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1.
Mine planning is influenced by many sources of uncertainty. Significant sources of geological uncertainty in mine planning include uncertainty in layout of geological domains and uncertainty in metal grades. These two sources of uncertainty cannot be modeled separately because the distribution of the grade is controlled usually by geological domains. Two approaches exist for combining these two sources of uncertainty: the joint simulation approach and the cascade approach. In this paper, these two approaches were compared using a real case study. To this end, uncertainty in iron grade (quantitative variable) and ore zones (qualitative variable) was modeled using both approaches. There were some considerable differences in the results obtained by each approach, which confirm the importance of choosing the most appropriate approach with consideration of the dominate features of a deposit.
相似文献2.
Knowledge representation structure and reasoning processes are very important issues in the knowledge-based approach of integrating multiple spatial data sets for resource exploration. An object-oriented knowledge representation structure and corresponding reasoning processes are formulated and tested in this research on the knowledge-based approach of integrating spatial exploration data. The map-based prototype expert system developed in this study has self-contained knowledge representation structure and inference mechanisms. It is important to distinguish between lack of information and information providing negative evidence for a map-based system because the spatial distribution of data sets are uneven in most cases. Error and uncertainty estimation is also an important component of any production expert system. The uncertainty propagation mechanisms developed here work well for this type of integrated exploration problem. Evidential bellef function theory provides a natural theoretical basis for representing and integrating spatially uneven geophysical and geological information. The prototype system is tested using real mineral exploration data sets from the Snow Lake area, northern Manitoba, Canada. The test results outline the favorable exploration areas successfully and show the effectiveness of the knowledge representation structure and inference mechanisms for the knowledge-based approach. 相似文献
3.
de Souza Luis Eduardo Costa João Felipe C. L. Koppe Jair C. 《Natural Resources Research》2004,13(1):1-15
For many decades the mining industry regarded resources/reserves estimation and classification as a mere calculation requiring basic mathematical and geological knowledge. Most methods were based on geometrical procedures and spatial data distribution. Therefore, uncertainty associated with tonnages and grades either were ignored or mishandled, although various mining codes require a measure of confidence in the values reported. Traditional methods fail in reporting the level of confidence in the quantities and grades. Conversely, kriging is known to provide the best estimate and its associated variance. Among kriging methods, Ordinary Kriging (OK) probably is the most widely used one for mineral resource/reserve estimation, mainly because of its robustness and its facility in uncertainty assessment by using the kriging variance. It also is known that OK variance is unable to recognize local data variability, an important issue when heterogeneous mineral deposits with higher and poorer grade zones are being evaluated. Altenatively, stochastic simulation are used to build local or global uncertainty about a geological attribute respecting its statistical moments. This study investigates methods capable of incorporating uncertainty to the estimates of resources and reserves via OK and sequential gaussian and sequential indicator simulation The results showed that for the type of mineralization studied all methods classified the tonnages similarly. The methods are illustrated using an exploration drill hole data sets from a large Brazilian coal deposit. 相似文献
4.
Gudrun Wallentin Adrijana Car 《International journal of geographical information science》2013,27(2):408-422
In this article, we introduce a conceptual framework for systematic identification and assessment of sources of uncertainty in simulation models. This concept builds on a novel typology of uncertainty in model validation and extends the GIScience research focus on uncertainty in spatial data to uncertainty in simulation modelling. Such a concept helps a modeller to interpret and handle uncertainty in order to efficiently optimise a model and better understand simulation results. To illustrate our approach, we apply the proposed framework for uncertainty assessment to the TREE LIne Model (TREELIM), an individual-based model that simulates forest succession at the alpine tree line. Using this example, uncertainty is identified in the modelling workflow during conceptualisation, formalisation, parameterisation, analysis and validation. With help of a set of indicators we quantify the emerging uncertainties and assess the overall model uncertainty as a function of all occurring sources of uncertainty. An understanding of the sources of uncertainty in an ecological model proves beneficial for: (1) developing a structurally valid model in a systematic way; (2) deciding if further refinement of the conceptual model is beneficial for the modelling purpose; and (3) interpreting the overall model uncertainty by understanding its sources. Our approach results in a guideline for assessing uncertainty in the validation of simulation models in a feasible and defensible way, and thus functions as a toolbox for modellers. We consider this work as a contribution towards a general concept of uncertainty in spatially explicit simulation models. 相似文献
5.
E.G. Paredes M. Bóo M. Amor J.D. Bruguera J. Döllner 《International journal of geographical information science》2013,27(5):771-793
Hybrid terrains are a convenient approach for the representation of digital terrain models, integrating heterogeneous data from different sources. In this article, we present a general, efficient scheme for achieving interactive level-of-detail rendering of hybrid terrain models, without the need for a costly preprocessing or resampling of the original data. The presented method works with hybrid digital terrains combining regular grid data and local high-resolution triangulated irregular networks. Since grid and triangulated irregular network data may belong to different datasets, a straightforward combination of both geometries would lead to meshes with holes and overlapping triangles. Our method generates a single multiresolution model integrating the different parts in a coherent way, by performing an adaptive tessellation of the region between their boundaries. Hence, our solution is one of the few existing approaches for integrating different multiresolution algorithms within the same terrain model, achieving a simple interactive rendering of complex hybrid terrains. 相似文献
6.
SWH双源蒸散模型模拟效果验证及不确定性分析 总被引：1，自引：0，他引：1
SWH模型是在经典Shuttleworth-Wallace双源蒸散模型的基础上发展起来的蒸散模型。过去的研究结果表明在站点尺度上SWH模型表现出较高模拟精度,但有关模型对主要参数及驱动变量的敏感性以及模型模拟的不确定性来源等缺乏深入理解与认识。本文通过与51个陆地生态系统站点多年的蒸散观测数据对比,在季尺度、年尺度上验证了全国范围内SWH模型的模拟效果,并分析了关键参数和驱动变量对模型不确定性的贡献大小。结果表明：SWH模型在区域尺度上取得了较好的模拟效果,模拟蒸散与实测值R2均在0.75以上。模型各参数中,冠层导度估算涉及的两个参数对蒸散模拟不确定性影响较大;驱动数据中,归一化植被指数对蒸散模拟不确定性影响较大。尽管部分数据（如降水）因插补存在较大的误差,但总体上气候驱动数据对蒸散模拟的不确定性的贡献仍低于NDVI。 相似文献
7.
8.
The objective of a field development optimization process, or workflow, is to investigate various options and determine a course of action that will deliver the largest expected value from an asset. The analysis is often complicated by uncertainty in important inputs. Ideally, operators desire workflows and tools that integrate reservoir engineering and optimization principles in a fast-solving model that can be used to explore the full range of the uncertain inputs. This need is acute in the screening and concept selection stage where the primary objective is to determine the sensitivity of competing concepts to the sources of uncertainty. In these early stages, model results can be used to determine whether additional information should be collected, and to narrow down the number of competing options. The objective of this research is the development of a workflow and tool that integrates reservoir response surfaces within a project optimization model that contains facility and operational options, and to use this model to investigate the impacts of uncertainty on decision making. The integration of technical options is critical because a static view of capital investment and facility constraints causes a systematic undervaluation and can introduce error to development decisions. The new workflow and integrated reservoir-economic optimization tool developed in this research leverage methods and engineering work products that are already known to industry, for example, experimental design (ED) and response surface methods (RSMs). A demonstration is provided for a gas flood project using a stylized reservoir. Specifically, we investigate the selection of initial well configurations and injection capacities while simultaneously accounting for the options to update these decisions after production information is acquired in the early periods of production. The workflow is used to optimize the development of a gas flood. As a second step, the workflow is used to solve a value of information problem. 相似文献
9.
Vanessa Cerqueira Koppe João Felipe Coimbra Leite Costa Jair Carlos Koppe Fernando Gambin Gary Fallon Nick Davies 《Natural Resources Research》2007,16(4):293-303
Seismic reflection methods measure the time a seismic wave takes to travel through the ground, from the user defined source
to a series of signal monitoring sensors known as geophones. The measured times need to be depth converted to allow for integration
with other geological data. In order to convert from time to depth, an estimate of the rock volume velocity field must be
made. The velocity field estimate can be made by assignment of velocity estimates to a geological model independent of the
seismic processing. This article presents the results of using the acoustic geophysical log data extrapolated via sequential
Gaussian simulation to derive the velocity field. The uncertainties associated with the velocity estimates were significant
and provided the means to assess confidence limits for the actual depth determination. The technique is assessed by application
to a major coal deposit, approximately 2.1 m thick and 210 m deep. Considering only the uncertainty associated with estimating
the velocity field, half of the confidence interval values showed approximately 1 m of uncertainty in depth. The application
of sequential Gaussian simulation to model the 3D distribution of acoustic velocity can be extended to other geophysical log
parameters or derived estimates. 相似文献
10.
以洪河国家级自然保护区为研究区,选取了多时相的Sentinel-1B和Sentinel-2A影像为数据源,制定出9种多时相主被动遥感数据组合方案,用于沼泽湿地遥感分类;分别对根据9种方案整合的多维数据集,进行基于尺度继承的多尺度分割,得到面向对象的分割影像,建立与不同方案对应的特征数据集;采用随机森林机器学习算法,对多维特征数据集进行特征优化,并进行参数调优,构建沼泽植物的最优遥感识别模型,实现对沼泽湿地中地物的识别与分类。研究结果表明,采用递归特征消除(recursive feature elimination,RFE)算法的变量优选和采样随机森林的参数调优,可以优化随机森林模型,显著减少数据冗余,整合多时相主被动遥感数据方案九的随机森林模型的最佳参数mtry和ntree分别为4和1500,模型训练精度为93.06%,Kappa系数为0.916,其模型训练精度在所有方案中最高;经过变量优选得到最佳特征变量组合,交叉极化方式的后向散射系数(Mean_VH)对于沼泽分类的重要性比同向极化方式的后向散射系数(Mean_VV)高;光谱特征是遥感图像分类的最主要特征,其中,红光和绿光波段(Mean_R和Mean_G)、多光谱红边波段(Mean_REG1和Mean_REG2)、近红外波段1(Mean_NIR1)、红边植被指数(CIgreen和CIreg)都对分类具有较高的重要性;纹理特征熵(GLCM_Entro、GLCM_Ent2)和位置特征像元坐标(X_Min_Pxl和Y_Max_Pxl)对沼泽湿地分类也起到重要作用,相对于其它特征,形状特征对分类的贡献性较小;利用方案九的数据得到的分类结果的总体分类精度为94.42%,主被动遥感数据的特征变量和不同时相的特征变量都对分类做出重要贡献,其中,6月的多光谱特征变量的贡献大于9月的变量;9月的SAR特征变量的贡献大于6月的变量;对分类贡献最大的9月的特征变量为多光谱红边波段2(Mean_REG2),对分类贡献最大的6月的特征变量为绿光波段(Mean_G);融合多时相主被动遥感数据源,可以将不同数据源、不同时相对分类具有较大贡献的特征变量集合在一起,充分利用光谱信息和雷达数据反映的结构信息,构建多维度最佳特征变量组合方案,有效提高沼泽湿地分类精度。 相似文献
11.
ABSTRACT. The Shimentai Nature Reserve in Yingde County, Guangdong Province, China, established recently in a subtropical upland forest area, has served for ages as an essential and customary source of livelihood for local people. Assessment of forest usage indicates heavy reliance by villagers on its diversified biotic resources. This forest dependence, associated with socioeconomic factors such as distance from village, ethnic origin, out‐migration of rural youngsters, and a local tradition of conservation, is unlikely to decline in the near future. The reserve management recognizes the need to address the livelihood issues of local people and to win local support. A pragmatic adherence to provincial and higher‐level policies that exclude forest‐tapping activities could lead to more people‐versus‐park conflicts, which would dilute fundamental conservation objectives. A more enlightened and localized approach that nurtures a synergy between limited forest use and conservation while helping to develop new income sources could furnish workable alternatives. 相似文献
12.
Amii R. Darnell Andrew A. Lovett Jenni Barclay Richard A. Herd 《International journal of geographical information science》2013,27(8):1171-1191
Terrain is a surface phenomenon that is measured, modelled, and mapped. However, it is continuously variable and must be simulated by points or mathematical equations that are inherently approximations. The error induced by digitally represented terrain can propagate to surface derivatives and geographical information science (GIS) applications where topography is considered. This can lead to uncertainty in model predictions and the use of data that are unfit for the application to which they are intended. This article outlines the problem of uncertainty in terrain representation and demonstrates the consequences for volcanic mudflow modelling. The response of a simple least-cost single flow algorithm to input parameters was investigated in order to assess output variation from the different sources of input variation. Elevation error was modelled with a probability density function (PDF) and propagated through stochastic simulation (Monte Carlo). Such combined uncertainty and sensitivity analyses enabled a qualitative judgement of the relative significance of elevation error on the flow model prediction. Different methods for terrain model construction were considered and show that supplementing global positioning system (GPS) measurements with information from field notes and reconnaissance photographs greatly improved the model performance and reduced the uncertainty. It is concluded that in terms of validity of model results, there is no substitute for constructing an elevation model that is informed by the terrain. 相似文献
13.
基于神经网络的单元自动机CA及真实和优化的城市模拟 总被引：78，自引：8，他引：78
提出了一种基于神经网络的单元自动机（CA）。CA已被越来越多地应用在城市及其它地理现象的模拟中。CA模拟所碰到的最大问题是如何确定模型的结构和参数。模拟真实的城市涉及到使用许多空间变量和参数。当模型较复杂时，很难确定模型的参数值。本模型的结构较简单，模型的参数能通过对神经网络的训练来自动获取。分析表明，所提出的方法能获得更高的模拟精度，并能大大缩短寻找参数所需要的时间。通过筛选训练数据，本模型还可以进行优化的城市模拟，为城市规划提供参考依据。 相似文献
14.
The reality of uncertain data cannot be ignored. Anytime that spatial data are used to assist planning, decision making, or policy generation, it is likely that error or uncertainty in the data will propagate through processing protocols and analytic techniques, potentially leading to biased or incorrect decision making. The ability to directly account for uncertainty in spatial analysis efforts is critically important. This article focuses on addressing data uncertainty in one of the most important and widely used exploratory spatial data analysis (ESDA) techniques—choropleth mapping—and proposes an alternative map classification method for uncertain spatial data. The classification approach maximizes within-class homogeneity under data uncertainty while explicitly integrating spatial characteristics to reduce visual map complexity and to facilitate pattern perception. The method is demonstrated by mapping the 2009 to 2013 American Community Survey estimates of median household income in Salt Lake County, Utah, at the census tract level. 相似文献
15.
An important aim of modern geostatistical modeling is to quantify uncertainty in geological systems. Geostatistical modeling
requires many input parameters. The input univariate distribution or histogram is perhaps the most important. A new method
for assessing uncertainty in the histogram, particularly uncertainty in the mean, is presented. This method, referred to as
the conditional finite-domain (CFD) approach, accounts for the size of the domain and the local conditioning data. It is a
stochastic approach based on a multivariate Gaussian distribution. The CFD approach is shown to be convergent, design independent,
and parameterization invariant. The performance of the CFD approach is illustrated in a case study focusing on the impact
of the number of data and the range of correlation on the limiting uncertainty in the parameters. The spatial bootstrap method
and CFD approach are compared. As the number of data increases, uncertainty in the sample mean decreases in both the spatial
bootstrap and the CFD. Contrary to spatial bootstrap, uncertainty in the sample mean in the CFD approach decreases as the
range of correlation increases. This is a direct result of the conditioning data being more correlated to unsampled locations
in the finite domain. The sensitivity of the limiting uncertainty relative to the variogram and the variable limits are also
discussed. 相似文献
16.
本文提出一种基于随机森林的元胞自动机城市扩展(RF-CA)模型。通过在多个决策树的生成过程中分别对训练样本集和分裂节点的候选空间变量引入随机因素,提取城市扩展元胞自动机的转换规则。该模型便于并行构建,能在运算量没有显著增加的前提下提高预测的精度,对城市扩展中存在的随机因素有较强的容忍度。RF-CA模型可进行袋外误差估计,以快速获取模型参数;也可度量空间变量重要性,解释各空间变量在城市扩展中的作用。将该模型应用于佛山市1988-2012年的城市扩展模拟中,结果表明,与常用的逻辑回归模型相比,RF-CA模型进行模拟和预测分别能够提高1.7%和2.6%的精度,非常适用于复杂非线性特征的城市系统演变模型与扩展研究;通过对影响佛山市城市扩展的空间变量进行重要性度量,发现对佛山城市扩张模拟研究而言,距国道的距离与距城市中心的距离具有最重要的作用。 相似文献
17.
Ground-level ozone has become a problem of major concern in urban airsheds in Canada, owing to its adverse effects on humans and crops. As a secondary pollutant, its formation is dependent on the presence of certain precursor gases in conjunction with appropriate meteorological conditions. Several studies have examined the relationship between maximum concentrations and key meteorological variables at the regional scale during episodic conditions. This study sought to understand this relationship at the local scale using surface and upper-air meteorological data for the Niagara Region. In the methodological approach, factor analysis and linear regression methods were used to determine the best combination of variables that would explain the highest percentage of variance in daily maximum ground-level ozone associated with different event categories. Each event category had a combination of unique meteorological characteristics. Factor analysis yielded seven factors that together constituted 20 of the original 59 variables in the data set. In the application of a series of regression analyses, the thermal factors of the lower atmosphere emerged as the most important variables, followed by variables related to persistence and advection characteristics. The daily maximum temperature was the single most important variable and accounted for the largest percentage of the variance explained, whereas the persistence factor was of secondary importance. The overall results suggest that a small number of surface variables based on the local meteorology of the Niagara Region can be used to estimate daily maximum ground-level ozone. 相似文献
18.
Jason A. McLennan Weishan Ren Oy Leuangthong C. V. Deutsch 《Natural Resources Research》2006,15(2):119-127
The application of steam-assisted gravity drainage (SAGD) to recover heavy oil sands is becoming increasingly important in
the northern Alberta McMurray Formation because of the vast resources/reserves accessible with this mechanism. Selecting the
stratigraphic elevations of SAGD well pairs is a vital decision for reservoir evaluation and planning. The inherent uncertainty
in the distribution of geological variables significantly influences this decision. Geostatistical simulation is used to capture
geological uncertainty, which is used can be transformed into a distribution of the best possible well pair elevations.
A simple exhaustive calculation scheme is used to determine the optimum stratigraphic location of a SAGD well pair where the
recovery R is maximized. There are three basic steps to the methodology: (1) model the uncertainty in the top continuous bitumen (TCB)
and bottom continuous bitumen (BCB) surfaces, (2) calculate the recovery at all possible elevation increments within the TCB
and BCB interval, and (3) identify the elevation that maximizes R. This is repeated for multiple TCB/BCB pairs of surfaces
to assess uncertainty. The methodology is described and implemented on a subset of data from the Athabasca Oilsands in Fort
McMurray, Alberta. 相似文献
19.
A Methodology for the Assessment of Unconventional (Continuous) Resources with an Application to the Greater Natural Buttes Gas Field,Utah 总被引：1，自引：0，他引：1
The Greater Natural Buttes tight natural gas field is an unconventional (continuous) accumulation in the Uinta Basin, Utah,
that began production in the early 1950s from the Upper Cretaceous Mesaverde Group. Three years later, production was extended
to the Eocene Wasatch Formation. With the exclusion of 1100 non-productive (“dry”) wells, we estimate that the final recovery
from the 2500 producing wells existing in 2007 will be about 1.7 trillion standard cubic feet (TSCF) (48.2 billion cubic meters
(BCM)). The use of estimated ultimate recovery (EUR) per well is common in assessments of unconventional resources, and it
is one of the main sources of information to forecast undiscovered resources. Each calculated recovery value has an associated
drainage area that generally varies from well to well and that can be mathematically subdivided into elemental subareas of
constant size and shape called cells. Recovery per 5-acre cells at Greater Natural Buttes shows spatial correlation; hence,
statistical approaches that ignore this correlation when inferring EUR values for untested cells do not take full advantage
of all the information contained in the data. More critically, resulting models do not match the style of spatial EUR fluctuations
observed in nature. This study takes a new approach by applying spatial statistics to model geographical variation of cell
EUR taking into account spatial correlation and the influence of fractures. We applied sequential indicator simulation to
model non-productive cells, while spatial mapping of cell EUR was obtained by applying sequential Gaussian simulation to provide
multiple versions of reality (realizations) having equal chances of being the correct model. For each realization, summation
of EUR in cells not drained by the existing wells allowed preparation of a stochastic prediction of undiscovered resources,
which range between 2.6 and 3.4 TSCF (73.6 and 96.3 BCM) with a mean of 2.9 TSCF (82.1 BCM) for Greater Natural Buttes. A
second approach illustrates the application of multiple-point simulation to assess a hypothetical frontier area for which
there is no production information but which is regarded as being similar to Greater Natural Buttes. 相似文献
20.
This study develops confidence intervals for estimates of inferred oil and gas reserves based on bootstrap procedures. Inferred reserves are expected additions to proved reserves in previously discovered conventional oil and gas fields. Estimates of inferred reserves accounted for 65% of the total oil and 34% of the total gas assessed in the U.S. Geological Survey's 1995 National Assessment of oil and gas in US onshore and State offshore areas. When the same computational methods used in the 1995 Assessment are applied to more recent data, the 80-year (from 1997 through 2076) inferred reserve estimates for pre-1997 discoveries located in the lower 48 onshore and state offshore areas amounted to a total of 39.7 billion barrels of oil (BBO) and 293 trillion cubic feet (TCF) of gas. The 90% confidence interval about the oil estimate derived from the bootstrap approach is 22.4 BBO to 69.5 BBO. The comparable 90% confidence interval for the inferred gas reserve estimate is 217 TCF to 413 TCF. The 90% confidence interval describes the uncertainty that should be attached to the estimates. It also provides a basis for developing scenarios to explore the implications for energy policy analysis. 相似文献