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1.
根据SAR信号对干燥地表的穿透性能,在对罗布泊湖盆区域复杂散射机制深入分析的基础上,结合野外考察和实验室测量的数据,利用双层散射结构模型对湖盆区域的微波散射特性进行描述,并对次地表稳定沉积物的体散射分量进行模拟.为了对模型进行验证,本文利用Cloude极化分解方法将ALOS PALSAR数据进行散射机制的分解,并以体散射贡献量作为标准数据,与模型模拟的结果进行对比,得到的水平和垂直极化方式的均方根误差分别为1.62%和1.68%,证明了模型的可用性和有效性.同时,对模型的相关参数进行扩展分析,结果表明,次地表稳定沉积物是罗布泊古湖盆演化结果的直接反映,沉积物的含盐量是罗布泊"大耳朵"特征形成的根本原因. 相似文献
2.
山脊线通常是地震引发的山地灾害的起始部位。在监测此类山地灾害时,需要明确山脊线所处位置,从而为制定出相关预防措施提供支持。根据实际经验,由于合成孔径雷达(Synthetic Aperture Radar,SAR)的成像特殊性,在检测含建筑物的全极化SAR(Polarimetric Synthetic Aperture Radar,PolSAR)影像山脊线时,往往受到高散射强度的建筑物干扰,从而出现误判。针对PolSAR影像中山脊线受到建筑物干扰出现误识的问题,提出一种结合区域生长法和变差函数的识别方法。在识别过程中,首先,对采集的PolSAR影像通过区域生长法进行分割处理,再通过模糊C均值(Fuzzy C-Means,FCM)分类方法对变差纹理等特征进行聚类分析,并进行相似度判断,获取建筑物区域,在此基础上,对比建筑物、山脊线的混分成分,进而提取山脊线。通过对该方法进行实验对比分析,发现其相较于阈值分割方法提取精度有明显提高,可以为PolSAR影像中山脊线识别提供一种新思路。 相似文献
3.
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
4.
本研究将边界层相似理论与对流理论应用到具有海洋大气边界层(Marine Atmospheric Boundary Layer, MABL)对流特征的星载合成孔径雷达(Synthetic Aperture Radar, SAR)遥感图像,探讨了星载SAR遥感图像描述海气应力作用下水平扰动尺度变化的潜在可能性.针对具有三维对流涡旋Cell和二维水平滚轴涡旋Roll特征的星载SAR遥感图像,反演了中国海海域MABL高度,并与同步实验获取的MABL高度结果进行对比.结果表明,利用具有对流特征的星载SAR遥感图像反演MABL高度是可行的,展示了以高分辨率、大面积观测为特点的星载SAR遥感图像探测MABL的广阔前景. 相似文献
5.
地学研究在掌握地表运动规律,寻求与突发或长期影响事件之间相关性,进而预防地质灾害工作中具有重要的作用.相对于GPS和水准等传统的大地测量技术,In SAR(Interferometric Synthetic Aperture Radar)技术可大范围高精度获取地表形变信息,具有较大优势;同时,地表形变时间序列的获取提供了更全面地表运动信息,进一步拓宽了地学的探究范围.然而,In SAR技术以微波信号传播记录卫星至地面之间距离变化,其会受传播路径、传感器位置等信息不精确的影响.因此,在多种误差干扰情况下,如何由In SAR观测量较为精确获取形变的时间序列也成为关注的问题.国内外学者已有多种研究成果,适当的分类汇总可以全面掌握时序求解方法发展过程、适用范围等,但是,目前缺少对其系统的总结.基于此,本文从观测对象、函数模型、随机模型、解算准则、质量评估五个方面,总结了利用In SAR技术获取地表形变时间序列的方法,为不同研究区域获取时间序列提供参考. 相似文献
6.
运用SAR图像和TM热红外图像定量反演地表空气动力学粗糙度的二维分布 总被引：2，自引：1，他引：2
在分析“陆地表面与大气相互作用”研究领域对地表空气动力学粗糙度二维分布的科学需求后, 确定以SAR (Synthetic Aperture Radar)图像的后向散射系数与地表的几何特征参数、介电常数等参数具有定量关系的SPM(Small Perturbation Model)模型为基础, 提出了运用TM热红外图像和地面同步观测的微气象数据相结合的热惯量-土壤湿度反演模型, 获取了试验区内土壤表层的湿度信息, 通过与介电常数的链结, 从SAR图像的后向散射的复合信息中解析出像元尺度的非体散射地表的几何特征信息; 经过形态因子的转换, 在SAR图像和TM图像空间尺度转换的基础上得出非植被区的等效几何粗糙度信息. 再应用作物高度的光谱模型, 计算出试验区的作物高度后, 转换为等效几何粗糙度. 采用分层镶嵌等图像处理方法, 生成了试验区像元尺度的地表等效几何粗糙度的二维分布图. 根据大气湍流理论和大气稳定度订正方法, 对测量的大气温度剖面数据和风速剖面数据进行迭代运算, 获取了试验区内裸土及小麦植被等类型地表风浪区的空气动力学粗糙度实测值. 在分析风浪区等效几何粗糙度、动力因子、热力因子对空气动力学粗糙度的共同作用后, 建立了由地表等效几何粗糙度向空气动力学粗糙度转换的尺度转换模型. 运用实测值验证了这一系列模型最终反演结果, 表明整个研究思路是可行的, 并可望应用于与空气动力学粗糙度有关的地-气相互作用的区域化研究领域. 相似文献
7.
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
8.
从磁场的积分方程出发,应用迭代方法推导了二次迭代条件下粗糙海面的近似电磁散射极化核函数,并对其进行了分析.这种函数的表示是在光学近似即KA近似的基础上的一种扩展形式,因而可称为扩展KA近似(EKA).Elfouhaily采用了与Holliday类似的方法分析了双站配置条件下散射的极化核函数,试图保留所有的高次项,但是由于处理的复杂性他只给出了斜率项在散射项中的表示形式,并称之为KA近似的"补充项".本文在此基础上进一步考虑了Elfouhaily近似的形式,给出了表示双站散射极化核函数的完整表达形式,并以此为基础推算了后向散射条件下极化核函数的理论结果,并与Elfouhaily的结果进行了对比,说明了极化核函数完整表达形式的合理性.近似散射极化核函数的分析对于深入理解粗糙表面(特别是海面)电磁散射特性以及散射近似模型的建立等问题的研究具有重要意义. 相似文献
9.
近年来,合成孔径雷达干涉测量(Interferometric Synthetic Aperture Radar,InSAR)技术在地面沉降监测方面展现了巨大的应用潜力,但受其重访周期和一维形变测量能力的限制,仅利用单一轨道卫星观测数据很难揭示真实的地表形变特征及其演化规律.随着在轨运行的SAR卫星系统不断增加,使得融合相同时间段内覆盖同一区域的多源多轨道InSAR数据成为可能.然而目前普遍采用的多源InSAR数据融合方法均为针对大尺度形变监测设计,或者忽略南北向形变甚至水平形变,容易造成误判.为此,本文对经典小基线集(Small Baseline Subset, SBAS)时序InSAR分析方法进行改进,在其形变反演模型中加入东西向和南北向形变参数,采用方差分量估计方法解算多源观测数据验后方差,通过迭代精化确定权重矩阵,从而获得形变参数的最优估值.使用美国南加州地区的ALOS PALSAR和ENVISAT ASAR数据开展实验,利用南加州综合GPS网(SCIGN)位于研究区域内的9个站点观测数据进行验证,结果表明本文方法得到的融合形变测量结果在垂直向上能够准确反映地表形变波动,周期性与GPS观测比较一致;同时,融合得到的三维形变场显示南加州洛杉矶地区存在不可忽略的水平形变,东西向形变测量精度略高于南北向.因此,基于方差分量估计的多源InSAR融合方法在提高形变测量时间序列连续性的同时,能够更准确地反演研究区域三维形变特征. 相似文献
10.
面向全球变化探测的月基成像雷达概念研究 总被引：2，自引：0，他引：2
全球变化研究日益受到世界各国政府与科学界的高度关注．合成孔径成像雷达（Synthetic Aperture Radar,SAR）作为一种主动微波遥感成像手段,在对地观测中发挥着重要作用．为实现对地球的大尺度、连续性、长期性动态观测,更好满足全球变化科学问题研究的需要,并形成与星机载对地观测技术互补的能力,本文提出在月球上建立一个成像雷达系统,基于月球平台展开面向全球变化的观测的设想．月基成像雷达系统具有高分辨率、宽测绘带幅宽的特点,条带模式下测绘带幅宽可达数千公里,采用扫描模式一天可以覆盖地球表面的40％,其空间分辨率可达10m级甚至更高．通过简化的观测模型,本文定量分析了月基成像雷达的空间分辨率和覆盖范围,并通过模拟观测青藏高原和亚马逊平原的覆盖范围．结果表明,该系统大部分天数能完全覆盖青藏高原,而观测亚马逊平原的覆盖率在40％～70％之间．通过月基成像雷达可以提供大范围、长期而且稳定的时间序列数据,为全球变化研究提供有力的支持． 相似文献
11.
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
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.
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
14.
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
15.
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
16.
In humid upland catchments wetlands are often a prominent feature in the vicinity of streams and have potential implications for runoff generation and nutrient export. Wetland surfaces are often characterized by distinct micro-topography (hollows and hummocks). The effects of such micro-topography on surface–subsurface exchange and runoff generation for a 10 by 20 m synthetic section of a riparian wetland were investigated in a virtual modeling experiment. A reference model with a planar surface was run for comparison. The geostatistically simulated structure of the micro-topography replicates the topography of a peat-forming riparian wetland in a small mountainous catchment in South-East Germany (Lehstenbach). Flow was modeled with the fully-integrated surface–subsurface code HydroGeoSphere. Simulation results showed that the specific structure of the wetland surface resulted in distinct shifts between surface and subsurface flow dominance. Surface depressions filled and started to drain via connected channel networks in a threshold controlled process, when groundwater levels intersected the land surface. These networks expanded and shrunk in a spill and fill mechanism when the shallow water table fluctuated around the mean surface elevation under variable rainfall inputs. The micro-topography efficiently buffered rainfall inputs and produced a hydrograph that was characterized by subsurface flow during most of the year and only temporarily shifted to surface flow dominance (> 80% of total discharge) during intense rainstorms. In contrast the hydrograph in the planar reference model was much “flashier” and more controlled by surface runoff. A non-linear, hysteretic relationship between groundwater level and discharge observed at the study site was reproduced with the micro-topography model. Hysteresis was also observed in the relationship between surface water storage and discharge, but over a relatively narrow range of surface water storage values. Therefore it was concluded that surface water storage was a better predictor for the occurrence of surface runoff than groundwater levels. 相似文献
17.
新疆艾比湖湿地土壤水盐空间变异性分析 总被引：2，自引：0，他引：2
为揭示艾比湖湿地土壤退化程度空间分布特征,在离艾比湖湖滨5~15 km,绕湖一周160 km范围内,以湖心质点为中心,将艾比湖划分为东北、东南、西南、西北4个区域,采用传统统计学和地统计学相结合的方法对表层(0~20 cm)土壤盐分、含水量与p H的空间分异特征进行研究.结果表明:绕湖一周不同区域的土壤盐分均属中等变异强度;土壤含水量在西北部属强变异性,而东北、东南和西南部均属中等变异强度;土壤p H在不同区域内均属弱变异强度.绕湖一周除西北部土壤盐分的半方差理论模型较符合球状模型外,其它区域土壤盐分、含水量和p H均符合高斯模型;受结构性因素影响,不同区域土壤盐分、含水量和p H均具有较强的空间相关性;西南部土壤盐分、含水量和p H的Moran's I系数比其它区域的波动大,表明空间相关性较强.艾比湖湿地常年大风、干旱、缺水及沙化盐化的自然因素与引水围堰、种植耐盐碱植物的人为活动造成了采样区表层土壤盐分、含水量和p H的空间分布多呈现不规则条带状格局.艾比湖湿地土壤以盐土为主,重度盐化土次之,土壤盐渍化日益严重. 相似文献
18.
1997年11月8日西藏玛尼79级地震发生在羌塘盆地北缘.本文利用LANDSAT影像，研究地震的地质构造背景，研究表明玛尼79级地震发生在NEE向玛尔盖茶卡—若拉错断裂带上，这是一条全新世明显活动的地壳深断裂.利用CBERS_1影像，研究地震地表破裂带的几何特征，100000分之一CBERS_1影像上由地震裂缝、地震陡坎和断塞塘组合显示的线性影像清楚地反映出地震地表主破裂带的形迹，可有效地进行破裂带的分段和长度量测.结果表明玛尼79级地震形成的地震地表主破裂带西起羌塘盆地北缘，绥加山南麓的白雪湖湖积平原上，向东延伸到双端湖西岸，长110km，走向N70 80°E.可分为白雪湖—玛尔盖茶卡、玛尔盖茶卡—朝阳湖、朝阳湖—双端湖３段.多时相MSS、TM影像分析表明，1997年玛尼79级地震是先存地震地表破裂带再次破裂的结果. 相似文献
19.
This paper reports results from field experiments and hydrological modelling on the dynamics of runoff generation in highly convergent parts of the landscape in a logged and burnt eucalypt forest in south‐eastern Victoria, Australia. Large‐scale rainfall simulation experiments were conducted to explore runoff generating mechanisms from harvested areas, and to assess the effectiveness of standard water quality protective measures, here a disturbed filter strip, in preventing accession of sediment to near‐stream areas. We then examined the likely effects of varying antecedent moisture conditions on surface and subsurface runoff generating mechanisms. Very small volumes of surface runoff were generated only at very high rainfall intensity rates that exceeded a 100 year recurrence interval event during the simulated experiments. There was little or no identifiable impact of either compaction from logging operations or fire‐induced hydrophobicity on surface infiltration or generation of surface runoff. Measured soil hydraulic properties and soil depths explained the paucity of surface runoff, and the dominance of subsurface storm flow as the prime runoff generating mechanism. Deep lateral subsurface flow was observed from the cut‐face of a fire access track and into a streamhead downslope of the experimental plots. Water balance modelling using Topog_Dynamic indicated the conditions under which saturated overland flow in this environment could be generated are rare, but that care should be taken in siting of roads and tracks in lower parts of convergent landscapes. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献