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通过对罗布泊古湖盆区域("大耳朵")湖相沉积物含水量与含盐量、介电性质、地表微地貌等理化参量的分析,本文提出了罗布泊古湖盆区域的散射过程与次地表散射结构;利用全极化测量技术(PolSAR, Polarimetric Synthetic Aperture Radar),本文对不同纹理区域进行了物理散射机制的定量化剖析,同极化相关分析与极化度推算结果表明整个"大耳朵"区域后向散射强烈,亮条带比暗条带的散射机制更为复杂,地表微地貌状态是造成"大耳朵"特征的表观原因.在此基础上,本文利用极化分解技术进一步分离不同散射机制分量,通过定量比较各部分贡献对于"大耳朵"特征的表征能力,提出次地表介质性质(如含盐量)是"大耳朵"特征的根本性成因,相关性可达0.784,同时分析了次地表高含水含盐湖相沉积物在SAR响应中的重要性及其与地表形态之间的动力学形成机制.最后,本文论证了合成孔径雷达(SAR, Synthetic Aperture Radar)在罗布泊地区的穿透能力,预示着SAR遥感技术在干旱区环境研究中的应用潜力. 相似文献
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辐射传输方程已广泛应用于森林雷达后向散射模拟.基于辐射传输方程建立起来的三维森林雷达后向散射模型可以考虑林分结构对后向散射的影响以及冠层、树干等与地表的二次散射.它可以较准确地估算同极化后向散射.但三维森林雷达后向散射模型只考虑了冠层内部的一次散射,而交叉极化主要来自于冠层体散射,因此模型常常低估交叉极化.为了提高模型对交叉极化的估算能力,将Matrix-Doubling方法引入到三维森林雷达后向散射模型中,用以计算冠层体散射.将改进模型的计算结果与原模型的计算结果进行了比较,并且使用野外观测数据和AIRSAR数据对改进模型做了验证.结果表明,对于不同密度的森林,模型对交叉极化的估算能力在一定程度上得到了改善. 相似文献
3.
沙漠具有较高的地表反照率和较广的面积分布, 是地球系统的重要组成部分之一, 了解沙漠地区地表散射的各向异性对于全球地表辐射和能量平衡研究非常重要. 多角度卫星遥感技术的发展为在区域尺度上反演沙漠地表散射各向异性提供了机会. 本文首先利用Hapke模型和模拟数据研究了多时相和单时相星载多角度传感器MISR数据反演非对称因子的精度, 在此基础上, 利用单时相MISR数据反演了我国西北沙漠地区典型地表的非对称因子, 并与实验室测试数据的反演结果进行了对比. 结果表明, 可以用单时相的MISR数据反演沙漠非对称因子. 对室内测试数据反演的非对称因子是正值, 为前向散射. 从遥感数据反演的非对称因子是负值, 为后向散射, 其大小与地表状况有关. 地表相对平坦的塔里木盆地东部楼兰地区具有较大的负非对称因子, 后向散射强; 而地表较为粗糙的库姆塔格沙漠沙丘的非对称因子为弱的负值, 不具有优先方位的散射. 就遥感数据来说, 地表越粗糙不一定后向散射越强, 今后在应用经验方法表征地表粗糙度时应慎重. 相似文献
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针对降雨雷达(PR)海面测风精度易受降雨影响的特点,本文从雨滴对雷达信号的二次路径衰减效应、体后向散射效应以及雨滴对海表的"溅射"效应这三个因素出发,推导了降雨条件下PR雷达方程,并利用Ku波段雨滴衰减模型、球形雨滴体后向散射模型结合2010年6~8月的PR观测数据以及TMI风速数据对PR降雨雷达方程进行逆向求解,定量分析了降雨对PR测风精度的影响,发现降雨对PR回波信号的影响主要表现为雨滴的二次路径衰减效应和雨滴对海表的"溅射"效应,雨滴的体后向散射效应相对最弱;而且,雨滴的二次路径衰减效应和雨滴的体后向散射效应均随降雨强度以及雷达波束在降雨层传输经过的路径增加而增强;雨滴对海表的"溅射"效应对回波能量具有衰减作用,且衰减作用随降雨强度以及入射角的增加而增强.最后,将雨滴体后向散射效应和雨滴对海表的"溅射"效应合并考虑,构建了降雨条件下PR雷达降雨辐射传输模型,并结合2012年6~10月三次台风观测数据对模型精度进行了验证,结果表明,校正前PR观测等与海面风场引起的σ0平均偏差为2.95 dB,均方差为3.10 dB;校正后二者之间的平均偏差为0.64 dB,均方差为1.61 dB,表明本文方法能有效补偿降雨对PR观测σ0衰减的部分. 相似文献
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本文针对Groom-Bailey分解法在消除地表电性不均匀体对MT数据的畸变效应时存在的问题引入遗传算法,对基于传统线性最优化方法的GB分解算法进行改进,提出基于遗传算法的大地电磁阻抗张量分解方法.通过对理论合成数据以及三维/二维模型正演数据的分解试验,并且对青藏高原北缘阿尔金断裂地区实际MT数据进行分解处理,证明了基于遗传算法的GB分解能够更加有效地校正三维/二维情况下近地表三维电性不均匀体所造成的畸变影响.最后,在已有算法基础上,研究了基于遗传算法的多频率GB分解算法和MT数据静校正算法,并通过实际MT数据的处理证明了这些算法的有效性. 相似文献
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针对InSAR技术在形变监测领域中的应用,本文从分析D-InSAR的干涉机理对其约束条件出发,重点研究空间去相关和形变梯度这两个关键指标对形变信息提取的影响.研究针对不同系统参数的传感器来展开,并论证这两个因素对干涉测量的限制.本文的创新性工作主要集中在以下几个方面: (1)分析了各传感器参数下的临界坡度范围,进而确立了SAR传感器监测的无信息区域;(2)证明了在植被覆盖区,相干性分解必须考虑体散射分量,并依此对模型进行了修正;(3)明确了形变梯度与相位梯度的差异以及两者的函数关系,并将入射角引入形变梯度函数模型.(4)通过模拟数据和真实数据比较各传感器在不同条件下形变监测的优缺点,在统计分析的基础上进一步验证结论.本文的研究是对干涉测量条件的进一步补充,对于理解干涉成像机理、完善InSAR数值计算模型(形变梯度模型和相干性分解模型)以及帮助研究人员根据研究区域特征选择合适的InSAR数据具有一定的参考价值. 相似文献
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《中国科学:地球科学》2016,(9)
综合运用自然、生态和人文等多元知识辅助计算机遥感自动分类,确保大区域地表覆盖遥感数据产品质量是多年来国际上致力于解决的科技难题.在全球30m地表覆盖遥感数据产品GlobeLand30的研制过程中,作者提出了一种顾及多元知识的检核优化模型,对基于"像元-对象"的遥感自动分类结果进行知识化检核,发现和修改错分/漏分问题.首先归纳总结全球地表覆盖分布相关的先验知识,凝练出有关地表覆盖的地域地形分布规律、时间连续性和空间关系等质量检核知识规则;继而发展了基于网络化服务平台的交互式协同检核技术,辅助发现与定位分类异常区域,并依据各类别最小图斑规定判定错分/漏分,进而标注和发布错误信息,供研制人员用于修改优化.以林灌草和裸地数据为例,抽取10%的图幅,进行优化前后的分类精度对比分析,得知质量明显改善,精度提高最多达到17.47%.运用该模型,对GlobeLand30数据进行了逐类检核与优化处理,有效地减少了错漏分问题,2010期产品的总体精度达到83.50%.这一模型还可用于其他全球或区域的地表覆盖数据产品研制. 相似文献
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复杂山区光学遥感反射率计算模型 总被引：1，自引：0，他引：1
提出一种复杂山区光学遥感反射率计算模型,以有效消除地形影响,计算地表反射率．通过推导地形影响下的方向反射,结合辐射传输方程,考虑地表反射目标接收的太阳直射辐射为方向．方向二向反射,反射目标接收的大气漫散射和周围地形背景反射辐射为半球．方向二向反射的综合过程,发展了基于方向反射的地形影响消除和地表反射率计算模型．利用GOMS模型模拟数据及真实光学遥感数据对模型应用能力进行了评价,结果表明此模型具有有效的地形消除能力以及大气校正能力,模型的建立为后续山区定量遥感的应用提供技术支持． 相似文献
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快速评估建筑物地震灾害信息对地震应急救援工作有着指导意义,而极化SAR具有全天候、全天时的特点,因此利用极化SAR图像提取震害信息已逐渐成为研究热点。虽然极化SAR具有丰富的极化信息,但其纹理信息不可忽略,尤其是完好的人工建筑物在图像上呈现规则的纹理特征,而倒塌建筑区域纹理分布杂乱,因此结合纹理信息也可以很好地提取建筑物信息。以2010年玉树地区的全极化SAR数据为研究对象,首先,利用Yamaguchi分解的体散射分量PV提取了SAR图像中的建筑物区域以及道路、水系等非建筑物信息,在此基础上,对相干散射矩阵T11分量中倒塌建筑物、完好建筑区域进行变差计算,根据变差曲线确定变程a后,再对建筑物区域采取窗口m*m(m=3*a)进行变差计算得到变差纹理信息,最后利用FCM算法对变差纹理信息分别提取完好建筑物和倒塌建筑物区域,为了对比分析,文章利用Yamaguchi分解的二次散射分量PD提取完好建筑物区域,与震后光学遥感图像对应样本点进行人工验证,得到完好建筑物的提取精度为80.18%,倒塌建筑物的提取精度为84.54%,道路水系的提取精度为77.58%。 相似文献
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罗布泊不是游移湖——从罗布泊的演化讨论罗布泊的游移问题 总被引：11，自引：0，他引：11
从构造、沉积学的观点出发,讨论了罗布泊的发展演化,明确提出罗布泊不是游移湖.罗布泊从中更新世以来,从淡水湖演化到盐湖直至1972年干涸,其沉积中心基本是固定的.在新构造运动、气候和水源补给等的共同影响下,尽管其水域大小有一定程度的变化,其沉积中心也有过一定距离的迁移,但从总体来说并没有变化,因此,它不是“游移”湖. 相似文献
12.
The Lop Nur Lake, a famous lake in the arid areas of China, is located in the communications center of the ancient Silk Road which facilitated the flow of culture between China and Western countries and enjoyed the great reputation in the ancient history of China. Since the recent 100 years, some Chinese and foreign scholars have explored and investigated here, they, however, could not get to the hinterland of the lake basin due to the hard and dangerous roads. Therefore, there are many divergences and controversies about the Lop Nur Lake region[1,2]. In order to clarify these issues, know the usable natural resources and sum up the historical experiences and lessons of dry-up of the Lop Nur Lake, a scientific investigation team was organized by Xinjiang Branch of the Chinese Academy of Sciences to carry out the investigation and research about the Lop Nur Lake region in the 1980s. Recently, some personnel from CCTV and other institutions went to the lower reaches of the Tarim River and the Lop Nur Lake region to undertake the research for coordinating the strategic decision of the Great Development of Western China and the synthetic harnessing of the Tarim River, and a series of achievements in scientific research have been achieved.
相似文献13.
The Lop Nur Lake, a famous lake in the arid areas of China, is located in the communi-cations center of the ancient Silk Road which facilitated the flow of culture between China andWestern countries and enjoyed the great reputation in the ancient history of China. Since the re-cent 100 years, some Chinese and foreign scholars have explored and investigated here, they,however, could not get to the hinterland of the lake basin due to the hard and dangerous roads.Therefore, there are many divergences and controversies about the Lop Nur Lake region[1'2]. Inorder to clarify these issues, know the usable natural resources and sum up the historical experi-ences and lessons of dry-up of the Lop Nur Lake, a scientific investigation team was organized byXinjiang Branch of the Chinese Academy of Sciences to carry out the investigation and researchabout the Lop Nur Lake region in the 1980s. Recently, some personnel from CCTV and other in-stitutions went to the lower reaches of the Tarim River and the Lop Nur Lake region to undertakethe research for coordinating the strategic decision of the Great Development of Western Chinaand the synthetic harnessing of the Tarim River, and a series of achievements in scientific researchhave been achieved. 相似文献
14.
Kangkang Li Xiaoguang Qin Xiaoyan Yang Bing Xu Lei Zhang Guijin Mu Dong Wei Chunxue Wang Yong Wu Xiaohong Tian Yongchong Lin Wen Li Jiaqi Liu Yinxin Jiao 《中国科学:地球科学(英文版)》2018,61(11):1659-1668
The Lop Nur region, in the east part of Tarim Basin, was an important transportation junction between west and east, north and south Eurasia. However, previous studies on prehistoric human activity have concentrated mostly on the Bronze Age, whereas that during the Stone Age remains largely unresearched. Here, we present a new direct evidence of human activity in the late Pleistocene, recorded on a grinding stone buried in a lacustrine sediment section of the Lop Nur region. The grain size distribution of the sediment section indicates that the site was probably in the center of a lake with weak hydrodynamic environment. Therefore, the stone artifact can only be carried to here by people instead of river and it was never move as soon as left here. Results of radiocarbon dating, the evident stratigraphic relations between the stone artifact and the sedimentary formation, indicate that the human activity could extend to approximately 13 ka BP. Furthermore, the results of starch-grain and use-wear analyses suggest that ancient humans gathered seeds of Triticeae, roots, and tubers and used the grinding stone to simply process selected plant as plant foodstuffs during this period. It implies that the environmental conditions in the river delta of the Lop Nur were inhabitable during the late Pleistocene. 相似文献
15.
ZHANG Renhua WANG Jinfeng ZHU Caiying SUN Xiaomin & ZHU Zhilin .Institute of Geographical Sciences Natural Resources Chinese Academy of Sciences Beijing China .Institute of Surveying Mapping Information Engineering University of the Chinese People''''s Liberation Army Zhengzhou China 《中国科学D辑(英文版)》2004,47(12):1134-1146
The research for the land surface fluxes has madea quiet great progress for its breakthroughs in the fieldof regional or global interactions between land surfaceand atmosphere. However, many remote sensing mod-els for estimating the land surface fluxes need the pa-rameters of surface momentum, heat, resistance ofwater vapor at a referenced height, which are the func-tion of aerodynamic surface roughness zad. It hasbeen validated that the retrieval of the land surfacefluxes is very sensitive to… 相似文献
16.
ZHOU Xuan YANG XiaoFeng LI ZiWei YU Yang BI HaiBo MA Sheng LI XiaoFeng 《中国科学:地球科学(英文版)》2013,56(11):1977-1987
The traditional method of Synthetic Aperture Radar(SAR)wind field retrieval is based on an empirical relation between the near surface winds and the normalized radar backscatter cross section to estimate wind speeds,where this relation is called the geophysical model function(GMF).However,the accuracy rapidly decreases due to the impact of rainfall on the measurement of SAR and the saturation of backscattered intensity under the condition of tropical cyclone.Because of no available instrument synchronously monitoring rain rate on the satellite platform of SAR,we have to derive the precipitation of the SAR observation time from non-simultaneous passive microwave observations of rain in combination with geostationary IR images,and then use the model of rain correction to remove the impact of rain on SAR wind field measurements.For the saturation of radar backscatter cross section in high wind speed conditions,we develop an approach to estimate tropical cyclone parameters and wind fields based on the improved Holland model and the SAR image features of tropical cyclone.To retrieve the low-to-moderate wind speed,the wind direction of tropical cyclone is estimated from the SAR image using wavelet analysis.And then the maximum wind speed and the central pressure of tropical cyclone are calculated by a least square minimization of the difference between the improved Holland model and the low-to-moderate wind speed retrieved from SAR.In addition,wind fields are estimated from the improved Holland model using the above-mentioned parameters of tropical cyclone as input.To evaluate the accuracy of our approach,the SAR images of typhoon Aere,typhoon Khanun,and hurricane Ophelia are used to estimate tropical cyclone parameters and wind fields,which are compared with the best track data and reanalyzed wind fields of the Joint Typhoon Warning Center(JTWC)and the Hurricane Research Division(HRD).The results indicate that the tropical cyclone center,maximum wind speed,and central pressure are generally consistent with the best track data,and wind fields agree well with reanalyzed data from HRD. 相似文献
17.
Lop Nur is a playa lake occupying the lowest part of the Tarim Basin, northwestern China, and is now a desolate and barren region. In the past decades, the ages of the lacustrine sediments from the lake were determined mainly by radiocarbon dating on bulk sediment. In this study, both optically stimulated luminescence (OSL) and radiocarbon methods were used to date the sediments from a pit in the central part of the lake. The OSL ages obtained for ten samples range from 0.5 to 9.4 ka, and are in stratigraphic order except for one sample. The 14C ages obtained for twenty-two bulk sediment samples range from 5.8 to 30.2 cal ka BP with erratic distribution. Based on the comparison of 14C with OSL ages and their age-depth models, we argue that the OSL ages are relatively reliable. The disequilibria in the U decay chain for some samples are deduced from the comparison of the NAA and TSAC results. We suggest that the OSL dating technique should preferably be applied to the playa sediments from Lop Nur, but the disequilibria in the U decay chain should be considered in evaluating dose rates. Additionally, radiocarbon reservoir effects in lakes in western China are reviewed. 相似文献
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Directional‐oriented wavefield imaging: a new wave‐based subsurface illumination imaging condition for reverse time migration 
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下载免费PDF全文 The key objective of an imaging algorithm is to produce accurate and high‐resolution images of the subsurface geology. However, significant wavefield distortions occur due to wave propagation through complex structures and irregular acquisition geometries causing uneven wavefield illumination at the target. Therefore, conventional imaging conditions are unable to correctly compensate for variable illumination effects. We propose a generalised wave‐based imaging condition, which incorporates a weighting function based on energy illumination at each subsurface reflection and azimuth angles. Our proposed imaging kernel, named as the directional‐oriented wavefield imaging, compensates for illumination effects produced by possible surface obstructions during acquisition, sparse geometries employed in the field, and complex velocity models. An integral part of the directional‐oriented wavefield imaging condition is a methodology for applying down‐going/up‐going wavefield decomposition to both source and receiver extrapolated wavefields. This type of wavefield decomposition eliminates low‐frequency artefacts and scattering noise caused by the two‐way wave equation and can facilitate the robust estimation for energy fluxes of wavefields required for the seismic illumination analysis. Then, based on the estimation of the respective wavefield propagation vectors and associated directions, we evaluate the illumination energy for each subsurface location as a function of image depth point and subsurface azimuth and reflection angles. Thus, the final directional‐oriented wavefield imaging kernel is a cross‐correlation of the decomposed source and receiver wavefields weighted by the illuminated energy estimated at each depth location. The application of the directional‐oriented wavefield imaging condition can be employed during the generation of both depth‐stacked images and azimuth–reflection angle‐domain common image gathers. Numerical examples using synthetic and real data demonstrate that the new imaging condition can properly image complex wave paths and produce high‐fidelity depth sections. 相似文献
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利用合成孔径雷达(Synthetic Aperture Radar,SAR)影像提取与地质活动相关的三维地表形变场,对深入理解地质灾害的形成机制及其潜在灾害风险评估非常重要.目前,利用SAR影像的同震三维形变场提取主要利用单个像素点的多次观测构建观测方程,然后基于加权最小二乘(Weighted Least Squares,WLS)方法分解从而获得同震三维形变场,因此该方法缺乏对相邻像素点空间相关性的约束.考虑相邻同震位移点的应力连续性,研究学者提出了顾及大地测量应变张量和卫星形变观测的SAR同震三维形变场方法(Extended Simultaneous and Integrated Strain Tensor Estimation from geodetic and satellite deformation Measurements,ESISTEM).本文以2016年MW7.0熊本地震为例,收集了覆盖此次地震的ALOS-2卫星升降轨影像,利用传统差分InSAR(DInSAR)方法和子孔径雷达干涉测量(Multiple Aperture InSAR,MAI)方法分别对升降轨SAR影像对进行处理,得到视线向(LOS)形变和方位向形变,最后利用ESISTEM方法获取此次地震的三维同震形变场.此外,利用GPS和野外考察观测对本文的三维形变场结果进行结果精度分析.研究结果表明,与传统WLS方法相比,ESISTEM方法不仅能有效抑制奇异像素点对形变结果的干扰,同时对近断层的失相干信号能进行较好的恢复,更有助于解释地表破裂区的地震形变特征和掌握地震发生机制.本文确定的三维同震形变场结果显示主形变区发生在Futagawa断层中部和Hinagu断层最北端,最大水平位移为2m,抬升为0.55m.断层破裂以NE-SW走向的右旋走滑为主兼有部分正断成分.应变张量分析表明发震断层处受到了明显的收缩力和剪切力的作用. 相似文献