A new algorithm based on Region Partitioning for Filtering candidate viewpoints of a multiple viewshed     

TianXing Yu  LiYang Xiong  Min Cao  ZhiHui Wang  YiChi Zhang 《International journal of geographical information science》2016,30(11):2171-2187

Selecting the set of candidate viewpoints (CVs) is one of the most important procedures in multiple viewshed analysis. However, the quantity of CVs remains excessive even when only terrain feature points are selected. Here we propose the Region Partitioning for Filtering (RPF) algorithm, which uses a region partitioning method to filter CVs of a multiple viewshed. The region partitioning method is used to decompose an entire area into several regions. The quality of CVs can be evaluated by summarizing the viewshed area of each CV in each region. First, the RPF algorithm apportions each CV to a region wherein the CV has a larger viewshed than that in other regions. Then, CVs with relatively small viewshed areas are removed from their original regions or reassigned to another region in each iterative step. In this way, a set of high-quality CVs can be preserved, and the size of the preserved CVs can be controlled by the RPF algorithm. To evaluate the computational efficiency of the RPF algorithm, its performance was compared with simple random (SR), simulated annealing (SA), and ant colony optimization (ACO) algorithms. Experimental results indicate that the RPF algorithm provides more than a 20% improvement over the SR algorithm, and that, on average, the computation time of the RPF algorithm is 63% that of the ACO algorithm.  相似文献   

The seismic signatures of the surge wave from the 2009 Xiaolin landslide‐dam breach in Taiwan     

Zheng‐yi Feng 《水文研究》2012,26(9):1342-1351

The catastrophic Xiaolin landslide occurred on 9 August 2009, after Typhoon Morakot struck Taiwan. This landslide formed a dam that subsequently breached, burying and flooding the village of Xiaolin. Seismic signals were induced by the landslide and dam breaching and recorded at the Jiaxian broadband seismic station in Taiwan. The time‐frequency spectra for the data from this station were analysed to extract the seismic characteristics of the landslide and to deduce the timing of processes associated with the landslide dam‐break flooding. The duration of the river blockage, the time of the dam breach, the duration of the surge wave and the mean speed of the surge wave were estimated, and the hydrological implications of the flood behaviour were interpreted. The spectral characteristics of the different stream discharges were also studied. Stream water level/discharge is closely related to the frequency of the seismic signals. The broadband stations are particularly useful for flood monitoring due to their ability to continuously record measurements and their high sensitivity. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

黄河下游悬河决溢风险评价指标体系的构建   总被引：1，自引：0，他引：1  

夏富强  康相武  吴绍洪  杨勤业  马欣  刘自强 《地理科学进展》2004,23(5):17-24

针对黄河下游存在决溢风险的现状,根据环境因素对悬河决溢的作用机制,通过对地质构造评价在决溢风险评价中的地位、洪水要素对悬河决溢的影响、不同决溢模式的形成机理进行了分析,从而建立了一套较为系统的黄河下游悬河决溢风险评价指标体系。文中提出了以下观点：1.将洪水要素纳入评价指标体系; 2. 决溢风险评价分为地质构造环境背景评价和决溢情景评价两部分; 3.决溢情景评价与决溢模式相结合; 4. 以不同决溢模式的形成机理为基础确定评价因子。  相似文献   

黄河下游不同洪水情景决溢风险评价   总被引：3，自引：2，他引：1  

夏富强  康相武  吴绍洪  杨勤业  马欣  杨佩国  李晓东 《地理研究》2008,27(1):229-240

本文提出黄河下游悬河决溢风险的影响因素应当包含水沙运动、区域地壳稳定性、河势演变和堤防稳定性4个方面,并据此建立了指标体系和基于GIS技术的多层次模糊综合评判模型,对不同洪水情景下黄河下游的决溢风险进行了评价。结果表明:(1)决溢风险随着洪水量的增大而增高;(2)决溢风险随河型的沿程变化而降低;(3)决溢风险较大的河段集中在游荡型河段,游荡型河段南岸风险高于北岸;(4)弯曲型河段北岸决溢风险高于南岸;这些结论能够应用于黄河下游河道的治理与防汛抗洪的实践。研究表明:本研究的评价指标体系和方法,能够用于解决黄河下游的决溢风险问题; GIS空间分析技术能够量化不同空间位置的决溢风险,客观地反映不同空间位置决溢风险的差别,对于指导防洪和河道治理的实践具有重要的现实意义。  相似文献   

局部结构约束下的宽基线影像直线特征匹配     

严少华  陈敏  赵怡涛  谭贵红  赵曦 《测绘通报》2020,(5):51-54

针对宽基线影像视角变化导致现有直线特征匹配方法难以获得可靠匹配结果的问题，本文在局部结构约束下提出了一种对影像视角变化具有较强稳健性的直线特征匹配方法。首先，对影像进行直线特征提取并按照一定的规则进行特征编组；其次，基于直线特征几何结构关系构建视角不变特征区域，计算其特征描述符并进行相似性度量，获取直线特征初始匹配结果；然后，利用初始匹配结果中的直线特征区域顶点坐标关系构建约束条件剔除错误匹配；最后，设计直线特征扩展匹配算法，提高直线特征匹配率。试验结果表明，与传统直线特征匹配算法相比，本文方法在有显著视角变化的宽基线影像之间能够获得更多的同名直线特征和更高的匹配正确率。  相似文献   

面向三维重建的无人机航拍路径规划技术研究综述北大核心CSCD     

吴昌松  彭业萍  曹广忠  闫妍 《测绘通报》2022,(8):98-103

在对城市大场景的三维重建中,使用无人机在低空采集图像成为主流方案,通过优化无人机的航拍路径,能有效提高场景三维重建的精度和效率。为此,近年来致力于发展新的无人机航拍路径规划技术和方法,包括视点规划和飞行路径规划,取得了显著成果。本文通过概述无人机航拍路径规划的基本流程,详述基于二维模型、三维模型和未知环境下的航拍路径规划技术,对比不同路径规划方法的优缺点,探讨无人机航拍路径规划的发展趋势,为开展无人机航拍控制、大场景三维重建研究提供重要参考。  相似文献