共查询到20条相似文献，搜索用时 484 毫秒
1.
顾勇为 《测绘科学技术学报》2001,18(1):75-78
通过对一族耦合非线性扩散方程及其相关的特征值问题的研究,证明了此特征问题的解空间与对应的非线性L.enard特征值问题的解空间是微分同胚的;文中引入的次Lenard算子对,拓展了非线性化方法的应用范围. 相似文献
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非线性函数空间平差方程的解法及其特征 总被引：3，自引：0，他引：3
非线性函数空间的测量数据处理问题是测量数据处理理论研究中的前沿课题之一，其宗旨是不对非线性函数作线性化处理而直接在非线性函数空间进行误差议程或目标函数的非线性解算，文中给出了两种参估计准则下的非线性目标函数，讨论了目标函数的常和算法－迭代法。在此基础上提出非线性函数空间目标函数的最优算法－不依赖函数导数的多维轮环搜索法和基于差分理论的迭代算法。 相似文献
4.
高光谱遥感影像具有丰富的光谱信息,在地物分类识别方面具有明显的优势。针对复杂高光谱影像分类问题,应用了一种广义判别分析特征提取技术。将输入样本通过非线性函数映射到特征空间,在特征空间中应用线性判别特征提取方法;算法求解过程中涉及到在特征空间的内积用核函数代替,简化计算的同时也使得算法与非线性函数的具体形式无关。通过影像分类试验表明,该方法较常用特征提取方法更有利于分类精度的提高。 相似文献
5.
高光谱遥感影像具有丰富的光谱信息,在地物分类识别方面具有明显的优势.针对复杂高光谱影像分类问题,应用了一种广义判别分析特征提取技术.将输入样本通过非线性函数映射到特征空间,在特征空间中应用线性判别特征提取方法;算法求解过程中涉及到在特征空间的内积用核函数代替,简化计算的同时也使得算法与非线性函数的具体形式无关.通过影像分类试验表明,该方法较常用特征提取方法更有利于分类精度的提高. 相似文献
6.
针对由于多视点云的密度不同，将同名特征点作为配准基元的点云配准方法无法找到具有精准对应关系的点对，从而存在配准精度不高的问题，该文提出一种基于同名特征平面的点云配准方法。该方法将坐标原点在同名特征平面上的投影点作为同名特征点，以空间点面关系具有旋转不变性为约束条件，引入对偶四元数描述空间变换参数，基于最小二乘准则构建目标函数，利用Levenberg-Marquardt法解决配准模型的非线性优化问题。最后通过实测数据实验验证算法的正确性与有效性。结果表明：该方法能够实现实际场景中建/构筑物的多视点云配准；采用Levenberg-Marquardt法在迭代过程中可有效避免局部最小陷阱；对偶四元数有效减少了解算空间变换参数中的耦合误差。 相似文献
7.
一种遥感影像核变化检测方法 总被引：1，自引：0，他引：1
提出了一种新的遥感影像核变化检测方法。该方法是将原始空间不同时相的输入矢量通过核函数非线性映射到高维特征空间，然后在高维特征空间中通过传统变化检测方法处理得到新的输入矢量，最后通过半监督的单类支持向量机算法对新的输入矢量构造变化区域与非变化区域的最优分割超平面。试验证实，本文的核变化检测方法具有较高的检测精度和效率。 相似文献
8.
利用元胞自动机(Cellular Automata,CA)模拟土地利用变化,已经成为认识和理解其复杂动态演化过程的有效手段.传统的元胞自动机基于线性转换规则,较难表达土地利用变化的非线性边界问题.本文研究利用最小二乘支持向量机方法(LS-SVM),将原空间下的非线性可分问题,通过高斯径向基核函数映射到高维特征空间,简化... 相似文献
9.
基于蚁群优化的特征选择新方法 总被引：3，自引：0，他引：3
利用蚁群优化算法解决特征选择问题，以获得能代表问题空间的较优特征子集，并能降低分类系统的搜索空间。以航空纹理影像的特征选择和分类问题为例，利用主分量变换和蚁群优化算法分别对原始纹理影像特征集合进行特征提取、选择和分类。结果表明，本文方法不仅能够降低图像特征空间维数，减少图像分类的工作量，而且还可以提高分类识别的正确率。 相似文献
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Stability investigations of a discrete downward continuation problem for geoid determination in the Canadian Rocky Mountains 总被引：6，自引：0，他引：6
Z. Martinec 《Journal of Geodesy》1996,70(11):805-828
We investigate the stability of a discrete downward continuation problem for geoid determination when the surface gravity observations are harmonically continued from the Earth's surface to the geoid. The discrete form of Poisson's integral is used to set up the system of linear algebraic equations describing the problem. The posedness of the downward continuation problem is then expressed by means of the conditionality of the matrix of a system of linear equations. The eigenvalue analysis of this matrix for a particularly rugged region of the Canadian Rocky Mountains shows that the discrete downward continuation problem is stable once the topographical heights are discretized with a grid step of size 5 arcmin or larger. We derive two simplified criteria for analysing the conditionality of the discrete downward continuation problem. A comparison with the proper eigenvalue analysis shows that these criteria provide a fairly reliable view into the conditionality of the problem.The compensation of topographical masses is a possible way how to stabilize the problem as the spectral contents of the gravity anomalies of compensated topographical masses may significantly differ from those of the original free-air gravity anomalies. Using surface gravity data from the Canadian Rocky Mountains, we investigate the efficiency of highly idealized compensation models, namely the Airy-Heiskanen model, the Pratt-Hayford model, and Helmert's 2nd condensation technique, to dampen high-frequency oscillations of the free-air gravity anomalies. We show that the Airy-Heiskanen model reduces high-frequencies of the data in the most efficient way, whereas Helmert's 2nd condensation technique in the least efficient way. We have found areas where a high-frequency part of the surface gravity data has been completely removed by adopting the Airy-Heiskanen model which is in contrast to the nearly negligible dampening effect of Helmert's 2nd condensation technique. Hence, for computation of the geoid over the Canadian Rocky Mountains, we recommend the use of the Airy-Heiskanen compensation model to reduce the gravitational effect of topographical masses.In addition, we propose to solve the discrete downward continuation problem by means of a simple Jacobi's iterative scheme which finds the solution without determining and storing the matrix of a system of equations. By computing the spectral norm of the matrix of a system of equations for the topographical 5 × 5 heights from a region of the Canadian Rocky Mountains, we rigorously show that Jacobi's iterations converge to the solution; that the problem was well posed then ensures that the solution is not contaminated by large roundoff errors. On the other hand, we demonstrate that for a rugged mountainous region of the Rocky Mountains the discrete downward continuation problem becomes ill-conditioned once the grid step size of both the surface observations and the solution is smaller than 1 arcmin. In this case, Jacobi's iterations converge very slowly which prevents their use for searching the solution due to accumulating roundoff errors. 相似文献
12.
Exploring the Solution Space of Semi-structured Geographical Problems Using Genetic Algorithms 总被引：1，自引：0，他引：1
Semi-structured geographical problems are often addressed by groups of decision-makers. Each group member is likely to have a specific set of objectives that they wish to address and a unique perspective on the way in which the problem should be solved. The solution to such problems often requires consensus building and compromise among decision-makers as they attempt to optimize their own criteria. The set of criteria adopted by a particular decision-maker constrains the set of solutions he/she will deem acceptable. Compromise among multiple decision-makers can occur at the intersection of these constrained solution sets. Knowledge about the criteria space, the solution space, and the relation between the two is often incomplete for semi-structured problems. New tools are needed to explore, analyze, and visualize the solution space of a problem with respect to multiple analytical models and criteria. In this research we explore the utility of genetic algorithms as an effective means to: (1) search the solution space of geographical problems; (2) visualize the spatial ramifications of alternative criteria spaces; and (3) identify compromise solutions. 相似文献
13.
随机误差和多径效应作为GPS变形监测中的主要误差源,严重影响着GPS测量精度。针对这一问题,本文将主成分分析(Principal Component Analysis,PCA)模型引入GPS变形监测领域,首先利用传统PCA方法将测量数据转换至特征空间,通过剔除小特征值对应的特征向量实现对高斯分布随机噪声的抑制,然后将多径噪声作为色噪声进行分析,提出一种广义PCA方法利用多径噪声的时间相关性对其进行滤除,基于实际工程测试数据的实验结果表明,相对于传统的小波噪声抑制方法,所提方法可以获得更好的噪声抑制性能。 相似文献
14.
Precision, volume and eigenspectra for GPS ambiguity
estimation based on the time-averaged satellite geometry 总被引：1，自引：1，他引：1
P. J. G. Teunissen 《Journal of Geodesy》1997,71(5):290-301
In this contribution we consider the
time-averaged GPS single-baseline model and study in a qualitative sense its
relation with the geometry-free model and the geometry-based model. The
least-squares estimators of the model are derived and their properties
discussed. Special attention is given to the ambiguity search space, since it
plays such a crucial role in the problem of integer ambiguity estimation and
validation. Easy-to-evaluate, closed-form expressions are presented for the
volumes of the ambiguity search spaces that belong to the geometry-free model,
the single-epoch geometry-based model and the time-averaged model. By means of
an eigenvalue analysis, the geometry of the ambiguity search spaces is revealed
and its impact on the search for the integer least-squares ambiguities
discussed.
Received: 3 April 1996; Accepted: 6 January 1997 相似文献
15.
Identifying a route that avoids obstacles in continuous space is important for infrastructure alignment, robotic travel, and virtual object path planning, among others, because movement through space is not restricted to a predefined road or other network. Vector and raster GIS (geographic information system) solution approaches have been developed to find good/efficient routes. On the vector side, recent solution approaches exploit spatial knowledge and utilize GIS functionality, offering significant computational advantages in finding an optimal solution to this path routing problem. Raster‐based shortest path techniques are widely applied in route planning for wayfinding, corridor alignment, robotics and video gaming to derive an obstacle avoiding path, but represent an approximation approach for solving this problem. This research compares vector and raster approaches for identifying obstacle‐avoiding shortest paths/routes. Empirical assessment is carried out for a number of planning applications, highlighting representational issues, computational requirements and resulting path efficiency. 相似文献
16.
R. G. Bellaire 《Journal of Geodesy》1977,51(2):149-161
The boundary condition and solution of a Dirichlet problem on the upper half space are treated as random processes. It is
shown that the first-and second-order statistics of the solution to this problem are completely determined by the corresponding
statistics of the boundary condition. The mean of the solution is the mean of the process on the boundary. The correlation
function of the solution above the boundary is related to its value on the boundary by a Poisson integral formula.
formerly of The Analytic Sciences Corporation, Reading, Massachusetts 01867.
This research was supported in part by the Naval Weapons Laboratory, Dahlgren, Virginia, under Contract N00178-70-C-0200. 相似文献
17.
Wei Wang Junwu Chen Ji Li Xin Wang 《Journal of the Indian Society of Remote Sensing》2018,46(11):1863-1870
With the improvement in resolution, more and more useful information is contained in the space of remote sensing images, which makes the processing of remote sensing data become more complex, and it is easy to cause the curse of dimensionality and the poor recognition effect. In this paper, a remote target recognition approach named AJRC is proposed, which uses joint feature dictionary for sparse representation based on different feature information for adaptive weighting. Firstly, the features of the images are extracted to calculate the contribution weight of each eigenvalue in sparse representation, and each eigenvalue contribution weight is calculated in sparse representation. Through the adaptive method, the contribution ability of each feature value in sparse representation is strengthened, and new atoms are formed to construct feature dictionary, which makes the dictionary more discriminative. Then, the common features of each category image and the private features of a single image are extracted from the feature vector, and a joint dictionary is formed to represent the test image sparse and recognize the output of the target. Aiming at the problem that the target visual contrast difference, the low resolution and the rotation of the target with different angles, the experiment is carried out by different feature extraction methods. At the same time, we use the PCA method to reduce the feature dictionary in order to avoid dimensionality. Experiments show that compared with the existing SRC method and JSM method, this method has better recognition rate. 相似文献
18.
E. W. Grafarend 《Journal of Geodesy》2001,75(7-8):363-390
In a comparison of the solution of the spherical horizontal and vertical boundary value problems of physical geodesy it is
aimed to construct downward continuation operators for vertical deflections (surface gradient of the incremental gravitational
potential) and for gravity disturbances (vertical derivative of the incremental gravitational potential) from points on the
Earth's topographic surface or of the three-dimensional (3-D) Euclidean space nearby down to the international reference sphere
(IRS). First the horizontal and vertical components of the gravity vector, namely spherical vertical deflections and spherical
gravity disturbances, are set up. Second, the horizontal and vertical boundary value problem in spherical gravity and geometry
space is considered. The incremental gravity vector is represented in terms of vector spherical harmonics. The solution of
horizontal spherical boundary problem in terms of the horizontal vector-valued Green function converts vertical deflections
given on the IRS to the incremental gravitational potential external in the 3-D Euclidean space. The horizontal Green functions
specialized to evaluation and source points on the IRS coincide with the Stokes kernel for vertical deflections. Third, the
vertical spherical boundary value problem is solved in terms of the vertical scalar-valued Green function. Fourth, the operators
for upward continuation of vertical deflections given on the IRS to vertical deflections in its external 3-D Euclidean space
are constructed. Fifth, the operators for upward continuation of incremental gravity given on the IRS to incremental gravity
to the external 3-D Euclidean space are generated. Finally, Meissl-type diagrams for upward continuation and regularized downward
continuation of horizontal and vertical gravity data, namely vertical deflection and incremental gravity, are produced.
Received: 10 May 2000 / Accepted: 26 February 2001 相似文献
19.
P. Holota 《Journal of Geodesy》1997,71(10):640-651
In this paper the linear gravimetric boundary-value problem is discussed in the sense of the so-called weak solution. For
this purpose a Sobolev weight space was constructed for an unbounded domain representing the exterior of the Earth and quantitative
estimates were deduced for the trace theorem and equivalent norms. In the generalized formulation of the problem a special
decomposition of the Laplace operator was used to express the oblique derivative in the boundary condition which has to be
met by the solution. The relation to the classical formulation was also shown. The main result concerns the coerciveness (ellipticity)
of a bilinear form associated with the problem under consideration. The Lax-Milgram theorem was used to decide about the existence,
uniqueness and stability of the weak solution of the problem. Finally, a clear geometrical interpretation was found for a
constant in the coerciveness inequality, and the convergence of approximation solutions constructed by means of the Galerkin
method was proved.
Received: 21 June 1996 / Accepted: 14 April 1997 相似文献
20.
A new form of boundary condition of the Stokes problem for geoid determination is derived. It has an unusual form, because
it contains the unknown disturbing potential referred to both the Earth's surface and the geoid coupled by the topographical
height. This is a consequence of the fact that the boundary condition utilizes the surface gravity data that has not been
continued from the Earth's surface to the geoid. To emphasize the `two-boundary' character, this boundary-value problem is
called the Stokes pseudo-boundary-value problem. The numerical analysis of this problem has revealed that the solution cannot
be guaranteed for all wavelengths. We demonstrate that geoidal wavelengths shorter than some critical finite value must be
excluded from the solution in order to ensure its existence and stability. This critical wavelength is, for instance, about
1 arcmin for the highest regions of the Earth's surface.
Furthermore, we discuss various approaches frequently used in geodesy to convert the `two-boundary' condition to a `one-boundary'
condition only, relating to the Earth's surface or the geoid. We show that, whereas the solution of the Stokes pseudo-boundary-value
problem need not exist for geoidal wavelengths shorter than a critical wavelength of finite length, the solutions of approximately
transformed boundary-value problems exist over a larger range of geoidal wavelengths. Hence, such regularizations change the
nature of the original problem; namely, they define geoidal heights even for the wavelengths for which the original Stokes
pseudo-boundary-value problem need not be solvable.
Received 11 September 1995; Accepted 2 September 1996 相似文献