北斗卫星导航系统的星座及XPL性能分析   总被引：3，自引：0，他引：3  

杨鑫春  李征航  吴云 《测绘学报》2011,(Z1):68-72

分析北斗卫星导航系统的组成结构,就系统在中国大陆区域内卫星的可见性、DOP值和定位精度进行仿真分析。借鉴SBAS完备性算法的原理分析在中国大陆区域内北斗卫星导航系统所能提供的XPL性能指标。表明在单频条件下,中国大陆区域内仿真的Compass系统能满足APV-Ⅰ飞行阶段的完备性要求。  相似文献   

目标轮廓直线特征的高精度提取   总被引：2，自引：0，他引：2  

李彩林  郭宝云  李畅 《测绘学报》2011,40(1):66-70

针对小型物体高精度量测的要求,提出一种结合精确单点定位方法和基于分裂的最小距离误差线段逼近法的高精度轮廓直线特征提取算法.通过利用直线特征精确逼近目标的轮廓,搜索相邻直线段并计算交点,从而实现轮廓分割点的精确定位,进而为基于轮廓的三维量测与重建提供高精度的直线特征数据.与其他方法(如最小二乘模板匹配、抛物线拟合等)相比...  相似文献   

基于时空尺度的线位统一不确定性模型   总被引：1，自引：1，他引：0  

蔡剑红  李德仁  朱道林 《测绘科学》2011,36(4):27-30

在GIS矢量数据中,线对象在建模过程中存在的建模误差是必然的,并且成为不确定性内容中的重要组成部分,而现有的线位不确定性模型则往往将其忽略,本文充分考虑建模误差,采用误差传播律,对附有建模误差的二维折线不确定性模型进行估计,其中,e带模型、g带模型是其中的一个特例,即当且仅当建模误差为零时,便是e带模型、g带模型.  相似文献   

利用GPS共视法确定重力位差及海拔高差的实验研究     

刘杨  申文斌  夏敏  易俊 《武汉大学学报(信息科学版)》2011,(6):640-643

阐述了GPS共视法的基本原理,讨论了利用重力频移法通过GPS共视观测数据确定重力位差和高程差的方法。利用国际权度局(BIPM)发布的时间序列数据,选取了4个守时台站之间的时间差序列进行实验。结果表明,受目前GPS共视法精度所限,高程差计算值与理论值之间的平均差异和标准差在几十m的量级水平。  相似文献   

Estimating quality factor from surface seismic data: A comparison of current approaches     

Bonnie Ives de Castro Nunes  Walter Eugênio de Medeiros  Aderson Farias do Nascimento  José Antonio de Morais Moreira 《Journal of Applied Geophysics》2011,75(2):161-170

The performances of the spectral ratio (SR), frequency centroid shift (FCS), and frequency peak shift (FPS) methods to estimate the effective quality factor Q are compared. These methods do not demand true amplitude data and their implementations were done following an “as simple as possible” approach to highlight their intrinsic potentials and limitations. We use synthetic zero-offset seismic data generated with a simple layer-cake isotropic model. The methods can be ranked from simple to complex in terms of automation as: FPS, FCS and SR. This is a consequence of: (i) peak identification consists basically of a sorting procedure, (ii) centroid estimation involves basically the evaluation of two well-behaved integrals, and (iii) implementation of the SR method involves at least choosing a usable frequency bandwidth and fitting a gradient. The methods can be ranked from robust to sensitive in the presence of noise content in the sequence SR, FCS, and FPS. This is consequence of: (i) the gradient estimate associated to the SR method averages out the noise content in the entire usable frequency bandwidth, (ii) in the presence of moderate-to-high noise level, the centroid estimation is biassed towards overestimating Q due to noise contribution in the tail of the amplitude spectrum, and (iii) peak identification is unstable due to local noise fluctuation in the amplitude spectrum around the peak frequency. Regarding the stability of the estimates relative to the attenuation amount, SR and FCS methods show similar behaviours, whereas FPS method presents an inferior performance. This fact is an indirect consequence of the sensitivity of FPS method to the noise content because the higher is the attenuation the lower is the signal-to-noise ratio. Finally, regarding the robustness of the methods to the presence of dipping layers, only SR and FCS methods provide good estimates, at least to typical dips in non-faulted sedimentary layers, with the estimates obtained with SR method being more accurate that those obtained with FCS method. Except in relation to the automation complexity, which is less important than the performances of the methods, SR method was superior or showed similar performance to FCS method in all scenarios we tried.  相似文献   

三维构造恢复中原位归属问题的方法技术     

王鹏昊  谢永海  李广业 《世界地质》2011,30(2):208-212

针对目前复杂构造三维恢复过程中地质体产生空间位置变化的不确定性,采用三维原位恢复方法,以巴楚断隆S1 构造为例,通过对比S1 构造恢复过程中所选取的标准区域与样本区域在构造变形前后的空间位置变化,分析构造变化过程中S1 构造整体模型的位置变化规律; 并据此将构造复原后的模型整体变化至初始位置,消除S1 构造因去掉石炭系顶面断距带来西南方向的位移,也消除了因去掉石炭系褶皱所带来西南方向的位移。研究表明,运用三维原位恢复技术,能够确保地质模型在构造复原前后空间位置不变,进而保证研究主体在构造恢复过程中空间位置的相对稳定,为分析构造变形带来的影响奠定空间比较基础。  相似文献   

桂西北典型峰丛洼地降雨过程中地表水溶解性碳和δ^13CDIC变化特征   总被引：3，自引：0，他引：3       下载免费PDF全文

丁虎  刘丛强  郎赟超  刘文景 《地学前缘》2011,18(6):182-189

文中研究了中国科学院环江喀斯特农业生态系统观测站内的地表水（地表径流和溪流）中溶解性有机碳（DOC）和溶解性无机碳（DIC）及其同位素组成在两次降雨事件中的连续变化特征。在两次降雨中DOC和DIC输移量分别为107．1和812．5kg,分别约为无降雨条件下相同时间内IX）C和DIC输移量的64和8倍。降雨时洼地溪流下游...  相似文献   

建筑物对浅埋隧道开挖地表沉降的影响     

许英姿  高伟  宋风超 《岩土工程技术》2011,25(4):195-198

采用解析法研究穿越地表建筑物浅埋隧道开挖引起的地表沉降。由无建筑物时岩土体开挖引起的地表沉降公式及半无限平面在均布荷载下的相对沉陷,推导出了穿越地表建筑物浅埋隧道施工引起的地表沉降公式,并通过实例验证了此方法的可行性。采用上述方法研究了地表建筑物的重量及其与浅埋隧道位置关系对地表沉降的影响,研究结果表明：浅埋隧道开挖引起的地表沉降随建筑物重量的增大而增大;建筑物中心到隧道轴线的水平距离是对地表沉降的一个重要影响因素,超过一定范围时建筑物的存在对地表沉降的影响可以忽略不计。研究结果可为类似隧道工程提供一定参考。  相似文献   

Characterization of humic substances by advanced solid state NMR spectroscopy: Demonstration of a systematic approach   总被引：2，自引：0，他引：2  

Jingdong Mao  Na ChenXiaoyan Cao 《Organic Geochemistry》2011,42(8):891-902

Characterization of humic substances is challenging due to their structural complexity and heterogeneity. Solid state nuclear magnetic resonance (NMR) is regarded as one of the best tools for elucidating structures of humic substances. The primary solid state NMR technique that has been used so far is the routine ¹³C cross polarization-magic angle spinning (CP-MAS) technique. Although this technique has markedly advanced our understanding of humic substances, the full potential of NMR for characterizing humic substances has yet to be realized. Recent technical developments and applications of advanced solid state NMR have revealed the promise to provide deeper insights into structures of humic substances. In this paper, we summarized and demonstrated the systematic solid state NMR protocol for characterization of humic substances using a humic acid as an example. This protocol included (1) identification of specific functional groups using spectral editing techniques, occasionally assisted by ¹H¹³C two-dimensional heteronuclear correlation (2D HETCOR) NMR, (2) quantification of specific functional groups based on direct polarization-magic angle spinning (DP-MAS) and DP-MAS with recoupled dipolar dephasing, combined with spectral editing techniques, (3) determination of connectivities and proximities of specific functional groups by ¹H¹³C 2D HETCOR or 2D HETCOR combined with spectral editing techniques, and (4) examination of domains and heterogeneities by ¹H¹³C 2D HETCOR with ¹H spin diffusion. We used a soil humic acid as an example to demonstrate how this protocol was applied to the characterization of humic substances step by step. Afterwards, based on typical ¹³C NMR spectra of humic substances we described how we could combine different NMR techniques to identify specific functional groups band by band from downfield to upfield. Finally, we briefly mentioned the potential new NMR techniques that could be developed to enrich the current systematic protocol. This systematic protocol is not only applicable to humic substances but also to other natural organic matter samples.  相似文献   

井下采掘三维定位自动监控系统功能架构设计   总被引：2，自引：0，他引：2  

曹洪松  田茂义  陈玉成  巩贵仁  彭慧妍  宁化展  杨逸飞 《山东地质》2011,(8):27-30

设计了井下采掘三维定位自动监控系统的总体结构,详细介绍各个功能模块的设计原理及系统实现的功能。应用三维GIS技术J、ava3D技术建立了矿山三维可视化平台,并在此基础上与矿山井下人员定位系统、矿业产量远程监控系统,集成开发了井下采掘三维定位自动监控系统,实现了井下采掘的实时监控、人员实时定位,降低了矿山开采的安全隐患,提高了对矿山开采的监管力度,能够为矿产资源开发与保护、矿山安全管理等提供信息服务。  相似文献