一定分布模式下的最优Lp估计   总被引：4，自引：0，他引：4  

周世健  邓康伟  陈永奇 《测绘学报》1999,28(1):45-50

观测数据在一定的分布模式下,需从理论上解决究竟用多大的ｐ值进行Ｌｐ估计（最优ｐ值的确定）,本文基于渐近方差整体最小的原则,给出了最优Ｌｐ估计的定义。观测数据中含有粗差（异常值）的扰动,其误差分布可视为污染分布,作者分析了最优ｐ值的大小,结果表明,若观测数据中含有不同大小、数量的粗差,为使Ｌｐ估计差最小,则ｐ将取［１．２,１．５］中的某一定值,Ｌｐ估计结果最优,此结论对测量数据处理具有一定的参考价值  相似文献   

10月份赤道东太平洋的海温与青岛汛期降水     

李德萍  黄明政  毕超 《气象》1999,25(1):52-54

历年１０月东太平洋赤道附近的海温变化与来年初夏（６月）西太平洋副高脊线位置呈明显的反相关;其海温的年际变化对于青岛地区来年汛期降水具有敏感的指示意义。  相似文献   

Some aspects of head‐variance evaluation     

Daniel M. Tartakovsky  Igor Mitkov 《Computational Geosciences》1999,3(1):89-92

We compare two methods of evaluating head covariance for two‐dimensional steady‐state flow in mildly heterogeneous bounded rectangular aquifers. The quasi‐analytical approach, widely used in stochastic subsurface hydrology, is based on the Green's function representation, and involves numerical four‐fold integration. We compare this approach with a numerical solution of the two‐dimensional boundary‐value problem for head covariance. We show that the finite differences integration of this problem is computationally less expensive than numerical four‐fold integration of slowly‐convergent infinite series. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

韧性剪切带内流体作用及成分变化与体积变化   总被引：1，自引：0，他引：1  

华永刚  刘树文 《世界地质》1999,18(1):1-8

韧性剪切带中的大量流体活动,影响了变形机制和矿物成分的变化。由于流体的渗透,造成某些元素的迁移,形成剪切带的物质成分变化和体积变化。流体与岩石的相互作用则是剪切带发展过程中的重要作用。应用成分变化计算体积变化已成为研究的热点问题  相似文献   

自动与人工雨量计观测降水量的差异分析   总被引：1，自引：0，他引：1  

吴立群 《内蒙古气象》2011,(6):94-95

通过对东胜国家基准气候站自动与人工两年观测数据资料的实时对比,分析判断出自动观测雨量计相对人工观测雨量计来说,误差率比较稳定。  相似文献   

Grain size along two gravel-bed rivers: statistical variation,spatial pattern and sedimentary links     

Stephen Rice  Michael Church 《地球表面变化过程与地形》1998,23(4):345-363

A new set of field data facilitates a detailed analysis of variations in bed material grain size within two confluent gravel-bed rivers in northeastern British Columbia, Canada. A preliminary assessment of grain-size variability establishes a basis for examination of the spatial pattern of grain-size change. Standard ANOVA techniques are inappropriate because individual samples have unequal variances and are not normally distributed. Alternative tests for homoscedasticity and comparison of means are therefore utilized. Within-site, between-sample variability is not significant. The grain-size distributions that were obtained at individual sites are therefore representative of the depositional environments that were sampled. In both rivers mean grain size does vary significantly between sites and there is therefore a basis for examining the data for spatial patterns such as downstream fining. Textural variations along the two rivers studied here are complex and show negligible overall fining (in over 100 km). This is the consequence of a large number of tributary inputs and non-alluvial sediment sources which are the legacy of Late Pleistocene glaciation. The identification of lateral sources like these is fundamental for understanding textural changes within rivers. The sedimentary link (a channel reach between significant lateral sediment inputs) provides a means of isolating fluvial maturation processes (abrasion and sorting) from contingent lateral inputs. Strong fining trends are apparent in most links and classification of grain-size measurements according to their location within particular links greatly improves the statistical explanation of textural variation. Identification of sedimentary links provides a means of applying models of fluvial fining processes, so isolation of link networks will aid the development of basin-scale models of textural variation. © 1998 John Wiley & Sons, Ltd.  相似文献   

TIN DEM线性内插不确定性的随机过程模型     

钟剑龙  花向红  陈华安 《武汉大学学报(信息科学版)》2010,(2)

基于随机过程模型导出了TIN DEM线性内插的随机过程模型,给出了不规则随机空间三角形的不确定性描述,讨论了TIN节点误差在线性内插中的传播问题。通过理论推导和实际算例,得到了TIN DEM线性内插点的点位方差和误差椭球半轴的解析表达式、线性内插精度最高点坐标的解析表达式,该结论与三角形的形状无关;对DEM线性外推导致精度急剧下降的必然性结论进行了理论证明;得到TIN线性内插的平均点位方差解析式,从理论上说明了本文结论的有效性。  相似文献   

VRS动态随机模型建模方法的综合比较     

徐锐  黄丁发  廖华  陈维锋 《武汉大学学报(信息科学版)》2010,(3)

阐述了4种传统虚拟参考站(virtual reference station,VRS)随机模型建模方法及VENUS随机模型建模方法的作业原理,从验后单位权方差、模糊度精度因子ADOP、F-ratio、滤波残差等多个角度综合分析了各方法作业水平的有效性及优劣程度。研究表明,传统的标准随机模型建模方法、信噪比建模方法及高度角建模方法在VRS中的应用有效性最弱,传统的自适应随机模型方法和VENUS建模方法在不同层面体现出各自的优势,有互相借鉴的科研价值。  相似文献   

一种削弱NLOS影响的定位算法     

杨扬  陈字波  戴吾蛟 《测绘科学》2010,35(2):30-31

通过获取坐标已知的基站间TOA值由此得到它们之间的伪距,与其真实距离做差再取平均值的方法,得到在NLOS误差改正值。具体定位时,先利用NLOS误差改正值对TOA观测值进行改正,然后采用附有约束条件的加权最小二乘法(CLW S)得到最终的定位结果。仿真结果表明,该方法可有效地削弱NLOS误差对定位精度的影响。  相似文献   

基于粒子群优化算法的最大类间方差多阈值图像分割     

周晓伟  葛永慧 《测绘科学》2010,35(2):88-89,122

最大类间方差法是图像分割中一种常用的阈值分割方法,对于单阈值分割具有显著的效果,但是对于多阈值分割,计算复杂度大、耗时较多。本文将粒子群优化算法与最大类间方差法结合,提出了一种新的图像分割方法,该方法利用粒子群优化算法的寻优高效性,并由灰度图像的最大类间方差值作为适应值,搜索最优分割阈值,实现图像的多阈值分割。实验结果显示,新方法大大缩短了寻找最优阈值的时间,降低了运算复杂度,提高了图像分割速度,说明基于粒子群优化算法的图像分割算法是可行的、有效的。  相似文献