A numerical method is put forward in this paper, using the boundary element method （BEM） to model 3D terrain effects on magnetotelluric （MT） surveys, Using vector integral theory and electromagnetic field boundary...A numerical method is put forward in this paper, using the boundary element method （BEM） to model 3D terrain effects on magnetotelluric （MT） surveys, Using vector integral theory and electromagnetic field boundary conditions, the boundary problem of two electromagnetic fields in the upper half space （air） and lower half space （earth medium） was transformed into two vector integral equations just related to the topography ： one magnetic equation for computing the magnetic field and the other electrical equation for computing the electrical field. The topography integral is decomposed into a series of integrals in a triangle element. For the integral in a triangle element, we suppose that the electromagnetic field in it is the stack of the electromagnetic field in the homogeneous earth and the topography response which is a constant; so the computation becomes simple, convenient and highly accurate. By decomposition and computation, each vector integral equation can be calculated by solving three linear equations that are related to the three Cartesian directions. The matrix of these linear equations is diagonally dominant and can be solved using the Symmetric Successive Over-Relaxation （SSOR） method. The apparent resistivity curve of MT on two 3D terrains calculated by BEM is shown in this paper.展开更多
3D terrain visualization of geographic information systems(GIS)data has become an important issue in recent years.This is due to the emergence of new geo-browsers such as Google Earth,widely popular among users.The av...3D terrain visualization of geographic information systems(GIS)data has become an important issue in recent years.This is due to the emergence of new geo-browsers such as Google Earth,widely popular among users.The availability of 3D representation tools has increased the demand for 3D terrain visualization.The aim of this paper is to review the literature related to the 3D terrain visualization of GIS data from the first map produced until the online mapping era.The reviews are divided into four different sections:manual visualization of 3D terrain,automated visualization of 3D terrain,online visualization of 3D terrain,and software for visualizing 3D terrain.Then,the paper compares between the different types of systems developed by various authors based on the capabilities and the limitations of the system.Some of the techniques have their own strengths and limitations which solve the problem in 3D terrain visualization.However,the research on improving 3D terrain visualization is still ongoing.This is due to the popularity of online environments and mobile devices that render 3D terrain.This review paper will help interested users understand the current state of 3D terrain visualization of GIS data in a better way.展开更多
Fast and accurate measurement of the volume of earthmoving materials is of great signifcance for the real-time evaluation of loader operation efciency and the realization of autonomous operation. Existing methods for ...Fast and accurate measurement of the volume of earthmoving materials is of great signifcance for the real-time evaluation of loader operation efciency and the realization of autonomous operation. Existing methods for volume measurement, such as total station-based methods, cannot measure the volume in real time, while the bucket-based method also has the disadvantage of poor universality. In this study, a fast estimation method for a loader’s shovel load volume by 3D reconstruction of material piles is proposed. First, a dense stereo matching method (QORB–MAPM) was proposed by integrating the improved quadtree ORB algorithm (QORB) and the maximum a posteriori probability model (MAPM), which achieves fast matching of feature points and dense 3D reconstruction of material piles. Second, the 3D point cloud model of the material piles before and after shoveling was registered and segmented to obtain the 3D point cloud model of the shoveling area, and the Alpha-shape algorithm of Delaunay triangulation was used to estimate the volume of the 3D point cloud model. Finally, a shovel loading volume measurement experiment was conducted under loose-soil working conditions. The results show that the shovel loading volume estimation method (QORB–MAPM VE) proposed in this study has higher estimation accuracy and less calculation time in volume estimation and bucket fll factor estimation, and it has signifcant theoretical research and engineering application value.展开更多
In the preprocessing phase, the global terrain model is partitioned into blocks with their feature points being picked out to generate TIN model for each terrain block, then the multi-resolution models of terrain orga...In the preprocessing phase, the global terrain model is partitioned into blocks with their feature points being picked out to generate TIN model for each terrain block, then the multi-resolution models of terrain organized in the form of quad-tree is created bottom-up. Cracks between terrain blocks are avoided by inserting vertices to form common boundaries. At run-time, a view-dependent LOD algorithm is used to control the loading and unloading of the proper blocks by an additional synchronous thread. To eliminate the artifacts created by LOD transitions, geomorphing is used in real-time. These rendering strategies increase the throughput of GPU and avoid imbalance of load among CPU, GPU and Disk I/O. Experimental results show that the system can perform visually smooth rendering of large-scale terrain scenes with fine quality at an average rate of 80 fps.展开更多
基金This paper is supported by the National Natural Science Foundation ofChina (No .40344002) .
文摘A numerical method is put forward in this paper, using the boundary element method （BEM） to model 3D terrain effects on magnetotelluric （MT） surveys, Using vector integral theory and electromagnetic field boundary conditions, the boundary problem of two electromagnetic fields in the upper half space （air） and lower half space （earth medium） was transformed into two vector integral equations just related to the topography ： one magnetic equation for computing the magnetic field and the other electrical equation for computing the electrical field. The topography integral is decomposed into a series of integrals in a triangle element. For the integral in a triangle element, we suppose that the electromagnetic field in it is the stack of the electromagnetic field in the homogeneous earth and the topography response which is a constant; so the computation becomes simple, convenient and highly accurate. By decomposition and computation, each vector integral equation can be calculated by solving three linear equations that are related to the three Cartesian directions. The matrix of these linear equations is diagonally dominant and can be solved using the Symmetric Successive Over-Relaxation （SSOR） method. The apparent resistivity curve of MT on two 3D terrains calculated by BEM is shown in this paper.
文摘3D terrain visualization of geographic information systems(GIS)data has become an important issue in recent years.This is due to the emergence of new geo-browsers such as Google Earth,widely popular among users.The availability of 3D representation tools has increased the demand for 3D terrain visualization.The aim of this paper is to review the literature related to the 3D terrain visualization of GIS data from the first map produced until the online mapping era.The reviews are divided into four different sections:manual visualization of 3D terrain,automated visualization of 3D terrain,online visualization of 3D terrain,and software for visualizing 3D terrain.Then,the paper compares between the different types of systems developed by various authors based on the capabilities and the limitations of the system.Some of the techniques have their own strengths and limitations which solve the problem in 3D terrain visualization.However,the research on improving 3D terrain visualization is still ongoing.This is due to the popularity of online environments and mobile devices that render 3D terrain.This review paper will help interested users understand the current state of 3D terrain visualization of GIS data in a better way.
基金Supported by National Key R&D Program of China(Grant Nos.2020YFB1709901 and 2020YFB1709904)National Natural Science Foundation of China(Grant Nos.51975495 and 51905460)+1 种基金Guangdong Provincial Basic and Applied Basic Research Foundation(Grant No.2021A1515012286)Guiding Funds of Central Government for Supporting the Development of the Local Science and Technology(Grant No.2022L3049).
文摘Fast and accurate measurement of the volume of earthmoving materials is of great signifcance for the real-time evaluation of loader operation efciency and the realization of autonomous operation. Existing methods for volume measurement, such as total station-based methods, cannot measure the volume in real time, while the bucket-based method also has the disadvantage of poor universality. In this study, a fast estimation method for a loader’s shovel load volume by 3D reconstruction of material piles is proposed. First, a dense stereo matching method (QORB–MAPM) was proposed by integrating the improved quadtree ORB algorithm (QORB) and the maximum a posteriori probability model (MAPM), which achieves fast matching of feature points and dense 3D reconstruction of material piles. Second, the 3D point cloud model of the material piles before and after shoveling was registered and segmented to obtain the 3D point cloud model of the shoveling area, and the Alpha-shape algorithm of Delaunay triangulation was used to estimate the volume of the 3D point cloud model. Finally, a shovel loading volume measurement experiment was conducted under loose-soil working conditions. The results show that the shovel loading volume estimation method (QORB–MAPM VE) proposed in this study has higher estimation accuracy and less calculation time in volume estimation and bucket fll factor estimation, and it has signifcant theoretical research and engineering application value.
基金Supported by National High Technology Research and Development Program(863) of China (2006AA01Z319)
文摘In the preprocessing phase, the global terrain model is partitioned into blocks with their feature points being picked out to generate TIN model for each terrain block, then the multi-resolution models of terrain organized in the form of quad-tree is created bottom-up. Cracks between terrain blocks are avoided by inserting vertices to form common boundaries. At run-time, a view-dependent LOD algorithm is used to control the loading and unloading of the proper blocks by an additional synchronous thread. To eliminate the artifacts created by LOD transitions, geomorphing is used in real-time. These rendering strategies increase the throughput of GPU and avoid imbalance of load among CPU, GPU and Disk I/O. Experimental results show that the system can perform visually smooth rendering of large-scale terrain scenes with fine quality at an average rate of 80 fps.
