三维地图符号视觉参量研究

在常规地图符号参量体系上,通过引入动态特征、交互式操作等方面的参量,提出了三维地图符号的视觉参量,它由状态、动态变化和操作三个方面的参量组成,并采用认知实验研究了这些符号参量在质量特征、数量特征、关系特征以及动态特征等信息表达上的应用及功效.     

基于TIN的公路三维表面模型建立方法

公路三维表面模型是公路三维设计的基础,其关键是设计模型和地表模型的叠加运算。本文提出了一种基于TIN的地面模型和道路设计模型叠加算法,基本原理是把参考模型的边界多边形当作约束边界线插入操作模型,在保持参考模型拓扑关系不变的条件下对其进行局部LOP优化,然后删除位于参考模型边界线内的点和三角形。本文算法具有实现简单、速度快和运算稳定的特点,已成功应用在公路三维可视化设计中。     

Mixed-Layer Depth Determination in the Barcelona Coastal Area From Regular Lidar Measurements: Methods, Results and Limitations

Regular aerosol backscatter measurements using an elastic-backscatter lidar were performed between May 2000 and December 2002 in Barcelona (Spain), within the framework of the European project EARLINET (European Aerosol Research Lidar Network). The mixed-layer depth was one of the major parameters to be retrieved. Three derivative methods have been tested in this complex coastal area using the range-squared-corrected lidar signal: (1) the minimum of its first derivative, (2) the minimum of its second derivative, and (3) the minimum of the first derivative of its logarithm. The second method was found to give statistically the best results when compared to radiosoundings, and was used to process the whole dataset. A number of 162 days and 660 profiles averaged over 30 min have been examined. Between 1000 and 1500 UTC, the mixed-layer depth oscillates between 300 and 1450 m in summer and between 390 and 1420 m in winter. The standard deviation for this portion of the day is 180 and 256 m, respectively, in summer and winter. In summer, low heights (mainly limited to 400–800 m) are associated with large mesoscale compensatory subsidence over the sea and to the thermal internal boundary-layer formation. The strong coastal and orographic influences and the climatological settling of Barcelona determine the complexity of the boundary-layer dynamics and the high heterogeneity of the lidar signals. In many cases, single lidar analyses do not allow an unambiguous determination of the mixed-layer depth. Two diurnal cycle measurements are discussed together with synoptic maps, backtrajectories and radiosoundings in order to outline the complexity of the area and the limitations of the methods.     

地形三维可视化在川藏公路典型路段中的应用

利用地形平面图的数据和有关区域地质资料的数字化方法实现川藏公路典型路段三维地形的显示和实时浏览,为进一步利用地理信息系统进行研究区地层岩性、地质构造和地质灾害分布的叠加分析进行地质灾害研究提供了矢量化的地形底图。川藏公路典型路段的三维地形可视化工作对于川藏铁路的选线、绕避不良地质灾害的发生和开凿铁路隧道的位置选择等将会有一定的参考价值。     

大规模地形实时可视化算法

大规模地形实时可视化在GIS、虚拟现实、游戏、仿真等领域有着广泛的应用。文中在总结现有地形数据简化算法的基础上,提出了一种基于数据分块、动态调度以及与视点相关的地形实时可视化算法,实现了大规模地形的快速漫游。运用视景体裁剪、三角形条带组织以及边界裂缝消除、视觉光滑处理等手段,提高了地形漫游的效率与可视化效果。     

野外地形匹配和重力测量自动布点系统

野外重力测量是精化全球和局部重力场模型的重要手段之一。以我国1∶5万数字高程数据库为基础,结合地形景观生成技术,构建了野外地形匹配可视化及重力测量的自动布点系统。在重力测量布点方案的设计中,给于用户施测区域所属地形及布点点位以直观的认知形式。尤其对于地形较为复杂的山区、特大山区,可对外业测量点位进行优化,减少外业的工作量,提高重力测量的外业工作效率。     

基于地学信息服务的Internet 3维 GIS：GeoEye 3D

随着Internet、分布式计算以及计算机图形学的飞速发展,开发基于Internet的3维GIS系统已成为可能。这3种技术的有力结合为地学领域开创了一个崭新的时代,促使网络GIS的概念由“地学数据服务”提高到“地学信息处理服务”的新阶段,不仅地学数据,地学信息处理功能也可以分布在基于客户／服务器的架构上,用户可以根据不同的需求“租用”和组合来自于Internet的不同功能。基于这一概念和作者提出的构件注册模型,我们从1998年开始着手研究和开发新一代的Internet 3维GIS：GeoEye 3D。这一系统集成了GIS、3维可视化、分布式计算及网络通信等技术,允许用户通过标准Internet浏览器来应用远程功能对远程和本地数据进行可视化分析。阐述了地学信息处理服务概念和构件注册模型以及GeoEye 3D的系统架构、算法和应用实例。     

高原地形对四川盆地西部突发性暴雨影响的数值试验

用η模式对1995年8月24日四川盆地西部一次突发性暴雨进行了数值模拟和地形减半、无地形数值试验。由对数值模拟与试验的结果分析得出:（1）青藏高原地形有利于高原东麓暴雨区的扩大与强度加大。（2）高原地形对其以北的天气系统南伸和以南的天气系统北扩有阻碍作用。（3）高原地形可影响高原附近以东地区的物理特征场分布,从而影响暴雨区的位置与强度。     

Metallogenic geodynamic background of Mesozoic gold deposits in granite-greenstone terrains of North China Craton

The spatial distribution map of 65 mid-large gold-deposits hosted in the granite-greenstone terrains of the North China Craton is first drawn. These gold deposits mainly concentrate in the Mesozoic remobilized Yinshan-Yan-shan-Liaoning-Jilin intracontinental collisional orogenic belt, the northern Qinling and the Jiaodong Mesozoic collisional orogenic belts, and the Mesozoic intracontinental fault-magmatic belts developed along the Taihangshan and the Tan-Lu faults; their mineralizing time is predominantly Jurassic-Cretaceous, i. e. the Yanshanian. The metallogenic geodynamic background is exactly the compression-to-extension transition regime during continental collision. The results are partly from the project entitled “The main types of gold mineralizations in China and their metallogenic model” (89-El) supported by the Ministry of Metallurgical Industry of China, and projects “Geology and metallogenesis of the main type gold deposits in East Chinaⁿ” (Grant No. 9488010) and “Study on ore-forming fluids of the Wangfeng gold deposit, Xinjiang” supported by the National Natural Science Foundation of China (Grant No. 49672119).     

Landscape Roughness Parameters for Sherwood Forest – Experimental Results

The aim of this work is to present experimentally evaluated effective roughnesses (zoe) of a partly forested landscape. Although the ratio of boundary-layer height to obstacle size was only of the order of 50, there still seemed to exist a height range of 75–200 m where surface-layer similarity was approximately valid. Attempts were made to use conventional wind profile analysis to evaluate zoe, but the small height range and the large number of variables initially led to unacceptable uncertainties. Fixing the displacement height zd, rather than fitting it, reduced the data scatter to an acceptable level. The profile-derived roughness lengths zop obtained in this way were in good agreement with previous work, and with an alternative roughness length estimate zof for which flux-derived profile parameters u* and * were used. This implies that the profile-derived roughnesses were consistent with the measured surface-layer momentum flux. Comparison of both roughness estimates also yielded an improved estimate of the displacement height. Besides this, the authors tested a landscape roughness evaluation method which makes use of the gustiness parameter Tu = u/U in the surface layer. The results obtained by this method were in fair agreement with the profile-derived data. In previous work, the gustiness method was advocated because it could be used at relatively low levels, perhaps even within the roughness sub-layer. At the present measuring site, this was not the case as the gustiness method was only valid in an approximate way, and for a limited height range.