地形TIN中地理实体拓扑关系表达     

曹学伟  王殷行  陶秋香 《测绘科学》2009,34(5)

传统地形TIN离散、独立的三角形结构限制了空间实体、空间关系的表达能力,分析和操作也比较困难,应用大多限制在可视化、渲染和光照分析等方面。由于不可能通过简单地扩展和改进现有模型来满足TIN中对空间实体关系表达的需求,从面向对象的角度出发,利用单纯剖分理论对TIN进行了实体划分和拓扑建模,使TIN具有了地理对象结构从而能够进行地理实体的表达与分析,建立了对象化不规则三角网(OTIN)与Euler示性数方向模型(EDM),使得TIN不但可以较好地表达地形起伏信息,还具有实体性和对象性,便于进行空间查询与分析。  相似文献   

利用数字高程模型生成地形三维仿真图   总被引：2，自引：0，他引：2  

高力 《地球科学与环境学报》2000,22(3):59-62

研究了以地面数字高程模型 (DEM )作为原始资料 ,采用透视变换和模拟光照的模拟算法 ,生成某一地区的三维实景图 ,实现地形仿真。给出了试验结果 ,试验表明这种方法可产生逼真的三维仿真图。  相似文献   

On the definition of the flow width for calculating specific catchment area patterns from gridded elevation data     

Giovanni Battista Chirico  Andrew W. Western  Rodger B. Grayson  Günter Blschl 《水文研究》2005,19(13):2539-2556

Specific catchment area (SCA) patterns are commonly computed on grids using flow direction algorithms that treat the flow as coming from a point source at the pixel centre. These algorithms are all ambiguous in the definition of the flow width to be associated with a pixel when computing the SCA. Different methods for computing the flow width have been suggested, without giving an objective reason. In the few cases where this issue has been specifically discussed, the flow width is derived from subjective analysis and incorrect conceptualizations. This paper evaluates alternative approaches for defining the flow width when computing SCA patterns using the D∞ and D8 algorithms, by comparing theoretical and computed SCA patterns on sloping planes, inward and outward cones. Two new methods of defining the flow width are also analysed for both the D∞ and D8 algorithms. The performances of the different methods are discussed in relation to two dimensionless parameters: (1) the global resolution, defined as the ratio of a characteristic length of the study area to the grid size and (2) the upslope area resolution, defined as the ratio of the theoretical SCA to the grid size. The optimal methods are identified by specific threshold values of these dimensionless parameters. We conclude that assuming the flow width invariant and equal to the grid size is generally the best approach in most practical circumstances, both for the D∞ and D8 algorithm. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

地形表面反射波镜面效应分析     

刘健  寇静行  喻峰  李明 《测绘学院学报》2009,(2)

地形是影响电磁波地表传播的重要因素,地形反射波对接收机天线的镜面效应直接影响相关电磁发射接收系统的电磁兼容性,甚至造成系统无法正常工作。通过对地表反射波产生镜面效应的原理进行分析,建立了天线藕合单向链路传播通道反射波地表镜面效应点分析判断模型,并对其应用进行了探索研究。  相似文献   

DEM地形可视化自增强技术     

王春  ;王占宏  ;李鹏  ;李伟涛 《测绘软科学研究》2009,(1):38-45

地形可视化是地形表达、虚拟地理环境与虚拟仿真领域中重要的组成部分。论文首先回顾了DEM地形分析与表达技术，然后重点阐述了如何利用DEM自身解译的地形信息，增强DEM地形等高线图、地形晕渲图等地形可视化效果，突出不同地形特征与细节，实现可量测性和直观性为一体的3维地形表达，提供用户更为直观、准确的地形认知。  相似文献   

The Last Glacial Maximum British–Irish Ice Sheet: a reconstruction using digital terrain mapping     

P. T. Fretwell  D. E. Smith  S. Harrison 《第四纪科学杂志》2008,23(3):241-248

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Terrain correcting Australian gravity observations using the national digital elevation model and the fast Fourier transform     

J. F. Kirby  W. E. Featherstone 《Australian Journal of Earth Sciences》2013,60(4):555-562

The release of a digital elevation model (DEM) for Australia on a 9″ (～250 m) grid has enabled the computation of gravimetric terrain corrections thus allowing the computation of complete Bouguer anomalies across the continent. The terrain correction was calculated through a two‐dimensional fast Fourier transform algorithm applied to a linear, planar approximation of the terrain‐correction formula, and with a constant topographic density of 2670 kg.m^‐3. The technique was applied to two datasets in order to test for instabilities in the terrain‐correction algorithm: the original 9″ DEM, and a 27″ DEM averaged from the 9″ data. The 27″ terrain corrections were compared with values supplied by the Australian Geological Survey Organisation in Tasmania: 86% of these data were found to agree within 3.91 μm.s^‐2; 98% agreed to within 5.32 μm.s^‐2 (1σ).  相似文献   

简化数字地形分析软件(SimDTA)及其应用——以嫩江流域鹤山农场区的坡位模糊分类为例   总被引：3，自引：0，他引：3  

秦承志  卢岩君  包黎莉  朱阿兴  邱维理  程维明 《地球信息科学学报》2009,11(6):737-743

为了在精细尺度下定量刻画地形特征,给地理建模提供更准确的定量地形参数,克服当今应用领域中常用商业软件的局限性,本研究讨论了面向栅格DEM的"简化数字地形分析软件"(SimDTA 1.0版本)。SimDTA实现了诸多计算局域和区域地形属性、定量描述地形部位信息的现有算法,以及新建算法。例如,针对一个实际的应用问题--坡位模糊分类,采用以坡位典型位置作为原型的新思路,在SimDTA中,实现了一个新的坡位模糊分类方法,能够克服现有其他方法忽略空间位置信息等问题。这一坡位模糊分类方法和SimDTA中实现的其他功能相结合,形成了一套完整的坡位模糊分类流程。本文通过在东北嫩江流域一个小区的实际应用和讨论来体现SimDTA的有效性和实用性。  相似文献   

基于图像分层搜索的地形轮廓匹配算法设计          下载免费PDF全文

于家城  晏磊  贺翔 《海洋测绘》2008,28(6):33-35

应用图像分层搜索序贯判决算法，进行海底地形轮廓匹配（TERCOM）算法设计。建立了上下两层同时匹配的比较控制逻辑，既提高了匹配速度，又减少了误匹配，增强了地形二维匹配的健壮性。应用实际海图原始数据进行仿真。结果表明，该算法在保持匹配速度的同时具有较高的匹配精度和抗差特性。  相似文献   

Topographic analysis for the prairie pothole region of Western Canada     

Dean A. Shaw  Al Pietroniro  L.W. Martz 《水文研究》2013,27(22):3105-3114

The unique topography of the pothole region of the North American prairies creates challenges for properly determining basin contributing area. Numerous depressions or potholes within the landscape impound runoff. However, potholes can ‘fill‐spill’ resulting in surface water connections between the potholes. Surface water connectivity between potholes ultimately influences basin contributing area. Currently, automated methods, such as landscape analysis tools, treat depressions in the landscape as artifacts and simply fill the depressions to delineate a drainage basin. Using this method to calculate contributing area assumes that all surface storage has been satisfied (threshold) and the drainage basin will contribute 100% of its area for all runoff events. However, most runoff events in the prairie pothole region are pre‐threshold events that contribute only a portion of surface runoff to the outlet. These pre‐threshold events have surface storage that varies because of antecedent water levels and have a variable or dynamic potential to store further runoff in the basin. Government agencies have developed methodologies for determining pre‐threshold contributing areas, but these methodologies do not incorporate current technologies and, as a result, have limitations. We propose an automated method for determining contributing area that incorporates the fill‐spill of prairie potholes. The algorithm, which uses the D‐8 drainage direction method, automates a methodology for identifying and quantifying runoff contributing area. Any algorithm that determines pre‐threshold contributing area, must allow the DEM to be filled in an incremental manner. This will simulate increasing pond levels, and the resulting decrease in available storage in the basin, in response to runoff events. The SPILL algorithm is an iterative solution that increases the magnitude of input runoff events and records the decreasing change in available surface storage and the increase in contributing area until the storage threshold is reached and the contributing area reaches 100%. Through application of the algorithm on prairie pothole region basins, we test proposed conceptual curves that describe a hypothesized non‐linear relationship between decreasing potential storage in the landscape and contributing area. Results indicate that the proposed conceptual curves represent the relationship between potential surface storage and contributing area in the test basins very well. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献