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1.
针对测量数据处理中常用的条件平差模型,该文介绍了条件平差模型按残差进行粗差探测的方法和实施步骤,导出了条件平差模型按观测值偏差进行粗差探测的公式,证明了当观测误差独立时,这两种检验方法对于检验单个粗差的等价性。并通过算例证实了直接利用偏差估值构建的检验单个独立观测值的统计量与按残差构建的统计量完全相同。 相似文献
2.
When applying single outlier detection techniques, such as the Tau () test, to examine the residuals of observations for outliers, the number of detected observations in any iteration of adjustment is most often more numerous than the actual number of true outliers. A new technique is proposed which estimates the number of outliers in a network by evaluating the redundancy contributions of the detected observations. In this way, a number of potential outliers can be identified and eliminated in each iteration of an adjustment. This leads to higher efficiency in data snooping of geodetic networks. The technique is illustrated with some numerical examples. 相似文献
3.
A new adjustment of the geodetic control networks in North America has been completed, resulting in a new continental datum—the
North American Datum of 1983 (NAD 83).
The establishment ofNAD 83 was the result of an international project involving the National Geodetic Survey of the United States, the Geodetic Survey
of Canada, and the Danish Geodetic Institute (responsible for surveying in Greenland). The geodetic data in Mexico and Central
America were collected by the Inter American Geodetic Survey and validated by the Defense Mapping Agency Hydrographic/Topographic
Center.
The fundamental task ofNAD 83 was a simultaneous least squares adjustment involving 266,436 stations in the United States, Canada, Mexico, and Central
America. The networks in Greenland, Hawaii, and the Caribbean islands were connected to the datum through Doppler satellite
and Very Long Baseline Interferometry (VLBI) observations.
The computations were performed with respect to the ellipsoid of the Geodetic Reference System of 1980. The ellipsoid is positioned
in such a way as to be geocentric, and its axes are oriented by the Bureau International de l'Heure Terrestrial System of
1984.
The mathematical model for theNAD readjustment was the height-controlled three-dimensional system. The least squares adjustment involved 1,785,772 observations
and 928,735 unknowns. The formation and solution of the normal equations were carried out according to the Helmert block method.
[Authors' note:This article is a condensation of the final report of the NAD 83 project. The full report (Schwarz,1989) contains a more complete discussion of all the topics.] 相似文献
4.
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
5.
Additional results are presented concerning a study that consider improvements over present Earth Rotation Parameter (ERP) determination methods by directly combining observations from various space geodetic systems in one adjustment. Earlier
results are extended, showing that in addition to slight improvements in accuracy substantial (a factor of three or more)
improvements in precision and significant reductions in correlations between various parameters can be obtained (by combining
Lunar Laser Ranging (LLR), Satellite Laser Ranging (SLR) to Lageos, and Very Long Baseline Interferometry (VLBI) data in one adjustment) as compared to results from individual systems. Smaller improvements are also seen over the weighted
means of the individual system results. Although data transmission would not be significantly reduced, negligible additional
computer time would be required if (standardized) normal equations were available from individual solutions. Suggestions for
future work and implications for the new International Earth Rotation Service (IERS) are also presented. 相似文献
6.
序贯平差方法是长距离网络RTK基准站间模糊度固定中的常用方法,该方法充分利用了卫星间的相关信息以及多余观测量,是理论严密且十分有效的方法。一般文献中只给出了参数不变的序贯平差公式。但是,观测过程中的参数是不断变化的,参数不变的序贯平差公式并不适用于网络RTK系统。此外,对于序贯平差而言,由于一般不存储历史观测值,因此,模糊度固定后无法将其带入原观测方程重新平差,这导致法方程更新困难。针对以上问题,本文给出了参数变化的序贯平差公式及严密的推导过程,并给出了模糊度固定后法方程的更新方法。结合长距离网络RTK基准站间模糊度固定问题,通过实验,证明了给出的序贯平差公式和法方程更新方法正确有效。 相似文献
7.
8.
O. Remmer 《Journal of Geodesy》1969,43(2):99-122
A method for filtering of geodetic observationwhich leaves the final result normally distributed, is presented. Furthermore, it is shown that if you sacrifice100.a% of all the observations you may be (1−β).100% sure that a gross error of the size Δ is rejected.
Another and, may be intuitively, more appealing method is presented; the two methods are compared and it is shown why Method
1 should be preferred to Method 2 for geodetic purposes.
Finally the two methods are demonstrated in some numerical examples. 相似文献
9.
Stochastic estimation of tropospheric path delays in global positioning system geodetic measurements 总被引：5，自引：2，他引：5
Water vapor radiometric (WVR) and surface meteorological (SM) measurements taken during three Global Positioning System (GPS) geodetic experiments are used to calculate process noise levels for random walk and first-order Gauss-Markov temporal models
of tropospheric path delays. Entire wet and combined wet and dry zenith delays at each network site then are estimated simultaneously
with the geodetic parameters without prior calibration. The path delays and corresponding baseline estimates are compared
to those obtained with calibrated data and stochastic residual delays. In this manner, the marginal utility of a priori tropospheric
calibration is assessed given the ability to estimate the path delays directly using only theGPS data. Estimation of total zenith path delays with appropriate random walk or Gauss-Markov models yields baseline repeatabilities
of a few parts in 108. This level of geodetic precision, and accuracy as suggested by analyses on collocated baselines estimated independently
by very long baseline interferometry, is comparable to or better than that obtained after path delay calibration usingWVR and/orSM measurements. Results suggest thatGPS data alone have sufficient strength to resolve centimeter-level zenith path delay fluctuations over periods of a few minutes. 相似文献
10.
Although total least squares (TLS) is more rigorous than the weighted least squares (LS) method to estimate the parameters in an errors-in-variables (EIV) model, it is computationally much more complicated than the weighted LS method. For some EIV problems, the TLS and weighted LS methods have been shown to produce practically negligible differences in the estimated parameters. To understand under what conditions we can safely use the usual weighted LS method, we systematically investigate the effects of the random errors of the design matrix on weighted LS adjustment. We derive the effects of EIV on the estimated quantities of geodetic interest, in particular, the model parameters, the variance–covariance matrix of the estimated parameters and the variance of unit weight. By simplifying our bias formulae, we can readily show that the corresponding statistical results obtained by Hodges and Moore (Appl Stat 21:185–195, 1972) and Davies and Hutton (Biometrika 62:383–391, 1975) are actually the special cases of our study. The theoretical analysis of bias has shown that the effect of random matrix on adjustment depends on the design matrix itself, the variance–covariance matrix of its elements and the model parameters. Using the derived formulae of bias, we can remove the effect of the random matrix from the weighted LS estimate and accordingly obtain the bias-corrected weighted LS estimate for the EIV model. We derive the bias of the weighted LS estimate of the variance of unit weight. The random errors of the design matrix can significantly affect the weighted LS estimate of the variance of unit weight. The theoretical analysis successfully explains all the anomalously large estimates of the variance of unit weight reported in the geodetic literature. We propose bias-corrected estimates for the variance of unit weight. Finally, we analyze two examples of coordinate transformation and climate change, which have shown that the bias-corrected weighted LS method can perform numerically as well as the weighted TLS method. 相似文献
11.
A. C. Campbell 《Journal of Geodesy》1968,42(3):293-300
Recent accuracy requirements for navigational positioning at sea are such as to require the refinements of recent and past
geodetic methods. The computational adjustment method, of this paper, is the technique of variation of parameters. All computations
are performed directly on the surface of a reference ellipsoid, so as to preclude any distance restrictions.
The methods presented are primarily for use with observations from electronic positioning systems of ranging (circular), and
time or phase difference (hyperbolic) type. A new type of observation equation is presented which, when used with a hyperbolic
system, results in the first non-iterative solution to the positioning problem.
When redundant observational data is obtained, as is frequently the case, full use should be made of the data by using weighted
observation equations. Through the use of the new equations, all electronic surveying observations can be processed simultaneously,
in real time, with an electronic computer. A continuing error analysis, in the form of a variance-covariance matrix for both
the observed and adjusted values, provides system error analysis and diagnoisis. 相似文献
12.
Modern geodetic positioning techniques likeVLBI, SLR, andGPS can be used for plate tectonic studies. A very simple model considers a number of rigid plates rotating individually with
a constant rotation rate.
An equally simple mathematical model, extended to deformable plates, is presented, based on vector calculus, which relates
both absolute and relative point positioning observations to the plate rotation and deformation parameters (rotation rate,
direction of rotation vector, deformation rate and direction of deformation center) in a consistent and elementary way. The
determination of these plate parameters from various geodetic positioning observations is outlined. 相似文献
13.
The authors address the issue of statistical testing in least squares collocation (LSC) in two stages. The first stage concerns the extension and focusing of theLSC equations to the task of statistical testing. The second stage deals with statistical testing titself and is introduced in
the second portion of the paper. The paper commences with an overview of the development ofLSC and its relationship to least squares adjustment (LSA). Expressions for the various random variables and their corresponding covariance matrices are derived and in some instances
are gleaned from the literature for the following quantities: (i) corrections to the unknown parameters with a priori covariance information; (ii) estimated signal at both the observation and computation points; and (iii) the noise at the observation points. Some of the needed covariance matrices are either obscurely hidden in the literature
or not available at all, but, nevertheless are given in the paper. Also given are expressions for the estimated variance factor
which forms the basis of various statistical tests. The paper closes with an overview and enumeration of possible statistical
tests for detection of outliers in the observations. 相似文献
14.
Richard A. Snay 《Journal of Geodesy》1990,64(1):1-27
The North American Datum of 1983 (NAD 83) provides horizontal coordinates for more than 250,000 geodetic stations. These coordinates were derived by a least squares
adjustment of existing terrestrial and space-based geodetic data. For pairs of first order stations with interstation distances
between 10km and 100km, therms discrepancy between distances derived fromNAD 83 coordinates and distances derived from independentGPS data may be suitably approximated by the empirical rulee=0.008 K0.7 where e denotes therms discrepancy in meters and K denotes interstation distance in kilometers. For the same station pairs, therms discrepancy in azimuth may be approximated by the empirical rule e=0.020 K0.5. Similar formulas characterize therms discrepancies for pairs involving second and third order stations. Distance and orientation accuracies, moreover, are well
within adopted standards. While these expressions indicate that the magnitudes of relative positional accuracies depend on
station order, absolute positional accuracies are similar in magnitude for first, second, and third order stations. Adjustment
residuals reveal a few local problems with theNAD 83 coordinates and with the weights assigned to certain classes of observations. 相似文献
15.
16.
基于有效约束的附不等式约束平差的一种新算法 总被引：2，自引：2，他引：0
不等式约束是客观实际中普遍存在的一种约束,但目前大地测量数据处理领域并没有成熟、完整并被普遍接受的处理理论和方法。首先简要总结附不等式约束平差的各种方法及其存在的问题。然后对现有测量平差中附有等式约束的平差模型进行扩展,提出一种新的处理附有线性约束(包括等式和不等式约束)的平差方法。该方法在有效约束概念下,通过库恩-塔克条件来寻找有效约束条件,把不等式约束平差问题转化为我们熟知的等式约束平差问题,因此实现解向量与观测向量之间的显式表达。最后,用一个数值算例验证新方法的可行性,同时算例分析表明:用等式约束代替有效约束或集成约束进行平差计算,能得到正确的平差结果,但得不到正确的精度评定结果。 相似文献
17.
M. S. Filmer C. W. Hughes P. L. Woodworth W. E. Featherstone R. J. Bingham 《Journal of Geodesy》2018,92(12):1413-1437
The direct method of vertical datum unification requires estimates of the ocean’s mean dynamic topography (MDT) at tide gauges, which can be sourced from either geodetic or oceanographic approaches. To assess the suitability of different types of MDT for this purpose, we evaluate 13 physics-based numerical ocean models and six MDTs computed from observed geodetic and/or ocean data at 32 tide gauges around the Australian coast. We focus on the viability of numerical ocean models for vertical datum unification, classifying the 13 ocean models used as either independent (do not contain assimilated geodetic data) or non-independent (do contain assimilated geodetic data). We find that the independent and non-independent ocean models deliver similar results. Maximum differences among ocean models and geodetic MDTs reach >150 mm at several Australian tide gauges and are considered anomalous at the 99% confidence level. These differences appear to be of geodetic origin, but without additional independent information, or formal error estimates for each model, some of these errors remain inseparable. Our results imply that some ocean models have standard deviations of differences with other MDTs (using geodetic and/or ocean observations) at Australian tide gauges, and with levelling between some Australian tide gauges, of \({\sim }\pm 50\,\hbox {mm}\). This indicates that they should be considered as an alternative to geodetic MDTs for the direct unification of vertical datums. They can also be used as diagnostics for errors in geodetic MDT in coastal zones, but the inseparability problem remains, where the error cannot be discriminated between the geoid model or altimeter-derived mean sea surface. 相似文献
18.
19.
. The excess radio-path delay due to the atmospheric water vapor, the wet delay, can be derived from water vapor radiometer
(WVR) measurements. WVR data used for external calibration of space geodetic measurements are not always acquired in the directions
of the space geodetic signal sources, thus extrapolation and interpolation methods for the wet delay are needed. We evaluate
three different methods using approximately 10 days of WVR measurements. Two methods, the gradient method and turbulence method,
use the directional information in the data, while the third method used is linear regression in time regardless of the direction
of the observations. The turbulence method yielded at least 10% less RMS estimation error than the errors from the other two
methods.
Received: 20 May 1997 / Accepted: 15 December 1997 相似文献
20.
单杰 《武汉大学学报(信息科学版)》1988,(4)
本文引入了摄影测量与非摄影测量观测值联合平差中大地测量观测值的严密数学模型——三维大地测量模型和常规的近似模型,针对这两种模型的局限性,提出了适合于联合平差的准三维大地测量模型。 相似文献