共查询到20条相似文献，搜索用时 62 毫秒
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无缝化GIS,由于其跨度巨大,导致曲平面之间的矛盾突出,这种矛盾不能通过简单的一种投影方法实现,因为地图投影有其固定的区域限定、变形规律和应用需求,应该通过动态投影和投影集成的方式,建立投影支持库解决。 相似文献
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一种基于标准纬线变更的瓦片索引方法 总被引：1，自引：0，他引：1
分析了常见的电子地图投影变形特征,提出了一种间断性变更标准纬线的非固定倍率瓦片索引方法。该方法在瓦片索引过程中,通过自动变更标准纬线来减小地图投影的变形程度。该方法在长度变形、角度变形和面积变形方面均具有整体变形较小的特点。在区域性电子地图表达中具有良好的变形可控性,具有较高的应用价值。 相似文献
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地图的数学基础包含了地图投影方式,在地图集设计中以地理空间数据集为基础,通过对各种多源数据的分析、处理、加工,使多源数据投影变换到一个统一地理坐标系中,达到数据使用的统一性。简要介绍了地图投影的原理及投影变形对地图的影响,阐述了在专题地图设计中选择确定地图投影的方式和对投影转换的应用。 相似文献
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针对中国地理格网(1°、10°等多级格网系统)的分割方法,设计了一种适合该格网系统的新型地图投影——分层组合投影。从微分几何的观点出发,把地球椭球按等纬度分割成若干层圆台,分别建立每个圆台的投影模型,即可得到一种地图投影。这种投影还可根据格网间隔的不同进行细分,从而发展成为一种适合多分辨率格网模型的动态地图投影。通过对该投影进行变形计算表明,该投影可以保持等角,而且面积和长度变形都很小,特别是在高纬度地区,与Mercator投影相比变形明显减小。 相似文献
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结合沪杭高速铁路,从满足投影长度小于10mm/km的要求出发,探讨了高速铁路控制网投影的选取方法,得出了一些有益的结论。 相似文献
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胡毓钜 《武汉大学学报(信息科学版)》1986,(3)
本文指出了地图投影分类系统中还有若干“空白”有补充的必要和可能,并以多圆柱投影为例,阐述了它的建立原理,用三个实例说明了多圆柱投影的建立过程。作者认为补充这一类投影既使地图投影分类得到进一步充实,同时对教学活动也有积极意义。 相似文献
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为了获得形式多样的地形可视化效果,投影方式的选择至关重要,通过对正投影、透视投影、渐进式投影和平斜投影等多种投影方式的原理与方法进行研究,分析了各种投影方式的适用性及其获得的地形可视化效果,为应用实践提供了有益借鉴。 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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借助复变函数理论讨论了拉格朗日投影与常用等角投影间的解析变换问题,导出了拉格朗日投影正反解的复变函数表达式,在此基础上系统地建立了该投影与高斯投影、墨卡托投影和等角圆锥投影间解析变换的复变函数表示模型。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投影变换问题,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,便于实际使用。 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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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
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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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Steven E. Greco 《地球空间信息科学学报》2013,16(4):288-293
ABSTRACTConceptually, the theory and implementation of “map projection” in geographic information system (GIS) technology is difficult to comprehend for most introductory students and novice users. Compounding this difficulty is the concept of a “map projection file” that defines map projection parameters of geo-spatial data. The problem of the “missing projection file” appears ubiquitous for all users, especially in practice where data is widely shared. Another common problem is inadvertent misapplication of the “Define Projection” tool that can result in a GIS dataset with an incorrectly defined map projection file. GIS education should provide more guidance in differentiating the concepts of map projection versus projection files by increasing understanding and minimizing common errors. A novel pedagogical device is introduced in this paper: the seven possible states of GIS data with respect to map projection and definition. The seven possible states are: (1) a projected coordinate system (PCS) that is correctly defined, (2) a PCS that is incorrectly defined, (3) a PCS that is undefined, (4) a geographic coordinate system (GCS) that is correctly defined, (5) a GCS that is incorrectly defined, (6) a GCS that is undefined, and (7) a non-GCS. Recently created automated troubleshooting tools to determine a missing map projection file are discussed. 相似文献