Wavefield continuation datuming using a near surface model     

Cui Xingfu Li Hongbing Hu Ying Liang Hong Qi Li 《应用地球物理》2007,4(2):94-100

When topography and low velocity zone differences vary greatly, conventional vertical static time shifts will cause wavefield distortion and influence wave equation seismic imaging for seismic data acquired on a complex near surface. In this paper, we propose an approach to datum correction that combines a joint tomography inversion with wavefield continuation to solve the static problem for seismic data on rugged acquisition topography. First, the near surface model is obtained by refracted wave tomography inversion. Second, the wavefield of sources and receivers are continued downward and upward to accomplish datum correction starting from a flat surface and locating the datum above topography. Based on the reciprocal theorem, Huygens＇ and Fresnel principles, the location of sources and receivers, and regarding the recorded data on the surface as a secondary emission, the sources and receivers are upward-continued to the datum above topography respectively. Thus, the datum correction using joint tomography inversion and wavefield continuation with the condition of a complex near surface is accomplished.  相似文献   

高含沙泥浆模型试验及其糙率纠正     

归豪域  刘曙光  吴晓峰 《上海国土资源》2007,35(1):36-39,53

国内许多年久失修的地下设施在废弃时面临巨大的安全隐患,而利用高含沙泥浆进行填充是有效而经济的方法。在进行填充前,对管道填充的可行性需要建立模型进行试验研究。在模型试验研究时遇到的模型不相似问题是影响模型试验准确性的重要因素,因此要对试验所得数据进行修正。在本次研究中我们通过对于试验所得流速数据进行糙率纠正解决了糙率不相似的问题。  相似文献   

基于PROSPECT＋SAIL模型的遥感叶面积指数反演   总被引：4，自引：1，他引：4  

蔡博峰  绍霞 《国土资源遥感》2007,18(2):39-43

以PROSPECT+SAIL模型为基础，从物理机理角度反演植被叶面积指数(LAI)。首先，通过FLAASH模型进行大气校正，使得图像像元值表达植被冠层反射率； 然后，根据LOPEX 93数据库和JHU光谱数据库选择植物生化参数和光谱数据，以PROSPECT模型模拟出的植物叶片反射率和透射率作为SAIL模型的输入参数，得到植被冠层反射率，将结果与遥感影像的植被冠层反射率对应，回归出植被LAI； 最后，以地面实测数据对遥感反演数据进行验证，并分析了误差的可能来源。  相似文献   

基于纠错编码的小波域自适应盲水印算法     

耿迅  龚志辉  张春美  黄艳 《测绘学院学报》2007,(3)

提出了一种小波域自适应盲水印算法,并采用(7,4)汉明码技术进行纠错编码。以伪随机二值序列作为水印,采用中值系数抖动的方法将水印嵌入到小波变换后的低频分量,并且根据小波域系数间隔的大小自适应地确定水印量化步长,水印检测过程不需要原始图像的参与。实验结果表明,算法的自适应性强,具有较好的不可见性,且可以有效地抵抗JPEG压缩、锐化、加噪、模糊和缩放等攻击。  相似文献   

区域极轨卫星ATOVS辐射偏差订正方法研究   总被引：19，自引：0，他引：19  

刘志权  张凤英  吴雪宝  薛纪善 《气象学报》2007,65(1):113-123

近年来,卫星辐射资料在数值天气预报(NWP)系统中的直接同化研究取得了长足进展。为了利用TIROS业务垂直探测器(ATOVS)的辐射资料,必须对卫星观测辐射值的系统性偏差进行订正。在ECMWF原全球TOVS辐射偏差订正方案基础上,结合ATOVS资料特征和中国的实际情况,建立了适用于区域NOAA-15/16/17极轨气象卫星ATOVS辐射资料的偏差订正方案。该方案偏差订正分两步进行:首先进行扫描偏差订正,然后进行气团偏差订正。扫描偏差是临边测量相对于星下点测量的系统偏差,统计显示该种偏差具有一定的纬度依赖性,所以订正时按每10度的纬度带分别进行订正。气团偏差订正主要就是根据当时的天气条件进行订正,而天气条件一般用预报因子来定量表示。文中从中国国家气象中心T213背景场导出预报因子:(1)1000—300 hPa的厚度,(2)200—50 hPa的厚度,(3)模式地表温度,(4)总可降水量。模式预报因子的使用从观念上将对观测值的订正变为对计算前向辐射值的订正问题。试验结果表明,订正结果显著。  相似文献   

Tilt corrections over complex terrain and their implication for CO<Subscript>2</Subscript> transport     

Jielun Sun 《Boundary-Layer Meteorology》2007,124(2):143-159

Observational data from sonic anemometers are commonly rotated from sonic to streamline coordinates, a procedure that is called tilt correction. Tilt corrections are often used to post-process air velocity data collected from sonic anemometers to allow objective interpretation of air flow data relative to the Earth. Since streamline coordinates depend on dynamical characteristics of the flow, the tilt correction depends not only on temporal and spatial variations of the flow, but also on local circulations. We found that ensemble- averaged slope flows are approximately parallel to the terrain slope close to the ground within the canopy layer, but not above, due to the influence of the diurnal variation of local vertical circulations. As a result, the diurnal variation of the observed vertical velocity in streamline coordinates at 21.5 m above the ground over 11-m tall forest canopies can be opposite to that calculated from the continuity equation. To estimate CO₂ transport over sloping terrain, a workable reference coordinate system is needed such that multiple sonic anemometers have a common reference relative to the Earth. Streamline coordinate systems can be the choice of the common reference coordinate system only if flow, at least ensemble-averaged flow, is parallel to terrain slopes. The choice of the reference coordinate system and its implication in investigation of CO₂ transport are discussed. The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

电感耦合等离子体发射光谱法测试地质样品中的基体效应及校正办法     

杨柳  唐振  王海娇 《地质与资源》2020,29(3):289-293

电感耦合等离子体发射光谱（ICP-AES）法分析速度快、干扰较少并能同时测定多种元素，被广泛应用于地质调查样品的分析测试中，成为通用的无机化学元素分析测试工具.在测定复杂基体样品时，由于基体效应产生的各种干扰也会影响分析测试结果，包括光谱干扰、物理干扰、化学干扰、电离干扰等.以ICAP-6000型号仪器为例，结合仪器特点及实际工作经验，对复杂基体地质样品测定中出现干扰的原因、特点进行分析，探讨基体消除的方法以保障测试结果的准确性.  相似文献   

遥测地表温度与比辐射率的迭代反演方法──理论推导与数值模拟   总被引：16，自引：0，他引：16  

柳钦火  徐希孺  陈家宜 《遥感学报》1998,2(1):1-9

首先在地表比辐射率为已知的条件下,提出一个非线性迭代温度反演模型,我们对不同的地表和大气条件进行了模拟计算,结果表明当大气温度廓线误差－２Ｋ－２Ｋ,水汽廓线误差±２０％时的温度均方根误差为０．４８Ｋ。当大气模式误差一个模式时反演的温度均方根误差为０．８５Ｋ。在此基础上,引人相邻像元的概念,相邻像元的大气状况可以认为是相同的,应用两个时相的遥感影像数据,假定在两个相近时相之间地表比辐射率值不变,建立地表比辐射率与温度的反演模型。我们对不同的地表和大气条件进行了模拟计算,结果表明当大气温度廓线误差－２Ｋ－２Ｋ,水汽廓线误差±２０％时地表温度均方根误差小于１．５Ｋ,地表比辐射率均方根误差小于０．０２,地表辐射均方根误差为１％;当大气温度廓线误差－２Ｋ－２Ｋ,水汽廓线误差±１０％时,地表温度均方根误差小于１．０Ｋ,地表辐射均方根误差小于０．６％。  相似文献   

中国地震速报台网走时残差分析与走时修正   总被引：4，自引：0，他引：4  

薛峰  赵永 《地震地磁观测与研究》1998,19(4):48-54

使用了３０个速报台站的观测数据,计算了１００多个中国境内外的地震事件初至波走时残差。在此基础上分析各台所记录的所有地震事件的残差随方位角和震中距的分布,及产生这些残差的地球深部非流体静力平衡状态和地球表面构造等方面的原因,并给出了不同区域地震走时的平均校正值,从而提高了地震定位精度。  相似文献   

Depth Distribution of Moho Discontinuity Beneath Beijing and Its Adjacent Area     

Ma Lin  Zheng Sihua  and Xue FengCenter for Analysis  Prediction  CSB  Beijing  China 《中国地震研究》1998,(3)

Based on the method of "two-dimensional depth structure of the crust" proposed by Horiuchi et al., about 5000 arrival times of 303 local shallow earthquakes recorded by the Beijing Seismographic Network from 1990 ~ 1993 are used to investigate the depth distribution of Moho discontinuity beneath Beijing and its adjacent area. We simultaneously determined the hypocenter parameters and P- and S-wave station corrections. The data of the North China Network were also investigated. The results are as follows: (1) The depth distribution of Moho discontinuity becomes shallower from the northwest to the southeast, i.e., in Zhangjiakou area, the Moho discontinuity is located at a depth range from 40~42 km. In the Beijing area, it is 36~39 km. However, at the eastern and southeastern part of this area, it is only 28-30 km and 30~32 km, respectively. (2) Beneath the Tangshan area, there is another elliptic interface shallower than the Moho discontinuity. Separately, its major and minor axis is approximately along  相似文献