泥石流沟谷地形的机载激光雷达点云滤波算法对比

为探究不同滤波算法对泥石流沟谷复杂地形机载激光雷达点云数据处理的普适性,选取昆明市东川区大白泥河沟作为研究区,采用改进的渐进加密三角网滤波(IPTDF)、布料模拟滤波(CSF)、基于坡度的滤波(SBF)3种常用滤波算法对研究区内的15个样本机载激光雷达点云数据进行滤波试验,结合国际摄影测量和遥感学会提出的交叉表评价体系对滤波的结果进行量化分析,探究坡度、植被覆盖度两类因素与滤波精度之间的关系.结果表明,当地形平坦、坡度较小时(样本1、 2、6、 7、 10), IPTDF、 SBF和CSF算法的平均总误差分别为8.73%、 8.81%、 8.90%,数值上十分接近, 3种算法都能达到分类地面点的目的,当地形复杂,坡度较大时(样本5、 8、 9、 12、 14), IPTDF、 SBF和CSF算法的平均总误差分别为13.4%、 36.4%、 30.2%, CSF与SBF算法在地形复杂的陡壁区域精度较低, IPTDF算法平均总误差远低于其他两种算法,能够很好地适应泥石流沟谷的复杂地形地貌特征;研究区内坡度和植被覆盖度呈显著正相关,坡度和植被覆盖度对CSF和SBF的误差影响较为明显,各算法Ⅰ...     

长江中下游河道岸滩低空机载LiDAR点云地形滤波算法

探索新兴的低空机载Li DAR技术,解决长江中下游植被高覆盖、高遮挡区岸滩地形测绘难题。提出一种针对多层次、高密度植被覆盖区的低空机载Li DAR点云植被滤波算法,该算法通过多回波分析对点云进行粗滤波后,采用数学形态学运算获取地面种子点,对地形局部进行趋势面拟合,再通过随机采样一致性检测,剔除植被点,保留地面点,从而获取测区的数字高程模型(DEM)。典型测区试验表明,该滤波算法能解决长江中下游河道岸滩地区地形起伏较大、植被高覆盖区域植被点云智能化剥离难题。根据测区实际情况,设计针对性的滤波算法,即使是植被与地面点云高度混淆、激光穿透率低于15%的复杂情形,仍能有效分离出地面和非地面点。     

基于曲率统计的LiDAR点云二次滤波方法

针对传统偏度平衡方法滤波结果中存在低矮植被、建筑物侧面墙脚等非地面点云问题,在传统偏度平衡方法的点云一次滤波算法的基础上,提出一种基于曲率统计的点云二次滤波方法。对该方法进行试验,并将试验结果与传统偏度平衡方法滤波结果进行对比分析。结果表明:基于曲率统计的点云二次滤波方法比传统偏度平衡法能够多滤除83%的植被点云、5%的建筑物点云,能够有效地滤除传统偏度平衡方法滤波结果中的低矮植被、建筑物侧面墙脚等非地面点云。     

基于倾斜影像颜色信息的建筑物点云提取

针对建筑物点云提取不完整问题,笔者采用一种组合方法从影像密集匹配获得的多视图像(MVS)点云中提取建筑物点云.首先运用布料模拟滤波(CSF)算法进行地面点滤波,去除MVS点云中的地面点;然后根据MVS点云的颜色信息,利用过绿指数(EXG)和植被密集成块特性将植被点云剔除;最后使用密度聚类从剩余的点云中分割出建筑物点云....     

适用于林区机载LiDAR点云的多分辨率层次插值滤波方法

针对现有机载激光雷达点云滤波算法在林区适用性不强的问题,提出一种基于多分辨率层次插值的林区LiDAR滤波方法.该方法首先借助形态学迭代开运算和稳健z-score方法获取大量地面种子点;然后从低层到高层滤波过程中,通过薄板样条函数构造地面参考面,并借助自适应坡度阈值选择地面点;最后将分类出的地面点更新地面参考面,层层迭代...     

K-邻域法对不同形态植被点云数据特征的提取

以三维激光扫描仪获取的点云数据为数据源,在分类裁剪得到不同自然地物的点云数据基础上,介绍了利用K-邻域法对不规则的自然地物点云数据进行邻域检索,通过设定尺度参数k的值对高矮不同的植被进行特征点的提取算法。通过实验对提取后的结果进行比较分析。结果表明:尺度参数的设置对点云密度较大的低矮植被效果明显,对于密度相对稀疏的高植被影响不大,参数k设置在3~5之间效果显著。     

改进迭代最近点算法支持下的LiDAR点云与正射影像粗-精配准方法

针对直接迭代最近点算法(Iterative Closest Point,ICP)算法难以满足无人机LiDAR点云与正射影像高精度高效配准等问题,提出基于改进ICP的LiDAR点云与正射影像配准方法,为遥感地物目标解译提供丰富的空间信息和语义信息。首先采用体素滤波算法消除原始点云数据冗余;然后,利用主成分分析算法(Principal Component Analysis,PCA)对点云进行粗配准和计算刚体变换参数初始值,最后使用ICP算法实现LiDAR点云与正射影像精配准。实验结果表明,基于改进ICP的配准方法能够实现复杂地物分布、地物遮挡等情况下点云与影像快速、高精度地配准和点云纹理精准着色,相比原始ICP算法精度和效率分别提高了约1.8倍和3倍。     

基于林地激光点云的树木胸径自动提取方法

提出了一种基于随机RANSAC模型的树木胸径自动提取算法。首先,采用布料模拟滤波（CSF）算法对林地点云数据进行滤波,获取树木、地面数据与数字地面模型（DEM）并提取树木胸径处点云,然后进行欧式距离聚类,最后基于随机random sample consensus（RANSAC）模型拟合树木模型,实现自动化的树木胸径提取。使用上海市青浦区某区域两林区样地的地面激光点云数据对该算法进行验证,与实际人工测量树木胸径的平均偏差分别为0.79cm和0.52cm。实验对比结果表明,该算法在精度与时间性能上均优于基于Hough变换的算法与基于最小二乘的算法。     

基于RANSAC模型的机载LiDAR数据中建筑轮廓提取算法

使用正交多项式分带滤波方法对机载LiDAR点云数据进行滤波处理,通过迭代不断剔除非地面高点数据,最终得到由贴近地面的数据拟合而成的正交多项式.通过设定高程阈值将数据分成地面部分与非地面部分.提出了一种基于随机抽样一致性(RANSAC)算法模型的建筑物面片识别和轮廓提取算法,实现在包含噪声的点云数据中快速准确地识别和提取建筑物轮廓.在实验中对长春市的机载LiDAR数据进行了滤波、建筑屋顶面及其轮廓的提取,验证了本文算法的较高效率和精度.     

基于机载LiDAR属性信息检测离群点云

无人机载LiDAR是一种新型遥感技术,可快速获取高密度、高精度的地物点云数据,随着获取精度越高,点云数据量越大。为减少参与点云滤波处理的数据量,提高滤波速度,本文结合点云回波次数、高度和点云回波强度三种属性信息,采用箱形图检验方法获取非地面点云,并使用反复建立三角网方法分别对处理前后的点云数据进行对比分析。结果表明:针对截取的试验区点云数据,可去除多次回波对应的噪声点云363个,得到第1次和第2次回波分别占点云总数的98.49%和1.49%;高度和强度离群的点云共占点云总数的1.46%。通过对点云进行滤波前期的处理,可降低滤波时间32.2s,且保留地面点云2551个。本文研究利用箱形图检测点云属性获取离群值,可提高点云处理速度和降低地面点云漏分的现象,为后期直接利用统计方法对点云属性信息分析和实现快速处理海量点云提供参考。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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