共查询到20条相似文献,搜索用时 15 毫秒
1.
Xu Peiliang 《Journal of Geodesy》1989,63(3):297-308
Nearly all work on the optimal design of networks has been confined to single objective optimal design. Less attention has
been paid to multi-objective optimal design where one must simultaneously optimize precision, reliability and other quantities.
This paper discusses the concept of multi-objective optimal second order design of networks and its properties, which proves
very different from that of single objective optimal design. To demonstrate its applications, a levelling network located
in an earthquake area in the north east of China is taken as an example. The result shows in this case that multi-objective
optimal design is optimal from the point of view of total objectives. 相似文献
2.
It is shown that also in a rank deficient Gauss-Markov model higher weights of the observations automatically improve the
precision of the estimated parameters as long as they are computed in thesame datum. However, the amount of improvement in terms of the trace of the dispersion matrix isminimum for the so-called “free datum” which corresponds to the pseudo-inverse normal equations matrix. This behaviour together with its consequences is discussed
by an example with special emphasis on geodetic networks for deformation analysis. 相似文献
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《国家一、二等水准测量规范》存在的问题及修改意见 总被引:2,自引:1,他引:2
水准测量规范作为测绘生产单位必须遵守的强制性标准,不应该存在缺陷与歧义。本文论述了水准测量规范国家标准GB/T 12897-2006存在的缺陷与不足,针对这些问题,作者给出了正确的方法。 相似文献
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Journal of Geodesy - A numerically efficient solution strategy is developed for the second-order design of a free distance network. It is based on the fact that the direct (non-canonical) way has a... 相似文献
6.
针对跨海长桥GNSS控制网精度要求高、测量难度大、无统一的精度标准等问题,以确保海中桥墩的精确定位为原则,从海中桥墩施工的平面坐标允许偏差出发,采用测量误差影响分析和配置方法,推导跨海长桥首级GNSS平面控制网必要精度的估算公式,即首级GNSS控制点的平面坐标精度不应低于海中桥墩平面坐标允许偏差的0.22倍.据此,进一步推导出最弱点点位精度、最弱边边长精度、跨海长边相对精度和同岸短边相对精度等基本精度指标.最后,通过港珠澳大桥首级GNSS控制网的精度设计和实际精度的统计分析,验证文中设计方法的合理性和可行性. 相似文献
7.
G. Even-Tzur 《Journal of Geodesy》2002,76(8):455-461
The performance of geodetic monitoring networks is heavily influenced by the configuration of the measured GPS vectors. As
an effective design of the GPS measurements will decrease GPS campaign costs and increase the accuracy and reliability of
the entire network, the identification of the preferred GPS vectors for measurement has been highlighted as a core problem
in the process of deformation monitoring. An algorithm based on a sensitivity analysis of the network, as dependent upon a
postulated velocity field, is suggested for the selection of the optimal GPS vectors. Relevant mathematical and statistical
concepts are presented as the basis for an improved method of vector configuration design. A sensitivity analysis of the geodetic
geodynamic network in the north of Israel is presented, where the method is examined against two deformation models, the Simple
Transform Fault and the Locked Fault. The proposed method is suggested as a means for the improvement of the design of monitoring
networks, a common practice worldwide.
Received: 30 July 2001 / Accepted: 3 June 2002
Acknowledgments. It is my pleasant duty to thank the Survey of Israel and Dr. E. Ostrovsky for providing the variance–covariance matrix of
the G1 network in northern Israel. I would like to thank the reviewers of this paper for their constructive and helpful remarks. 相似文献
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Klaus-Peter Schwarz 《Journal of Geodesy》1974,48(2):171-186
When combining satellite and terrestrial networks, covariance matrices are used which have been estimated from previous data.
It can be shown that the least-squares estimator of the unknown parameters using such an estimated covariance matrix is not
necessarily the best. There are a number of cases where a more efficient estimator can be obtained in a different way. The
problem occurs frequently in geodesy, since in least-squares adjustment of correlated observations estimated covariance matrices
are often used.
If the general structure of the covariance matrix is known, results can often be improved by a method called covariance adjustment.
The statistical model used in least-squares collocation leads to a type of covariance matrix which fits into this framework.
It is shown in which way improvements can be made using a modified approach of principal component analysis.
As a numerical example the combination of a satellite and a terrestrial network has been computed with varying assumptions
on the covariance matrix. It is shown which types of matrices are critical and where the usual least-squares approach can
be applied without hesitation. Finally, a simplified representation of covariances for spatial networks by means of a suitable
covariance function is suggested.
Paper presented at the International Symposium on Computational Methods in Geometrical Geodesy-Oxford, 2–8 September, 1973. 相似文献
12.
The analysis of Global Positioning System (GPS) coordinates time series is a valuable tool in quantifying crustal deformations. The longer continuous GPS time series allow estimation of nonlinear signatures. As a matter of fact, besides the linear and periodic behaviors, other relevant signals are present in such time series as the so-called transient deformations. They can be related to, e.g., slow slip events, which play a crucial role in studying fault mechanisms. To give reliable estimates of these signals, an appropriate and rigorous approach for defining the deterministic and the stochastic models of the data is needed. We prove that the theory of the second order stationary random process (SOSRP) can be used to describe the stochastic behavior of the daily GPS time series. In particular, the second order stationarity condition has to be verified for the daily GPS coordinate time series to be described as a SOSRP. This method has been already used for modeling the gravity field of the earth and in predicting/filtering problems, and this work shows that it can also be useful for characterizing the colored noise in the GPS time series. 相似文献
13.
H. Müller 《Journal of Geodesy》1985,59(4):316-331
The paper deals with the solution of the weight problem for linear-angular networks on the base of criterion matrices. The
observation plan of combined linear-angular networks consists of distances as well as of directions in any form. In particular
the role of criterion matrices of completely isotropic structure for this type of two-dimensional network is discussed. Starting
from an extreme network design, the results of a least-squares approximation are described analytically. In this case, the
observation plan contains all geometrical point connections. Finally, the considerations are completed by giving as an example
the second-order design of a control network for a dam of a water reservoir. 相似文献
14.
J. Gazdzicki 《Journal of Geodesy》1976,50(4):363-376
In strength analysis of horizontal geodetic networks it is appropriate to use pairs of functions which involve the relative
position of two points and relative position of three points. Using properly chosen pairs of functions, formulae are given
which allow the computation of precision criteria for the orientation and scale of the network as well as its shape. To illustrate
the presentation of results, new types of errors ellipses are introduced. Analogies and correlations existing among the adopted
functions are introduced by using the concept of orthogonal networks which are defined in the paper. 相似文献
15.
The general problem of the optimal design for a geodetic network subject to any extrinsic factors, namely the first-order design problem, can be dealt with as a numeric optimization problem. The classic theory of this problem and the optimization methods are revised. Then the innovative use of the simulated annealing method, which has been successfully applied in other fields, is presented for this classical geodetic problem. This method, belonging to iterative heuristic techniques in operational research, uses a thermodynamical analogy to crystalline networks to offer a solution that converges probabilistically to the global optimum. Basic formulation and some examples are studied. 相似文献
16.
A. Sárhidai 《Journal of Geodesy》1986,60(4):355-376
Techniques will be presented for the design of one-dimensional gravity nets by means of given variance-covariance matrices.
After a critical review of the methods for the solution of the matrix equation
, we shall compare different numerical results in order to judge the quality of the designs carried out by means of anSVD criterion matrix, by a criterion matrix created according to an assumed distance-dependence of the mean errors of the grid
points, and by means of an iteratively improved criterion matrix respectively. 相似文献
17.
Deformation measurements have a repeatable nature. This means that deformation measurements are performed often with the same equipment, methods, geometric conditions and in a similar environment in epochs 1 and 2 (e.g., a fully automated, continuous control measurements). It is, therefore, reasonable to assume that the results of deformation measurements can be distorted by both random errors and by some non-random errors, which are constant in both epochs. In other words, there is a high probability that the difference in the accuracy and precision of measurement of the same geometric element of the network in both epochs has a constant value and sign. The constant errors are understood, but the manifestation of these errors is difficult to determine in practice. For free control networks (the group of potential reference points in absolute control networks or the group of potential stable points in relative networks), the results of deformation measurements are most often processed using robust methods. Classical robust methods do not completely eliminate the effect of constant errors. This paper proposes a new robust alternative method called REDOD. The performed tests showed that if the results of deformation measurements were additionally distorted by constant errors, the REDOD method completely eliminated their effect from deformation analysis results. If the results of deformation measurements are only distorted by random errors, the REDOD method yields very similar deformation analysis results as the classical IWST method. The numerical tests were preceded by a theoretical part. The theoretical part describes the algorithm of classical robust methods. Particular attention was paid to the IWST method. In relation to classical robust methods, the optimization problem of the new REDOD method was formulated and the algorithm for its solution was derived. 相似文献
18.
Huang Youcai 《Journal of Geodesy》1995,69(4):292-299
For detection of gross errors in processing triangulation networks, this paper introduces the principle of designing robust estimators with high breakdown points based on the median approach. Three examples presented in the paper show how to form the combinations of observations while considering geometrical constraints necessary for computing the median estimate, and how to calculate the breakdown points as a measure of global reliability of the estimate. 相似文献
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