使用UAV系统采集的遥感图像结合倾斜摄影测量技术绘制的城市OSGB(Open Scene Graph Binary)模型是目前广泛采用的城市数字化模型。然而,由于建筑物相互遮挡和相机倾斜角度偏差等问题,由航空倾斜影像生成的3D模型可能存在几何缺陷和模糊...使用UAV系统采集的遥感图像结合倾斜摄影测量技术绘制的城市OSGB(Open Scene Graph Binary)模型是目前广泛采用的城市数字化模型。然而,由于建筑物相互遮挡和相机倾斜角度偏差等问题,由航空倾斜影像生成的3D模型可能存在几何缺陷和模糊纹理。为解决这一问题,本文提出了一种基于3D点云重建的拓扑表面优化方法,以改进实景三维模型的几何形状和纹理特征。研究结果表明,本方法有效地弥补了实景三维模型的几何缺陷,改善了模糊纹理,提高了城市地区三维建模的精度和可视化效果。展开更多
针对传统点云滤波算法参数多、端到端的深度学习点云滤波算法计算成本高等问题,设计了一种基于多尺度语义分割网络的点云滤波算法(multi-scale semantic segmenta⁃tion network for point cloud filtering,MSSF)。首先,对点云进行栅格...针对传统点云滤波算法参数多、端到端的深度学习点云滤波算法计算成本高等问题,设计了一种基于多尺度语义分割网络的点云滤波算法(multi-scale semantic segmenta⁃tion network for point cloud filtering,MSSF)。首先,对点云进行栅格化并提取高程、强度等特征,得到多通道特征图;然后,基于多尺度跨层连接模块构建语义分割网络,以特征图为输入提取地面像素,映射到三维点云获取初始高程基准点,经过插值拟合得到地面高程基准面;最后,设置点到该基准面的距离阈值,实现点云滤波。实验结果表明:该算法减少了参数设置,获得了更高的精度,能实现城市区域的Li⁃DAR点云稳健滤波。展开更多
Gridless method is developed for unsteady viscous flows involving moving boundaries. The point distri- bution of gridless method is implemented in an isotropic or anisotropic way according to the features of viscous f...Gridless method is developed for unsteady viscous flows involving moving boundaries. The point distri- bution of gridless method is implemented in an isotropic or anisotropic way according to the features of viscous flows. In the area far away from the body, the traditional cloud of isotropic points is used, while in the adjacent area, the cloud of anisotropic points is distributed. In this way, the point spacing normal to the wall can be small enough for simulating the boundary layer, and meanwhile, the total number of points in the computational do- main can be controlled due to large spacing in other tangential direction through the anisotropic way. A fast mov- ing technique of clouds of points at each time-step is presented based on the attenuation law of disturbed motion for unsteady flows involving moving boundaries. In the mentioned cloud of points, a uniform weighted least- square curve fit method is utilized to discretize the spatial derivatives of the Navier-Stokes equations. The pro- posed gridless method, coupled with a dual time-stepping method and the Spalart-Allmaras turbulence model, is implemented for the Navier-Stokes equations. The computational results of unsteady viscous flows around a NLR7301 airfoil with an oscillating flap and a pitching NACA0012 airfoil are presented in a good agreement with the available experimental data.展开更多
文摘使用UAV系统采集的遥感图像结合倾斜摄影测量技术绘制的城市OSGB(Open Scene Graph Binary)模型是目前广泛采用的城市数字化模型。然而,由于建筑物相互遮挡和相机倾斜角度偏差等问题,由航空倾斜影像生成的3D模型可能存在几何缺陷和模糊纹理。为解决这一问题,本文提出了一种基于3D点云重建的拓扑表面优化方法,以改进实景三维模型的几何形状和纹理特征。研究结果表明,本方法有效地弥补了实景三维模型的几何缺陷,改善了模糊纹理,提高了城市地区三维建模的精度和可视化效果。
文摘针对传统点云滤波算法参数多、端到端的深度学习点云滤波算法计算成本高等问题,设计了一种基于多尺度语义分割网络的点云滤波算法(multi-scale semantic segmenta⁃tion network for point cloud filtering,MSSF)。首先,对点云进行栅格化并提取高程、强度等特征,得到多通道特征图;然后,基于多尺度跨层连接模块构建语义分割网络,以特征图为输入提取地面像素,映射到三维点云获取初始高程基准点,经过插值拟合得到地面高程基准面;最后,设置点到该基准面的距离阈值,实现点云滤波。实验结果表明:该算法减少了参数设置,获得了更高的精度,能实现城市区域的Li⁃DAR点云稳健滤波。
基金Supported by the National Natural Science Foundation of China(10372043,11172134)the Fundingof Jiangsu Innovation Program for Graduate Education(CXZZ11-0192)~~
文摘Gridless method is developed for unsteady viscous flows involving moving boundaries. The point distri- bution of gridless method is implemented in an isotropic or anisotropic way according to the features of viscous flows. In the area far away from the body, the traditional cloud of isotropic points is used, while in the adjacent area, the cloud of anisotropic points is distributed. In this way, the point spacing normal to the wall can be small enough for simulating the boundary layer, and meanwhile, the total number of points in the computational do- main can be controlled due to large spacing in other tangential direction through the anisotropic way. A fast mov- ing technique of clouds of points at each time-step is presented based on the attenuation law of disturbed motion for unsteady flows involving moving boundaries. In the mentioned cloud of points, a uniform weighted least- square curve fit method is utilized to discretize the spatial derivatives of the Navier-Stokes equations. The pro- posed gridless method, coupled with a dual time-stepping method and the Spalart-Allmaras turbulence model, is implemented for the Navier-Stokes equations. The computational results of unsteady viscous flows around a NLR7301 airfoil with an oscillating flap and a pitching NACA0012 airfoil are presented in a good agreement with the available experimental data.
