共查询到18条相似文献,搜索用时 140 毫秒
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内定标利用雷达系统内部设备和定标通路来测量系统各部分幅度和相位在成像过程中的相对变化,是保证雷达图像辐射精度的重要手段。该文针对传统有线内定标方案定标通路未覆盖相控阵天线TR输出端至无源阵面路径、定标网络庞大且自身误差控制难等不足,提出了一种新颖的利用辅助天线的无线内定标方法,给出了定标原理和分析模型,推导了SAR天线TR通道幅相特性和系统传递函数的标定方法,并在典型星载SAR系统参数下对标定误差进行了仿真分析,仿真结果表明,辅助天线支撑杆位置引起的TR通道幅度标定误差在10–3 dB量级,可以忽略;引起相位标定误差与支撑杆位置偏差密切相关,可依据文中给出的仿真曲线得到。支持杆位置引起的系统传递函数幅度标定误差小于0.1 dB;引起的相位标定误差对支撑杆位置偏差不敏感。最后在实际相控阵天线上对无线内定标方法进行了验证,获取了TR通道幅相特性标定的实测结果,表明了该方案的可行性和有效性。 相似文献
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《现代电子技术》2019,(8):113-117
"高分四号"是我国高分辨率对地观测系统中唯一一颗地球同步轨道遥感卫星,应用于环境及林火监测等领域。GF-4数据有很高的空间分辨率,但是辐射特性存在偏差从而导致辐射精度并不是很高。为了提高GF-4卫星数据辐射和LandSat8数据为基准影像,以敦煌辐射校正场作为试验区对GF-4可见光及近红外谱段进行交叉辐射定标。结果表明,通过GF-4的DN值与MODIS和LandSat8的表观辐射亮度数据分析对比,的可见光及近红外波段的定标误差均在10%以内;而LandSat8的可见光及近红外波段的定标误差均在5%以内,比的定标精度接近官方定标系数,满足遥感定量需求。 相似文献
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为分析分布目标基线定标方法的L波段适用性,本文结合我国于2021年发射的L波段编队InSAR卫星(TwinSAR-L)的系统参数,从典型分布目标的穿透和后向散射系数特性出发,指出分布目标参考高程误差不仅包括自身测量误差还包含由穿透和信噪比去相干引入的参考高程误差ΔherrPen和ΔherrSNR,并利用TwinSAR-L数据及TanDEM-X分布目标基线定标模型分析了这两项误差与基线定标误差之间的关系。最后,利用ALOS-2数据定量分析发现研究区域L波段的ΔherrPen,ΔherrSNR分别为1.09 m, 1.39 m。这将分别引入7.9 mm, 10 mm的基线定标误差,严重影响基线定标和后续DEM产品精度。本文的研究工作对TwinSAR-L的基线定标具有一定的理论指导意义。 相似文献
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天线外定标是实现星载SAR天线方向图在轨测试的主要手段。天线方向图的准确测量,对星载SAR图像的应用具有重要作用。分布目标辐射定标在星载SAR天线方向图测试中受到广泛重视。亚马逊热带雨林的后向散射系数呈现大面积的均匀性和稳定性,故成为分布目标定标最主要的定标场。该文在分布目标定标原理的基础上,对基于亚马逊热带雨林的星载SAR天线方向图测量算法进行了研究,提出了采用K.Pearson统计量非参数假设检验的一致性处理算法,并采用Levenberg-Marquard算法(LM算法)估计俯仰向天线方向图模型参数。仿真数据验证了算法的可靠性和准确性。 相似文献
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卫星遥感器绝对辐射定标系数的有效性检验,是对卫星遥感精度进行全面评价的最有效手段之一。利用绝对辐射定标系数反演反射率值与实测值对比的方法,对CBERS-2CCD相机绝对辐射定标结果进行了有效性检验与误差分析,根据分析结果对CCD相机4个波段的绝对辐射定标系数作出了客观的评价。验证表明,两点法获得的CCD相机定标系数可靠,定标效果较好,而单点法获得的定标系数对CCD相机不适用。 相似文献
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SAR图像质量评估是评判SAR系统性能的关键指标,常用SAR图像质量评估参数包括目标分辨率、峰值旁瓣比和积分旁瓣比等。首先介绍了SAR图像质量评估参数的定义;其次分析了SAR图像质量评估参数测试误差,给出了单个角反射体时积分区间对积分旁瓣比的影响,以及多个角反射体时图像质量评估参数测试误差,并进一步给出了定标场地设计要求;最后介绍了SAR图像质量评估软件系统。SAR图像质量评估技术研究已在SAR系统试验中得到应用,开发的评估软件系统在sAR图像质量评估中具有一定的推广价值。 相似文献
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A model that estimates a relative error bound for the radiometric calibration of synthetic aperture radar (SAR) imagery is presented. This model is based on a statistical `Coefficient of Variation of Error Model', which produces a relative error bound by propagating the measured or estimated uncertainties in the radar system parameters utilized to correct digitally processed SAR image intensity values. Using this model, algorithms are generated for absolute and relative radiometric calibration of SAR imagery. These algorithms are parametrically exercised using radar system parameters from an existing airborne SAR system to determine their impact on the relative error bound 相似文献
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Ulander L.M.H. Hawkins R.K. Livingstone C.E. Lukowski T.I. 《Geoscience and Remote Sensing, IEEE Transactions on》1991,29(6):922-933
Determining the radar scattering coefficients from SAR (synthetic aperture radar) image data requires absolute radiometric calibration of the SAR system. The authors describe an internal calibration methodology for the airborne Canada Centre for Remote Sensing (CCRS) SAR system, based on radar theory, a detailed model of the radar system, and measurements of system parameters. The methodology is verified by analyzing external calibration data acquired over a six-month period in 1988 by the C -band radar using HH polarization. The results indicate that the overall error is ±0.8 dB (1σ) for incidence angles ±20° from antenna boresight. The dominant error contributions are due to the antenna radome and uncertainties in the elevation angle relative to the antenna boresight 相似文献
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地面平面场是用于进行全尺寸或缩比目标模型静态散射特性测量的室外场地。该文从地面平面场的特点入手,分析了在进行目标雷达散射截面(RCS)测量时,目标和定标体因受到测量环境影响而产生的定标误差。在简要阐述地面平面场中的异地定标技术的基础上,综合考虑地面反射和天线方向性两方面的因素,研究了定标体回波强度与放置位置的关系,分析了地面平面场与自由空间的定标之间的差异以及由此所带来的测量误差。最后,通过计算机仿真得到了异地定标误差随定标体测量距离、测量频率以及天线波束宽度的变化规律。通常情况下,定标体放置在靠近目标的位置有利于减小异地定标误差。 相似文献
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Sarabandi K. Pierce L.E. Oh Y. Dobson M.C. Ulaby F.T. Freeman A. Dubois P. 《Geoscience and Remote Sensing, IEEE Transactions on》1994,32(5):975-985
When point calibration targets are used to calibrate a SAR image, the calibration accuracy is governed by two major factors. The first factor stems from the stringent requirement on the radar cross section (RCS) of the point calibration target. To reduce the effect of radar return from the background, the RCS of a point calibration target must be much larger than that of the background. Calibration targets with large RCS require large physical dimensions for passive targets or high amplifier gain for active targets, which in practice leads to uncertainty in the nominal RCS of the targets. The second factor is related to the fact that point calibration targets are used to develop a calibration algorithm which is applied to distributed targets. To this end, accurate knowledge of the impulse response (ambiguity function) of the SAR system is required. To evaluate the accuracy of such a calibration process, a cross-calibration experiment was conducted at a test site near Pellston, MI, using the JPL aircraft SAR and the University of Michigan truck-mounted polarimetric scatterometer. Five different types of distributed surfaces, all in the same area, were chosen: three of these were bare surfaces with varying roughnesses, and the other two were covered with vegetation. Trihedral corner reflectors were used for calibrating the aircraft SAR, and the UM scatterometer was calibrated using a metallic sphere. The scatterometer data were collected at L and C bands immediately after the aircraft flew over the test site. This paper presents results of the cross calibration between the polarimetric SAR and ground-based polarimetric scatterometer measurements at L and C bands. Comparison of the data measured by the two radar systems shows that SAR calibration with trihedrals may lead to unreliable results. A distributed-target calibration technique is introduced and applied to the data with good results 相似文献
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SAR calibration: an overview 总被引:30,自引:0,他引:30
Progress in synthetic-aperture radar, (SAR) calibration is reviewed. The difficulties of calibrating both airborne and spaceborne SAR image data are addressed. The quantities measured by a SAR, i.e. radar backscatter, are defined and mathematical formulations for the three basic types of SAR image are developed. The difficulties in establishing science requirements for calibration are discussed. The measurement of SAR image quality is briefly addressed. The problem of radiometric calibration is introduced via the SAR form of the radar equation, with both internal and external calibration approaches considered. The development of algorithms for polarimetric radar calibration is reviewed and the problems involved in phase calibration of interferometric SAR are discussed. Future challenges in the field of SAR calibration are considered 相似文献
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目标的雷达散射截面积是判断雷达系统中能否检测到目标的重要参数指标之一,为研究以GNSS为辐射源的被动雷达系统下飞行目标的RCS散射特性,仿真了不同机型在被动雷达系统中的静态RCS数据,分析了同一视线角下不同机型的RCS共性及辐射源-目标-接收机位置关系对目标RCS的影响。另外根据设定航路的目标飞行姿态计算得出的雷达视线角,结合飞机静态双基地RCS起伏特性数据,计算了空域中不同位置辐射源对应该航路目标的RCS时间序列,为被动雷达系统的辐射源选择提供了一定参考。 相似文献