融合主成分分析和局部邻域的平面点云去噪     

陈建华 《测绘通报》2020,(5):47

大型水工建筑物和城市地下轨道是国家的重要基础设施，人工变形监测耗时费力，利用激光雷达扫描对其进行自动化的变形监测已成为研究热点。而此类建筑物具有较多的平面结构特征，为了高效去除平面结构扫描点云中的噪声点，本文提出了一种融合主成分分析和局部邻域的噪声剔除方法，首先利用主成分分析剔除全局噪声，然后利用局部邻域对局部小噪声进行剔除，结合实例对该方法进行了验证。应用结果表明，该方法效率高、算法简单可行，具有较高的推广应用价值。  相似文献   

关于Stokes公式的球面卷积和平面卷积的注记   总被引：2，自引：0，他引：2  

晁定波 《武汉大学学报(信息科学版)》2003,28(6):651-654

讨论了Stokes公式球面卷积和平面卷积形式的近似性和严密性问题,分析了Stokes函数球面卷积形式和平面卷积形式的关系,推导了其间的差值表达式,估算了最大差值及其对计算大地水准面差距的误差影响。同时指出,将顾及Stokes函数全项的平面卷积公式称为严密公式的提法,仅仅是相对仅顾及Stokes函数首项的简单平面卷积公式而言,认为更合理的提法应该是“高精度Stokes平面近似卷积公式”。理论分析表明,球面卷积不可能严格转化为等效的平面卷积。  相似文献   

卫星三线阵CCD影像光束法平差研究   总被引：9，自引：0，他引：9  

王任享 《武汉大学学报(信息科学版)》2003,28(4):379-385

简单回顾了“定向片法”和“EFP法”计算外方位元素的原理 ,指出仅仅利用三线阵CCD影像及地面控制点的空中三角测量 ,不能实现单航线角隅各一个控制点的平差计算模型与实地的相似性 (不计像点观测误差 )。利用EFP法空中三角测量的原理 ,进一步分析了其原因 ,提出了在相邻EFP像片之间增设连接点 ,同时要求在航线首末基线范围内的连接点带地面坐标或连接点在其左、右EFP像片上的坐标之一是其真中心投影坐标。在其控制下 ,平差结果实现了包括基线数B =2在内的单航线平差计算的模型基本与实地相似 ,并列出了在多种情况下利用计算机模拟数据进行平差精度统计的结果。最后就解决连接点真中心投影坐标获取问题 ,对三线阵CCD相机提出了附加要求 ,即在正视CCD线阵右侧附加两个 1 5 0 0像元× 1 5 0 0像元 (或更小 )的CCD面阵的构想方案  相似文献   

Study on relationship between deep and shallow structures along north boundary fault of Yanqing-Fanshan basin     

于贵华  徐锡伟  朱艾澜  马文涛  刁桂苓  张四昌  张先康  刘保金  孙振国 《地震学报(英文版)》2004,17(1):70-79

IntroductionTheYanqing-Huailaibasin,whichconsistsoftheYanqing-FanshanandHuailai-Zhuolusub-basins,ismainlycontrolledbythenorthboundaryfaultsofthesub-basins.AsabasictectonicunitattheintersectionofthenortheasternendoftheNNE-trendingShanxigrabensystemandtheNW-trendingZhangjiakou-Penglaifaultzone,ithaskepttheintensivetectonicactivityintheQuaternary(YANG,1982;XU,DENG,1988;XU,MA,1992;FANG,etal,1993;Pavlides,etal,1999).Overthepastdecade,manyresearchershaveconductedstudiesonthedetailedstr…  相似文献   

爆炸应力波近似处理的分析与研究     

朱传云  许桂生 《岩土力学》2002,23(4):455-458

通过弹性球面波的势函数求得了爆炸应力波BSW模型中弹性球面波的径向应力、质点振速等的显式解析解，并据此通过数值模拟得出实际计算中将球面波按平面波近似处理的误差及该误差随爆源距离，泊松比等的变化而产生变化的曲线。分析结果表明：距离是影响误差的决定性因素；在此条件下，当距离大于2－5m时，弹性球面波即可近似按平面波处理，其误差不超过5％，当距离小于此范围时，误差较大。  相似文献   

基于kd-tree的建筑物散乱点云平面分割   总被引：2，自引：0，他引：2  

石波  卢秀山  陈允芳 《测绘科学》2008,33(1):135-136

应用kd-tree快速确定散乱点云数据中某一个点的邻域,不需要先验地知道点云数据之间的拓扑(邻接)关系,使得建筑物点云平面分割算法更一般化,应用面更广。根据建筑物平面特征的先验信息,并采用高效数据结构,优化了平面分割算法,给出了散乱点云平面分割的实现和相应结果,说明了基于kd-tree的建筑物散乱点云平面分割算法的有效性。  相似文献   

GPS在国外无控制点公路平面测量中的应用     

刘文斌  史晓明  喻鸣 《地理空间信息》2010,8(6):34-36

GPS技术在公路测量中已日趋成熟,如何针对欠发达国家在没有自身坐标系统和控制点的情况下进行公路测量,是研究的目标。以南苏丹公路测绘项目为研究背景,所采用的GPS控制方法成功解决了该测区在没有椭球参数、任何控制点及测量资料的情况下的平面控制测量的问题,并提高了工作效率,对GPS技术在公路测量中的普及起到了推进作用。  相似文献   

Damage‐based seismic planar pounding analysis of adjacent symmetric buildings considering inelastic structure–soil–structure interaction          下载免费PDF全文

《地震工程与结构动力学》2017,46(7):1141-1159

In cities and urban areas, building structures located at close proximities inevitably interact under dynamic loading by direct pounding and indirectly through the underlying soil. Majority of the previous adjacent building pounding studies that have taken the structure–soil–structure interaction (SSSI) problem into account have used simple lumped mass–spring–dashpot models under plane strain conditions. In this research, the problem of SSSI‐included pounding problem of two adjacent symmetric in plan buildings resting on a soft soil profile excited by uniaxial earthquake loadings is investigated. To this end, a series of SSSI models considering one‐directional nonlinear impact elements between adjacent co‐planar stories and using a method for direct finite element modeling of 3D inelastic underlying soil volume has been developed to accurately study the problem. An advanced inelastic structural behavior parameter, the seismic damage index, has been considered in this study as the key nonlinear structural response of adjacent buildings. Based on the results of SSSI and fixed base case analyses presented herein, two main problems are investigated, namely, the minimum building separation distance for pounding prevention and seismic pounding effects on structural damage in adjacent buildings. The final results show that at least three times, the International Building Code 2009 minimum distance for building separation recommended value is required as a clear distance for adjacent symmetric buildings to prevent the occurrence of seismic pounding. At the International Building Code‐recommended distance, adjacent buildings experienced severe seismic pounding and therefore significant variations in storey shear forces and damage indices. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

雨滴对水-气界面溶解氧与pH扩散影响的平面光极观测方法     

姜子可  于新生  靳卫卫 《海洋学报》2018,40(7):134-142

水-气界面是一个重要的物质交换过程界面,对生态系统及生物地球化学循环过程有着重要影响。自然界的降雨可以改变水体表面平衡状态,提高气体在界面的通量交换速率,使得水体界面溶解氧和pH的水平、垂直方向浓度分布发生变化。本文利用平面传感膜具有高时空分辨率、可提供两维浓度分布信息的特点,开展了雨滴对水-气微界面层中的氧气扩散和pH值分布变化模拟实验,采用双参数平面光极同步测量获取低溶解气体在水-气界面的两维分布浓度变化。实验结果证明在受风速、温度影响较小区域,降雨过程对调节表层水体的溶解氧含量和pH值变化具有重要作用,雨滴可以打破水-气界面的微表层平衡机制,促进大气中氧气在表层水体的溶解,使得水面垂直方向23 mm内的溶解氧平均升高2.3 mg/L;降雨对水面12 mm之内表层水体pH值产生的影响较为明显,pH值平均降低了0.2~0.4个单位,表明降雨雨滴促进大气在水-气界面的迁移进程,溶解的CO₂使得表层水体向酸性方向转化。本文提出的基于平面光极两维观测方法为评估低风速、高降雨或低降雨区域的海岸带溶解氧和pH值的变化提供高空间分辨率的水-气界面实时观测新的技术支撑。  相似文献   

Computer program for stability analysis of steep,cohesive riverbanks     

Stephen E. Darby  Dan Gessler  Colin R. Thorne 《地球表面变化过程与地形》2000,25(2):175-190

The ability to predict the stability of eroding riverbanks is a prerequisite for modelling alluvial channel width adjustment and a requirement for predicting bank erosion rates and sediment yield associated with bank erosion. Mass‐wasting of bank materials under gravity occurs through a variety of specific mechanisms, with a separate analysis required for each type of failure. This paper presents a computer program for the analysis of the stability of steep, cohesive riverbanks with respect to planar‐type failures. Planar‐type failures are common along stream channels destabilized by severe bed degradation. Existing stability analyses for planar‐type failures have a number of limitations that affect their physical basis and predictive ability. The computer program presented here is based on an analysis developed by Darby and Thorne. The software takes account of the geotechnical characteristics of the bank materials, the shape of the bank profile, and the relative elevations of the groundwater and surface water to estimate stability with respect to mass failure along a planar‐type failure surface. Results can be displayed either in terms of a factor of safety (ratio of resisting to driving forces), or probability of failure. The computer analysis is able to determine the relative amounts of bed degradation and bank‐toe erosion required to destabilize an initially stable bank. Data for the analysis are supplied in the form of either HEC‐2 hydrographic survey data files or user‐supplied bank profile data, in conjunction with user‐supplied geotechnical parameter values. Some examples, using data from the Upper Missouri River in Montana, are used to demonstrate potential applications of the software. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献