Extensions of GAP‐tree and its implementation based on a non‐topological data model     

Changxiu Cheng  Fangqu Niu  Jun Cai  Yanlu Zhu 《International journal of geographical information science》2013,27(6):657-673

This paper discusses extensions of GAP‐trees from three aspects and its implementation based on non‐topological structure in order to enhance access to large vector data sets. First of all, we apply cartographic generalization rules to build a generalization procedure of the GAP‐tree, which makes coarse representations more consistent with human cognition. Second, we replace the three‐dimensional (pseudo‐) Reactive‐tree index with a 2D R‐tree index and a B‐tree index to improve the system efficiency. Finally, we compress a binary GAP‐tree into multi‐way GAP‐trees in order to reduce data redundancy. The shallower multi‐way GAP‐trees not only eliminate redundant data but also accelerate the system's response time. The extensions have been successfully implemented in PostgreSQL. A test of Beijing's land‐use data at the 1:10 000 scale demonstrates that the extended GAP‐trees are efficient, compact, and easy to implement.  相似文献   

THE PRAIRIE PENINSULA: A CLIMATIC PERSPECTIVE     

Chelvadurai Manogaran 《自然地理学》2013,34(2):153-166

The adequacy of climate to explain the distribution of the tallgrass-prairie—oak-hickory forest in the United States has been investigated and it is shown that the prairie peninsula originated due to a unique combination of climatic conditions prevailing in the Middle West. The climate which is unique to the peninsula has been defined in terms of effective moisture as determined by soil moisture deficit, water surplus, and the index of moisture using the Thornthwaite's water budget procedure.

The results of this study demonstrate that definite quantities of soil moisture deficit, water surplus, and the index of moisture restrict the growth and development of the tallgrass-prairie-oak-hickory forest to a well-defined geographic region in the United States. Vegetational response to effective climate is expressed in the closeness of fit between the critical isolines of soil moisture deficit, water surplus, and the index of moisture and the boundaries of the prairie peninsula. In particular, the moisture index isolines of 15 and 30 enclose the study area virtually on all sides and this shows that the climate of the prairie peninsula resembles neither the climate of the “true prairie” nor the climates of the surrounding forest regions.  相似文献   

Modelling of infiltration using artificial intelligence techniques in semi-arid Iran     

Parveen Sihag  Vijay P. Singh  Anastasia Angelaki  Vinod Kumar  Alireza Sepahvand  Evangelia Golia 《水文科学杂志》2013,58(13):1647-1658

ABSTRACT

Infiltration plays a fundamental role in streamflow, groundwater recharge, subsurface flow, and surface and subsurface water quality and quantity. In this study, adaptive neuro-fuzzy inference system (ANFIS), support vector machine (SVM) and random forest (RF) models were used to determine cumulative infiltration and infiltration rate in arid areas in Iran. The input data were sand, clay, silt, density of soil and soil moisture, while the output data were cumulative infiltration and infiltration rate, the latter measured using a double-ring infiltrometer at 16 locations. The results show that SVM with radial basis kernel function better estimated cumulative infiltration (RMSE = 0.2791 cm) compared to the other models. Also, SVM with M4 radial basis kernel function better estimated the infiltration rate (RMSE = 0.0633 cm/h) than the ANFIS and RF models. Thus, SVM was found to be the most suitable model for modelling infiltration in the study area.  相似文献   

Estimation of daily suspended sediments using support vector machines     

《水文科学杂志》2013,58(3):656-666

Abstract

The use of support vector machines—a new regression procedure in water resources—was investigated for predicting suspended sediment concentration/load in rivers. The method was applied to the observed streamflow and suspended sediment data of two rivers in the USA, which have already been used in earlier studies using soft computing techniques. The estimated suspended sediment values were found to be in good agreement with the observed ones. Negative sediment estimates, which were encountered in the soft computing calculations, are not produced by this method. The results indicate that this approach may give better performance than those described in the literature using different methodologies.  相似文献   

An efficient measure of compactness for two-dimensional shapes and its application in regionalization problems     

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   

基于ICEEMD-ICA准则进行数据处理的基坑变形组合预测研究     

马琳 《地质与勘探》2023,59(5):1074-1082

为确保基坑变形的高精度预测，基于基坑现场变形监测成果，先利用ICEEMD-ICA准则进行数据处理，即将变形数据分解为趋势项和随机项，再通过ISFLA-RVM-GRNN模型实现其组合预测。最后，再引入若干传统预测模型进行类似预测，通过预测结果对比，验证本文组合预测思路的合理性。实例分析表明：ICEEMD-ICA准则能实现基坑变形数据的合理分解，其分解能力要优于传统分解模型，且在5个监测点的预测结果中，ISFLA-RVM-GRNN模型的预测精度较高，预测结果的平均相对误差间于1.97%～2.07%。经外推预测，得基坑变形趋于稳定方向发展。同时，通过不同模型预测结果的对比性验证，得出ISFLA-RVM-GRNN模型相较传统预测模型具有更优的预测效果，验证了其构建思路是合理有效的。  相似文献   

Application of statistical learning algorithms to ultimate bearing capacity of shallow foundation on cohesionless soil     

Pijush Samui 《国际地质力学数值与分析法杂志》2012,36(1):100-110

This study employs two statistical learning algorithms (Support Vector Machine (SVM) and Relevance Vector Machine (RVM)) for the determination of ultimate bearing capacity (q_u) of shallow foundation on cohesionless soil. SVM is firmly based on the theory of statistical learning, uses regression technique by introducing varepsilon‐insensitive loss function. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. It also gives variance of predicted data. The inputs of models are width of footing (B), depth of footing (D), footing geometry (L/B), unit weight of sand (γ) and angle of shearing resistance (?). Equations have been developed for the determination of q_u of shallow foundation on cohesionless soil based on the SVM and RVM models. Sensitivity analysis has also been carried out to determine the effect of each input parameter. This study shows that the developed SVM and RVM are robust models for the prediction of q_u of shallow foundation on cohesionless soil. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

非Dedekind完备的序拓扑向量空间中集值映射的一类扩张     

肖赟  刘信东 《成都信息工程学院学报》2010,(6):336-340

在泛函分析中有着重要作用的Hahn-Banach扩张定理及其很多推广定理的条件都要求值域空间是Dedekind完备的,这是一个非常强的条件,因而在一定程度上局限了这些扩张定理的应用。主要考虑弱化这些定理的条件,讨论当值域空间是由锥引人序的非Dedekind完备的序拓扑向量空间时,一类集值映射的扩张。  相似文献   

基于支持向量机理论的地下水动态遥感监测模型与应用   总被引：2，自引：0，他引：2  

付俊娥  苏庆珣  潘世兵  路京选 《地球信息科学学报》2010,12(4):466-472

地下水是我国内陆干旱地区水资源的重要组成部分,也是极为敏感的生态环境因素之一。地下水动态变化影响着绿洲和湿地的演化,以及土地资源的开发。西北地区地下水监测网尚不完善,动态资料相对缺乏。遥感技术可以弥补传统地下水位监测手段的不足。由于降水极少,西北干旱区地表反射率与地下水水位埋深关系极其密切。选用归一化植被指数(NDVI)、地表温度(LST)数据,应用支持向量机回归方法,建立西北干旱地区地下水位遥感监测模型。提取MODIS影像中的NDVI和LST产品上的地表温度和植被指数信息,作为模型的输入,通过合理选择核函数进行支持向量机的回归分析,从而建立地表植被指数、地表温度与地下水位的相关数学模型,并分析了不同核函数所拟合结果。在河西走廊疏勒河流域的研究成果表明,运用MODIS数据开发地下水动态模型反演水位变化是可行的,模型拟合的结果比较符合实际情况,尤其是对于细土平原地下水浅埋地区模型应用效果更为理想。一次多项式核函数适合模拟埋深小于3m浅埋地下水,径向基函数RBF核函数和三次多项式核函数法则更适合模拟较大埋深情况。开发的地下水位遥感监测模型可为西北干旱区水循环研究和流域水资源管理提供技术手段。  相似文献   

北京一号小卫星数据的城市景观格局监测分析——以徐州市城区为例   总被引：1，自引：0，他引：1  

杜培军  单丹丹  夏俊士  刘培 《地球信息科学学报》2010,12(6):855-862

为了推进北京一号小卫星遥感数据在城市景观生态研究中的应用,针对其全色影像4m分辨率、多光谱影像32m分辨率的特点,试验分析北京一号小卫星影像在城市景观格局变化中的应用效果和特点。通过对不同分类器的比较,选择支持向量机分类器对多光谱影像、全色影像、全色与多光谱融合影像三个数据集进行景观组分分类,结果表明,全色与多光谱融合影像的分类精度最高。利用多时相、多光谱遥感数据统计分析了城市景观组分与格局变化,表明32m空间分辨率的多光谱影像可以用于城市景观格局变化和土地覆盖变化分析。本文全面试验和分析评价了北京一号多分辨率数据在城市景观格局研究中的应用效果。通过对同一年份全色影像和多光谱影像计算的景观格局指标的分析表明,全色数据能更有效地描述景观详细信息,多光谱数据可展现城市景观的整体格局,而融合后对景观格局分析能够获得优于单一数据的效果。试验和分析表明,北京一号小卫星4m全色高分辨率影像和32m多光谱数据的波段组合,能从不同尺度揭示城市景观格局和变化过程。  相似文献