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1.
Estimating regional deformation from a combination of space and terrestrial geodetic data 总被引：26，自引：1，他引：25
We discuss an approach for efficiently combining different types of geodetic data to estimate time-dependent motions of stations
in a region of active deformation. The primary observations are analyzed separately to produce loosely constrained estimates
of station positions and coordinate system parameters which are then combined with appropriate constraints to estimate velocities
and coseismic displacements. We define noninteger degrees of freedom to handle the case of finite constraints and stochastic
perturbation of parameters and develop statistical tests for determining compatibility between different data sets. With these
developments, we show an example of combining space and terrestrial geodetic data to obtain the deformation field in southern
California.
Received: 23 January 1997 / Accepted: 30 September 1997 相似文献
2.
Atmospheric Angular Momentum Time-Series: Characterization of their Internal Noise and Creation of a Combined Series 总被引：1，自引：0，他引：1
The atmosphere induces variations in Earth rotation. These effects are classically computed using the “angular momentum approach”. In this method, the variations in Earth rotation are estimated from the variations in the atmospheric angular momentum (AAM). Several AAM time-series are available from different meteorological centers. However, the estimation of atmospheric effects on Earth rotation differs when using one atmospheric model or the other. The purpose of this work is to build an objective criterion that justifies the use of one series in particular. Because the atmosphere is not the only cause of Earth rotation variations, this criterion cannot rely only on a comparison of AAM series with geodetic data. Instead, we determine the quality of each series by making an estimation of their noise level, using a generalized formulation of the “three-cornered hat method”. We show the existence of a link between the noise of the AAM series and their correlation with geodetic data: a noisy series is usually less correlated with Earth orientation data. As the quality of the series varies in time, we construct a combined AAM series, using time-dependent weights chosen so that the noise level of the combined series is minimal. To determine the influence of a minimal noise level on the correlation with geodetic data, we compute the correlation between the combined series and Earth orientation data. We note that the combined series is always amongst the best correlated series, which confirms the link established before. The quality criterion, while totally independent of Earth orientation observations, appears to be physically convincing when atmospheric and geodetic data are compared 相似文献
3.
R. Lehmann 《Journal of Geodesy》2000,74(3-4):327-334
The definition and connection of vertical datums in geodetic height networks is a fundamental problem in geodesy. Today,
the standard approach to solve it is based on the joint processing of terrestrial and satellite geodetic data. It is generalized
to cases where the coverage with terrestrial data may change from region to region, typically across coastlines. The principal
difficulty is that such problems, so-called altimetry–gravimetry boundary-value problems (AGPs), do not admit analytical solutions
such as Stokes' integral. A numerical solution strategy for the free-datum problem is presented. Analysis of AGPs in spherical
and constant radius approximation shows that two of them are mathematically well-posed problems, while the classical AGP-I
may be ill posed in special situations.
Received: 2 December 1998 / Accepted: 30 November 1999 相似文献
4.
A. A. Seemkooei 《Journal of Geodesy》2001,75(4):227-233
The proper and optimal design and subsequent assessment of geodetic networks is an integral part of most surveying engineering
projects. Optimization and design are carried out before the measurements are actually made. A geodetic network is designed
and optimized in terms of high reliability and the results are compared with those obtained by the robustness analysis technique.
The purpose of an optimal design is to solve for both the network configuration (first-order design) and observations accuracy
(second-order design) in order to meet the desired criteria. For this purpose, an analytical method is presented for performing
the first-order design, second-order design, and/or the combined design. In order to evaluate the geometrical strength of
a geodetic network, the results of robustness analysis are displayed in terms of robustness in rotation, robustness in shear,
and robustness in scale. Results showed that the robustness parameters were affected by redundancy numbers. The largest robustness
parameters were due to the observations with minimum redundancy numbers.
Received: 14 August 2000 / Accepted: 2 January 2001 相似文献
5.
Research on the deformations in Qinghai-Tibet plateau and its margins by inverting seismic moment tensors and GPS velocities 总被引：1，自引：0，他引：1
We have determined approximate average rates of deformation in the Qinghai-Tibet plateau and its margins from the GPS data for last 10 years and the moment tensors from earthquakes between 1900 and 1999.We also determined the strain rate (seismic strain rate) associated with the seismic deformation using 254 Mw≥5.0 earthquakes,and estimated the shortening and extension rates for every block in the area as well.We also estimated the strain rate (geodetic strain rate)by 80 GPS sites' velocity vectors and analyzed characteristic of kinematics by two kinds of strain rates and discussed earthquake potential in the area.As a result,the deformation rates from seismic moment tensors and from GPS velocities are basically agreed with each other.It is feasible to analyze seismic risk by comparing geodetic strain rate with seismic strain rate based on the opinion that strain energy will be released through earthquake.It is concluded that there is no strong earthquake potential (＞M7) in the Qinghai-Tibet plateau and its margins,but there is earthquake potential (＞M5) in middle Tibet in a few years. 相似文献
6.
7.
R. Lehmann 《Journal of Geodesy》1999,73(9):491-500
A review of recent progress and current activities towards an improved formulation and solution of geodetic boundary value
problems is given. Improvements stimulated and required by the dramatic changes of the real world of geodetic measurements
are focused upon. Altimetry–gravimetry problems taking into account various scenarios of non-homogeneous data coverage are
discussed in detail. Other problems are related to free geodetic datum parameters, most of all the vertical datum, overdetermination
or additional constraints imposed by satellite geodetic observations or models. Some brief remarks are made on pseudo-boundary
value problems for geoid determination and on purely gravitational boundary-value problems.
Received: 17 March 1999 / Accepted: 19 April 1999 相似文献
8.
Y. Fukuzaki K. Shibuya K. Doi T. Ozawa A. Nothnagel T. Jike S. Iwano D. L. Jauncey G. D. Nicolson P. M. McCulloch 《Journal of Geodesy》2005,79(6-7):379-388
The first successful geodetic Very Long Baseline Interferometry (VLBI) observations to Antarctica were made on baselines from Syowa Station (Antarctica) to Tidbinbilla (Australia) and to Kashima (Japan) in January 1990. Regular geodetic experiments started in 1998 with the installation of a permanent VLBI terminal at Syowa Station. These observations are conducted at the standard geodetic VLBI frequencies of 2.3 and 8.4 GHz, S- and X-Bands. In the first year, the 11-m multipurpose antenna at Syowa Station observed together with the 26-m radio telescope of the University of Tasmania in Australia and the 26-m radio telescope of the Hartebeesthoek Radio Astronomy Observatory in South Africa. From 1999, the experiments were expanded to also include the O’Higgins Station in Antarctica, Fortaleza in Brazil and Kokee on Hawaii. From 1999 until the end of 2003, 25 observing sessions have been reduced and analyzed using the CALC/SOLVE geodetic VLBI data reduction package. The results show that the horizontal baseline of Syowa-Hobart is increasing at the rate of 57.0±1.9 mm/year. The baseline Syowa-Hartebeesthoek is also increasing, but at the lower rate of 9.8±1.9 mm/year. The VLBI result of 2.0±3.1 mm/year and the GPS result of −1.9±0.7 mm/year for the Syowa-O’Higgins horizontal baseline support the hypothesis of one rigid Antarctic plate without intra-plate deformation, which is consistent with the NNR-NUVEL-1A global plate motion model. The location of the Euler pole of the Antarctic plate by VLBI is estimated as 59.7°S and 62.6°E with a rotation rate of 0.190 deg/Myr, while that by GPS in our study is estimated as 60.6°S and 42.2°E with a rotation rate of 0.221 deg/Myr. These pole positions are slightly different to that implied by the NNR-NUVEL-1A model of 63.0°S and 64.2°E with a rotation rate of 0.238 deg/Myr. VLBI observations over a longer time span may resolve small discrepancy of current plate motion from the NNR-NUVEL-1A model. The consistency of the VLBI coordinates with the GPS coordinates at Syowa Station, after correction for the local tie vector components between the two reference markers, is also discussed. 相似文献
9.
V. S. Schwarze 《Journal of Geodesy》1999,73(11):594-602
The reformulation of geodetic measurement processes within the framework of general relativity is discussed. The metric tensor
plays an important role in general relativity and has to be represented with respect to a set of appropriate charts. Almost
every quantity of interest in geodetic or geophysical applications refers to a geocentric, Earth-fixed coordinate system (chart),
therefore they are of great importance in geodesy and geophysics. The space–time metric with respect to an Earth-fixed chart
is derived at first post-Newtonian order. The field equations determining the terrestrial gravitational field are derived
and its explicit representation is outlined. The impact of the results on the modelling of geodetic measurement processes
including space–time positioning scenarios as well as the high-precision gravitational field estimation is outlined.
Received: 7 January 1998 / Accepted: 17 August 1999 相似文献
10.
P. Schwintzer C. Reigber A. Bode Z. Kang S. Y. Zhu F.-H. Massmann J. C. Raimondo R. Biancale G. Balmino J. M. Lemoine B. Moynot J. C. Marty F. Barlier Y. Boudon 《Journal of Geodesy》1997,71(4):189-208
Summary. GFZ Potsdam and GRGS Toulouse/Grasse jointly developed a new pair of global models of the Earth's gravity field to satisfy
the requirements of the recent and future geodetic and altimeter satellite missions. A precise gravity model is a prerequisite
for precise satellite orbit restitution, tracking station positioning and altimeter data reduction. According to different
applications envisaged, the new model exists in two parallel versions: the first one being derived exclusively from satellite
tracking data acquired on 34 satellites, the second one further incorporating satellite altimeter data over the oceans and
terrestrial gravity data. The most recent “satellite-only” gravity model is labelled GRIM4-S4 and the “combined” gravity model
GRIM4-C4. The models are solutions in spherical harmonics and have a resolution up to degree and order 60 plus a few resonance
terms in the case of GRIM4-S4, and up to degree/order 72 in the case of GRIM4-C4, corresponding to a spatial resolution of
555 km at the Earth's surface. The gravitational coefficients were estimated in a rigorous least squares adjustment simultaneously
with ocean tidal terms and tracking station position parameters, so that each gravity model is associated with a consistent
ocean tide model and a terrestrial reference frame built up by over 300 optical, laser and Doppler tracking stations. Comprehensive
quality tests with external data and models, and test arc computations over a wide range of satellites have demonstrated the
state-of-the-art capabilities of both solutions in long-wavelength geoid representation and in precise orbit computation.
Received 1 February 1996; Accepted 17 July 1996 相似文献
11.
Simplified formulae for the BIQUE estimation of variance components in disjunctive observation groups 总被引：7，自引：1，他引：6
General rigorous and simplified formulae are reported for the best invariant quadratic unbiased estimates of the variance–covariance
components, which can be applied to all least-squares adjustments with the general linear stochastic model. Simplified procedures
are given for two cases frequently recurring in geodetic applications: uncorrelated groups of correlated or uncorrelated observations,
with more than one variance component in each group.
Received: 19 November 1998 / Accepted: 21 March 2000 相似文献
12.
Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis 总被引：2，自引：2，他引：0
The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry
(VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes
were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying
these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9
and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations
on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for
other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [−3, 73] mm
and a net scale increase of 0.3–0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying
the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need
to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply
them in routine geodetic data analysis. 相似文献
13.
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
14.
A global plate motion model is established based on the ITRF97 velocity fields and geological model NUVEL1. Sub-plate models
are estimated by using the velocity fields derived from 45 global positioning system (GPS) sites under the ITRF97 reference
frame in China. Comparisons between space geodesy and geological models are given. It is found that the Euler vector of the
AFRC–EURA pair has an obvious discrepancy between space geodetic and geological models. The motion patterns of tectonic blocks
in China predicted by GPS are consistent with those of geological data on the whole.
Received: 9 November 2000 / Accepted: 17 September 2001 相似文献
15.
Data weighting and solution assessment in combination 总被引：4，自引：0，他引：4
A data weighting method for combining different geodetic data based on statistical tests of the residuals is discussed. By
requiring the residuals of combination solution to be white Gaussian as a sample of random noise, the relative weight factors
can be determined internally, independent of external comparisons. To achieve this goal and to assess the solution, the Pearson
χ2 and higher-order moments of residuals are used to measure quantitatively the discrepancies between the residuals and white
Gaussian noise.
Received: 30 June 1998 / Accepted: 19 April 1999 相似文献
16.
为提高变形预测的精度,采用GM(1,1)与BP神经网络组合模型进行预测。灰色GM(1,1)模型使用方便,在样本数据较少的情况下能够取得不错的预测效果,但对预测序列存在规律性波动或突变时的预测能力不强;而神经网络模型建模过程相对复杂,需要较多的训练样本,但对于数据存在规律性波动和突变时有很好的预测能力。组合模型融合两者优点,将其应用于基坑沉降数据预测,结果表明,该模型预测精度优于传统的单一预测模型。 相似文献
17.
The empirical model GPT (Global Pressure and Temperature), which is based on spherical harmonics up to degree and order nine,
provides pressure and temperature at any site in the vicinity of the Earth’s surface. It can be used for geodetic applications
such as the determination of a priori hydrostatic zenith delays, reference pressure values for atmospheric loading, or thermal
deformation of Very Long Baseline Interferometry (VLBI) radio telescopes. Input parameters of GPT are the station coordinates
and the day of the year, thus also allowing one to model the annual variations of the parameters. As an improvement compared
with previous models, it reproduces the large pressure anomaly over Antarctica, which can cause station height errors in the
analysis of space-geodetic data of up to 1 cm if not considered properly in troposphere modelling. First tests at selected
geodetic observing stations show that the pressure biases considerably decrease when using GPT instead of the very simple
approaches applied to various Global Navigation Satellite Systems (GNSS) software packages so far. GPT also provides an appropriate
model for the annual variability of global temperature.
Electronic supplementary material The online version of this article (doi: contains supplementary material, which is available to authorized users. 相似文献
18.
International compilations of marine gravity, such as the International Gravity Bureau (BGI) contain tens of millions of point
data. Lemoine et al. (The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential
Model EGM96, NASA/TP-1998-206861) chose not to include any marine gravity in the construction of the global gravity model
EGM96. Instead they used synthetic anomalies derived from altimetry, so that no independent information about Mean Dynamic
Topography (MDT) can be deduced. Software has been developed not only to identify and correct those aspects of marine gravity
data that are unreliable, but to do so in a way that can be applied to very large, ocean-wide data sets. First, we select
only straight-line parts of ship-tracks and fit each one with a high-degree series of Chebyshev polynomials, whose misfit
standard deviation is σ
line and measures the random error associated with point gravity data. Then, network adjustment determines how the gravity datum is offset for each survey.
A free least squares adjustment minimises the gravity anomaly mismatch at line-crossing points, using σ
line to weight the estimate for each line. For a long, well crossed survey, the instrumental drift rate is also adjusted. For
some 42,000 cross-over points in the northern Atlantic Ocean, network adjustment reduces the unweighted standard deviation
of the cross-over errors from 4.03 to 1.58 mGal; when quality weighted, the statistic reduces from 1.32 to 0.39 mGal. The
geodetic MDT is calculated combining the adjusted gravity anomalies and satellite altimetry, and a priori global ocean model
through a new algorithm called the Iterative Combination Method. This paper reports a first demonstration that geodetic oceanography
can characterise the details of basin wide ocean circulation with a resolution better than global ocean circulation models.
The result matches regional models of ocean circulation from hydrography measurements (Geophys Res Lett 29:1896, 2002; J Geophys
Res 108:3251, 2003). 相似文献
19.
Fast transform from geocentric to geodetic coordinates 总被引：3，自引：0，他引：3
T. Fukushima 《Journal of Geodesy》1999,73(11):603-610
A new iterative procedure to transform geocentric rectangular coordinates to geodetic coordinates is derived. The procedure
solves a modification of Borkowski's quartic equation by the Newton method from a set of stable starters. The new method runs
a little faster than the single application of Bowring's formula, which has been known as the most efficient procedure. The
new method is sufficiently precise because the resulting relative error is less than 10−15, and this method is stable in the sense that the iteration converges for all coordinates including the near-geocenter region
where Bowring's iterative method diverges and the near-polar axis region where Borkowski's non-iterative method suffers a
loss of precision.
Received: 13 November 1998 / Accepted: 27 August 1999 相似文献
20.
Kamil Eren 《Journal of Geodesy》1984,58(2):137-150
In earthquake prediction studies geodetic surveys play a very significant role. For this purpose, in Turkey, three micro geodetic
networks have been established across the North Anatolian Fault. Of these, the Ismetpa§a Network is the subject of this paper.
From the observations in combined triangulation—trilateration mode in 1972 and 1982 the horizontal movements and strain components
were determined. Afterwards the parameters of the best fitting deformation model were computed and analyzed. The results show
that the Anatolian plate has about a 1 cm/year westward motion, and there exists considerable strain accumulation in the area. 相似文献