整合GIS的生态环境建模与EDSS研究进展   总被引：1，自引：0，他引：1  

阚瑷珂  王绪本  李国庆  高志勇  汪涵 《地理与地理信息科学》2009,25(4)

围绕生态环境的空间问题建模及模型集成机制,综合评述了环境建模及其应用软件的研究现状和发展趋势,对比分析了生态环境模型与GIS集成的多种方式,重点讨论了当前环境决策支持系统的开发策略和研究热点,并结合本体技术和语义网服务展望了未来环境决策支持系统解决方案的特征。  相似文献   

基于电场矢量波动方程的三维可控源电磁法有限单元法数值模拟   总被引：7，自引：5，他引：2       下载免费PDF全文

张继锋  汤井田  喻言  王烨  刘长生  肖晓 《地球物理学报》2009,52(12):3132-3141

从可控源电磁法的基本原理出发,推导了基于电场矢量波动方程的三维边值问题,利用广义变分原理,把边值问题转换为变分问题,并引入散度条件,避免了伪解的出现,使有限元计算在理论上更加完备.在准静态近似条件下,把水平电偶极子在空中和大地的远区电场闭合表达式作为有限元计算中的区域外边界条件,解决了边界条件加载的困难;把应用于地震模拟中的伪delta函数引入到可控源电磁法中的三维有限元模拟中,消除了源点的奇异性,提高了方程组的稳定性.通过对均匀大地和层状介质模型的模拟,检验了程序的正确性,并对典型的地质体模型进行了数值模拟,分析了其变化规律.  相似文献   

时空Kriging算法在区域地磁场插值中的应用及改进          下载免费PDF全文

陈鼎新  刘代志  曾小牛  孟亮  杨晓君 《地球物理学报》2016,59(5):1743-1752

本文以区域地磁场为应用背景,研究了时间域信息对地磁场插值效果的影响.用时空Kriging算法进行插值时,在时空Kriging变差函数的拟合过程中,将角度信息引入向量距离,定义了新的向量距离形式,提出了改进的时空Kriging算法,并对权重的选取进行讨论.对经度87.2°E—126.6°E,纬度19.0°N—49.6°N范围内的32个台站时均值地磁场数据进行插值实验.在添加了时间信息之后,插值结果在兼顾经度方向和纬度方向变化的同时,边值问题也得以缓解,明显优于传统方法.交叉验证结果表明,随着时间域信息和向量角度的加入,Kriging算法的性能得到改进,地磁场的插值精度依次提高.对比实验中,改进Kriging算法的精度最高、性能最稳定,MAE集中在1nT左右,MSE集中在[0,5]的范围内.  相似文献   

基于SVG的WebGIS     

颜立志  陶海燕 《测绘与空间地理信息》2005,28(6):23-26

网络技术的飞速发展不但在于技术的深化．更在于新技术元素的创立。SVG作为网络图形的新家族成员,一改过去网络图形只重形式,忽略内容的缺点,渐渐显示其独特且强大之处,也为GIS提供了一个方便快捷的网络平台。本文探究基础地理信息系统功能在SVG中的实现技术。  相似文献   

Forecasting the ionospheric f₀F₂ parameter one hour ahead using a support vector machine technique     

Chun Chen  Zhensen Wu  Shuji Sun  Panpan Ban  Zhonghua Ding  Zhengwen Xu   《Journal of Atmospheric and Solar》2010,72(18):1341-1347

This paper proposes a method for forecasting the ionospheric critical frequency, f₀F₂, 1 h in advance, using the support vector machine (SVM) approach. The inputs to the SVM network are the time of day, seasonal information, 2 month running mean sunspot number (R2), 3 day running mean of the 3 h planetary magnetic ap index, the solar zenith angle, the present value f₀F₂(t) and its first and second increments, the observation of f₀F₂ at t?23 h, the 30-day mean value at time, t, f_mF₂ (t) and the previous 30 day running mean of f₀F₂ at t?23 h f_mF₂(t?23). The output is the predicted f₀F₂ 1 h ahead. The network is trained to use the ionospheric sounding data at Haikou, Guangzhou, Chongqing, Lanzhou, Beijing, Changchun and Manzhouli stations at high and low solar activities. The performance of the SVM model was verified with observed data. It is shown that the predicted f₀F₂ has good agreement with the observed f₀F₂. The performance of the SVM model is superior to that of the autocorrelation and persistence models, and that it is comparable to that of the neural network model.  相似文献   

Discrimination of crop types with TerraSAR-X-derived information     

《Physics and Chemistry of the Earth》2015

Although classification maps are required for management and for the estimation of agricultural disaster compensation, those techniques have yet to be established. This paper describes the comparison of three different classification algorithms for mapping crops in Hokkaido, Japan, using TerraSAR-X (including TanDEM-X) dual-polarimetric data. In the study area, beans, beets, grasslands, maize, potatoes and winter wheat were cultivated. In this study, classification using TerraSAR-X-derived information was performed. Coherence values, polarimetric parameters and gamma nought values were also obtained and evaluated regarding their usefulness in crop classification. Accurate classification may be possible with currently existing supervised learning models. A comparison between the classification and regression tree (CART), support vector machine (SVM) and random forests (RF) algorithms was performed. Even though J–M distances were lower than 1.0 on all TerraSAR-X acquisition days, good results were achieved (e.g., separability between winter wheat and grass) due to the characteristics of the machine learning algorithm. It was found that SVM performed best, achieving an overall accuracy of 95.0% based on the polarimetric parameters and gamma nought values for HH and VV polarizations. The misclassified fields were less than 100 a in area and 79.5–96.3% were less than 200 a with the exception of grassland. When some feature such as a road or windbreak forest is present in the TerraSAR-X data, the ratio of its extent to that of the field is relatively higher for the smaller fields, which leads to misclassifications.  相似文献   

Data-driven topo-climatic mapping with machine learning methods   总被引：1，自引：1，他引：0  

A. Pozdnoukhov  L. Foresti  M. Kanevski 《Natural Hazards》2009,50(3):497-518

Automatic environmental monitoring networks enforced by wireless communication technologies provide large and ever increasing volumes of data nowadays. The use of this information in natural hazard research is an important issue. Particularly useful for risk assessment and decision making are the spatial maps of hazard-related parameters produced from point observations and available auxiliary information. The purpose of this article is to present and explore the appropriate tools to process large amounts of available data and produce predictions at fine spatial scales. These are the algorithms of machine learning, which are aimed at non-parametric robust modelling of non-linear dependencies from empirical data. The computational efficiency of the data-driven methods allows producing the prediction maps in real time which makes them superior to physical models for the operational use in risk assessment and mitigation. Particularly, this situation encounters in spatial prediction of climatic variables (topo-climatic mapping). In complex topographies of the mountainous regions, the meteorological processes are highly influenced by the relief. The article shows how these relations, possibly regionalized and non-linear, can be modelled from data using the information from digital elevation models. The particular illustration of the developed methodology concerns the mapping of temperatures (including the situations of Föhn and temperature inversion) given the measurements taken from the Swiss meteorological monitoring network. The range of the methods used in the study includes data-driven feature selection, support vector algorithms and artificial neural networks.  相似文献   

用矢量有限元方法模拟随钻测井仪在倾斜各向异性地层中的电磁响应   总被引：25，自引：11，他引：14       下载免费PDF全文

孙向阳  聂在平  赵延文  李爱勇  罗曦 《地球物理学报》2008,51(5):1600-1607

用矢量有限元法模拟和分析了电各向异性倾斜沉积岩层的随钻测井电磁响应,为很好地模拟钻铤、井眼和激励线圈等,采用了基于圆柱坐标下的六面体剖分;同时采用了高阶叠层矢量基函数来描述每个剖分单元内的场,有利于减少剖分单元数和未知量.三维有限元程序采用数值模式匹配(当处于简单地层时)以及时域有限差分法计算的结果进行了验证,显示吻合非常好.最后仿真了不同各向异性系数和不同倾角的各向异性地层的随钻电阻率测井响应,有助于对各向异性及地层倾角的校正,以及对储层作出正确评价.  相似文献   

基于SVM的泥石流危险度评价研究   总被引：5，自引：4，他引：1  

原立峰 《地理科学》2008,28(2):296-300

选取泥石流一次(可能)最大冲出量(L₁)、泥石流发生频率(L₂)、流域面积(S₁)、主沟长度(S₂)、流域最大相对高差(S₃)、流域切割密度(S₆)和泥沙补给段长度比(S₉)7个因子作为泥石流沟谷危险度评价因子,运用支持向量机理论,以云南省37条泥石流沟的259个基础数据为样本进行学习训练和测试,建立泥石流危险度评价的支持向量机模型,通过实例验证,取得良好效果。  相似文献   

全波场地震勘探技术   总被引：6，自引：4，他引：2       下载免费PDF全文

佘德平  严建文  吴继敏 《地球物理学进展》2006,21(2):472-477

全波场地震勘探是近年来出现的一个全新的勘探理念,它包括全波场采集和全波场处理等各方面.本文首先描述了全波场地震勘探的特点,然后从观测系统设计、对采集设备要求及布置方式、矢量滤波、各向异性速度分析以及各向异性成像等方面介绍了其与常规3D地震勘探的差异,说明了全波场勘探可以从根本上解决有关储层物性和流体性质方面的信息问题,将引起地震勘探技术的革命.  相似文献