针对建筑物三维模型建立自动化程度与效率无法并存的问题,本文提出一种自动提取机载激光雷达(light detection and ranging,LiDAR)点云的建筑物关键点算法,针对规则建筑物实现快速三维重建。该方法通过阿尔法-形状(Alpha-Shape)边缘检...针对建筑物三维模型建立自动化程度与效率无法并存的问题,本文提出一种自动提取机载激光雷达(light detection and ranging,LiDAR)点云的建筑物关键点算法,针对规则建筑物实现快速三维重建。该方法通过阿尔法-形状(Alpha-Shape)边缘检测算法和屋顶分割算法完成建筑物关键点提取,再利用夏普·格尔(SharpGL)工具包完成基于关键点建筑物的三维重建。并与经典建筑三维重建方法做对比实验,结果表明本文方法在建筑物提取与三维重建中具有较高的效率,实现0.05 km^(2)区域的建筑物三维重建仅耗时6 min。展开更多
为了使用四旋翼无人机搭载二维激光雷达进行空间环境探测与建模,设计了无人机LIDAR(Light Detection and Ranging)探测方案,提出了基于欧式聚类与Alpha-shape算法的点云数据建模方法。以室内环境建模为例,通过无人机LIDAR测得室内多位...为了使用四旋翼无人机搭载二维激光雷达进行空间环境探测与建模,设计了无人机LIDAR(Light Detection and Ranging)探测方案,提出了基于欧式聚类与Alpha-shape算法的点云数据建模方法。以室内环境建模为例,通过无人机LIDAR测得室内多位置、多高度的平面点云数据。根据室内环境点云数据分块聚集的特性,对数据进行统计滤波消噪,并采用欧式聚类算法对点云数据进行聚类,对每个聚类分别选取合适的参数α绘制其Alpha-shape图形。对于采样高度均匀、雷达扫描频率稳定的点云数据,考虑到无人机激光雷达的数据特点,以每个聚类中点的数量和其包络在x-y平面的投影面积为参数,结合测量经验提出了α的计算式。利用此方法可以实现使用二维激光雷达进行空间建模,相较于使用三维激光雷达成本更低,测量更灵活。展开更多
Simulators play an important role in training surgery residents to perform laparoscopy surgery. Some of these simulators have the capability to track tool motion to assess performance. However, most have not utilized ...Simulators play an important role in training surgery residents to perform laparoscopy surgery. Some of these simulators have the capability to track tool motion to assess performance. However, most have not utilized the data to analyze trainee performance in a meaningful way. The alpha shape method can be used to construct a geometric surface based on motion data to enable visualization of the performance, while the surface derivative (surface/time to completion)—efficiency—can be used as a metric to evaluate complex surgical performance. The utility of the alpha shape method was demonstrated in a pick-and-place task, where the motion path of laparoscopic graspers was recorded by a position sensor, miniBIRD 500?. An alpha shape method was used to measure the surface area of the 3D points in space occupied by the tool tips during task performance. Results show that the surface derivative measure alone may be able to model the speed-accuracy tradeoff function, thereby simplifying the analysis and evaluation of complex motion in surgical performance.展开更多
精确分割建筑物屋顶激光雷达(light detection and ranging,LiDAR)点云是三维模型重建的重要环节。针对现有算法分割复杂建筑物屋顶面结构精度差的问题,提出一种以三角面为基元的基于区域生长算法的复杂建筑物屋顶点云分割方法。首先,构...精确分割建筑物屋顶激光雷达(light detection and ranging,LiDAR)点云是三维模型重建的重要环节。针对现有算法分割复杂建筑物屋顶面结构精度差的问题,提出一种以三角面为基元的基于区域生长算法的复杂建筑物屋顶点云分割方法。首先,构建Delaunay三角网建立各激光点间相互关系,计算各三角面法向量,利用同一建筑物面片上各三角面法向量基本一致的特征对点云进行初步划分;然后,由于点云散乱性及误差影响产生诸多散乱三角面,对各构成散乱三角面的点进行剖分,并基于具有良好鲁棒性的随机采样一致性算法(random sample consensus,RANSAC),结合Alpha Shape算法获取建筑物各面片边界,合并过度分割的面片及孤立点,完成建筑物屋顶点云分割。实验结果表明,该方法对复杂建筑物屋顶点云分割的完整性、正确性及质量均较为理想。展开更多
文摘为了使用四旋翼无人机搭载二维激光雷达进行空间环境探测与建模,设计了无人机LIDAR(Light Detection and Ranging)探测方案,提出了基于欧式聚类与Alpha-shape算法的点云数据建模方法。以室内环境建模为例,通过无人机LIDAR测得室内多位置、多高度的平面点云数据。根据室内环境点云数据分块聚集的特性,对数据进行统计滤波消噪,并采用欧式聚类算法对点云数据进行聚类,对每个聚类分别选取合适的参数α绘制其Alpha-shape图形。对于采样高度均匀、雷达扫描频率稳定的点云数据,考虑到无人机激光雷达的数据特点,以每个聚类中点的数量和其包络在x-y平面的投影面积为参数,结合测量经验提出了α的计算式。利用此方法可以实现使用二维激光雷达进行空间建模,相较于使用三维激光雷达成本更低,测量更灵活。
文摘Simulators play an important role in training surgery residents to perform laparoscopy surgery. Some of these simulators have the capability to track tool motion to assess performance. However, most have not utilized the data to analyze trainee performance in a meaningful way. The alpha shape method can be used to construct a geometric surface based on motion data to enable visualization of the performance, while the surface derivative (surface/time to completion)—efficiency—can be used as a metric to evaluate complex surgical performance. The utility of the alpha shape method was demonstrated in a pick-and-place task, where the motion path of laparoscopic graspers was recorded by a position sensor, miniBIRD 500?. An alpha shape method was used to measure the surface area of the 3D points in space occupied by the tool tips during task performance. Results show that the surface derivative measure alone may be able to model the speed-accuracy tradeoff function, thereby simplifying the analysis and evaluation of complex motion in surgical performance.
