基于最优对比度准则的SAR图像相位梯度自聚焦算法

相位梯度自聚焦（PGA）算法是SAR图像自聚焦领域的经典算法。在分析经典PGA算法性能的基础上，提出了基于最优对比度准则的SAR图像相位梯度自聚焦算法。该算法改进了PGA算法的加窗方法和迭代终止条件，提高了PGA算法的鲁棒性和实时应用性能。理论分析和实验结果证明了该算法的有效性。     

Waterline mapping in flooded vegetation from airborne SAR imagery

Multifrequency, polarimetric airborne synthetic aperture radar (SAR) survey of a salt marsh on the east coast of the UK is used to investigate the radar backscattering properties of emergent salt marsh vegetation. Two characteristics of flooded vegetation are observed: backscatter enhanced by approximately 1.2 dB at C-band, and 180° HH-VV phase differences at L-band. Both are indicative of a double bounce backscattering mechanism between the horizontal water surface and upright emergent vegetation. The mapping of inundated vegetation is demonstrated for both these signatures, using a statistical active contour model for the C-band enhanced backscatter, and median filtering and thresholding for the L-band HH-VV phase difference. The two techniques are validated against the waterline derived from tidal elevation measured at the time of overpass intersected with an intertidal DEM derived from airborne laser altimetry. The inclusion of flooded vegetation is found to reduce errors in waterline location by a factor of approximately 2, equivalent to a reduction in waterline location error from 120 to 70 m. The DEM is also used to derive SAR waterline heights, which are observed to underpredict the tidal elevation due to the effects of vegetation. The underprediction can be corrected for vegetation effects using canopy height maps derived from the laser altimetry. This third technique is found to improve the systematic error in waterline heights from 20 to 4 cm, but little improvement in random error is evident, chiefly due to significant noise in the vegetation height map.     

滤波器组实现SAR图像中主要道路提取

合成孔径雷达(SAR)图像中道路目标自动提取既是当前遥感技术应用中的热点又是急待解决的难点.着眼SAR图像中道路目标的自动提取,在分析SAR图像特征的基础上,绕开常见的利用边缘检测算子提取图像中道路线段的作法,通过适当选择滤波窗口在去噪的同时尽量保持道路边缘,再通过二次二维方向性滤波、去枝滤波准确高效地提取了SAR图像中的道路目标.实验证明该方法在提取SAR图像中主要道路目标时几乎不需要调整参数,人工干预少,自动化程度高.     

双峰海浪谱的SAR图像交叉谱仿真研究

由6参数双峰频谱和cos-2s型分布函数得到了双峰海浪方向谱的波数谱形式,并利用海浪谱到合成孔径雷达(Synthetic Aperture Radar,SAR)图像交叉谱的非线性转换关系,对双峰海浪谱的SAR图像交叉谱进行了仿真,分析了不同海浪参数和SAR平台参数对SAR图像交叉谱的影响,并与SAR图像谱进行了比较。     

SAR自动聚焦处理器的设计与实现

合成孔径雷达(SAR)成像具有数据量巨大、算法比较复杂等特点。如何实时实现SAR成像的相关算法是嵌入式高性能计算领域一个值得研究的问题。针对SAR成像中多普勒调频率估计的经典算法PGA算法，阐述了算法的实时化改进。介绍了基于FPGA的SAR自动聚焦处理器的系统级设计及PGA算法到FPGA逻辑实现的映射过程。     

SAR图像道路目标提取研究

和大多数侧重于后处理的算法不同,文中在研究了合成孔径雷达(SAR)图像中道路的灰度及几何特征之后,着重在图像预处理中提出了非线性自适应保边缘滤波及局部均方差加权边缘增强算法,在去除乘性斑点噪声的同时较好地保持了道路边缘特征,再从全局的角度考虑提出了一种改进的随机Hough变换(GRHT)算法来确立道路边缘线,继而进一步确定道路中心线.整个算法可以自动进行,具有很高的处理速度及较低的储存需求,实验证明该算法能够准确有效地提取SAR图像中道路目标.     

Generation of geometrically and radiometrically terrain corrected SAR image products

Terrain undulations affect the geometric and radiometric quality of synthetic aperture radar images. The correction of these effects becomes indispensable when quantitative image analysis is performed with respect to the derivation of geo- and biophysical parameters. The paper presents a rigorous approach for geometric and radiometric correction of SAR images. Using a digital elevation model, the imaging geometry is reconstructed and is used to perform geometric and radiometric correction of terrain induced distortions. The importance of a stringent radiometric correction based on the integration of the image brightness is emphasized. The approach guarantees that the energy contained in the image data is preserved throughout the geocoding process. The resulting backscattering images are fully terrain corrected and can be used for further quantitative investigations and may also improve qualitative studies as e.g. land cover classifications. The technique is applicable for different sensor types and image products, including already geocoded SAR images. The effect of different resolutions of digital elevation models used for the correction of the backscattering coefficient is investigated.     

多区域SAR图像分割的改进水平集方法

由于合成孔径雷达（SAR）图像易受相干斑噪声的影响,光学图像的分割方法并不适用于SAR图像,更不能获得精确的分割结果对比,因此,首先基于GA^0统计模型定义能量映射函数以代替像素值进行后续处理,减小相干斑的影响;其次,使用水平集算法对处理后的图像进行分割处理,选用了一种形式更为简单的水平集函数,并可以较容易地推广到多区域SAR图像分割情况。实验结果表明,该方法可以减少相干斑噪声对SAR图像分割过程的不良影响,具有较好的准确性。     

一种子像素精度SAR图像目标峰值提取方法

SAR图像目标峰值是SAR图像目标识别的重要特征 ,它本质对应于目标散射中心 ,目标峰值提取是SAR图像目标识别的一个重要步骤。基于峰值SAR图像目标识别系统要求目标峰值提取方法应具有快速、高精度的特点。现有的SAR图像目标峰值提取方法精度较低 ,其对目标峰值位置的估计精度只能达到像素级。为了提高SAR图像目标峰值提取精度 ,该文在分析SAR图像峰值模型基础上 ,提出了一种子像素精度SAR图像目标峰值提取方法 ,并通过仿真实验 ,分析了该方法对目标峰值位置、幅度的估计性能 ,结果表明在SNR =2 0dB的情况下 ,该方法对目标峰值位置估计的标准偏差 <0 .1个像素 ,峰值幅度估计的标准偏差小于 0 .0 5 H(这里H表示目标峰值的真实幅度 ) ,文中还给出了该方法对实测MSTARSAR图像的目标峰值提取结果。     

基于云环境下的资源评价模型研究

分析了己有的调度机制和常用的任务调度算法,并在此基础上设计了资源评价模型。将资源评价模型加入调度系统中,资源信息由评价模块进行分析和评价,并提供给任务调度器,实现资源和任务的优化匹配,提高了服务质量(QoS)。     

Effects of soil moisture and water depth on ERS SAR backscatter measurements from an Alaskan wetland complex

We conducted a preliminary investigation of the response of ERS C-band SAR backscatter to variations in soil moisture and surface inundation in wetlands of interior Alaska. Data were collected from 5 wetlands over a three-week period in 2007. Results showed a positive correlation between backscatter and soil moisture in sites dominated by herbaceous vegetation cover (r = 0.74, p < 0.04). ERS SAR backscatter was negatively correlated to water depth in all open (non-forested) wetlands when water table levels were more than 6 cm above the wetland surface (r = − 0.82, p < 0.001). There was no relationship between backscatter and soil moisture in the forested (black spruce-dominated) wetland site. Our preliminary results show that ERS SAR data can be used to monitor variations in hydrologic conditions in high northern latitude wetlands (including peatlands), particularly sites with sparse tree cover.     

MRPM: three visual basic programs for mineral resource potential mapping

A traditional method for mineral resource potential mapping is to superimpose a number of indicator maps, and to combine geological information with or without the use of multivariate statistical models. More recently, GISs have become widely applied in mineral resource assessment and many statistical models for geological information synthesis have been proposed. GIS-based mineral resource potential mapping has facilitated modern mineral resource assessment. As a contribution to publicly available computer software for GIS-based mineral resource assessment, integrated three Visual Basic programs have been developed on MapInfo platform. The programs integrate map patterns using weights of evidence, applied general C-F, and evidence theory models, and generate posterior probability, combined certainty factor, and combined basic probability assignment maps, respectively. The software is demonstrated by a case study based on a real data set.     

Fast implementation of ground maneuvering target focusing

Ground maneuvering target detection is a hot topic in the applications of synthetic aperture radar (SAR), whereas its focusing performance is severely deteriorated by range migration and Doppler frequency migration during a long integration time. This paper proposes a novel method to image the target and estimate its parameters via performing two independent 2-dimensional (2-D) searches after a parameter separation operation. In order to improve the search speed, we set the limited search ranges and propose local mapping sparse Fourier transform (LMSFT) to replace fast Fourier transform (FFT). Compared with the traditional algorithms, the proposed method can realize fast coherent integration of multiple maneuvering targets via compensating the high-order range migration and Doppler frequency migration. In addition, the proposed method is stable under noise. Several simulation results have validated the effectiveness of the proposed method.     

一种高性能SAR图像边缘点特征匹配方法

针对合成孔径雷达（Synthetic aperture radar,SAR）图像特征匹配中特征提取的不稳定性和相似度优化搜索的复杂性问题,提出了一种精确高效稳健的SAR图像边缘点集匹配方法. 首先,分析了仿射变换模型在遥感图像匹配中的适应性,并对仿射变换模型进行了参数分解;其次,提出了基于方向模板的SAR图像边缘检测算子,并利用SAR图像边缘的梯度和方向特征,建立了基于像素迁移的多源SAR边缘点集相似性匹配准则,以及图像匹配的联合相似度-联合特征均方和（Square summation joint feature,SSJF）;然后,利用改进的遗传算法（Genetic algorithm,GA）来进行相似度的全局极值优化搜索,获取变换模型参数和边缘点集的对应关系;最后,从理论上分析了本文方法的性能,并利用多幅SAR图像的匹配实验以及与原有方法的对比分析,对本文方法的性能进行了验证.     

基于高亮模型匹配的SAR建筑物高度反演方法

针对高分辨率SAR图像中的建筑物高度提取问题,提出了一种基于高亮模型匹配的建筑物高度反演方法。通过对建筑物的成像特征进行分析构建出高亮特征模型,建立模型与SAR图像之间的匹配度函数,运用多种群遗传算法对匹配度函数进行优化搜索出最优的高度参数。基于模拟和实测SAR图像的实验结果表明该算法可以用于SAR图像建筑物高度反演,并具有较高的反演精度。