共查询到20条相似文献，搜索用时 31 毫秒
1.
In every map, irrespective of its theme, objects are represented at a reduced scale. Map contents do not decrease proportionally to the reduction of the map size. Usually an increasing density of the map contents occurs at smaller scales. That is where the generalization plays an important role. Generalization is the process of creating a legible map at a given scale from a more detailed geographical dataset. It is done in such a manner that the character or essence of the original features is retained at successively smaller scales. Though the purposes and benefits of generalization are manifold it is indeed a complex decision-making process which must be intelligently steered by goals and rules from the geographical application domain such that the generalized representation conveys knowledge consistent with the reality. In recent past, lot of work has been done in 2D generalization (Beard, 1991; Weibel, 1995; Bealla, 1995; Ruas and Plazanet, 1996; Sarjakoski and Kilpeläinen, 1999) which defines a set of operations to be performed with the goal to achieve the similar results to those from manual generalization. But 3D generalization is altogether perceived differently. A given 3D urban area mostly consists of roads and buildings. These buildings are of different styles and features. Further the city area may be viewed from different angles and at different heights. So generalization in general and aggregation in particular must deal with all these issues. In this paper, an effort has been made to address these issues. 相似文献
2.
基于TIN数据三维地质体的折剖面切割算法 总被引：1，自引：0，他引：1
为有效分析地质模型的内部结构,研究直接利用折切面对模型数据进行几何切割的算法。该算法面向基于TIN数据表达的三维地质体,包括"折剖面的生成"和"被切割地质体的拆分"两大关键步骤;采用向二维平面投影的策略,将复杂的切割转化为交线的快速连接、三角形重新剖分和点与多边形的包含测试等简单操作。对不同复杂程度的三维地质模型进行切割实验,发现化繁为简和二维投影策略极大地提高了算法效率。 相似文献
3.
Hierarchies of superimposed structures are found in maps of geological horizons in sedimentary basins. Mapping based on three‐dimensional (3D) seismic data includes structures that range in scale from tens of metres to hundreds of kilometres. Extraction of structures from these maps without a priori knowledge of scale and shape is analogous to pattern recognition problems that have been widely researched in disciplines outside of Geoscience. A number of these lessons are integrated and applied within a geological context here. We describe a method for generating multiscale representations from two‐dimensional sections and 3D surfaces, and illustrate how superimposed geological structures can be topologically analysed. Multiscale analysis is done in two stages – generation of scale‐space as a geometrical attribute, followed by identification of significant scale‐space objects. Results indicate that Gaussian filtering is a more robust method than conventional moving average filtering for deriving multiscale geological structure. We introduce the concept of natural scales for identifying the most significant scales in a geological cross section. In three dimensions, scale‐dependent structures are identified via an analogous process as discrete topological entities within a four‐dimensional scale‐space cube. Motivation for this work is to take advantage of the completeness of seismic data coverage to see ‘beyond the outcrop’ and yield multiscale geological structure. Applications include identifying artefacts, scale‐specific features and large‐scale structural domains, facilitating multiscale structural attribute mapping for reservoir characterisation, and a novel approach to fold structure classification. 相似文献
4.
基于TIN的体布尔算法及其地质应用 总被引：3，自引：0，他引：3
提出一种基于TIN的体布尔操作算法,即采用快速碰撞检测方法、改进的三角形求交算法和三角形包含测试算法,能解决复杂地质体的交、并、差等布尔操作。该方法不仅可以有效处理具有侵入、交错等复杂空间关系的地质体建模问题,还适用于基于地质模型的工程分析应用,如开挖模拟等,并在北京市某岩土工程信息系统建设项目中得到了检验。 相似文献
5.
Huang Jixian Mao Xiancheng Chen Jin Deng Hao Dick Jeffrey M. Liu Zhankun 《Natural Resources Research》2020,29(1):439-458
Exploring the spatial relationships between various geological features and mineralization is not only conducive to understanding the genesis of ore deposits but can also help to guide mineral exploration by providing predictive mineral maps. However, most current methods assume spatially constant determinants of mineralization and therefore have limited applicability to detecting possible spatially non-stationary relationships between the geological features and the mineralization. In this paper, the spatial variation between the distribution of mineralization and its determining factors is described for a case study in the Dingjiashan Pb–Zn deposit, China. A local regression modeling technique, geological weighted regression (GWR), was leveraged to study the spatial non-stationarity in the 3D geological space. First, ordinary least-squares (OLS) regression was applied, the redundancy and significance of the controlling factors were tested, and the spatial dependency in Zn and Pb ore grade measurements was confirmed. Second, GWR models with different kernel functions in 3D space were applied, and their results were compared to the OLS model. The results show a superior performance of GWR compared with OLS and a significant spatial non-stationarity in the determinants of ore grade. Third, a non-stationarity test was performed. The stationarity index and the Monte Carlo stationarity test demonstrate the non-stationarity of all the variables throughout the area. Finally, the influences of the degree of non-stationary of all controlling factors on mineralization are discussed. The existence of significant non-stationarity of mineral ore determinants in 3D space opens up an exciting avenue for research into the prediction of underground ore bodies.
相似文献6.
一种基于面积紧凑度的二维空间形状指数及其应用 总被引：2，自引：0，他引：2
空间形状指数是重要的空间形态分析指标,目前应用较为广泛的基于边界紧凑度的一维空间形状指数在参照形状选择及一维测度应用等方面都存在局限性。针对一维空间形状指数的缺陷,定义一种基于面积紧凑度的二维空间形状指数,并以矩形为参照形状,讨论其计算方法。结合浙江省桐庐县标准农田立地条件评价的实例,比较分析两种维度空间形状指数的应用效果。结果表明,二维空间形状指数能够更精确地描述地物图斑相对于非紧凑参照形状的偏离程度,且在标准农田规划、建设等应用中更具实用价值。 相似文献
7.
Dr Helen Mounsey 《International journal of geographical information science》2013,27(3):259-261
Spatial data uncertainty models (SDUM) are necessary tools that quantify the reliability of results from geographical information system (GIS) applications. One technique used by SDUM is Monte Carlo simulation, a technique that quantifies spatial data and application uncertainty by determining the possible range of application results. A complete Monte Carlo SDUM for generalized continuous surfaces typically has three components: an error magnitude model, a spatial statistical model defining error shapes, and a heuristic that creates multiple realizations of error fields added to the generalized elevation map. This paper introduces a spatial statistical model that represents multiple statistics simultaneously and weighted against each other. This paper's case study builds a SDUM for a digital elevation model (DEM). The case study accounts for relevant shape patterns in elevation errors by reintroducing specific topological shapes, such as ridges and valleys, in appropriate localized positions. The spatial statistical model also minimizes topological artefacts, such as cells without outward drainage and inappropriate gradient distributions, which are frequent problems with random field-based SDUM. Multiple weighted spatial statistics enable two conflicting SDUM philosophies to co-exist. The two philosophies are ‘errors are only measured from higher quality data’ and ‘SDUM need to model reality’. This article uses an automatic parameter fitting random field model to initialize Monte Carlo input realizations followed by an inter-map cell-swapping heuristic to adjust the realizations to fit multiple spatial statistics. The inter-map cell-swapping heuristic allows spatial data uncertainty modelers to choose the appropriate probability model and weighted multiple spatial statistics which best represent errors caused by map generalization. This article also presents a lag-based measure to better represent gradient within a SDUM. This article covers the inter-map cell-swapping heuristic as well as both probability and spatial statistical models in detail. 相似文献
8.
Discrete displacement analysis for geographic linear features and the application to glacier termini
Joon Heo Seongsu Jeong Soohee Han Changjae Kim Sungchul Hong Hong-Gyoo Sohn 《International journal of geographical information science》2013,27(8):1631-1650
The extent of glacier terminus displacement is instrumental in investigations of natural or artificial geographic changes. Its importance to earth science and engineering is reflected in the considerable efforts that have been devoted to the development of several boundary displacement analysis methods. Among the methods, the buffering-based approach compares favorably with other approaches in objectivity and robustness. However, it does not consider the relative positions of boundaries, because its buffering operation cannot determine features' relative directions. This limitation incurs inaccurate calculation results – underestimation of mean shifts and overestimation of shape variations, especially when the two compared boundaries intersect. Discrete displacement analysis (DDA), an alternative method that considers given geographic objects as a set of a finite number of points, is proposed here. In a series of tests carried out, including Jakobshavn glacier's calving front, DDA was found to correctly calculate mean shift and shape variation even in cases where the conventional buffering-based method failed. Moreover, this approach is independent of the dimension of space in which it is implemented, and thus is expected to be utilized for analysis of 3D geographic object displacement. 相似文献
9.
10.
城市地下空间开发地质环境质量评价可为城市地下空间规划和工程建设提供重要决策支持。该文以合肥市滨湖新区为例,构建城市地下空间开发地质环境质量三维评价方法:利用三维隐式建模方法融合多源数据进行三维地质建模,从工程地质、水文地质、地质构造和不良地质体等方面构建三维评价模型,利用三维距离场分析、三维空间统计分析等方法对三维评价因子进行分析、提取,最后基于确权和综合评价方法得到地下空间开发地质环境质量三维综合评价结果。实例研究表明:该方法能够显著提高评价结果的深度方向分辨率,相关成果可为城市地下空间精细规划及可持续开发利用提供方法参考。 相似文献
11.
基于虚拟钻孔的工程地质三维剖切的实现 总被引：1，自引：0，他引：1
梁师俊 《地理与地理信息科学》2010,26(1)
给出工程地质数据库的结构,并利用标准地层层序表和钻孔数据,根据层面TIN模型,建立了工程地质三维模型;在此基础上提出一种实用的工程地质三维剖切的实施方法,该方法通过剖切平面与层面TIN边的交点生成虚拟钻孔,把虚拟钻孔所在的地质剖面作为约束条件,将虚拟钻孔和实测钻孔一起重新构建层面TIN模型,并实现工程地质三维剖切。该方法简易可行,对层状地质结构的三维剖切效果较好,能满足工程地质分析和地质解释等应用的实际需要。 相似文献
12.
13.
Wenwen Li Michael F. Goodchild Richard Church 《International journal of geographical information science》2013,27(6):1227-1250
A measure of shape compactness is a numerical quantity representing the degree to which a shape is compact. Ways to provide an accurate measure have been given great attention due to its application in a broad range of GIS problems, such as detecting clustering patterns from remote-sensing images, understanding urban sprawl, and redrawing electoral districts to avoid gerrymandering. In this article, we propose an effective and efficient approach to computing shape compactness based on the moment of inertia (MI), a well-known concept in physics. The mathematical framework and the computer implementation for both raster and vector models are discussed in detail. In addition to computing compactness for a single shape, we propose a computational method that is capable of calculating the variations in compactness as a shape grows or shrinks, which is a typical application found in regionalization problems. We conducted a number of experiments that demonstrate the superiority of the MI over the popular isoperimetric quotient approach in terms of (1) computational efficiency; (2) tolerance of positional uncertainty and irregular boundaries; (3) ability to handle shapes with holes and multiple parts; and (4) applicability and efficacy in districting/zonation/regionalization problems. 相似文献
14.
Cause-Effect Analysis in Assessment of Mineral Resources 总被引：1，自引：0，他引：1
Cause-effect analyses is a deterministic methodology intended for processing qualitative (e.g. texts, conventional maps) and mixed, qualitative and quantitative, data. The main idea, employed in cause-effect analysis, is the plurality and interaction of causes. This idea is described by mathematical logic formulae that can be converted into a single Boolean equation. The latter represents a mathematical model of a general shape of cause-effect relations for the study problem. In particular, such a model can express relations between some property of the mineralization and features of other geological phenomena. By processing data, logical dependencies satisfying to the theoretical model are determined in a data file. These dependences, expressed by Boolean function formulae, describe cause-effect relations for a case study, and they are used for predicting. Software realizing the cause-effect analysis is an expert system with artificial intelligence capabilities. There are two methods of using the cause-effect analysis in assessment of mineral resources. The first method consists in detecting the regularity in locations of known mineral deposits and occurrences with the following using the regularity formula for generation of predictive maps. The second method is the evaluation of individual mineral occurrences by obtained Boolean formulae expressing cause-effect relations between deposit sizes and geological environment of deposits. Both methods are illustrated by case studies of predicting gold-bearing deposits of Middle Asia in the former USSR. 相似文献
15.
Huang Leilei Wang Gongwen Carranza Emmanuel John M. Du Jingguo Li Junjian Zhou Zhangbing Zhang Zhiqiang Wang Hao Liu Xiaoning Peng Yongming Gao Fulei Zhao Xianyong 《Natural Resources Research》2020,29(1):415-438
In this study, deposit- and district-scale three-dimensional (3D) fault-and-intrusion structure models were constructed, based on which a numerical simulation was implemented in the Jiaojia gold district, China. The numerical simulation of the models shows the basic metallogenic path and trap of the gold deposits using mineral system theory. The objective of this study was to delineate the uncertainty of the geometry or buffer zones of the ore-forming and ore-controlling fault-and-intrusion domains in 3D environment representing the exploration criteria extraction and the gold potential targeting in the study area. The fast Lagrangian analysis of continua in three dimensions was used as the platform to define the stress deformation fracture ore storage and the hydrothermal seepage channel zone based on the gold deposit features and metallogenic model in the study area. The validity of the numerical simulation was verified by comparing it with robust 3D geological models of the large Xincheng gold deposit. The potential targeting zones are analyzed for uncertainty and then evaluated by Boolean operation in a 3D geological model using the computer-aided design platform. The research results are summarized as follows. (1) In the pre-mineralization period, the Jiaodong fault’s left lateral movement created the Jiaojia network faults and formed a fracture zone with NW- to NNW-trending dips of 20° to 40°. (2) During the mineralization period, hydrothermal flow was associated with the intrusion geometry and features. However, it was constrained by the Jiaojia fault, which blocked the vadose flow into the upper wall rock and made the hydrothermal route close to the fault in the footwall fracture zones. (3) Three gold potential targets were identified by the numerical simulation results in the study area: the NW-trending Sizhuang gold deposit, the NW-trending zone of Jiaojia gold deposit, and the NE-trending zone of the Xincheng gold deposit. (4) The numerical simulation results show the fault-and-intrusion metallogenic domain and the hydrothermal alteration zones, which reflect the main ore-controlling and ore-forming factors of mineralization. The information obtained through the numerical simulation discussed here can be used to define exploration criteria in the study area.
相似文献16.
Geologically Constrained Fuzzy Mapping of Gold Mineralization Potential,Baguio District,Philippines 总被引：2，自引：0，他引：2
An application of the theory of fuzzy sets to the mapping of gold mineralization potential in the Baguio gold mining district of the Philippines is described. Proximity to geological features is translated into fuzzy membership functions based upon qualitative and quantitative knowledge of spatial associations between known gold occurrences and geological features in the area. Fuzzy sets of favorable distances to geological features and favorable lithologic formations are combined using fuzzy logic as the inference engine. The data capture, map operations, and spatial data analyses are carried out using a geographic information system. The fuzzy predictive maps delineate at least 68% of the known gold occurrences that are used to generate the model. The fuzzy predictive maps delineate at least 76% of the unknown gold occurrences that are not used to generate the model. The results are highly comparable with the results of previous stream-sediment geochemical survey in the area. The results demonstrate the usefulness of a geologically constrained fuzzy set approach to map mineral potential and to redirect surficial exploration work in the search for yet undiscovered gold mineralization in the mining district. The method described is applicable to other mining districts elsewhere. 相似文献
17.
Abstract The accumulation of geological information in digital form, due to modern exploration methods, has introduced the possibility of applying geographical information system technology to the field of geology. To achieve the benefits in information management and in data analysis and interpretation, however, it will be necessary to develop spatial models and associated data structures which are specifically designed for working in three dimensions. Some progress in this direction has already been demonstrated, with the application of octree spatial subdivision techniques to the storage of uniform volume elements representing mineral properties. By imposing octree tessellations on more precisely-defined geometric data, such as triangulated surfaces and polygon line segments, it may now be possible to combine efficient spatial addressing with topologically-coded boundary representations of geological strata. The development of storage schemes capable of representing such geological boundary models at different scales poses a particular problem, a possible solution to which may be by means of hierarchical classification of the vertices of triangulated surfaces according to shape contribution. 相似文献
18.
Jiangfeng She Chuang Li Jiaqi Li Qiujun Wei 《International journal of geographical information science》2018,32(3):476-497
With the extensive application of virtual geographic environments and the rapid development of 3D visualization analysis, the rendering of complex vector lines has attracted significant attention. Although there are many rendering algorithms in 3D geographic information system (GIS), they are not sufficiently flexible to meet the requirements for rendering linear symbols composed of diverse colors and shapes. However, the interactive rendering of a scene and the accuracy of the symbols are important components for large-scale, complex vector lines. In this paper, we propose a graphics processing unit (GPU)-accelerated algorithm for rendering linear symbols on 3D terrain. Symbol rendering is embedded within the terrain-rendering process, and vector lines are encoded in a 3D texture and then transferred to the GPU. A set of visual properties are used to enrich the expression of symbols with the help of geometric operations in the fragment shader. A series of experiments demonstrate that the proposed method can be utilized for drawing various pixel-exact linear symbols and can achieve real-time rendering efficiency. 相似文献
19.
Mineral Favorability Mapping: A Comparison of Artificial Neural Networks,Logistic Regression,and Discriminant Analysis 总被引：1，自引：0，他引：1
A Probabilistic Neural Network (PNN) was trained to classify mineralized and nonmineralized cells using eight geological, geochemical, and geophysical variables. When applied to a second (validation) set of well-explored cells that had been excluded from the training set, the trained PNN generalized well, giving true positive percentages of 86.7 and 93.8 for the mineralized and nonmineralized cells, respectively. All artifical neural networks and statistical models were analyzed and compared by the percentages of mineralized cells and barren cells that would be retained and rejected correctly respectively, for specified cutoff probabilities for mineralization. For example, a cutoff probability for mineralization of 0.5 applied to the PNN probabilities would have retained correctly 87.66% of the mineralized cells and correctly rejected 93.25% of the barren cells of the validation set. Nonparametric discriminant analysis, based upon the Epanechnikov Kernel performed better than logistic regression or parametric discriminant analysis. Moreover, it generalized well to the validation set of well-explored cells, particularly to those cells that were mineralized. However, PNN performed better overall than nonparametric discriminant analysis in that it achieved higher percentages of correct retention and correct rejection of mineralized and barren cells, respectively. Although the generalized regression neural network (GRNN) is not designed for a binary—presence or absence of mineralization— dependent variable, it also performed well in mapping favorability by an index valued on the interval [0, 1]. However, PNN outperformed GRNN in correctly retaining mineralized cells and rejecting barren cells of the validation set. 相似文献
20.
基于GIS的斜坡单元划分方法改进与实现 总被引：5，自引：0，他引：5
斜坡单元已广泛应用于滑坡易发性制图和地质灾害评价。然而在山间盆地或大型宽谷处,常规方法划分出的斜坡单元与地貌背景难以匹配。依据高程及其衍生变量的基本形态系统和曲率的流域分割原理,基于ArcGIS技术,通过叠加曲率和反转曲率的流域边界,改进了斜坡单元划分方法。结果表明：与常规方法相比,改进方法不仅能够使用山脊线和山谷线以划分斜坡单元,还能利用台地边界和宽谷边界以分割水平地表与倾斜地表;划分出的单元大小相对均匀,单元形状总体介于圆形和正三角形之间。对于水平成分较多的地区,如黄土塬区和水库库区,该方法与传统方法相比,具有较好的应用前景。 相似文献