一种基于点对应的激光扫描仪外方位参数检校方法

本文设计了一种检校标志用以激光扫描仪的检校,利用三平面相交得到检校标志中的特征点在激光扫描仪坐标系和全站仪坐标系中的坐标值,根据点点对应采用平差的方法计算得到两坐标系之间的变换矩阵,最后给出实验结果和精度分析.     

激光扫描数据的可视化技术

激光扫描数据是离散的矢量点构成的“点云”,没有任何明显的形体信息和拓扑关系信息。对移动激光扫描数据的处理与信息提取过程中,提出了三种不同的可视化方案将其可视化,可满足不同的任务需求。     

基于三维激光扫描技术的不规则物体表面积的测定方法

采用三维激光扫描技术可以快速获取物体表面的三维信息。对包含这些三维信息的点云进行处理能够获得广泛的应用。本文介绍了三维激光扫描仪的原理,并对其进行表面积计算和可行性研究,并在实际测量中进行应用。经验证采用三维激光扫描技术可以高精度、快速、便捷地实现不规则物体表面积的计算。     

基于地面三维激光扫描技术的滑坡模型监测与预测

地面三维激光扫描技术可以高精度、高密度、高速度、非接触地测量滑坡表面三维空间坐标,从而得到滑坡模型地表的整体变形资料.文章结合滑坡模型试验,利用灰色模型GM(1,1)对模型中提取的两个监测点的三维坐标位移进行预测,经由实测值与预测值比较、误差检验、图形对比等得出结论:灰色模型可以应用于长期的滑坡控制点三维坐标位移预测中.     

X线CT机选型的依据

本文描述了X 线CT 机的几个主要技术特性,并根据这些特性,计论如何去选择一台价格低、图像质量高的CT 扫描机。     

PZ-600型全身CT机反投影原理及其框图

目前大部分CT机常用的成像方法仍是卷积反投影法。对于在医院工作的某些工程技术人员来说是很想了解该方法在计算上是如何实现的。笔者在对我院 PZ-600型 CT 机的有关资料进行了分析和整理后,试图较直观地说明 PZ-600型 CT 机反投影成像的具体实现过程。PZ-600型机也有专用硬件,本文介绍其硬件框图。     

Qualitative and Quantitative Description of Multibeam Echosounder Systematic Errors on Rocky Areas

This paper deals with the problem of systematic depth errors made in surveying dumped rocks with multibeam echosounder. These errors may induce dangers for navigation in very shallow water areas or huge costs for coastal engineering contractors who perform rock dumping operation and surveying. We analyze results from four different multibeam echosounder systems and compare those data to a reference digital terrain model of a dumped rocks area obtained from a 3D terrestrial laser scanner. The systematic depth errors are statistically described and analysed on local areas. Finally, we propose a look-up table linking the error amplitude with the rock size, resulting from our error analysis.     

Accurate 3D comparison of complex topography with terrestrial laser scanner: Application to the Rangitikei canyon (N-Z)

Surveying techniques such as terrestrial laser scanner have recently been used to measure surface changes via 3D point cloud (PC) comparison. Two types of approaches have been pursued: 3D tracking of homologous parts of the surface to compute a displacement field, and distance calculation between two point clouds when homologous parts cannot be defined. This study deals with the second approach, typical of natural surfaces altered by erosion, sedimentation or vegetation between surveys. Current comparison methods are based on a closest point distance or require at least one of the PC to be meshed with severe limitations when surfaces present roughness elements at all scales. To solve these issues, we introduce a new algorithm performing a direct comparison of point clouds in 3D. The method has two steps: (1) surface normal estimation and orientation in 3D at a scale consistent with the local surface roughness; (2) measurement of the mean surface change along the normal direction with explicit calculation of a local confidence interval. Comparison with existing methods demonstrates the higher accuracy of our approach, as well as an easier workflow due to the absence of surface meshing or Digital Elevation Model (DEM) generation. Application of the method in a rapidly eroding, meandering bedrock river (Rangitikei River canyon) illustrates its ability to handle 3D differences in complex situations (flat and vertical surfaces on the same scene), to reduce uncertainty related to point cloud roughness by local averaging and to generate 3D maps of uncertainty levels. We also demonstrate that for high precision survey scanners, the total error budget on change detection is dominated by the point clouds registration error and the surface roughness. Combined with mm-range local georeferencing of the point clouds, levels of detection down to 6 mm (defined at 95% confidence) can be routinely attained in situ over ranges of 50 m. We provide evidence for the self-affine behaviour of different surfaces. We show how this impacts the calculation of normal vectors and demonstrate the scaling behaviour of the level of change detection. The algorithm has been implemented in a freely available open source software package. It operates in complex 3D cases and can also be used as a simpler and more robust alternative to DEM differencing for the 2D cases.     

逆向工程技术在建筑物倾斜测量中的应用

针对目前传统倾斜测量方法不能够全面反映建筑物倾斜变形的问题,提出一种新的基于逆向工程技术的倾斜观测方法,该方法能够较全面地反映建筑物各个部位的倾斜变形情况。基于烟囱倾斜测量的实验结果表明,所提方法不仅可以快速获取监测物体的三维点云数据,还能够准确计算出建筑物的重点监测部位。研究结果可应用于一般建筑物和塔形建筑物的倾斜观测。论文将逆向工程技术引入到倾斜测量领域中,可以更加全面、直观、形象地反映建筑物的倾斜情况。