基于四叉树的LOD地形模型及其数据组织方法研究   总被引：2，自引：0，他引：2  

姚慧敏  崔铁军  邵世新  袁建峰 《地理信息世界》2007,5(6):56-59

针对大规模地形可视化中地形数据的组织方法进行了研究,设计了一种基于线性四叉树结构的静态LOD地形模型,采用重采样、分层分块的方法来组织任意格网大小的海量地形数据。在此基础上,对数据动态调度过程中的相关问题进行了分析,地形块的快速索引、边界裂缝消除等方法的运用,提高了地形漫游的效率与可视化效果。实验结果表明,该研究成果可以满足大规模地形数据的实时可视化操作要求。  相似文献   

地形起伏度最佳分析区域预测模型   总被引：3，自引：0，他引：3  

张锦明  游雄 《遥感学报》2013,17(4):728-741

地形起伏度指分析区域内最高点和最低点之差,反映宏观区域内地形的起伏特征,是描述地貌形态的定量指标。确定最佳分析区域是地形起伏度提取算法的核心步骤,以及决定地形起伏度提取结果有效性的关键。本文以全国范围内随机选取的78个实验区域、三种不同尺度的DEM数据作为实验对象,分别进行系列分析区域尺度的地形起伏度计算,建立了基于微观地形特征因子的地形起伏度最佳分析区域预测模型。实验表明：相同区域、不同尺度的DEM数据提取的地形起伏度存在差异,DEM尺度相差较小时,地形起伏度的差异也较小;地形起伏度和实验区域的最大高程、区域高差、平均坡度和平均坡度变率等地形特征因子存在强相关关系;当置信水平为0.05时,预测模型拟合参数的准确率达到95%以上,证明预测模型可以有效地确定最佳分析区域的取值范围。  相似文献   

Multi‐visibility maps of triangulated terrains     

N. Coll  N. Madern  J. A. Sellarès 《International journal of geographical information science》2013,27(10):1115-1134

Visibility computation on terrain models is an important research topic with many applications in Geographical Information Systems. A multi‐visibility map is the subdivision of the domain of a terrain into regions that, according to different criteria, encodes the visibility with respect to a set of view elements. We present an approach for visualising approximated multi‐visibility maps of a triangulated terrain corresponding to a set of view elements by using graphics hardware. Our method supports heterogeneous sets of view elements containing points, segments, polygonal chains and polygons and works for weak and strong visibility. Moreover, we are also able to efficiently solve approximated point and polygonal region multi‐visibility queries. To illustrate the usefulness of our approach we present results obtained with an implementation of the proposed algorithms.  相似文献   

Morphometric characterisation of landform from DEMs     

Daming Wang  Shawn W. Laffan  Yu Liu  Lun Wu 《International journal of geographical information science》2013,27(2):305-326

We describe a method of morphometric characterisation of landform from digital elevation models (DEMs). The method is implemented first by classifying every location into morphometric classes based on the mathematical shape of a locally fitted quadratic surface and its positional relationship with the analysis window. Single‐scale fuzzy terrain indices of peakness, pitness, passness, ridgeness, and valleyness are then calculated based on the distance of the analysis location from the ideal cases. These can then be combined into multi‐scale terrain indices to summarise terrain information across different operational scales. The algorithm has four characteristics: (1) the ideal cases of different geomorphometric features are simply and clearly defined; (2) the output is spatially continuous to reflect the inherent fuzziness of geomorphometric features; (3) the output is easily combined into a multi‐scale index across a range of operational scales; and (4) the standard general morphometric parameters are quantified as the first and second order derivatives of the quadratic surface. An additional benefit of the quadratic surface is the derivation of the R ² goodness of fit statistic, which allows an assessment of both the reliability of the results and the complexity of the terrain. An application of the method using a test DEM indicates that the single‐ and multi‐scale terrain indices perform well when characterising the different geomorphometric features.  相似文献   

Comparing the terrain reversal effect in satellite images and in shaded relief maps: an examination of the effects of color and texture on 3D shape perception from shading     

Arzu Çöltekin  Julien Biland 《International Journal of Digital Earth》2019,12(4):442-459

Terrain reversal effect (TRE) causes reversed 3D shape perception in satellite images and shaded relief maps (SRMs), and introduces difficulties in identifying landforms such as valleys and ridges. With this paper, in a controlled laboratory experiment, we compare how well 27 participants could identify valleys and ridges over 33 locations using SRMs, color satellite images and grayscale satellite images. The main depth cue is shadow both in vertical-view images and SRMs. However, the presence of texture and color in images also affect 3D shape perception. All our participants experience the illusion strongly: with the SRMs, it is very severe (2% accuracy), with grayscale images low but considerably better than SRMs (17.6% accuracy), and slightly worse with color imagery (15.3% accuracy). These differences between SRMs and imagery suggest that the participants who are able to bypass the illusion consciously or subconsciously interpret the photographic information. We support this observation further with a cue-strength analysis. Furthermore, we provide exploratory analyses of the effects of expertise, global convexity bias, and bistable perception. Our original empirical observations serve towards a better understanding of this visual illusion, and contribute towards nuanced and appropriate solutions to correcting for TRE differently for satellite images and SRMs.  相似文献   

TERRA: Terrain Extraction from elevation Rasters through Repetitive Anisotropic filtering     

《International Journal of Applied Earth Observation and Geoinformation》2020

Over the past decades, several filters have been developed to derive a Digital Terrain Model (DTM) from a Digital Surface Model (DSM), by means of filtering out aboveground objects such as vegetation. In this filtering process, however, one of the major challenges remains to precisely distinguish sharp terrain features, e.g. ridges, agricultural terraces or other anthropogenic geomorphology such as open-pit mines, riverbanks or road ramps. Hence, loss of elevation data around terrain edges (and consequent smoothing) is very common with existing algorithms. In terraced landscapes, the preservation of precise geomorphology is of key importance in digital terrain analyses, such as hydrologic and erosion modelling, or automatic feature recognition and inventorying. In this work, we propose a new filtering method called TERRA (Terrain Extraction from elevation Rasters through Repetitive Anisotropic filtering). The novelty of the algorithm lies within its usage of terrain aspect to guide the anisotropic filtering direction, therefore maximising the preservation of terrain edges. We derived six DTMs from DSMs using UAV Structure from Motion (SfM) photogrammetry, laser altimetry and satellite sources (grid resolutions ranging from 0.1–1.0 m). The results indicated a close agreement of DTMs filtered using the TERRA algorithm and reference DTMs, while terrace risers were well preserved even under thick canopies of vines and trees. Compared to existing filtering approaches, TERRA performed well in minimising Type I errors (false ground removal), while Type II errors occurred locally where vegetation was covering the terrace edges. Given the promising filtering performance, and supported by the minimal requirements of parameterisation and computation, the TERRA algorithm could be a useful tool in DTM preparation for digital terrain analysis of agricultural terraces and similar hillslopes characterised by a complex mosaic of sharp terrain and non-terrain features.  相似文献   

基于地形精化的金星重力场模型VGM2013          下载免费PDF全文

徐璐媛  李斐  鄢建国 《地球物理学报》2014,57(8):2484-2494

高精度金星重力场的获取,是金星探测的重要内容.本文利用最新的金星地形和重力模型,通过高通滤波后的残差地形（RTM）并在考虑均衡改正的情况下改进了重力的短波成分,最终提出了一个新的金星重力模型VGM2013,该模型赤道分辨率达10 km量级,大大高于现有的金星重力场模型,最终结果是金星表面重力加速度和重力扰动.研究中同时发现金星在Airy-Heiskanen均衡模型下的全球最优补偿深度为30 km,金星地壳的密度可能小于当前认为的2700~2900 kg·m^-3.VGM2013模型的结果可为将来的金星探测器定轨和着陆导航提供参考,作为重力计算的先验模型.但由于该模型没有包含短波重力观测信息,不建议直接用于更小尺度的地质和地球物理解释.  相似文献   

The influence of topography on the cloud-to-ground lightning density in South Brazil   总被引：2，自引：0，他引：2  

V. Bourscheidt  O. Pinto Junior  K.P. Naccarato  I.R.C.A. Pinto 《Atmospheric Research》2009,91(2-4):508-513

A comparative analysis between cloud-to-ground (CG) lightning density and terrain parameters (altitude and terrain slope) in South Brazil is presented. This region is characterized by a contrasting topography, where a mountain chain separates lower (depression) and higher (plateau) landscapes. The altitude and terrain slope data were obtained from the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM). Two years of CG lightning data (from June 2005 to May 2007) obtained by the Brazilian Lightning Detection Network (BrasilDAT) were used in the study. To avoid intracloud contamination, positive CG flashes with peak currents less than 20 kA were removed from the data set. A relative detection efficiency model was used to correct the lightning data. The results indicate that, for localized areas (following the mountain shape) within this region of Brazil, the CG lightning density is correlated with the terrain slope and not the altitude. This suggests that terrain slope has more influence than altitude on the thunderstorm occurrence and lightning activity. In addition, a temporal analysis shows that over high altitude regions the diurnal variation (amplitude) of lightning activity is stronger and the peak occurs 1 h earlier than over low altitude regions.  相似文献   

祁连山冬季降雪个例模拟分析(Ⅰ):降雪过程和地形影响   总被引：2，自引：1，他引：1       下载免费PDF全文

孙晶  楼小凤  胡志晋 《高原气象》2009,28(3)

利用部分改进了的中尺度数值模式MM5V3对2006年2月7～8日祁连山一次降雪过程进行了三重双向影响嵌套模拟研究,模式对雪带分布的模拟与实测基本吻合.重点分析了此次降雪过程中的热力动力特征和云的微物理结构,并通过地形敏感性试验,研究了祁连山地形对降雪的作用.结果表明:降雪过程中有低层西北湿冷气流向祁连山区输送水汽在山前形成大值区,气流除在祁连山周围绕流外同时沿祁连山北坡爬升.降雪前期空气饱和层和上升气流区比较深厚,为祁连山北坡降雪中心的形成提供了有利的动力热力条件,降雪后期有高空干冷下沉气流侵入使降雪减弱.这次过程为冷性稳定层云降雪过程,水成物含水量大值区也主要分布于祁连山北坡和山顶附近,冰晶和雪分布在6 km以下,在冷云顶存在0.06 g·kg-1的过冷云水.祁连山高大地形对大范围降雪落区无明显影响,但对祁连山北坡降雪中心形成有直接影响.降低地形高度后,山顶无法形成上升运动和云粒子,迎风坡云体发展减弱.地形对降雪增幅中心主要位于祁连山北坡,24 h最大增幅达3 mm.  相似文献   

From Discrete Gravity Survey Data to a High-resolution Gravity Field Representation in the Nordic-Baltic Region     

Silja Märdla  Jonas Ågren  Gabriel Strykowski  Tõnis Oja  Artu Ellmann  René Forsberg 《Marine Geodesy》2017,40(6):416-453

The deduction of a regularly spaced gravity anomaly grid from scattered survey data is studied, addressing mainly two aspects: reduction of gravity to anomalies and subsequent interpolation by various methods. The problem is illustrated in a heterogeneous study area and contrasting test areas including mountains, low terrains, and a marine area. Provided with realistic error estimates, Least Squares Collocation interpolation of Residual Terrain Model anomalies yields the highest quality gravity grid. In most cases, the Bouguer reduction and other interpolation methods tested are equally viable. However, spline-based interpolation should be avoided in marine areas with trackwise survey data.  相似文献