Direct georeferencing of airborne LiDAR data in national coordinates

The topographic mapping products of airborne light detection and ranging (LiDAR) are usually required in the national coordinates (i.e., using the national datum and a conformal map projection). Since the spatial scale of the national datum is usually slightly different from the World Geodetic System 1984 (WGS 84) datum, and the map projection frame is not Cartesian, the georeferencing process in the national coordinates is inevitably affected by various geometric distortions. In this paper, all the major direct georeferencing distortion factors in the national coordinates, including one 3D scale distortion (the datum scale factor distortion), one height distortion (the earth curvature distortion), two length distortions (the horizontal-to-geodesic length distortion and the geodesic-to-projected length distortion), and three angle distortions (the skew-normal distortion, the normal-section-to-geodesic distortion, and the arc-to-chord distortion) are identified and demonstrated in detail; and high-precision map projection correction formulas are provided for the direct georeferencing of the airborne LiDAR data. Given the high computational complexity of the high-precision map projection correction approach, some more approximate correction formulas are also derived for the practical calculations. The simulated experiments show that the magnitude of the datum scale distortion can reach several centimeters to decimeters for the low (e.g., 500 m) and high (e.g., 8000 m) flying heights, and therefore it always needs to be corrected. Our proposed practical map projection correction approach has better accuracy than Legat’s approach,¹ but it needs 25% more computational cost. As the correction accuracy of Legat’s approach can meet the requirements of airborne LiDAR data with low and medium flight height (up to 3000 m above ground), our practical correction approach is more suitable to the high-altitude aerial imagery. The residuals of our proposed high-precision map projection correction approach are trivial even for the high flight height of 8000 m. It can be used for the theoretical applications such as the accurate evaluation of different GPS/INS attitude transformation methods to the national coordinates.     

公开版地图符号的标准化研究

以公开版地图符号和表示方法的多样性为研究对象,结合公开版地图的应用需求,提出公开版地图符号标准化研究的基本原则、符号标准的设计流程、标准化符号的发布应用等整体思路,对增强公开版地图的系统性、易读性、美观性,提高公开版地图的制作效率具有很强的现实意义。     

通用地图符号表达机制的研究

地理信息共享是地理信息系统（GIS）研究中的一大热点,其中地图符号的共享尤为重要。针对目前地图符号共享所面临的主要障碍,文中从地图符号的定义出发,利用图元参数法建立通用地图符号表达模型,并采用XML语言完成符号的描述,最后通过符号配置,生成由通用几何图形组成的符号化结果,从而实现地图符号的共享。在vc＋＋环境下开发通用地图符号化组件和符号制作软件,通过实例符号的制作和应用,验证该地图符号表达机制的可行性和通用性,符号化效果理想。     

The Military Map of the United Kingdom and its Impact on Mapping in the Twentieth Century

Abstract

Considerable attention has been paid in the literature to the changing style of Ordnance Survey mapping in the twentieth century. However, little has been written about the origins of the characteristic appearance of the first multi-colour editions, other that the Ordnance Survey used a military edition that was already in production. The distinctive style grew out of the work of a committee established in 1892 by the War Office to consider future army requirements for a map of the UK. This paper explores the work of the committee and its long-term implications for the look of mapping in the twentieth century.     

驻村帮扶“一张图”设计与实现——以明溪县为例

结合明溪县驻村帮扶工作的开展情况,探索基于地理信息技术下开展驻村帮扶工作的关键技术,依托"数字明溪地理空间框架"的建设成果,设计并实现了明溪县驻村帮扶"一张图",实现了明溪县驻村帮扶信息可视化、透明化和精准化的管理,增强了明溪县驻村帮扶项目管理的科学性。     

基于“天地图·永定”的永定旅游地图服务网设计与实现

"天地图·永定"是永定区统一、权威、标准的地理信息公共平台,本文利用"天地图·永定"提供的丰富的数据服务和二次开发接口,开发了永定旅游地图服务网,实现了永定旅游服务和"天地图"的融合,为游客提供便捷、丰富的旅游服务,对永定区的旅游发展起到了一定的推动作用。     

Point grid map: a new type of thematic map for statistical data associated with geographic points

ABSTRACT

Social, economic, and environmental statistical data associated with geographic points are currently globally available in large amounts. When conventional thematic maps, such as proportional symbol maps or point diagram maps, are used to represent these data, the maps appear cluttered if the point data volumes are relatively large or cover a relatively dense region. To overcome these limitations, we propose a new type of thematic map for statistical data associated with geographic points: the point grid map. In a point grid map, an input point data set is transformed into a grid in which each point is represented by a square grid cell of equal size while preserving the relative position of each point, which leads to a clear and uncluttered appearance, and the grid cells can be shaded or patterned with symbols or diagrams according to the attributes of the points. We present an algorithm to construct a point grid map and test it with several simulated and real data sets. Furthermore, we present some variants of the point grid map.     

基于SVG的地质灾害在线应急态势符号设计与实现

针对地质灾害的应急响应及处理技术系统成为近几年地质灾害领域研究的热点和重点,然而在已有的研究中,应急决策系统多为桌面应用程序,难以满足应急部署的实时性和灵活性,同时现有的地质灾害应急技术中对地质灾害应急态势标绘技术的研究较少,而应急部署又十分需要态势符号的支撑。为此,本文在分析多种在线符号绘制语言特点的基础上,提出了一种基于SVG的地质灾害在线应急态势标绘方法,对地质灾害应急需要使用的态势标绘符号进行了算法设计与系统实现。现场应用案例表明:该方法可以实现地质灾害应急态势符号的在线交互式标绘,为决策者快速、实时部署应急方案提供有效支撑。     

现代地图语言

地图符号发展到今天,已经超越了其符号本身,应当把它当作一种语言来研究,即地图语言。地图语言使人们使用地图进行空间认识更加贴近现实,使地理空间信息的传输更加准确、生动和形象。文中主要对现代地图语言的形成,现代地图语言的主要表现形式即视觉符号、听觉符号和触觉符号,以及地图语言的本质即视觉变量、听觉变量和触觉变量进行了探讨。