引：1，自引：0，他引：1  

Paul M. Markowski   《Atmospheric Research》2008,88(3-4):314-322

The midlevel kinematic characteristics of two supercell thunderstorms observed during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX), one tornadic and the other nontornadic, are compared using airborne pseudo-dual-Doppler wind retrievals. The most significant difference between the two cases was that a midlevel rear-inflow jet was observed in the nontornadic supercell (12 May 1995), whereas such rear-to-front, storm-relative flow was absent at midlevels in the tornadic supercell (16 May 1995). The midlevel jet in the nontornadic supercell was located on the north flank of a prominent region of anticyclonic vertical vorticity. Some speculations are provided pertaining to the possible importance of the midlevel kinematic differences between the two storms.  相似文献   

X波段双线偏振雷达不同衰减订正方法对比及其对降水估测影响研究   总被引：6，自引：1，他引：5  

胡志群  刘黎平  楚荣忠  金荣花 《气象学报》2008,66(2):251-261

文中分析了X波段双线偏振雷达衰减订正各种方法的特点,考虑到差传播相移率(KDP)作为衰减订正的一种有效途径,以及由于KDP值较小,数据质量不稳定,往往导致订正误差较大,因此提出了同时利用水平反射率因子ZH与KDP进行衰减订正的ZH-KDP综合法.基于同样的考虑,在随后利用ZH、KDP进行降水估测时,提出了ZH-KDP-R综合估测方法.利用中国科学院寒区旱区环境与工程研究所和成都锦江电子系统工程有限公司,在研制3.2 cm波长同时收发式多普勒偏振天气雷达过程中,2005年8月在平凉外场试验取得的一批观测资料,对提出的衰减订正综合法及降水估测综合法的效果进行了分析检验,结果表明,ZH-KDP综合法对ZH、ZDR有稳定的订正效果,并且订正速度快,能够达到实时运行的要求.2005年8月11日15:08:03-22:05:46,间隔5-12 min不等,雷达开机取得了连续的观测资料,通过对这次降水过程的对比分析表明,ZH-KDP-R综合估测法比单因子KDP-R法、Z-R关系法,适用估测的降水强度变化范围广,与自动雨量记的观测结果较为吻合.Z-R关系法中,利用订正后的ZH值,比利用订正前的ZH值,降水估测值与雨量记实测值的误差明显减小,说明衰减订正后的雷达数据质量有明显的改善.  相似文献   

Application of Radar Reflectivity Factor in Initializing Cloud-Resolving Mesoscale Model. Part Ⅰ: Retrieval of Microphysical Elements and Vertical Velocity          下载免费PDF全文

LIU Hongya  XU Haiming  HU Zhijin  XUE Jishan  SHEN Tongli 《Acta Meteorologica Sinica》2008,22(2)

Assuming that cloud reaches static state in the warm microphysical processes, water vapor mixing ratio(qv), cloud water mixing ratio (qc), and vertical velocity (w) can be calculated from rain water mixing ratio (qr)- Through relation of Z-qr, qr can be retrieved by radar reflectivity factor (Z). Retrieval results indicate that the distributions of mixing ratios of vapor, cloud, rain, and vertical velocity are consistent with radar images, and the three-dimensional spatial structure of the convective cloud is presented. Treating q,v saturated at the echo area, the retrieved qr is about 0.1 g kg-1, qc is always less than 0.3 g kg-1, w is usually below 0.5 m s-1, and rain droplet terminal velocity (vr) is around 5.0 m s-1 in the place where radar reflectivity factor is about 25 dBz; in the place where echo is 45 dBz, the retrieved qr and qc are always about 3.0 g kg-1, w is greater than 5.0 m s-1, and vr is around 7.0 m s-1. In the vertical, the maximum updraft velocity is greater than 3.0 m s-1 at the height of around 5.0 kin, the maximum cloud water content is about 3.0 g kg-1 above 5 km and the maximum rain water content is about 3.0 g kg-1 below 6 kin. Due to the assumption that the cloud is in static state, there will be some errors in the retrieved variables within the clouds which axe rapidly growing or dying-out, and in such cases, more sophisticated radar data control technique will help to improve the retrieval results.  相似文献