共查询到20条相似文献，搜索用时 234 毫秒
1.
基于投影体积与八叉树的三维网格模型体素化方法 总被引：1，自引：0，他引：1
使用八叉树结构生成三维多边形网格模型的体素表示,提出了基于投影体积判断体素是否位于模型内部、再利用6-邻接关系快速准确获得模型内部体素的方法,避免了Flooding方法在处理内部封闭空腔时产生的错误.实例测试表明,该文提出的体素化方法能正确处理内部含有空腔的模型,并且效率较高,在三维GIS、地学建模和CAD等体图形学相关的领域具有一定的应用价值. 相似文献
2.
基于TIN的体布尔算法及其地质应用 总被引：3，自引：0，他引：3
提出一种基于TIN的体布尔操作算法,即采用快速碰撞检测方法、改进的三角形求交算法和三角形包含测试算法,能解决复杂地质体的交、并、差等布尔操作。该方法不仅可以有效处理具有侵入、交错等复杂空间关系的地质体建模问题,还适用于基于地质模型的工程分析应用,如开挖模拟等,并在北京市某岩土工程信息系统建设项目中得到了检验。 相似文献
3.
地图叠加分析是一种计算密集型算法,并行化计算是加快算法执行速度的一种有效方法。该文研究分布式环境下的点面图层并行化叠加分析方法与实现。首先根据点面叠加的特点设置并行数据分解的方式,基于分治法分解空间数据,在并行系统下将地理要素分而治之。然后引入双层索引的并行叠加机制,一是对面图层根据Hilbert空间索引的排序方式分发数据,二是对点图层建立四叉树索引,对每一个进行相交运算的多边形进行快速过滤和求交。最后在Linux集群系统下实现该并行算法,其一利用MPI分布式计算环境实现在整体计算框架下的消息通讯模式的并行,其二在每个子节点中实现基于多核OpenMP工具的本地并行化。结果表明,利用双层空间索引分治的方法可实现并行数据分块,各子节点实现独立计算,减少并行系统中的I/O冲突,并行加速比明显。该方法对矢量地图运算的并行化进行了有益的尝试,为大数据时代的空间数据分析提供一种有效的途径。 相似文献
4.
通过研究煤层构造的特征和煤田勘察数据的生产特点,提出一种基于三维格网的虚拟不规则六面体层状包络体动态建模方法,可较好地描述煤层的地质形态;根据煤层格网数据单元格种类(5种类型)的不同和每个单元中无效点分布情况,提出一种基于上述六面体单元的三角网剖分算法,可实时地从数据库中调用分块的层状格网模型数据,经过一次六面体格网单元的遍历,即可将格网数据动态剖分成无缝、不重复、具有方向的三角面片,然后由显示引擎进行实时三维可视化表达。该模型结合了三角网具有利于实体表面三维可视化渲染的特性和四边形规则格网模型有利于通过插值生成的优势,模型构建算法可基于数据库中的数据进行动态渲染,有利于数据更新,使模型简洁、高效,冗余较少。 相似文献
5.
《地理与地理信息科学》2020,(2)
多边形求交是GIS空间分析的基本操作之一,提高海量复杂多边形求交计算效率对大数据时代的空间分析具有重要意义。该文针对海量复杂多边形求交计算耗时长、数据与计算资源分配不均的问题,提出了基于时间预测模型的高性能并行求交方法:首先通过多级包围盒进行二次检测,减少求交对象的一对多关系;然后通过包围盒检测洞、岛的方法减少不参与计算的多边形,优化复杂多边形求交处理流程;最后,通过建立非线性回归模型度量求交运算的计算耗时,并据此优化并行计算负载,有效提高了海量复杂多边形求交效率。 相似文献
6.
体绘制技术在地学3D GIS 可视化中的应用研究 总被引：1，自引：0，他引：1
体绘制技术是目前科学计算可视化研究的一个重要组成部分，对地质体内部属性分布的可视化有重要意义。该文针对地学研究中几何建模和属性建模同样重要的特点，基于一种矢栅一体化的混合数据模型，对地质体表面采用三角面片描述几何形状，对地质体内部采用基于八叉树的自适应网格剖分技术描述内部属性特征。对网格剖分后的体数据，采用体元投射的体绘制技术进行地质体内部属性可视化，显示出很好的效果，具有实际应用意义。 相似文献
7.
王殷行 《地理与地理信息科学》2019,35(1)
目前的三维地质体空间关系模型表达能力较弱,限制了其在空间分析、查询等方面的应用。三维模型的应用与发展迫切需要一种新的底层分解与理论建模解决此类问题。该文基于凸凹理论重新对地质体进行结构定义与空间关系建模,提出了内凸体、外凸体、内缘体、外缘体等构造,并在此基础上建立了三维地质体R7×7空间关系模型,将地质体间空间关系表达能力理论上扩充至249种,实际能够表达40余种空间关系;给出了包容、镶嵌、部分镶嵌等关系的定义并对其进行了模型表达;针对不同应用,给出了R7×7模型的变换模型R(5×5 3×3)等。为能够表达地质体交集的边界长度、交面面积、地质体体积、外缘体体积、镶嵌体积等地质空间重要关系,基于凸凹理论建立了地质体度量关系模型,是矿区地质体拓扑关系查询、空间分析推理等应用的基础模型。给出了模型与地质体模糊理论的相契性分析,二者模型能够相辅相成,相互借鉴使用。 相似文献
8.
《地理与地理信息科学》2016,(5)
提出一种适合于栅格地理数据版权保护的变换域盲水印算法。在分析栅格地理数据及其水印特征的基础上,引入数学映射思想,依据分块数据经傅立叶变换后的首个系数构建数据-水印同步函数,在水印信息与分块数据之间建立起稳健的具有双向定位性质的对应关系;采用量化思想设计水印嵌入规则,并在同步函数的指导下,将对应的水印信息嵌入分块数据中频分量系数的相位和幅值,在水印嵌入过程中建立了水印误差控制机制,以满足栅格地理数据精度要求。实验结果表明,所提出的算法既具有较好的不可感知性,又能有效保证栅格地理数据质量,尤为重要的是,算法对常规攻击、几何攻击及一定程度的复合攻击等具有好的鲁棒性,适用于栅格地理数据的版权保护。 相似文献
9.
北京中关村高新技术企业的集聚与扩散 总被引：25，自引：3，他引：25
本文在调查研究的基础上，对北京中关村新技术集聚区域的企业衍生，集聚与扩散因素，以及企业的异地发展和地区内的商业区化趋势进行了讨论。结论指出，中关村新技术集聚体是我国高新技术产业的重要措施，国家对高新技术企业必须进行及时的有效支持和引导，使之获得健康的持续发展。 相似文献
10.
《地理与地理信息科学》2020,(3)
相对较粗空间分辨率(1 km)的水文网络或水文地理数据集是大尺度水文及陆面过程模型的基本输入数据,需要从数字高程模型中提取高分辨率河网并通过升尺度化获取。MERIT DEM是消除了复合误差的新版全球高分辨率(90 m)数字高程模型,提取的高分辨率河网信息更为精准。DRT是当前国际水文领域常用的高效河网自动升尺度化算法之一,可将高分辨率河网的结构特性完好地输出到粗分辨率河网。该文选取MERIT DEM的中国部分作为数据源,通过DRT升尺度化算法获取全国1°、1/2°、1/4°、1/8°、1/10°、1/16°分辨率的河网数据(流向、河网、流域面积、流距),并采用目视检验、流域面积一致性检验、流距评估等方法综合验证了DRT升尺度数据集的质量。结果表明,DRT算法性能优越,生产的大尺度数据集准确地保护了河道位置、流动方向和流域面积等在高分辨率DEM中描绘的水文特征,将有效降低我国境内流域水文模拟中由水文地形参数化引起的不确定性。 相似文献
11.
Huanping Wu Lingqing Yao Bing Luo 《International journal of geographical information science》2013,27(9):955-964
As increasingly large‐scale and higher‐resolution terrain data have become available, for example air‐form and space‐borne sensors, the volume of these datasets reveals scalability problems with existing GIS algorithms. To address this problem, a kind of serial algorithm was developed to generate viewshed on large grid‐based digital elevation models (DEMs). We first divided the whole DEM into rectangular blocks in row and column directions (called block partitioning), then processed these blocks with four axes followed by four sectors sequentially. When processing the particular block, we adopted the ‘reference plane’ algorithm to calculate the visibility of the target point on the block, and adjusted the calculation sequence according to the different spatial relationships between the block and the viewpoint since the viewpoint is not always inside the DEM. By adopting the ‘Reference Plane’ algorithm and using a block partitioning method to segment and load the DEM dynamically, it is possible to generate viewshed efficiently in PC‐based environments. Experiments showed that the divided block should be dynamically loaded whole into computer main memory when partitioning, and the suggested approach retains the accuracy of the reference plane algorithm and has near linear compute complexity. 相似文献
12.
Andrej Osterman Lucas Benedičič Patrik Ritoša 《International journal of geographical information science》2014,28(11):2304-2327
A rapid and flexible parallel approach for viewshed computation on large digital elevation models is presented. Our work is focused on the implementation of a derivate of the R2 viewshed algorithm. Emphasis has been placed on input/output (IO) efficiency that can be achieved by memory segmentation and coalesced memory access. An implementation of the parallel viewshed algorithm on the Compute Unified Device Architecture (CUDA), which exploits the high parallelism of the graphics processing unit, is presented. This version is referred to as r.cuda.visibility. The accuracy of our algorithm is compared to the r.los R3 algorithm (integrated into the open-source Geographic Resources Analysis Support System geographic information system environment) and other IO-efficient algorithms. Our results demonstrate that the proposed implementation of the R2 algorithm is faster and more IO efficient than previously presented IO-efficient algorithms, and that it achieves moderate calculation precision compared to the R3 algorithm. Thus, to the best of our knowledge, the algorithm presented here is the most efficient viewshed approach, in terms of computational speed, for large data sets. 相似文献
13.
D. C. Mason M. O'Conaill I. McKendrick 《International journal of geographical information science》2013,27(5):429-449
Abstract Kriging is an optimal method of spatial interpolation that produces an error for each interpolated value. Block kriging is a form of kriging that computes averaged estimates over blocks (areas or volumes) within the interpolation space. If this space is sampled sparsely, and divided into blocks of a constant size, a variable estimation error is obtained for each block, with blocks near to sample points having smaller errors than blocks farther away. An alternative strategy for sparsely sampled spaces is to vary the sizes of blocks in such away that a block's interpolated value is just sufficiently different from that of an adjacent block given the errors on both blocks. This has the advantage of increasing spatial resolution in many regions, and conversely reducing it in others where maintaining a constant size of block is unjustified (hence achieving data compression). Such a variable subdivision of space can be achieved by regular recursive decomposition using a hierarchical data structure. An implementation of this alternative strategy employing a split-and-merge algorithm operating on a hierarchical data structure is discussed. The technique is illustrated using an oceanographic example involving the interpolation of satellite sea surface temperature data. Consideration is given to the problem of error propagation when combining variable resolution interpolated fields in GIS modelling operations. 相似文献
14.
以2003年5月29日福州市LandsmETM＋影像为数据源,对2种地表温度空间降尺度算法——EM算法和HUTS算法进行实验、比较与分析,EM算法是利用高空间分辨率的地表比辐射率对低空间分辨率的亮度温度影像进行调节,从而达到提高热红外影像空间分辨率的目的;HUTS算法则是引入了归一化差异植被指数NDVI和地表反照率d,通过在低空间分辨率拟合二者与地表温度LST之间的关系,然后根据其尺度不变性,将该关系应用到高空间分辨率的影像上,从而达到提高热红外影像空间分辨率的目的．研究结果表明：1）2种算法所得结果影像都能在有效提高空间分辨率的同时较好地保持了原始地表温度影像的空间分布特征,达到了较好的降尺度效果;2）以RMSE为定量评价指标,HUTS算法要略优于EM算法,其中,EM算法的RMSE为1．2494,而HUTS算法仅为0．9869． 相似文献
15.
地表温度作为监测陆地表面与大气变化的重要参数,对于研究地表能量平衡和全球气候变化具有重要作用。可见光红外成像辐射仪套件（Visible Infrared Imaging Radiometer Suite,VIIRS）是搭载在新一代对地观测卫星NPP上的一个重要传感器。与其他传感器相比,VIIRS拥有更高的空间分辨率。分裂窗算法是反演地表温度最常用的方法,主要是利用两个热红外通道来反演地表温度,经过多年的研究和改进,发展了多种形式的分裂窗算法。由于过去很少有人利用VIIRS数据对多种分裂窗算法进行对比分析,因此利用VIIRS传感器上M15和M16两个热红外通道数据计算辐亮度和星上亮温,采用多种形式的分裂窗算法反演获得多组地表温度数据,再利用海拉尔野外观测站点的实测数据对结果进行验证,对比各算法精度,得到反演精度较高的算法。结果显示PR84算法的反演误差最大达到1.8 K,其余各算法反演地表温度的RMSE都在1.5 K以内,算法中加入二次项和水汽项可以提高算法精度,其中BL95的算法精度最高达到了1.23 K。研究结果表明,BL95算法更适用于VIIRS热红外数据地表温度反演。 相似文献
16.
大规模地形实时绘制算法 总被引：8，自引：3，他引：5
该文提出一种适合大规模地形实时绘制的简单高效的LOD简化算法。该算法使用一种紧凑有效的规则网格表示方法,优化网格节点的数目,减少可视化过程中的计算量,降低额外内存开销。探讨该算法相关的数据组织、视域裁剪、LOD层次选择、裂缝消除、三角形化等关键问题。实验结果表明,该算法实现简单,内存开销较少,CPU耗费小,对图形卡要求低,能够在普通机器上实现大规模地形的实时漫游。 相似文献
17.
18.
A high-performance cellular automata model for urban simulation based on vectorization and parallel computing technology 总被引：1，自引：0，他引：1
Chang Xia Anqi Zhang Wenting Zhang 《International journal of geographical information science》2018,32(2):399-424
Cellular automata (CA) models can simulate complex urban systems through simple rules and have become important tools for studying the spatio-temporal evolution of urban land use. However, the multiple and large-volume data layers, massive geospatial processing and complicated algorithms for automatic calibration in the urban CA models require a high level of computational capability. Unfortunately, the limited performance of sequential computation on a single computing unit (i.e. a central processing unit (CPU) or a graphics processing unit (GPU)) and the high cost of parallel design and programming make it difficult to establish a high-performance urban CA model. As a result of its powerful computational ability and scalability, the vectorization paradigm is becoming increasingly important and has received wide attention with regard to this kind of computational problem. This paper presents a high-performance CA model using vectorization and parallel computing technology for the computation-intensive and data-intensive geospatial processing in urban simulation. To transfer the original algorithm to a vectorized algorithm, we define the neighborhood set of the cell space and improve the operation paradigm of neighborhood computation, transition probability calculation, and cell state transition. The experiments undertaken in this study demonstrate that the vectorized algorithm can greatly reduce the computation time, especially in the environment of a vector programming language, and it is possible to parallelize the algorithm as the data volume increases. The execution time for the simulation of 5-m resolution and 3 × 3 neighborhood decreased from 38,220.43 s to 803.36 s with the vectorized algorithm and was further shortened to 476.54 s by dividing the domain into four computing units. The experiments also indicated that the computational efficiency of the vectorized algorithm is closely related to the neighborhood size and configuration, as well as the shape of the research domain. We can conclude that the combination of vectorization and parallel computing technology can provide scalable solutions to significantly improve the applicability of urban CA. 相似文献
19.
冰川冰储量不仅是冰川的重要属性,而且是核算冰川水资源及预测冰川变化的基础数据,因此准确计算冰川冰储量及其变化具有重要的理论与现实意义。目前冰川储量估算的主要方法有经验公式法、冰厚模型估算法、探地雷达法;冰川储量相对变化计算方法有实地测量法和遥感监测法。通过系统分析和讨论各计算方法的原理、现状及存在的问题,以期为冰川储量估算提供方法参考。研究表明：对于冰川冰储量计算而言,经验公式法适用于区域性或全球性的冰川储量估算;模型估算法适用于个体或小范围冰川储量估算;探地雷达法适用于人类易到达区域冰川储量的估算。对于冰川冰储量相对变化计算,实地测量法适用于对精度要求高且满足实地测量条件的单条或中小型冰川,遥感监测法适用于全球性冰储量变化估算,但需改进算法和提高数据空间分辨率。目前,随着无人机技术的逐步应用,以及冰川流速等理论模型的提出,为冰川冰储量估算方法的发展提供了新契机。 相似文献
20.
Xiao-Guang Zhou Jun Chen F. Benjamin Zhan Zhilin Li Marguerite Madden Ren-Liang Zhao 《International journal of geographical information science》2013,27(10):1983-2005
Intersection relations are important topological considerations in database update processes. The differentiation and identification of non-empty intersection relations between new updates and existing objects is one of the first steps in the automatic incremental update process for a land parcel database. The basic non-empty intersection relations are meet, overlap, cover, equal and inside, but these basic relationships cannot reflect the complex and detailed non-empty relations between a new update and the existing objects. It is therefore necessary to refine the basic non-empty topological relations to support and trigger the relevant update operations. Such relations have been refined by several researchers using topological invariants (e.g., dimension, type and sequence) to represent the intersection components. However, the intersection components often include only points and lines, and the refined types of 2-dimensional intersection components that occur between land parcels have not been defined. This study examines the refinement of non-empty relations among 2-dimensional land parcels and proposes a computation model. In this model, an entire spatial object is directly used as the operand, and two set operations (i.e., intersection (∩) and difference (\)) are applied to form the basic topological computation model. The Euler number is introduced to refine the relations with a single 2-dimensional intersection (i.e., cover, inside and overlap) and to distinguish the refined types of 2-dimensional intersection components for the relations with multiple intersections. In this study, the cover and overlap relations with single intersections between regions are refined into seven cases, and nine basic types of 2-dimensional intersection components are distinguished. A composite computation model is formed with both Euler number values and dimensional differences. In this model, the topological relations with single intersections are differentiated by the value of the dimension and the Euler number of the resulting set of the whole-object intersection and differences, whereas the relations with multiple intersections are discriminated by the value of the resulting set at a coarse level and are further differentiated by the type and sequence of the whole-object intersection component in a hierarchical manner. Based on the refined topological relations, an improved method for automatic and incremental updating of the land parcel database is presented. The effectiveness of the models and algorithms was verified by the incremental update of a land cover database. The results of this study represent a new avenue for automatic spatial data handling in incremental update processes. 相似文献