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潮流是水下地形SAR成像的决定性因素之一,潮流的周期性变化使水下地形SAR成像与潮流场有密切的关系,同一水下地形不同时刻SAR影像不同。以台湾浅滩为例,基于5景不同时相的ERS-2 SAR影像和台湾浅滩实测水深数据,开展了水下地形SAR成像与潮流场的相关性分析。为了排除SAR影像自身成像质量对研究的影响,首先对5景SAR影像的成像质量进行评价,然后通过潮汐潮流数值计算确定SAR成像时刻的潮流场以及基于QuikScat散射计数据确定SAR成像时刻的海面风向。在上述基础上开展了SAR影像后向散射系数与实测水深的相关性分析,总结出水下地形SAR成像与潮流场的关系,结果表明,潮流场与水下地形SAR成像密切相关,当潮流流向与水下地形梯度方向一致或接近时,水下地形SAR成像效果最佳;对于同一水下地形,流向相反的两种潮流对应的SAR影像后向散射系数恰好相反,即SAR影像中的明暗条纹不同。相对于潮流流向的顺流与逆流风向的不同对水下地形SAR成像无影响。 相似文献
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星载SAR浅海水下地形和水深测量模拟仿真──水下地形高度、坡度和方向与可测水深分析 总被引：7，自引：0，他引：7
根据星载合成孔径雷达(SAR)浅海水下地形和水深成像机理,建立了浅海水下地形和水深雷达后向散射截面仿真模型.利用该模型模拟并分析了不同地形条件下,浅海水下地形的雷达后向散射截面.分析结果表明,水下地形高度越高,SAR可测量的水深越深;水下地形坡度越大,越易被SAR所观测.水下地形的星载SAR测量还与水下地形的方向有关,与卫星飞行方向平行的水下地形最易被SAR观测,与卫星飞行方向垂直的水下地形最不易被SAR观测. 相似文献
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浅海水下地形的SAR遥感仿真研究 总被引：2，自引：0，他引：2
结合连续性方程和布拉格后向散射模型,在准一维简化浅海水下地形情况下,建立了浅海水下地形SAR海面相对后向散射强度仿真模型,将浅海水下地形区域的SAR海面后向散射强度的相对变化与大尺度背景流场、海面风场和雷达系统参数等联系起来.海上实验和研究结果表明,浅海水下地形的SAR成像主要由通过受水下地形影响的海表层流场对海表面风引起的微尺度波的水动力调制而获取浅海水下地形信息,其中潮流与水下地形的相互作用过程改变海表层流场,变化的海表层流与海表面微尺度波之间的相互作用改变海表面波的空间分布,雷达波与海表面波之间的相互作用决定雷达海面后向散射强度.因此SAR图像中浅海水下地形或水深信息量的多少不仅与海表层流场和海面风速有关,而且与雷达工作波段、雷达波束入射角和极化方式也密切相关.认为由水下地形变化引起的缓慢变化的表层流场中海表面定常微尺度波谱能量密度的变化满足波作用量谱平衡方程;而在波数空间中,海表面微尺度波谱的成长过程也可以用波数谱平衡方程描述,在此基础上,得出了海表面波高频谱(毛细-重力波)形式的解析表达式.众所周知,浅海水下地形信息是由于水下地形影响下SAR海面后向散射强度与背景海面后向散射强度的相对差异而在SAR图像上的呈现,从而在建立浅海水下地形SAR海面相对后向散射强度仿真模型的基础上,仿真计算了浅海水下地形SAR海面相对后向散射强度相对于海表层流场、海面风场等海况参数和SAR工作波段、SAR波束入射角、极化方式等雷达系统参数的数值仿真结果,分析得到了有关浅海水下地形SAR海面相对后向散射强度的特征和SAR浅海水下地形遥感的最佳海况参数与最佳雷达系统参数,为研究和开展SAR浅海水下地形遥感研究提供了有价值的参考. 相似文献
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塘沽海区海底地形的SAR影像仿真与反演研究 总被引：1，自引：0，他引：1
利用袁业立、金梅兵(1997)提出的海底地形SAR影像仿真与反演模型，对渤海塘沽海区的一张Radarsat SAR影像进行了仿真和水深反演研究。研究结果表明：仿真影像与真实SAR影像基本吻合，反演水深与实际水深也有较好的一致性；进一步证实了袁业立(1997)SAR成像机理的正确性和在中国近海利用SAR影像进行浅海水深探测的可行性。 相似文献
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波流共同作用下废黄河河口水下三角洲地形演变预测模式 总被引：9，自引：0，他引：9
通过对废黄河河口水下三角洲海域水文、泥沙、沉积和地形的调查分析，对组成水下三角洲-10--15m以深的平坦海床、-5--10m间的水下斜坡、-5m以浅的近岸浅滩三个地貌单元的水动力特征以及在波流和潮流作用下底部泥沙冲刷率的横向分布进行计算分析，并建立了水下三角洲地形横向剖面地形的演变预测模式。结果表明，在三角洲不同地貌单元内。由于所处不同的水动力条件和底部泥沙特性，出现了不同的侵蚀状态，其中在-10--15m以深的平坦海床，除了3m以上的大浪外，水动力作用以强劲的潮流冲刷为主，目前已接近冲刷相对平衡的状态，在-5--10m间的水下斜坡，受波浪和潮流的共同作用，冲刷强度大，地形剖面呈继续平行后退状态；-5m以浅的近岸浅滩，潮流作用相对较弱，以波浪为滩面的剧低为主，水深线不断向岸方向移动、滩宽变窄；0m以上的潮间带滩地，则波浪和潮流作用均较弱，近岸高滩接近相对稳定状态，有利于海岸线的工程防护。 相似文献
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利用卫星合成孔径雷达(SAR)图像信息探测海底地形是海洋遥感物理学和海洋动力学研究具有挑战性的问题,这是因为根据电磁波传播原理,雷达脉冲没有能力穿透海水,因而不可能直接探测到海底地形特征,可是,许多卫星SAR图像上确实显示出海底地形特征。这些海底地形不仅分布在水深小于100m的浅海,而且在600~800m甚至2 000~3 000m的深海区也有发现。本文概略介绍该领域的发展前沿和研究进展,主要内容包括海面过程雷达成像基本理论,我国辽东浅滩、台湾滩以及美国东部湾流海域等3个海区海底地形特征SAR成像理论:分别为速度切变流纵向流经平行海底地形、层化流体横向流流经平行(周期性)海底地形和强海流流经孤立海底地形。据此建立的理论和分析方法可做为研究更复杂情况和探索新应用领域的基础和出发点。 相似文献
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利用均匀分布于滦河水下三角洲的85个表层沉积物粒度数据,基于地统计学的粒径输运趋势方法对滦河水下三角洲沉积物的输运趋势及影响因素进行了研究。半方差函数分析表明,以0.015°(地球大圆弧度)为插值半径加密后(规则分布)的平均粒径半方差值具有随变程增加而增加的趋势,并在变程值达到0.09°后趋于稳定,而原始数据的半方差值与变程相关性较差。以此(0.09°)为特征距离计算的粒径输运结果显示,滦河水下三角洲南部水深12 m以浅区域粒径输运趋势以向南为主,北部具有向西和向北的趋势;水深12～15 m范围内粒径输运趋势近似西南方向,且趋势较大;南部水深15 m以深地区粒径输运趋势方向为西北向,北部为东南向。粒径输运趋势整体上与实测潮流、余流和泥沙输运方向一致,显示潮流对研究区沉积物的输运具有控制作用。滦河水下三角洲地区沉积环境和输运趋势受河流、波浪、潮流、残留沉积和地形等多种因素影响,粒径输运趋势仅能够较好地解释潮流影响,对于残留沉积等复杂沉积过程的解释则相对有限。 相似文献
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A detection model of underwater topography with a series of SAR images acquired at different time 总被引：1，自引：1，他引：0
underwater topography is one of oceanic features detected by Synthetic Aperture Radar. Underwater topography SAR imaging mechanism shows that tidal current is the important factor for underwater topography SAR imaging. Thus under the same wind field condition, SAR images for the same area acquired at different time include different information of the underwater topography. To utilize synchronously SAR images acquired at different time for the underwater topography SAR detection and improve the precision of detection, based on the detection model of underwater topography with single SAR image and the periodicity of tidal current, a detection model of underwater topography with a series of SAR images acquired at different time is developed by combing with tide and tidal current numerical simulation. To testify the feasibility of the presented model, Taiwan Shoal located at the south outlet of Taiwan Strait is selected as study area and three SAR images are used in the underwater topography detection. The detection results are compared with the field observation data of water depth carried out by R/V Dongfanghong 2, and the errors of the detection are compared with those of the single SAR image. All comparisons show that the detection model presented in the paper improves the precision of underwater topography SAR detection, and the presented model is feasible. 相似文献
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Underwater topography detection of Shuangzi Reefs with SAR images acquired in different time 总被引：3，自引：1，他引：3
1 IntroductionSynthetic aperture radar (SAR) is one of theadvanced microwave remote sensors of environmentand resource. It can observe targets in all weathersand all day and night in a multi-band, multi-polari-zation and multi-look angle mode. SAR has bee… 相似文献
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用合成孔径雷达图像反演浅海水下地形的一种方法 总被引：2，自引：0，他引：2
海流与海底地形的相互作用导致了海表面的粗糙起伏,从而引起对海面观测的雷达散射截面的变化。在浅海海流速度垂直分布廓线为均匀的假定下,由流体连续性方程和驰豫时间近似下流体力学弱相互作用的理论,已证明雷达散射截面的空间变化正比于海流方向上海流速度变化的梯度。研究了合成孔径雷达(SAR)对海面的观测图像在无槽道信息和海流方向预知条件下,提出用散射系数的二维相关函数确定海流方向。在海流速度和方向已知条件下,推导了由雷达散射截面的空间变化迭推反演浅海水下地形的公式,并研究了航天飞机SIR-CSAR在我香港特区海域的二维图像反演浅海水下地形的应用。 相似文献
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I~IOXThe image technology of the synthetic aperture radar (SAR) is one of most important advances in spaceberne microwave remote sensing (Larson et al., 1976). It has extensive application in the ocean remote sensing, such as inversion of the sea subdue winds and currentS, reconstruction of underwater hatom topography and so on. Owing tO the high conductivity of sea water, an electromagnetic wave actually cannot penetrate into the sea water, with extremely smallPenetration depth (abbot 1 c… 相似文献
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利用实测资料分析重构了大亚湾和大鹏湾潮汐水位“双峰”现象,确定了浅水分潮的异常增长是潮位“双峰”现象的主要成因,其中四分之一日分潮和六分之一日分潮起着至关重要的作用。通过SCHISM模型构建大亚湾和大鹏湾附近海域高分辨率水动力模型,模拟结果表明近岸海域,在大亚湾以东,潮汐类型为不规则全日潮,以西为不规则半日潮,在两个海湾内均为不规则半日潮;研究海域的潮流均表现为不规则半日潮流。四分之一日分潮和六分之一日分潮在大亚湾和大鹏湾的不同变形过程是造成两个相邻海湾水文差异的直接原因。通过构建不同底摩擦强度、消除水底地形以及改变海湾水深的数值实验研究表明,分潮传播方向与水深变浅方向是否一致,是导致两个海湾潮波浅水变形不同的根本原因。 相似文献
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全极化合成孔径雷达近岸风场反演研究 总被引：2，自引：2，他引：0
Coastal winds are strongly influenced by topology and discontinuity between land and sea surfaces. Wind assessment from remote sensing in such a complex area remains a challenge. Space-borne scatterometer does not provide any information about the coastal wind field, as the coarse spatial resolution hampers the radar backscattering. Synthetic aperture radar （SAR） with a high spatial resolution and all-weather observation abilities has become one of the most important tools for ocean wind retrieval, especially in the coastal area. Conventional methods of wind field retrieval from SAR, however, require wind direction as initial information, such as the wind direction from numerical weather prediction models （NWP）, which may not match the time of SAR image acquiring. Fortunately, the polarimetric observations of SAR enable independent wind retrieval from SAR images alone. In order to accurately measure coastal wind fields, this paper proposes a new method of using co-polarization backscattering coefficients from polarimetric SAR observations up to polarimetric correlation backscattering coefficients, which are acquired from the conjugate product of co-polarization backscatter and cross-polarization backscatter. Co-polarization backscattering coefficients and polarimetric correlation backscattering coefficients are obtained form Radarsat-2 single-look complex （SLC） data.The maximum likelihood estimation is used to gain the initial results followed by the coarse spatial filtering and fine spatial filtering. Wind direction accuracy of the final inversion results is 10.67 with a wind speed accuracy of 0.32 m/s. Unlike previous methods, the methods described in this article utilize the SAR data itself to obtain the wind vectors and do not need external wind directional information. High spatial resolution and high accuracy are the most important features of the method described herein since the use of full polarimetric observations contains more information about the space measured.This article is a useful addition to the work of independent SAR wind retrieval. The experimental results herein show that it is feasible to employ the co-polarimetric backscattering coefficients and the polarimetric correlation backscattering coefficients for coastal wind field retrieval. 相似文献
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Shallow water depth retrieval from space-borne SAR imagery 总被引：1，自引：1，他引：0
Kaiguo Fan Weigen Huang Hui Lin Jiayi Pan Bin Fu Yanzhen Gu 《Journal of Oceanography》2011,67(4):405-413
Based on shallow water bathymetry synthetic aperture radar (SAR) imaging mechanism and the microwave scattering imaging model
for oceanic surface features, we developed a new method for shallow water depth retrieval from space-borne SAR images. The
first guess of surface currents and winds are estimated from the normalized radar crossing section (NRCS) profile of shallow
water bathymetry SAR imagery, according to the linear theory and geophysical model function. The NRCS profile is then simulated
by the microwave scattering imaging model. Both the surface currents and winds are adjusted by using the dichotomy method
step by step to make the M4S-simulated NRCS profiles approach those observed by SAR. Then, the surface currents and the wind
speeds are retrieved when a best fit between simulated signals and the SAR image appears. Finally, water depths are derived
using the Navier–Stokes equation and finite difference method with the best estimated currents and the surface winds. The
method is tested on two SAR images of the Taiwan Shoal. Results show that the simulated shallow water NRCS profile is in good
agreement with those measured by SAR with the correlation coefficient as high as 85%. In addition, when water depths retrieved
from the SAR image are compared with in situ measurements, both the root mean square and relative error are less than 3.0 m
and 6.5%, respectively, indicating that SAR images are useful for shallow water depth retrieval and suggesting that the proposed
method in this paper is convergent and applicable. 相似文献