共查询到17条相似文献,搜索用时 109 毫秒
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光照模型是影响数字地貌晕渲的一个关键因素.在参照传统晕渲着色规则的基础上,结合数字地貌晕渲的投影方式及视点、光源的设置方法,从理论上分析了Lambert漫反射模型、基于坡向光照模型的特征;分别利用规则物体和地形数据对这两种光照模型所产生的效果进行了实验和对比;结果表明漫反射模型更适合起伏较平缓地区的晕渲,基于坡向的光照模型更能突出山体的起伏特征.最后结合理论分析讨论了产生这种实验结果的原因并提出了3点改进意见. 相似文献
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在总结传统手工晕渲经验和方法的基础上,深入分析了计算机地貌晕渲的原理,着重研究了坡度和坡向对地貌晕渲中阴影强弱和明暗程度的影响,提出了变比例调整高程和晕渲笔调调整两种方法。实验表明,利用本文方法能有效改善地貌晕渲图的三维立体视觉效果。 相似文献
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基于规则格网DEM的坡度坡向分析研究 总被引:2,自引:0,他引:2
坡度坡向是描述地貌特征的重要参数,从晕渲图制作的角度出发,对不同数据情况、不同坡度坡向计算方法得到的坡度坡向进行对比,研究制图区域数据分辨率,地区类型对坡度坡向计算的影响。 相似文献
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光照模型是地貌晕渲图能够在2维平面获得地貌3维立体形态的主要原因.在计算机图形学的基础上,推导了基于数字高程模型的晕渲光照模型计算公式;通过对相关文献公式的分析,指出了数字地貌晕渲采用的光照模型与传统地貌晕渲几何光学原理的关系;并对该模型下地表灰度值的计算与变化进行了分析研究. 相似文献
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以晕渲中的几何光学原理为基础,利用坡度坡向计算格网点灰度的方法,对晕渲中的光源设置和应用情况进行研究,提出利用地貌特征设置和调整光源方位及个数的方法,并针对不同的数据情况分析了光源应用的情况,对几种光源的设置和调整应用情况进行了说明和实验。本文对数字晕渲中光源的设置和应用的研究,提高了晕渲中光源使用技术的灵活性,可以有效改善数字晕渲图的质量。 相似文献
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阐述了数字城市晕渲地势电子地图的制作流程,对基于DEM的晕渲底图制作及在ArcGIS环境下进行电子地图配置过程进行了详细的分析和论述,为晕渲地势电子地图制作提供了完整的技术路线及解决方案。 相似文献
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Gully boundary extraction based on multidirectional hill‐shading from high‐resolution DEMs 下载免费PDF全文
The gully boundary, which distinguishes gully from non‐gully areas, is a significant geomorphologic feature for research on gully development and gully erosion. This study presents a new method based on multidirectional hill‐shading maps, which identify the gully (i.e., shadow area) from inter‐gully (i.e., non‐shadow area). These shadows obtained from various illumination azimuths are merged; consequently, the border of the shadows, which is the gully boundary line, can be achieved. In this process, two key parameters, namely, altitude and azimuth of light, affect the accuracy of gully boundary extraction. The experiments in Yaojiawan area of China show that the method of average median slope of all sampling profiles across the gully boundary is effective and practical for light altitude selection. Moreover, the six azimuths are sufficient for gully boundary extraction in a loess hilly area. The application in the Madigou area indicates the replicability and rationality of this method. A comparison with the positive‐negative terrain and slope variation method confirms a higher accuracy of gully boundary extraction by the proposed method in terms of visual interpretation, length, and contour‐matching difference with reference to manually digitalized results. Accuracy assessment indicates that the proposed method is applicable for gully boundary extraction based on high‐resolution DEMs. 相似文献
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In this study, landslide susceptibility assessments were achieved using logistic regression, in a 523 km2 area around the Eastern Mediterranean region of Southern Turkey. In reliable landslide susceptibility modeling, among others, an appropriate landslide sampling technique is always essential. In susceptibility assessments, two different random selection methods, ranging 78–83% for the train and 17–22% validation set in landslide affected areas, were applied. For the first, the landslides were selected based on their identity numbers considering the whole polygon while in the second, random grid cells of equal size of the former one was selected in any part of the landslides. Three random selections for the landslide free grid cells of equal proportion were also applied for each of the landslide affected data set. Among the landslide preparatory factors; geology, landform classification, land use, elevation, slope, plan curvature, profile curvature, slope length factor, solar radiation, stream power index, slope second derivate, topographic wetness index, heat load index, mean slope, slope position, roughness, dissection, surface relief ratio, linear aspect, slope/aspect ratio have been considered. The results showed that the susceptibility maps produced using the random selections considering the entire landslide polygons have higher performances by means of success and prediction rates. 相似文献