共查询到20条相似文献，搜索用时 15 毫秒
1.
Viewshed analysis is widely used in many terrain applications such as siting problem, path planning problem, and etc. But viewshed computation is very time-consuming, in particular for applications with large-scale terrain data. Parallel computing as a mainstream technique with the tremendous potential has been introduced to enhance the computation performance of viewshed analysis. This paper presents a revised parallel viewshed computation approach based on the existing serial XDraw algorithm in a distributed parallel computing environment. A layered data-dependent model for processing data dependency in the XDraw algorithm is built to explore scheduling strategy so that a fine-granularity scheduling strategy on the process-level and thread-level parallel computing model can be accepted to improve the efficiency of the viewshed computation. And a parallel computing algorithm, XDraw-L, is designed and implemented taken into account this scheduling strategy. The experimental results demonstrate a distinct improvement of computation performance of the XDraw-L algorithm in this paper compared with the coarse-partition algorithm, like XDraw-E which is presented by Song et al. (Earth Sci Inf 10(5):511–523, 2016), and XDraw-B that is the basic algorithm of serial XDraw. Our fine-granularity scheduling algorithm can greatly improve the scheduling performance of the grid cells between the layers within a triangle region. 相似文献
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The simple yet powerful steady state data analysis algorithm and software described herein have proven most useful in industrial grinding circuit studies at ANAMAX. Examples are drawn from that work. A process configuration can include up to 50 process streams connecting up to 30 pieces of equipment. “Steady state” plant data (e.g., solids, water, slurry flow rates, percent solids; sieve analyses) are collected where feasible, input, analyzed for consistency and, if the process is “overdefined”, adjusted in a least squares sense to achieve overall mass balance as well as mass balance within each size fraction. The combined sampling and analysis errors are assumed random with a weighting factor based upon whether the specific data point is believed to be “fair”, “good” or “excellent”. Extension of the technique to overall plant material balances is straightforward. 相似文献
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Barbara S. Jessup W. Jesse Hahm Scott N. Miller James W. Kirchner Clifford S. Riebe 《Applied Geochemistry》2011
The dynamics of granitic landscapes are modulated by bimodal weathering, which produces patchy granular soils and expanses of bare rock ranging from meter-scale boulders to mountain-scale domes. We used terrain analysis and with cosmogenic nuclide measurements of erosion rates to quantitatively explore Wahrhaftig’s decades-old hypothesis for the development of “stepped topography” by differential weathering of bare and soil-mantled granite. According to Wahrhaftig’s hypothesis, bare granite weathers slower than soil-mantled granite; thus random erosional exposure of bare rock leads to an alternating sequence of steep, slowly weathering bedrock “steps” and gently sloped, but rapidly weathering, soil-mantled “treads.” Our investigation focused on the terrain surrounding the Southern Sierra Critical Zone Observatory (CZO), which is underlain by granitic bedrock and lies outside the limits of recent glaciation, in the heart of the stepped topography described by Wahrhaftig. Our digital terrain analysis confirms that steep steps often grade into gentle treads, consistent with Wahrhaftig’s hypothesis. However, we observe a mix-and-match of soil and bare rock on treads and steps, contrary to one of the hypothesis’ major underpinnings – that bare rock should be much more common on steps than on treads. Moreover, the data show that bare rock is not as common as expected at step tops; Wahrhaftig’s hypothesis dictates that step tops should act as slowly eroding base levels for the treads above them. The data indicate that, within each landscape class (i.e., the steps and treads), bare rock erodes more slowly than surrounding soil. This suggests that the coupling between soil production and denudation in granitic landscapes harbors a tipping point wherein erosion rates decrease when soils are stripped to bedrock. Although broadly consistent with the differential weathering invoked by Wahrhaftig, the data also show that steps are eroding faster than treads, undermining Wahrhaftig’s explanation for the origins of the steps. The revised interpretation proposed here is that the landscape evolves by back-wearing of steps in addition to differential erosion due to differences in weathering of bare and soil-mantled granite. 相似文献
5.
Analysis of empirical data considered to be mixtures of a finite number of end members has been a topic of increasing interest recently. The algorithms EXTENDED CABFAC and QMODEL by Klovan and Miesch (1976) represent a satisfactory solution to this problem if pure end members are captured within the data set or if the composition of “true” end members are known a priori. Where neither condition is satisfied, the composition of “external” end members can, under certain conditions, be deduced from the structure of the data. Described herein is an algorithm termed EXTENDED QMODEL which defines feasible end members which are “closest” to the data envelope. 相似文献
6.
A polynomial chaos (PC) surrogate is proposed to reconstruct seismic time series in one-dimensional (1D) uncertain media. Our approach overcomes the deterioration of the PC convergence rate during long time integration. It is based on a double decomposition of the signal: a damped harmonic decomposition combined with a polynomial chaos expansion of the four coefficients of each harmonic term (amplitude, decay constant, pulsation, and phase). These PC expansions are obtained through the least squares method which requires the solution of nonlinear least squares problems for each sample point of the stochastic domain. The use of the surrogate is illustrated on vertically incident plane waves traveling in 1D layered, vertically stratified, isotropic, viscoelastic soil structure with uncertainties in the geological data (geometry, wave velocities, quality factors). Computational tests show that the stochastic coefficients can be efficiently represented with a low-order PC expansion involving few evaluations of the direct model. For the test cases, a global sensitivity analysis is performed in time and frequency domains to investigate the relative impact of the random parameters. 相似文献
7.
作为一种描述地形起伏特征的数据模型,数字高程模型（Digital Elevation Model,DEM）通过有限的地形高程数据实现对地形曲面的数字化模拟（即地形表面形态的数字化表示）,为研究地表的演化过程提供了数据基础。文章归纳梳理了DEM在基本地形因子、流域地貌特征、古地貌面的重塑、构造地貌发育模式、地貌分类与制图以及地形特征提取算法等领域的应用现状。总的来看,DEM研究对象以陆地为重点,以河流地貌和山地地貌为主要内容;研究过程从早期对地貌形态的定性描述向多种地貌参数的半定量、定量分析转变;研究尺度空间上从某个小流域到整个造山带,时间上从数小时向百万年扩展。构造地貌演化时间序列的不确定性、地貌参数获取的复杂性、地形模型算法的多样化以及DEM生成过程中的误差因素,这些均影响构造地貌定量分析结果的准确度,因此在归纳梳理已有研究成果的同时,对DEM在构造地貌研究领域的应用进行了一些思考。 相似文献
8.
Cross validation of kriging in a unique neighborhood 总被引：1，自引：0，他引：1
Olivier Dubrule 《Mathematical Geosciences》1983,15(6):687-699
Cross validation is an appropriate tool for testing interpolation methods: it consists of leaving out one data point at a time, and determining how well this point can be estimated from the other data. Cross validation is often used for testing “moving neighborhood” kriging models; in this case, each unknown value is predicted from a small number of surrounding data. In “unique neighborhood” kriging algorithms, each estimation uses all the available data; as a result, cross validation would spend much computer time. For instance, with ndata points it would cost at least the resolution of nsystems of n × nlinear equations (each with a different matrix).Here, we present a much faster method for cross validation in a unique neighborhood. Instead of solving nsystems n × n,it only requires the inversion of one n × nmatrix. We also generalized this method to leaving out several points instead of one. 相似文献
9.
In mountainous areas, topographic shading effects exert significant influence on the spatial distribution of solar irradiance on the land surface, which should be considered in estimating and modeling physical, biological, and hydrological processes. Various algorithms have been proposed for quantitative assessment of the impact of topography on the arriving solar radiation on slopes in mountainous area based on digital elevation model (DEM). However, different algorithms tend to produce different results even based on the same DEM. In this study, two algorithms for determining the maximum horizontal viewing angle of terrain obstruction were compared in a catchment in the Qilian Mountains, Northwest China, which were identical except for the way in interpreting DEM. Two algorithms for calculating sky view factor were also compared. Then, different algorithm combinations were compared and their sensitivities to the horizontal resolution of DEM were investigated. Results showed that the differences in outputs of different algorithms and combinations were significant and cannot be ignored in estimating the spatial distribution of solar irradiance in mountainous areas. A simple ground validation concluded that the algorithm assuming a linear variation in elevation was a little better than that assuming a stepped variation in elevation in and among neighboring DEM cells. For calculating diffuse solar radiation, the algorithm based on a sloped coordinate system was theoretically better than that based on a horizontal coordinate system. It is worth noting that even though the estimated annual mean of solar irradiance over the study area was almost the same among some algorithm combinations, the difference in spatial distribution was significant, which may lead to consequent difference in assessing or modeling some other environmental variables relevant to surface energy exchange, e.g., evaporation, snowmelt, and ground temperature. However, the analysis in this study was mainly theoretical, and further ground-based validations should be made in future. 相似文献
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在贵州岩溶山区开展地质灾害风险调查时,由于局部存在高差较大的复杂山体,传统的地面调查手段往往具有局限性。为有效地识别及测量潜在的高位隐蔽性地质灾害隐患,采用无人机载LiDAR和地面三维激光扫描的方法,通过“俯视”数据与“正视”数据相融合,可完整、精确地获取崩塌危岩带的高精度点云及三维模型等数据。以贵州省水城区鸡场镇独家寨崩塌为例,通过野外数据采集-原始点云处理-不同数据融合-整体着色修复等步骤,最后得到研究区高精度三维模型数据,在此基础上对岩体结构和裂隙进行提取,解译出层面和两组节理裂隙产状,进而有效识别危岩体的空间分布,并基于网格划分方法计算出危岩带的规模约6.6×104 m3。结果表明无人机载LiDAR与地面三维激光扫描相融合的方法可优势互补,具有可操作性强、精度高、识别准等特点,可有效地获取解译并识别危岩体的分布及规模,为后续稳定性分析及风险评价提供基础。 相似文献
12.
以云南省东川区小江流域中游左岸大白泥河支流的泥石流沟谷为研究对象,利用无人机遥感技术采集该泥石流沟谷地表地貌数据,提出结合地面三维激光扫描建模数据进行同名地物控制点提取,实现无人机影像数据的绝对定向方法。通过Smart3D影像数据处理,构建研究区三维地形模型,得到数字正射影像（Digital Orthophoto Map,DOM）、数字表面模型（Digital Surface Model,DSM）和高密集匹配点云。利用PhotoScan软件中的不规则三角网渐进加密技术对点云数据进行处理,得到0.5 m分辨率的数字高程模型（Digital Elevation Model,DEM）。结合ArcGIS和Cloud Compare中的相关地形分析模块,实现对该段泥石流沟谷地区的地形特征分析。基于无人机遥感的泥石流沟谷地形建模及特征分析研究中采用的技术路线和方法,对于定性、定量探测高原复杂山区地质灾害及其监测、防治等具有重要实证案例参考价值与实践指导意义。 相似文献
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根据造山带地层学地层划分原则,“龙泉关群”可划分为两个性质截然不同的地层单元:其一是“龙泉关构造岩层”,为构造地层单元;其二是“跑泉厂变沉积岩组”,属经典地层单元。前者经历了至少两期变形、变质作用,保留着走向近SN和近EW两组矿物拉伸线理以及角闪岩相和角闪岩相→绿片岩相退变质特征;后者仅发育有一组走向近SN矿物拉伸线理和一期绿片岩相变质作用。这表明:(1)“龙泉关群”实际上包含着两个世代不同的地层单元,应予解体。其中,“龙泉关构造岩层”形成于晚太古代末期,属于“阜平古陆块”刚性基底一部分;“跑泉厂变沉积岩组”的地层层位相当于“五台群”,是“阜平古陆块”西北陆缘带沉积,时代归属早元古代早、中期。(2)“龙泉关群”不是由一个统一的应力场同时形成的一套构造岩,因而不应将其作为一个大型韧性剪切带。(3)“龙泉关群”构成五台碰撞造山带前陆地区的活化基底和活化盖层两个大地构造相。“龙泉关群”的解体及其地层时代的重新厘定支持“板峪口组应归属滹沱群一部分”和“铁堡运动即为五台运动”的看法。 相似文献
15.
Wei Yang Yun Xu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(2):189-196
The Bayesian approach has been proved useful to geotechnical engineering especially when project-specific data/measurements are very limited. In this paper, we introduced a new Bayesian algorithm to estimate soil properties at each location of a study area, with very limited project-specific data. In addition to the proposed methodology and algorithms, we also conducted a model application to estimate soil permeability for each of the 64 locations within a 4-by-4 m2 area, based on very limited project-specific data, that is, one measurement from each location. 相似文献
16.
environment. As one of the most important tasks in augmented scene modeling, terrain simplification research has gained more and more attention. In this paper, we mainly focus on point selection problem in terrain simplification using triangulated irregular network. Based on the analysis and comparison of traditional importance measures for each input point, we put forward a new importance measure based on local entropy. The results demonstrate that the local entropy criterion has a better performance than any traditional methods. In addition, it can effectively conquer the "short-sight" problem associated with the traditional methods. 相似文献
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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
18.
A prospecting cost-benefit strategy is developed by quantitatively defining the prospecting cost and benefit in mineral potential mapping. Suppose that some mineral deposits have been discovered in a study area of a set of grid cells, the prospecting cost and benefit of a “unique” condition can be defined as the percentage of non-deposit-bearing and deposit-bearing cells within the “unique” condition, respectively. By replacing the false positive and true positive rates in the receiver operating characteristic (ROC) curve analysis with the prospecting cost and benefit, the Youden index, likelihood ratio, and lift index can be computed and used to express the mineral potential of the “unique” condition. Thus, the mineral potential mapping in a study area can be implemented by identifying all the possible “unique” conditions and then computing their mineral potential indicators such as the Youden index, likelihood ratio, and lift index. By integrating an automatic “unique” condition searching algorithm with the techniques for computing the mineral potential indicators for each “unique” condition, the following prospecting cost-benefit strategy is developed for mineral potential mapping: (a) select map patterns closely associated with the discovered mineral deposits using their mineral potential indicators, (b) automatically search for all the possible “unique” conditions, (c) evaluate the mineral potential of each “unique” condition using its mineral potential indicators, and (d) assess mineral potential mapping performance using the mineral potential indicator diagrams. For demonstration purposes, the Baishan district in Southern Jilin Province in China, which has a complex geological setting, is chosen as a case study area. The weights of evidence (WofE) modeling posterior probability, Youden index, likelihood ratio, and lift index are applied in the mineral potential mapping and their performance are assessed using their ROC curves, cumulative lift charts, and Youden and likelihood ratio diagrams. The results show that (a) the likelihood ratio and lift index perform similarly well and (b) the posterior probability performs a little bit worse than the likelihood ratio and lift index while a little bit better than the Youden index. Therefore, the prospecting cost-benefit strategy provides a common paradigm for both mineral potential mapping and the performance assessment. 相似文献
19.
This article presents a new Barrier recognition algorithm with learning, designed for recognition of earthquake-prone areas. In comparison to the Crust (Kora) algorithm, used by the classical EPA approach, the Barrier algorithm proceeds with learning just on one “pure” high-seismic class. The new algorithm operates in the space of absolute values of the geological–geophysical parameters of the objects. The algorithm is used for recognition of earthquake-prone areas with М ≥ 6.0 in the Caucasus region. Comparative analysis of the Crust and Barrier algorithms justifies their productive coherence. 相似文献