粒度Hough变换及其在遥感影像直线检测中的应用   总被引：1，自引：0，他引：1  

巫兆聪  万茜婷  梁静  周正 《武汉大学学报(信息科学版)》2007,32(10):860-863

在基于Hough变换的遥感影像直线检测的过程中引入粒度计算的概念,利用粒度计算具有多角度、多层次观察问题的能力,对遥感影像中的直线边缘特征进行不同粗细的粒度分析,建立粒度计算概念下的直线检测算法,实现对不同长短、粗细直线的识别。真实的IKONOS遥感影像机场跑道提取试验证明了该方法的有效性。  相似文献   

Anomaly Detection in MODIS Land Products via Time Series Analysis     

ZHANG Jingxiong David Roy Sadashiva Devadiga ZHENG Min 《地球空间信息科学学报》2007,10(1):44-50

With remote sensing information products becoming increasingly varied and arguably improved, scientific applications of such products rely on their quality assessment. In an operational context such as the NASA (National Aeronautics and Space Administration) information production based on the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on board Earth Observing System (EOS) Terra and Aqua satellites, efficient ways of detecting product anomaly, i.e., to discriminate between product artifacts and real changes in Earth processes being monitored, are extremely important to assist and inform the user communities about potential unreliability in the products. A technique for anomaly detection, known as MAD (the median of absolute deviate from the median), in MODIS land products via time series analysis is described, which can handle intra- and in-ter-annual variation in the data by using MAD statistics of the original data and their first-order difference. This method is shown to be robust and work across major land products, including NDVI, active fire, snow cover, and surface reflectance, and its applicabil-ity to multi-disciplinary products is anticipated.  相似文献   

A Bayesian approach to the detection of gross errors based on posterior probability     

Q. Gui  Y. Gong  G. Li  B. Li 《Journal of Geodesy》2007,81(10):651-659

Existing methods for gross error detection, based on the mean shift model or the variance inflation model, have hardly considered or taken advantage of the potential prior information on the unknown parameters. This paper puts forward a Bayesian approach for gross error detection when prior information on the unknown parameters is available. Firstly, based on the basic principle of Bayesian statistical inference, the Bayesian method—posterior probability method—for the detection of gross errors is established. Secondly, considering either non-informative priors or normal-gamma priors on the unknown parameters, the computational formula of the posterior probability is given for both the mean shift model and the variance inflation model, respectively, under the condition of unequal weight and independent observations. Finally, as an example, a triangulation network is computed and analyzed, which shows that the method given here is feasible.  相似文献   

Application of clan member signal method in structural damage detection     

郭迅  卢书楠 《地震工程与工程振动(英文版)》2007,6(1):29-34

It is well known that in most cases, a reference is necessary for structural health diagnosis, and it is very difficult to obtain such a reference for a given structure. In this paper, a clan member signal method (CMSM) is proposed for use in structures consisting of groups (or clans) that have the same geometry, i.e., the same cross section and length, and identical boundary conditions. It is expected that signals measured on any undamaged member in a clan after an event could be used as a reference for any other members in the clan. To verify the applicability of the proposed method, a steel truss model is tested and the results show that the CMSM is very effective in detecting local damage in structures composed of identical slender members.  相似文献   

Sensitivity equations for hyperbolic conservation law-based flow models     

Vincent Guinot  Matthieu LeménagerBernard Cappelaere 《Advances in water resources》2007

The present paper focuses on the governing equations for the sensitivity of the variables to the parameters in flow models that can be described by one-dimensional scalar, hyperbolic conservation laws. The sensitivity is shown to obey a hyperbolic, scalar conservation law. The sensitivity is a conserved scalar except in the case of discontinuous flow solutions, where an extra, point source term must be added to the equations in order to enforce conservation. The propagation speed of the sensitivity waves being identical to that of the conserved variable in the original conservation law, the system of conservation laws formed by the original hyperbolic equation and the equation satisfied by the sensitivity is linearly degenerate. A consequence on the solution of the Riemann problem is that rarefaction waves for the variable of the original equation result in vacuum regions for the sensitivity. The numerical solution of the hyperbolic conservation law for the sensitivity by finite volume methods requires the implementation of a specific shock detection procedure. A set of necessary conditions is defined for the discretisation of the source term in the sensitivity equation. An application to the one-dimensional kinematic wave equation shows that the proposed numerical technique allows analytical solutions to be reproduced correctly. The computational examples show that first-order numerical schemes do not yield satisfactory numerical solutions in the neighbourhood of moving shocks and that higher-order schemes, such as the MUSCL scheme, should be used for sharp transients.  相似文献   

Effects of underground cavities on Rayleigh waves—Field and numerical experiments     

A. Nasseri-Moghaddam  G. Cascante  C. Phillips  D.J. Hutchinson 《Soil Dynamics and Earthquake Engineering》2007,27(4):300-313

This paper presents the results of a multi-channel analysis of surface waves (MASW) test conducted over near-surface mine workings, with the objective of delineating the underlying. Numerical studies were carried out to explain and extend the results. The displacement time histories at the surface show amplitude changes in the region over the void, and the Fourier spectra show significant energy concentration on and in the vicinity of the cavity. Different numerical models are constructed and the responses at the surface of the medium and around voids of different sizes and embedment depths are monitored. The numerical results show that part of the incident energy is trapped within the void. The trapped energy bounces back and forth inside the void, until it is attenuated by radiation. The effect of the trapped energy is seen as a concentration of energy over the void region in the frequency domain. The amount of trapped energy is a function of the size and embedment of the void, as well as of the frequency content of the source. The void absorbs part of the energy and radiates it as body waves. Therefore, the recorded responses at the surface carry valuable information about the void. The characteristics of the void can be extracted from the surface responses by analyzing the responses in time, frequency, and spatial domains.  相似文献   

Radar measurements of integral parameters of hailstorms used on hail suppression projects     

Viktor Makitov   《Atmospheric Research》2007,83(2-4):380-388

The exact quantitative estimation of hailstorm precipitation intensity, allowing determining successfully the crop hail damage, is extremely necessary while carrying out of programs of experimental researches of the hail clouds as well as at realization of operative projects on hail suppression. On the other hand, the possibility of obtaining a trustworthy information about changes of hailfall intensity during cloud seeding operations enables to judge more objectively about seeding effect and to make a decision about its beginning and termination. Just because of such a parameter, the kinetic energy of hailfalls presents a great interest for the researchers. As it is known, measuring the kinetic energy of hailfalls is carried out both directly by ground network of hailpads, and by radar methods. The accuracy of the radar methods of the hail kinetic energy measurement strongly depends not only on the choice of an optimum formula for calculation but also on the algorithm used for separating hail and rain parts of radar echo and on the way it was used in the hail–rain mixture zone of precipitation.The method of calculating the kinetic energy of the hailfalls, based on empirical dependence of hail probability P_h on a height of a zone of a radar echo with a reflectivity of 45 dBZ above a level of zero isotherm ΔH₄₅, is offered in the given work. The algorithm of separating hail and rain parts of a radar echo and the way it was applied in a hail–rain mixture zone is described. The examples of hail streaks in contours of radar reflectivity and in isopleths of hail kinetic energy obtained using the given algorithm are shown.In Mendoza province (Argentina), a hail suppression project (1993–1997) for the analysis of the vertical structure of a radar echo with Z_max > 45 dBZ, such new parameter is an integral altitude, was used. This dimensionless parameter is most sensitive to such a condition of radar echo when all four contours of increased reflectivity Z₄₅, Z₅₅, Z₆₅, and Z₇₅ synchronously reach the maximal values. The analysis of time distributions of the main radar parameters of hailstorms on a background of values of integral altitude is resulted. It is shown that local hailfall maximum intensities on the ground are observed after the achievement of maximum integral altitude with a certain delay. It enables to predict zones of the greatest hail damage in a mode of radar observation.  相似文献   

基于边缘特征匹配的遥感影像变化检测预处理方法   总被引：1，自引：0，他引：1  

袁修孝  宋妍 《武汉大学学报(信息科学版)》2007,32(5):381-386

提出了一种基于边缘特征匹配的遥感影像变化检测预处理方法，在进行不同时相遥感影像配准时，一并解求两期影像的辐射校正系数，同时实现两期影像的配准和辐射校正。实验表明，经预处理后，两期影像的色调基本一致，地物没有明显的几何变形。  相似文献   

一种运用纹理和光谱特征消除投影差影响的建筑物变化检测方法     

袁修孝  宋妍 《武汉大学学报(信息科学版)》2007,32(6):489-493

针对不同时期高分辨率遥感影像变化检测中城区建筑物因投影差差异所产生的误检测现象,提出了一种综合应用光谱和纹理特征的建筑物变化检测方法。以变化和未发生变化地物影像的散度作为可分性依据,首先对光谱差分影像在混合高斯密度模型下建模,并采用马尔可夫最小错误概率准则提取初始变化区域,往往含有错判的建筑物。然后将误判建筑物影像类和真实变化影像类构成训练集,通过引入多通道Gabor滤波器,提取训练集的纹理差分特征,并采用分类别PCA变换实施纹理差分特征的选择。最后对选择出的纹理差分特征依据高斯混合密度模型建模,并用马尔可夫最小错误概率提取真变化区域,即可去除光谱信息检测所产生的伪变化。试验表明,本文方法能够较好地解决建筑物变化的错判问题,提高了影像变化检测的精度。  相似文献   

基于正常轮廓更新的自适应异常检测方法     

熊平 《武汉大学学报(信息科学版)》2007,32(9):842-845

根据网络系统发生正常改变的基本特征,提出了确定网络系统正常改变的“三条件”计算方法,其计算结果可作为更新正常轮廓的依据。对正常轮廓的更新问题进行了深入探讨,提出了自适应异常检测的实现机制。并以网络流量分析为例,验证了在异常检测中应用这一方法的可行性。  相似文献