共查询到20条相似文献,搜索用时 109 毫秒
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针对机载LiDAR点云的岛屿岸线提取过程复杂、附属岛屿岸线难以提取等问题,提出一种基于改进Alpha Shape算法的点云数据岛屿边界提取方法。首先利用布料模拟滤波算法剔除非岛屿点云数据,通过欧式聚类进行不同岛屿的提取,再将岛屿点云数据投影至二维平面,并根据岛屿点云构建格网。在此基础上使用自适应Alpha Shape算法,对提取出的岛屿点云进行边界提取,即可得到岛屿的岸线轮廓。选取新西兰的玛提尤/萨姆斯岛作为研究区域,并将本文算法与Alpha Shape算法进行对比,结果表明:本文算法提取岛屿边界点云的精准度为97.78%,可以准确地提取岛屿岸线,为海岛规划提供参考。 相似文献
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针对无人机匹配点云经地面点滤波后会存在较多孔洞的问题,提出利用哈里斯鹰算法(harris hawks optimization, HHO)优化最小二乘支持向量机(least squares support vector machine, LSSVM)来进行地面点云孔洞修补。首先利用八叉树结构法对滤波后点云数据进行地面特征点提取,其次采用哈里斯鹰算法对最小二乘支持向量机中的核参数和正则化参数进行优化,并利用组合算法构建匹配地面点云孔洞修补模型。实验结果表明,与单一最小二乘支持向量机相比,组合模型的孔洞修补精度提高了22.3%,其稳定性也得到增强,具备一定的时效性及现实性。 相似文献
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多波束测深数据广泛服务于水下地形测量。一些基于测深数据的应用需要提取测深数据的边缘轮廓和探测数据中的空洞。针对已有边缘识别算法执行效率低、边界点提取不完整等问题,通过分析点云模型的局部几何属性,提出一种新的基于k-d树的由粗到精的边缘提取算法。首先抽稀测深数据,基于k-d树建立散乱点云的拓扑关系;然后计算散乱点云法向量,采用距离及角度阈值法进一步提取孔洞与边缘轮廓点并去除错误识别的点;最后基于凹包算法,精确获取边缘轮廓点。在西太平洋海域的实验表明:相较于Alpha-shape和Boundary estimation算法,本算法能够更为精确地识别出散乱点云中的边界点,实用性强。 相似文献
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基于格网的坐标转换,其过程可分为建立格网和格网内插两部分。建立格网过程中生成的格网文件是格网内插的前提,为了使格网文件便于解释和应用,需要制订合理的格网文件格式。目前,有NADCON和NTv2两种格式可供参考。通过这两种格式的比较分析,认为NTv2格式更优,并将其作为参考,研究了面向CGCS2000的格网坐标转换中所使用的格网文件的具体格式,并以1954北京坐标系(BJS54)到2000国家大地坐标系(CGCS2000)的转换为例,提供了设计样本。 相似文献
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随着激光扫描技术和定位技术的快速发展,船载激光扫描系统的应用得到逐步推广。但由于商业机密,当前船载激光扫描系统中的点云数据坐标解算方法几乎都没有公开。以由Optech公司的ILRIS-LR型激光扫描仪和Applanix公司的POS MV 320系统组成的船载激光扫描系统的工作原理为基础,分析船载激光扫描点云数据坐标解算中的空间转换过程,推导船载激光扫描点云数据坐标解算的数学模型,实现了面向该系统的点云数据生成。结果表明,该点云数据坐标解算模型具有较好的可靠性和稳定性,可有效地用于船载激光扫描点云数据生成,对船载激光扫描系统具有重要的应用和推广价值。 相似文献
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为了获取大倾斜航空摄影图像中目标点的位置,提出了参照基准图像,基于改进的6参数仿射变换模型进行几何纠正的方法。该方法对基准图像和大倾斜航空摄影图像分别进行角点检测,然后进行配对处理,配对后的相邻角点进行分组后,构建Delaunay三角网,在局部范围内分别进行仿射变换。实验表明,对大倾斜航空摄影图像赋予地理坐标能够达到较好的结果。 相似文献
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针对普通孔洞修补方法在修补复杂曲面的孔洞无效或者所修补的曲面不光滑等缺点,提出基于自适应切片的孔洞修补方法。首先,在考虑点云局部特征的情况下对整体点云进行自适应切片,在得到切片后引入总体最小二乘进行拟合,最后,在线上取点填充缺失的点云。实验结果表明,采用自适应切片法修补孔洞能够顾及到点云的曲率和密度变化,保持点云的局部特征,用总体最小二乘法拟合切片得到的孔洞填充点云精度较高,光滑性好。通过对比常规方法,可以得到基于总体最小二乘自适应切片方法修补效果更优。 相似文献
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渤海沿岸固定冰粗糙特征的实测研究 总被引:1,自引:0,他引:1
The surface roughness characteristics(e.g., height and slope) of sea ice are critical for determining the parameters of an electromagnetic scattering, a surface emission and a surface drag coefficients. It is also important in identifying various ice types, retrieval ice thickness, surface temperature and drag coefficients from remote sensing data. The point clouds(a set of points which are usually defined by X, Y, and Z coordinates that represents the external surface of an object on earth) of land fast ice in five in situ sites in the eastern coast Bohai Sea were measured using a laser scanner-Trimble GX during 2011–2012 winter season. Two hundred and fifty profiles selected from the point clouds of different samples have been used to calculate the height root mean square, height skewness, height kurtosis, slope root mean square, slope skewness and slope kurtosis of them. The root mean square of the height, the root mean square of the slope and the correlation length are about 0.090, 0.075 and 11.74 m, respectively. The heights of 150 profiles in three sites manifest the Gaussian distribution and the slopes of total 250 profiles distributed exponentially. In addition, the fractal dimension and power spectral density profiles were calculated. The results show that the fractal dimension of land fast ice in the Bohai Sea is about 1.132. The power spectral densities of 250 profiles can be expressed through an exponential autocorrelation function. 相似文献
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SHI Fengyan DING Pingxing KONG Yazhen
Associate Professor State Key Laboratory of Estuarine Coastal Research East China Normal University Shanghai P. R. China.
Professor State Key Laboratory of Estuarine Coastal Research East China Normal University Shanghai P. R. China.
Senior Engineer State Key Laboratory of Estuarine Coastal Research East China Normal University Shanghai P. R. China. 《中国海洋工程》1999,(2)
Fine grids with small spacing in boundary-fitted coordinates are normally used to treat thecomputation of fluid dynamics for estuarine areas and tidal flats.However,the adoption of Cartesian com-ponents of velocity vectors in this kind of non-orthogonal coordinates will definitely result in a diffculty insolving implicitly the transformed momentum equations,and also complicate the wet-dry point judgementused for flood areas.To solve this problem,equations in terms of generalized contravariant velocityvectors in curvilinear coordinates are derived in the present study,by virtue of which,anAlternative-Direction-Implicit numerical scheme in non-orthogonal grids would then be easily obtained,and wet-dry point judgement would as well be largely simplified.A comparison is made between the explic-it scheme and implicit scheme,showing that the present model is accurate and numerically stable for com-putations of fluid dynamics for estuarine areas and tidal flats. 相似文献
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Milan Horemuz 《Marine Geodesy》1999,22(1):1-17
The sea boundary between two states with opposite or adjacent coasts is defined by the median line between baselines realized on shore lines. As defined in UNCLOS (United Nations Convention on the Law of the Sea), every point of the median line must be equidistant from the nearest points on the baselines from which the breadth of the territorialseas of each ofthe two states is measured. The coordinates of breakpoints of the median line are computed based on known coordinates of baseline points on the shores. What is the precision of computed coordinates? Here we study the error propagation on two reference surfaces: (1) plane and (2) sphere. Moreover, four approaches to breakpoint determination are investigated. Algorithms for computation of the covariance matrix of median line breakpoints both on sphere and plane were developed. 相似文献
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轮廓与特征点研究是头足类角质颚形态特征鉴别的基本方法,对于轮廓与特征点的提取最常用的方法是手动描绘与标定,利用计算机视觉进行轮廓与特征点的提取,不仅可以降低手动提取带来的误差、提高准确性,而且更加快速、便捷。文章将利用计算机视觉提取头足类角质颚的轮廓与特征点,首先将自制装置拍摄得到的角质颚三视图放入MTALAB软件中进行编程处理,然后利用Canny算法提取角质颚轮廓,最后根据地标点的定义标定特征点位置并建立空间坐标系得到角质颚的特征点坐标。研究结果显示,利用计算机视觉提取角质颚的轮廓图像以及特征点坐标是可行的,当标准差σ取值为0.1时角质颚轮廓图效果最佳,在得到的轮廓图上进行特征点的标定,通过迭代遍历轮廓图获得各个特征点的空间坐标。研究分析认为,将计算机视觉应用于头足类角质颚形态学的研究可以提高研究的便捷性,同时也为后续的研究提供了新的实验思路和方法。 相似文献