Inferring trip purposes and uncovering travel patterns from taxi trajectory data   总被引：9，自引：0，他引：9  

Li Gong  Xi Liu  Lun Wu 《制图学和地理信息科学》2016,43(2):103-114

Global positioning system-enabled vehicles provide an efficient way to obtain large quantities of movement data for individuals. However, the raw data usually lack activity information, which is highly valuable for a range of applications and services. This study provides a novel and practical framework for inferring the trip purposes of taxi passengers such that the semantics of taxi trajectory data can be enriched. The probability of points of interest to be visited is modeled by Bayes’ rules, which take both spatial and temporal constraints into consideration. Combining this approach with Monte Carlo simulations, we conduct a study on Shanghai taxi trajectory data. Our results closely approximate the residents’ travel survey data in Shanghai. Furthermore, we reveal the spatiotemporal characteristics of nine daily activity types based on inference results, including their temporal regularities, spatial dynamics, and distributions of trip lengths and directions. In the era of big data, we encounter the dilemma of “trajectory data rich but activity information poor” when investigating human movements from various data sources. This study presents a promising step toward mining abundant activity information from individuals’ trajectories.  相似文献   

基于多源信息的区域尺度山地植被带数字化提取     

孙然好  张百平  许娟 《山地学报》2011,29(5)

山地植被带的提取及分析是地学和生态学研究的基础问题之一.利用野外点/线调查和历史文献资料,可以对局域尺度山体的植被带进行归纳和描绘,而在区域乃至全球尺度上更多依赖于学者的经验和知识.利用内蒙古大青山地区1∶100万植被图、1∶10万土地利用图、1∶25万DEM等,设计逻辑判别规则,提取典型的山地植被带斑块;然后基于贝叶斯识别算法,利用地形、水热和太阳辐射等因子对区域尺度山地植被带进行空间分布模拟,最终提取的植被带具有较高的精度,总体精度为74.53％,Kappa系数为0.69.研究表明,利用多源数据可以提取和模拟区域尺度山地植被带连续分布格局,中小比例尺空间数据的集成应用使得该方法的推广具有较大的可行性,为进一步获取大陆及全球尺度的山地植被带数据奠定了基础.  相似文献   

浅谈粗差探测方法     

傅伟  胡辉  龙美林 《北京测绘》2011,(3):51-54

由于受到自然界、仪器、人为等一些因素的影响,观测数据中不但存在偶然误差而且还存在着由这些因素引起的粗差。因此,对观测数据进行认真检测,定位并修正粗差观测,以提高参数估计的准确度和精度,一直是测绘工程领域的热点问题。本文对粗差探测进行了简要概述,同时详细地介绍了三种粗差探测方法。  相似文献   

基于贝叶斯原理的PP波和PS波AVO联合反演方法研究(英文)   总被引：2，自引：1，他引：1  

胡国庆  刘洋  魏修成  陈天胜 《应用地球物理》2011,8(4):293-302

基于Aki-Richards公式和贝叶斯原理,本文发展了利用叠前PP波和PS波资料联合反演P波速度比、S波速度比和密度比的方法。该方法假设参数之间满足正态分布,引入参数协方差矩阵来描述反演参数之间的相关性以提高反演过程的稳定性,并同时使反演的参数序列服从Cauchy分布,引入矩阵Q来描述参数序列的稀疏性以提高反演结果的分辨率。采用本文提出的方法对模型数据和实际多波资料进行反演,结果表明:本文方法正确有效;与传统的单一PP波反演相比,PP波和PS波AVO联合反演具有稳定性更好和反演精度更高等优点。  相似文献   

时空地统计学方法研究及进展     

叶近天  季世民  杨勇 《东北测绘》2014,(1):38-43

随着理论技术的不断发展,对环境因子仅进行空间估计和量化已不再满足精准农业等地理分支学科的精度要求,因此人们在传统地统计方法的基础上衍生出时空地统计学。该方法将时间域和空间域紧密联系起来,运用时空插值和随机模拟,更客观全面地描述地物的区域性时空分布。本文首先阐明了时空地统计学的主要概念及历史应用领域,随后介绍了当前主流的时空地统计方法及其各自的精度与适用领域,最后总结了时空地统计方法研究的不足和方向。  相似文献   

基于精确Zoeppritz方程的非线性AVO三参数反演          下载免费PDF全文

周林  李景叶  陈小宏 《地球物理学报》2016,59(7):2663-2673

常规AVO三参数反演通常存在密度反演不准确的问题,而密度参数对常规油气藏中的流体识别、流体饱和度计算、孔隙度计算以及非常规油气藏中TOC含量计算、裂缝预测等都至关重要,因此对于研究如何利用大偏移距振幅信息和富含密度信息的PS波地震资料来提高密度反演结果的稳定性和精度显得尤为重要.研究基于贝叶斯反演理论框架,引入三变量Cauchy分布先验约束,利用精确Zoeppritz方程构建了AVO三参数联合反演的目标函数,对目标函数进行Taylor二阶非线性简化,得到模型参数的迭代更新公式,实现了大偏移距地震振幅信息的利用和PP波、PS波联合反演.合成数据和实际地震数据的方法测试结果表明,新方法不仅可以直接反演纵波速度、横波速度和密度,而且还具有很高的精度,尤其是密度反演结果.基于合成数据的PP波、PS波单独反演结果与PP波和PS波联合反演结果对比显示,联合反演稳定性更好,精度更高,抗噪能力更强,验证了该方法的可行性和有效性.与基于Aki-Richards近似公式的反演结果对比表明,该反演方法具有更高的反演精度和更好的抗噪性.  相似文献   

处理高杠杆异常值的抗隐差型Bayes方法   总被引：1，自引：1，他引：0  

张倩倩  归庆明  王延停 《武汉大学学报(信息科学版)》2012,37(5):582-585

给出了一种剔除初始子集中高杠杆异常值的方法。首先根据高杠杆异常值在总观测值集中所占的比例选出若干组观测值,使得至少有一组不含高杠杆异常值的概率很高;然后根据残差最小准则从中选出不含高杠杆异常值的那组作为初始子集;最后用这种初始子集确定方法结合Gibbs抽样给出了相应的Bayes多粗差定位算法。  相似文献   

Bayes逐步判别分析法在煤矿瓦斯分区评价中的应用   总被引：4，自引：0，他引：4  

彭苏萍  段延娥  孟召平  戈连柱 《煤田地质与勘探》2003,31(2):10-12

瓦斯是影响煤矿安全生产的主要因素，本文探索了依据Bayes逐步判别分析法建立评价预测模型，进行矿区瓦斯地质条件分析评价的一般方法，并结合淮南潘三矿的具体数据资料，进行实际应用研究，通过该区瓦斯地质条件评价指标体系的构建和等性块段的划分，实现了该区瓦斯地质条件的分区评价，为制定煤矿开采方案和进行瓦斯防治提供了重要依据。  相似文献   

A Bayesian/maximum-entropy view to the spatial estimation problem   总被引：12，自引：0，他引：12  

George Christakos 《Mathematical Geology》1990,22(7):763-777

The purpose of this paper is to stress the importance of a Bayesian/maximum-entropy view toward the spatial estimation problem. According to this view, the estimation equations emerge through a process that balances two requirements: High prior information about the spatial variability and high posterior probability about the estimated map. The first requirement uses a variety of sources of prior information and involves the maximization of an entropy function. The second requirement leads to the maximization of a so-called Bayes function. Certain fundamental results and attractive features of the proposed approach in the context of the random field theory are discussed, and a systematic spatial estimation scheme is presented. The latter satisfies a variety of useful properties beyond those implied by the traditional stochastic estimation methods.  相似文献   

Evaluating Proportions of Undetected Geological Events in the Case of Erroneous Identifications     

Jerry L. Jensen  Jeffrey D. Hart  Brian J. Willis 《Mathematical Geology》2006,38(2):103-112

Some geological events occur infrequently but still have a significant impact upon reservoir characteristics. By their very nature, however, it can be difficult to properly estimate the proportions of uncommon events because they may not appear during limited sampling. For example, even with 40 observations and an event proportion of 0.05, there is a 0.13 chance that no events will be observed. We provide some results and guidance concerning methods to estimate proportions when such events are not detected. Two cases are discussed, estimating proportions without errors in identification and estimating proportions when errors may arise. It is well-known that the distribution of possible proportions in the error-free case can be calculated using Bayesian analysis. If one assumes a standard uniform distribution as the prior for the proportion, Bayesian analysis gives a Beta distribution for the posterior. The situation becomes more complicated, however, when detection errors are included; the true proportion has a distribution consisting of several Beta distributions. The difference in results between the error-free and with-error situations can be considerable. For example, when 10 error-free observations are made and no uncommon events are detected, there is a 0.50 chance that the true proportion exceeds 0.06 and a 0.10 chance that it exceeds 0.19. Including the effects of erroneous identifications, however, increases the median proportion to 0.09 and the upper decile to 0.27. We also examine the case where there may be prior geological information, which can be incorporated by amending the prior distribution of the proportion. We find that the use of such a prior makes little difference unless there are very few observations or there are major differences between the anticipated and the observed proportions.  相似文献