共查询到20条相似文献，搜索用时 171 毫秒
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陈明晶 《测绘与空间地理信息》2024,(4):162-165+168
为满足公路工程的勘察设计及后期现场施工的需要,建立适宜的平面坐标系是一项极具必要性与重要性的工作。基于高斯投影变形的2个主要影响因素以及二者之和可部分抵消的特征,结合实例分析了复杂地形条件下公路工程平面坐标系的建立过程;同时,为了克服常规方法建立过程存在以平均代表整体、变形检验方式又存在“以点代面”的局限性,研究了应用DEM检验投影变形的方法,可实现全测区范围内投影变形量的统计分析与可视化展示,为在复杂地形条件下建立公路工程平面坐标系提供了参考。实例表明该方法在复杂地形条件下是适用的、有效的,具有一定的理论与现实意义。 相似文献
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在独立坐标系的建立过程中,投影面的选取是一个非常重要的问题。传统的投影面选取方法是选取各个控制点的平均高程面作为投影面,这种做法虽然简单,但是在某些高海拔地区或山区往往由于控制点少且分布不均匀,无法较为准确地计算投影变形来选取投影面。提出了一种基于航天飞机雷达地形测绘任务全球地形起伏数据的可视化选取投影面的方法,可以直观、准确地选取测区投影高程面。与传统方法相比,该方法能够在测区内均匀地选取格网点,克服了传统方法控制点少的缺点,并且利用GMT(generic mapping tools)软件将投影变形按区域直观地呈现出来,实现了投影面选取的可视化。 相似文献
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投影网格算法从投影后的网格入手,通过反算获取投影前的位置,进而完成3维地形的绘制.分析了传统投影网格算法存在的缺陷,提出了改进的投影网格算法,并对改进后的算法进行了测试和分析.认为投影网格算法具有简单直观、易构建高分辨率地形的优点,最后指出了需要进一步研究的方向. 相似文献
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虚拟地形投影与地球同步卫星定位解全集 总被引：1，自引：0，他引：1
程芦颖 《武汉大学学报(信息科学版)》2005,30(7):629-631
基于地球同步卫星定位原理,分析了当利用数字化地形图提供测站高程时测站的多解和无解现象。利用观测方程给出了判断多解和无解的依据,提出了虚拟地形投影方法,获得了“亚稳定”收敛点的定位解子集π2。 相似文献
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针对目前常用的几种世界地图投影中,南北极区的投影变形较大,且各大洲与南北极区的相对位置关系描述得并不十分准确的问题,需要寻找一种适用于小比例尺世界地图的投影方法,克服传统小比例尺世界地图在极区附近投影变形较大的缺点,保证各大陆的轮廓完整性以及投影变形。以墨卡托投影及其衍生投影为研究对象,对比分析了正轴、横轴和斜轴墨卡托投影,发现斜轴墨卡托投影在新极点选取合理的情况下,可以较好地表达世界范围内包括南北极区在内的主要陆地形状与它们之间的相对位置关系。给出了斜轴墨卡托投影应用于小比例尺世界地图时的地理坐标,并展绘了新极点下的世界地图,对比分析了新投影下的主要陆地面积变形情况。在斜轴墨卡托投影展绘的世界地图上,可以从全局视角描述北极航道、跨越北极区域的航空线路、一带一路等线路,为研究与分析提供可视化载体。 相似文献
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针对嫦娥三号将携带巡视器在月面展开科学探测任务过程中对高精度撞击坑地形的需求,提出了透视投影下基于SFS的月面撞击坑地形恢复算法。采用Lommel-Seeliger反射模型模拟月表反射,得到透视投影下的反射方程,通过撞击坑边缘点梯度约束以及地形表面连续性约束,将反射方程正则化,最终通过求解,实现了撞击坑在透视投影下的三维恢复。采用模拟影像和真实月面影像对算法的正确性和可行性进行了测试。实验表明,所提出的算法能够有效的进行透视投影下的撞击坑地形恢复,且精度高于现有SFS算法。 相似文献
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在建立大型水利工程GPS控制网的内业处理过程中,为满足地形测图和已有地形图利用的精度要求,降低高斯投影变形和高程面投影变形对平差成果的影响,经常会在水利测绘中采用分段投影的方法.其中,测区抵偿高程面和移动中央子午线的选择是最困难的工作.本文对引大济岷工程GPS控制网的分段投影计算进行了简单剖析.分析结果表明:选取分段测... 相似文献
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Daniel “daan” Strebe 《制图学和地理信息科学》2013,40(3):260-276
ABSTRACTSometimes map projection designers need to create equal-area projections to best fill the projections’ purposes. However, unlike for conformal projections, few transformations have been described that can be applied to equal-area projections to develop new equal-area projections. Here, I survey area-preserving transformations, giving examples of their applications and proposing an efficient way of deploying an equal-area system for raster-based Web mapping. Together, these transformations provide a toolbox for the map projection designer working in the area-preserving domain. 相似文献
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针对基于面模型的战场地形要素建模与可视化的不足,提出利用体素模型实现战场环境地形要素的建模与可视化方法和基本思路。对基于特征点的双重移动立方体算法进行改进,实现体素地形的可视化表达,引入体素地形可视化的影响因子便于对体素地形可视化效果的控制,通过实验进行分析,得出最佳取值空间。 相似文献
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The virtual globe is the default visualization for Digital Earth applications, but it can only show one half of the Earth. This article introduces user-adjustable, on-the-fly projection of georeferenced raster images for web mapping and web GIS applications. This technique allows users to center a map on arbitrary locations, while still seeing the entire Earth surface. Modern web mapping libraries can apply map projection transformations to vector data in the browser, but they do not currently support the projection of raster images at interactive frame rates. We use the cross-platform WebGL (Web Graphics Library) graphics pipeline for hardware-accelerated projection of raster data in web browsers. Two algorithmic techniques – inverse per-fragment projection, and combined forward per-triangle and inverse per-fragment projection – for georeferenced raster imagery are documented. The resulting raster maps combine the ease of use and flexibility of interactive virtual globes with the ability to show the entire Earth. The adjustable projection of raster imagery allows users to observe global phenomena that are difficult to visualize on virtual globes or traditional maps with static projections. 相似文献
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借助复变函数理论讨论了常用等角投影及其解析变换的复变函数表示;给出了高斯投影、墨卡托投影和等角圆锥投影正反解的复变函数表示模型;在此基础上系统地推导出了高斯投影、墨卡托投影和等角圆锥投影间解析变换的复变函数表达式.这些复数变换公式是含参考椭球第一偏心率的符号形式,可解决不同参考椭球下的变换问题.与传统的实数变换公式相比,其结构更为简单、理论更为严密. 相似文献
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An adaptable equal-area pseudoconic map projection 总被引：1，自引：1，他引：0
Daniel “daan” Strebe 《制图学和地理信息科学》2016,43(4):338-345
Equivalence (the equal-area property of a map projection) is important to some categories of maps. However, unlike conformal projections, completely general techniques do not exist for creating new, computationally reasonable equal-area projections. The literature describes many specific equal-area projections and a few equal-area projections that are more or less configurable, but flexibility is still sparse. This work describes a new, highly configurable equal-area projection system consisting of arcs of concentric circles, placing it in the pseudoconic class. The system uses a novel technique to hybridize the Bonne pseudoconic projection and the Albers conic projection, subsuming many existing projections as degenerate cases. With the resulting system and the technique used to develop it, map projection designers will have greater choice in tailoring the projection to the need. The system may be particularly suited to maps that dynamically adapt to changing scale and region of interest, such as required for online maps. 相似文献
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Daniel “daan” Strebe 《制图学和地理信息科学》2018,45(6):529-538
Equivalence (the equal-area property of a map projection) is important to some categories of maps. However, unlike for conformal projections, completely general techniques have not been developed for creating new, computationally reasonable equal-area projections. The literature describes many specific equal-area projections and a few equal-area projections that are more or less configurable, but flexibility is still sparse. This work develops a tractable technique for generating a continuum of equal-area projections between two chosen equal-area projections. The technique gives map projection designers unlimited choice in tailoring the projection to the need. The technique is particularly suited to maps that dynamically adapt optimally to changing scale and region of interest, such as required for online maps. 相似文献
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The adaptive composite map projection technique changes the projection to minimize distortion for the geographic area shown on a map. This article improves the transition between the Lambert azimuthal projection and the transverse equal-area cylindrical projection that are used by adaptive composite projections for portrait-format maps. Originally, a transverse Albers conic projection was suggested for transforming between these two projections, resulting in graticules that are not symmetric relative to the central meridian. We propose the alternative transverse Wagner transformation between the two projections and provide equations and parameters for the transition. The suggested technique results in a graticule that is symmetric relative to the central meridian, and a map transformation that is visually continuous with changing map scale. 相似文献