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361.
Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements: 2003 总被引:1,自引:1,他引:0
P. K. Seidelmann B. A. Archinal M. F. A’Hearn D. P. Cruikshank J. L. Hilton H. U. Keller J. Oberst J. L. Simon P. Stooke D. J. Tholen P. C. Thomas 《Celestial Mechanics and Dynamical Astronomy》2005,91(3-4):203-215
Every three years the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the
directions of the north poles of rotation and the prime meridians of the planets, satellites, and asteroids. This report introduces
a system of cartographic coordinates for asteroids and comets. A topographic reference surface for Mars is recommended. Tables
for the rotational elements of the planets and satellites and size and shape of the planets and satellites are not included,
since there were no changes to the values. They are available in the previous report (Celest. Mech. Dyn. Astron., 82, 83–110, 2002), a version of which is also available on a web site. 相似文献
362.
实验数据表明土体参数具有很大的空间变异性,而随机场理论为模拟土体参数空间变异性提供了有效途径。因为传统的谱表示法(SRM)无法正确模拟多维多元随机场参数间的互相关性,提出支持向量机法(SVM)与SRM耦合的方法。SVM是基于统计学习理论和结构风险最小化原理基础上的通用机器学习方法,它在解决小样本、非线性和高维模式识别问题中表现出诸多优势。以土体抗剪强度参数:黏聚力c和内摩擦角φ为例,通过实验证明二者之间存在天然负相关性,即为二维二元随机场。结果表明,在样本数量较少的条件下,基于耦合算法模拟随机场不仅能有效地描述变量的自相关性,而且能够准确地描述变量间的互相关性,为解决小样本条件下模拟多维多元随机场提供了一种有效的方法。 相似文献
363.
Çetin Koca 《International journal of geographical information science》2014,28(9):1821-1847
Terrain rendering is a crucial part of many real-time applications. The easiest way to process and visualize terrain data in real time is to constrain the terrain model in several ways. This decreases the amount of data to be processed and the amount of processing power needed, but at the cost of expressivity and the ability to create complex terrains. The most popular terrain representation is a regular 2D grid, where the vertices are displaced in a third dimension by a displacement map, called a heightmap. This is the simplest way to represent terrain, and although it allows fast processing, it cannot model terrains with volumetric features. Volumetric approaches sample the 3D space by subdividing it into a 3D grid and represent the terrain as occupied voxels. They can represent volumetric features but they require computationally intensive algorithms for rendering, and their memory requirements are high. We propose a novel representation that combines the voxel and heightmap approaches, and is expressive enough to allow creating terrains with caves, overhangs, cliffs, and arches, and efficient enough to allow terrain editing, deformations, and rendering in real time. 相似文献
364.
Javier Lacasta Francisco Javier Lopez-Pellicer Aneta Florczyk Francisco Javier Zarazaga-Soria Javier Nogueras-Iso 《International journal of geographical information science》2014,28(9):1964-1987
Jurisdictional domains are legal divisions of the Earth’s surface frequently used in classification and search systems for location-based queries. However, there are few compilations of jurisdictional domains that include their evolution. One of the causes is the complexity of their generation. As an advance in this area, this paper describes a process that facilitates the creation of knowledge bases containing the evolution of jurisdictional domains. As application example, this paper presents the creation of a jurisdictional knowledge base of Spain with its evolution between 1830 and 2011. 相似文献
365.
A multiple representation data structure for dynamic visualisation of generalised 3D city models 总被引:2,自引:0,他引:2
In this paper, a novel multiple representation data structure for dynamic visualisation of 3D city models, called CityTree, is proposed. To create a CityTree, the ground plans of the buildings are generated and simplified. Then, the buildings are divided into clusters by the road network and one CityTree is created for each cluster. The leaf nodes of the CityTree represent the original 3D objects of each building, and the intermediate nodes represent groups of close buildings. By utilising CityTree, it is possible to have dynamic zoom functionality in real time. The CityTree methodology is implemented in a framework where the original city model is stored in CityGML and the CityTree is stored as X3D scenes. A case study confirms the applicability of the CityTree for dynamic visualisation of 3D city models. 相似文献
366.
367.
扼要分析了地理数据库的概念和当前社会对地理信息服务的需求,据此研究了以地理要素符号化表达为核心的地理数据库的构建和维护方法,对地形图的自动缩编进行了尝试,解决了在桌面软件上使用不同层次的地理信息服务等问题。 相似文献
368.
基于MapGIS编制城镇土地利用现状图的研究 总被引:1,自引:0,他引:1
唐秋祥 《测绘与空间地理信息》2011,34(1):136-138
阐述了城镇土地利用现状图的编制原则和编制方法。详细介绍了基于MapGIS软件下制作城镇土地利用现状图的步骤,并给出了实例。 相似文献
369.
曾菲 《测绘与空间地理信息》2011,34(4):161-163
对执行《国家基本比例尺地图图式第2部分:1∶5 000 1∶10 000地形图图式》(GB/T 20257.2-2006)过程中有关图外整饰存在问题进行探讨,结合在汕头全要素项目中遇到的案例加以分析和说明,并建议建立与图式匹配的标准字库和规则库。 相似文献
370.
提出了一种拓扑关系和方向关系组合描述框架,在统一的框架下研究拓扑和方向关系。采用9交模型描述拓扑关系,方向关系矩阵模型表达方向关系,并给出了有意义的方向片组合,将两者统一到一个框架下进行描述。在统一描述框架下,拓扑关系与方向关系相互约束。阐述了7个定理及其证明,描述了拓扑关系与方向关系之间的相互约束,实现拓扑关系和方向关系有效性的相互检测。拓扑关系和方向关系组合描述能够提高空间关系描述的准确性和有效性。 相似文献