共查询到19条相似文献,搜索用时 140 毫秒
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针对传统极区航行通常采用格网导航执行大圆航线,大圆航线上格网航向角不同不利于航行控制以及大圆航线在极区投影图上不完全投影为直线引起固有原理性误差的问题,借鉴中低纬度地区等角航线上地理航向角相等以及在墨卡托投影图上为直线便于航行控制和绘算的思想,提出了一种在极球面投影图中表现为直线的"等角航线"——格网等角航线。在研究双重投影的极球面投影以及格网导航方法的基础上,提出了格网等角航线的定义,推导了航线方程,并根据该航线的航程和航向角计算方法进行航线仿真设计。理论分析和仿真验证表明:航线上格网航向角处处相等,在极区投影图上表现为直线;格网等角航线与大圆航线、大椭圆航线相近,航程较短。因此,极区格网等角航线可以与格网导航方法、极球面投影精确配合应用,适合于极区航行。 相似文献
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极地海区等距离正圆柱投影平面上等角航线的展绘方法 总被引:1,自引:0,他引:1
墨卡托投影由于其纬度渐长的特性导致在极地海区投影存在严重的长度变形,无法在南北纬80°以外高纬度海区航海图中较好地应用。将长度变形程度明显低于墨卡托投影的等距离正圆柱投影作为极地海区的海图投影,研究了该投影平面中等角航线在极地海区的展绘方法。建立了等距离正圆柱投影平面上等角航线方程并对其曲率进行了分析,推导了绘制一般曲线形态的"以直代曲"公式;最后提出了一种可满足给定精度要求的等角航线展绘算法。实验结果表明:该算法简单易行,可在海图编绘规范规定的误差范围内,实现等角航线的精确展绘。 相似文献
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随着GIS应用的深入,人们越来越多地要求在真三维空间中处理问题,怎样将地图中的二维场景转换为视觉上逼真的三维立体空间是三维虚拟技术的关键所在。三维GIS为立体空间信息的展示提供了更加丰富、逼真的平台,使人们将抽象难懂的空间信息进行可视化和直观化。小范围的二维地图的三维可视化景观格局的构建为三维场景的虚拟化提供了底层支持。其中,数字校园的三维可视化建模就是三维地理信息的一个重要分支。本文以辽宁工程技术大学北校区为研究区域,利用3DS MAX对校园的建筑及基础设施进行三维场景建模,以ArcGIS为平台支撑,最终实现了校园景观格局的三维可视化,拓展了属性实时查询及实时实地视觉体验等功能,实现了真正意义上的三维可视化虚拟校园。虚拟化数字校园的构建,可以提高学校知名度,也为学校的后期规划和管理提供了直观的模拟,具有十分重要的潜在价值。 相似文献
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航线的分析与管理是机场全寿命周期里一项重要的工作,航线可视化是分析与管理的前提。通过对各种航线进行研究并结合GIS平台的特点,对机场坐标系与世界坐标系的转化以及投影坐标系的选择进行了讨论,为适应可视化与分析的要求,对航线进行分解,提出通用航线段模型,并结合GIS平台实现了基于上述模型的航线可视化与管理系统。 相似文献
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为解决网络地理信息应用二、三维一体化显示需要,通常做法是处理并存储两套不同投影的地图瓦片数据,一套采用Web墨卡托投影,面向二维地图应用;一套采用经纬度坐标,面向三维地图应用。这在一定程度上降低数据处理效率、浪费存储资源。文中提出一种改进Web墨卡托地图投影方法,并设计一种面向影像地图和DEM数据的瓦片化方法。方法生成的影像地图瓦片数据既能同时面向二维地图和三维可视化场景使用,又有效解决Web墨卡托投影不支持高纬度地区栅格地图表达的缺陷。将新型的地图投影和数据模型通过瓦片地图服务系统进行验证,证明这种新改进的投影和影像,以及DEM瓦片化方法具备较高的实用性。 相似文献
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Abstract Introductory Remarks.—A line of constant bearing was known as a Rhumb line. Later Snel invented the name Loxodrome for the same line. The drawing of this line on a curvilinear graticule was naturally difficult and attempts at graphical working in the chart-house were not very successfuL Consequently, according to Germain, in 1318 Petrus Vesconte de Janua devised the Plate Carree projection (“Plane” Chart). This had a rectilinear graticule and parallel meridians, and distances on the meridians were made true. The projection gave a rectilinear rhumb line; but the bearing of this rhumb line was in general far from true and the representation of the earth's surface was greatly distorted in high latitudes. For the former reason it offered no real solution of the problem of the navigator, who required a chart on which any straight line would be a line not alone of constant bearing but also of true bearing; the first condition necessarily postulated a chart with rectilinear meridians, since a meridian is itself a rhumb line, and for the same reason it postulated rectilinear parallels. It follows, therefore, that the meridians also must be parallel inter se, like the parallels of latitude. The remaining desideratum—that for a true bearing—was attained in I569 by Gerhard Kramer, usually known by his Latin name of Mercator, in early life a pupil of Gemma Frisius of Louvain, who was the first to teach triangulation as a means for surveying a country. Let us consider, then, that a chart is required to show a straight line as a rhumb line of true bearing and let us consider the Mercator projection from this point of view. 相似文献
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路线剖面图是区域地质调查平面图的重要补充,其三维重建可明确反映地质层面的地表展布与地下发育情况,是重建区域三维地质模型的必要数据。针对区域地质调查路线距离长、褶曲多、地质结构复杂的特点,本文建立了一种基于纵向定位线的剖面特征点三维坐标转换模型,提出了地质界线特征点加密算法,能够有效地提高重建路线三维剖面的准确度与光滑度。研发的剖面三维重建模块已应用于多幅实际区调数据工程项目,应用结果表明:该方法可满足区域地质调查建模需求,剖面重建效果良好,具有较好的实用价值和应用前景。 相似文献
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Transect-based three-dimensional road modeling and visualization 总被引:3,自引:0,他引:3
LIQingquan TANGLuliang ZUOXiaoqing LIHanwu 《地球空间信息科学学报》2004,7(1):14-17
On the basis of the study on road elements and the existing three-dimensional road data models, this paper puts forward the transect-based road modeling, resolves the modeling of the simplest road with two road transects, and fulfils the visualization of the road. OpenGL is applied as the tool of visualization. The map texture technology, LOD algorithm and dynamic multi-differentiating texture technology are of benefit to the construction of 3D road GIS, and improve the speed of roaming and effective visualization. This paper also disusses the combination of 2D digitall road map and 3D road scene, and the dynamic response between them. Finally, on the basis of the research on the transect-based road model, this paper develops the three-dimen-sional road geographic information system called virtual road ( VRoad ), which not only supplies road designers with a set of tool which can turn the designed 2D road data into 3D road and the high road assistant function area in computer, but also supplies the road management with a set of tool which can realize the road real time and interactive roaming, high-efficiency management. 相似文献
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Web墨卡托投影是目前网络地图服务广泛采用的地图投影方法,但是该投影在使用之初便引起广泛争议,而且关于该投影目前仍缺乏统一的理解与认识。本文以Web墨卡托投影的定义为基本依据,推导了其变形公式,深入分析了该投影的变形特点,并从变形差异、坐标值、等角航线投影后形状等3个方面与墨卡托投影进行比较分析,在此基础之上归纳出关于Web墨卡托投影性质的3点结论。 相似文献