共查询到20条相似文献,搜索用时 15 毫秒
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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
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Numerical simulation of troposphere-induced errors in GPS-derived geodetic time series over Japan 总被引:2,自引:2,他引:0
Troposphere-induced errors in GPS-derived geodetic time series, namely, height and zenith total delays (ZTDs), over Japan
are quantitatively evaluated through the analyses of simulated GPS data using realistic cumulative tropospheric delays and
observed GPS data. The numerical simulations show that the use of a priori zenith hydrostatic delays (ZHDs) derived from the
European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather model data and gridded Vienna mapping function
1 (gridded VMF1) results in smaller spurious annual height errors and height repeatabilities (0.45 and 2.55 mm on average,
respectively) as compared to those derived from the global pressure and temperature (GPT) model and global mapping function
(GMF) (1.08 and 3.22 mm on average, respectively). On the other hand, the use of a priori ZHDs derived from the GPT and GMF
would be sufficient for applications involving ZTDs, given the current discrepancies between GPS-derived ZTDs and those derived
from numerical weather models. The numerical simulations reveal that the use of mapping functions constructed with fine-scale
numerical weather models will potentially improve height repeatabilities as compared to the gridded VMF1 (2.09 mm against
2.55 mm on average). However, they do not presently outperform the gridded VMF1 with the observed GPS data (6.52 mm against
6.50 mm on average). Finally, the commonly observed colored components in GPS-derived height time series are not primarily
the result of troposphere-induced errors, since they become white in numerical simulations with the proper choice of a priori
ZHDs and mapping functions. 相似文献
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Mathis Bloßfeld Sergei Rudenko Alexander Kehm Natalia Panafidina Horst Müller Detlef Angermann Urs Hugentobler Manuela Seitz 《Journal of Geodesy》2018,92(9):1003-1021
In this paper, we consistently estimate geodetic parameters such as weekly 3-D station coordinates, Earth orientation parameters (EOP) including daily x/y-pole coordinates and the excess length of day \(\Delta \hbox {LOD}\), and selected weekly Earth’s gravitational field (Stokes) coefficients up to degree and order 6 from Satellite Laser Ranging measurements to up to 11 geodetic satellites. The SLR constellation consists of LAGEOS-1/2, Etalon-1/2, Stella, Starlette, Ajisai, Larets, LARES, BLITS and WESTPAC, and its observations cover a time span of 38 years ranging from February 16, 1979, to April 30, 2017. If multiple satellites with various altitudes and orbit inclinations are combined, correlations between estimated parameters are significantly reduced. This allows us (i) to investigate the ability of satellite constellations to reduce existing correlations and (ii) to estimate reliable parameters with higher precision compared to the standard 4-satellite constellation (LAGEOS-1/2, Etalon-1/2) which is currently used by the International Laser Ranging Service for the determination of the Terrestrial Reference Frame (TRF) and EOP products. In particular, the Stokes coefficients, EOP and TRF datum parameters (three translations, three rotations, one scale factor), which are highly correlated with satellite-specific orbit parameters, are improved. From our investigations, we found for an 11-satellite solution compared to the above-mentioned 4-satellite solution a decrease in the scatter of the TRF datum parameters of up to 37%, the transformation residuals are decreased by up to 22%, the scatter of the EOP is decreased by up to 22%, and their mean values are decreased by up to 84% w.r.t. the reference solutions. The largest improvement is obtained for the Stokes coefficients which significantly benefit from a combination of multiple satellites (inclinations and orbit altitudes). In total, single coefficients are improved by up to 93% and the overall improvement is up to 74%. Moreover, it could be clearly identified that Ajisai significantly disturbs the TRF solution due to an erroneous center-of-mass correction. We further quantify the impact of specific satellites on the determination of different geodetic parameters and finally evaluate the potential of the existing SLR-tracked spherical satellite constellation to support the goals of GGOS. 相似文献
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European geodetic very long baseline interferometry (VLBI) sessions (also known as EUROPE sessions) have been carried out
on a regular basis for the past 15 years to study relative crustal motions within Europe. These sessions are based on observations
of extragalactic radio sources, which serve as distant fiducial marks to establish an accurate and stable celestial reference
frame for long-term geodetic measurements. The radio sources, however, are not always point-like on milliarcsecond scales,
as VLBI imaging has revealed. In this work, we quantify the magnitude of the expected effect of intrinsic source structure
on geodetic bandwidth synthesis delay VLBI measurements for a subset of 14 sources regularly observed during the EUROPE sessions.
These sources have been imaged at both X-band (8.4 GHz) and S-band (2.3 GHz) based on dedicated observations acquired with
the European VLBI Network (EVN) in November 1996. The results of this calculation indicate that the reference source 0457+024
causes significant structural effects in measurements obtained on European VLBI baselines (about 10 picoseconds on average),
whereas most of the other sources produce effects that are only occasionally larger than a few picoseconds. Applying the derived
source structure models to the data of the EUROPE5-96 session carried out at the same epoch as the EVN experiment shows no
noticeable changes in the estimated VLBI station locations. 相似文献
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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
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陀螺随机漂移是影响惯性导航和组合导航精度的重要因素。为了有效辨识出光纤陀螺随机漂移噪声的参数,采用了自相关函数、功率谱密度和Allan方差对实测陀螺数据进行分析。实验结果表明:自相关函数、功率谱密度和Allan方差都能有效辨识出陀螺输出信号中的角度随机游走噪声,只有Allan方差能辨识出其中的角速率随机游走噪声。Allan方差可以为光纤陀螺随机漂移建模提供参考。 相似文献
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针对在七参数坐标转换过程中,控制点本身含有的各种误差会对坐标转换的结果产生影响的问题,该文探讨了随机误差对七参数转换模型的影响:以七参数坐标转换模型为研究对象,模拟不同尺度范围的空间直角坐标,给定七参数数值求解另一组空间直角坐标,然后加入不同幅度的随机误差,利用最小二乘准则求解参数,从数值角度分析随机误差对七参数数值以及坐标转换结果的影响。实验结果显示,大范围的七参数模型解算的稳定性优于小范围的模型解算,以及X、Y、Z方向某一方向上的误差对另两个方向的解算结果影响较小。 相似文献
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R. J. Anderle 《Journal of Geodesy》1979,53(2):109-116
A dual frequency Doppler receiver is being developed by the Naval Surface Weapons Center for possible use by the Defense Mapping
Agency in determining the position of ground sites based on observations of NAVSTAR Global Positioning satellites. Preliminary
analysis indicates that the relative position of widely separated sites can be computed to better than 40 cm accuracy at eight
hour intervals. A number of possibilities are being explored to improve the accuracy to the sub-decimeter level. 相似文献
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Z. Wiśniewski 《Journal of Geodesy》2014,88(10):941-957
The paper concerns \(M\) -estimation with probabilistic models of geodetic observations that is called \(M_{\mathcal {P}}\) estimation. The special attention is paid to \(M_{\mathcal {P}}\) estimation that includes the asymmetry and the excess kurtosis, which are basic anomalies of empiric distributions of errors of geodetic or astrometric observations (in comparison to the Gaussian errors). It is assumed that the influence function of \(M_{\mathcal {P}}\) estimation is equal to the differential equation that defines the system of the Pearson distributions. The central moments \(\mu _{k},\, k=2,3,4\) , are the parameters of that system and thus, they are also the parameters of the chosen influence function. The \(M_{\mathcal {P}}\) estimation that includes the Pearson type IV and VII distributions ( \(M_{\mathrm{PD(l)}}\) method) is analyzed in great detail from a theoretical point of view as well as by applying numerical tests. The chosen distributions are leptokurtic with asymmetry which refers to the general characteristic of empirical distributions. Considering \(M\) -estimation with probabilistic models, the Gram–Charlier series are also applied to approximate the models in question ( \(M_{\mathrm{G-C}}\) method). The paper shows that \(M_{\mathcal {P}}\) estimation with the application of probabilistic models belongs to the class of robust estimations; \(M_{\mathrm{PD(l)}}\) method is especially effective in that case. It is suggested that even in the absence of significant anomalies the method in question should be regarded as robust against gross errors while its robustness is controlled by the pseudo-kurtosis. 相似文献
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风云3号B星(FY-3B)上的微波成像仪(MWRI)通过10.65 GHz,18.7 GHz,23.8GHz,36.5 GHz和189.0 GHz5个频率的双极化通道对地球表面进行监测。自卫星发射至今,MWRI资料的地理定位误差还未进行深入研究。为了提高FY-3B MWRI L1级数据地理定位精度,基于海、陆响应的升、降轨亮温差理论NDM(Node Differential Method),通过卫星位置和速度矢量建立卫星姿态模型、采用非线性最优化方法估计卫星姿态偏差,进而对MWRI 89 GHz通道的地理定位误差进行分析与订正。结果表明,2015年1—9月份俯仰、滚动和偏航角度的平均偏差分别为-0.220°,0.068°和0.062°,对应沿轨误差大约3—4 km,跨轨误差小于1 km。定位误差订正后,地中海、澳大利亚区域海岸线附近的升降轨亮温差明显减小;观测亮温在红海和南美洲东南部区域的分布和海岸线更加吻合,定位精度得到明显提高。 相似文献
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Computer values of the mean square error of the Nigerian Geodetic Levelling based on the model xij = ρij/R
ij
1/2
showed a uniformity between the lines of levelling, of a nature which suggest that xij = ρij/R
ij
1/2
is a good fit for the data. Values of the mean square error of the levelling based on wij = ρij/Rij showed such significant variation between the lines that this alternative model does not seem to be supported by the data
used in this study. 相似文献
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L. A. Kivioja 《Journal of Geodesy》1971,45(1):55-63
By choosing sufficiently small elements of the length of the geodetic line, or of the latitude or longitude difference, the
other two can be computed at each element and the results can be accumulated to solve the problem with more than twenty significant
number accuracy if desired. Ten to twelve number accuracy was computed in the examples of this paper. The geodetic line elements
are kept in correct azimuth by Clairaut’s equation for the geodetic line. The computers can do millions of necessary computations
very economically in a few seconds. All other published methods solving the direct or indirect problem can be reliably checked
against results obtained by this method. The run of geodetic lines around the back side of the Ellipsoid is outlined. 相似文献
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Characterization of errors in vector wind retrievals from satellite-based polarimetric microwave radiometer measurements 总被引:2,自引:0,他引:2
Laws K.E. Lyzenga D.R. Wiberg D.M. Vesecky J.F. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(1):45-48
We present a method for evaluating characteristics of wind vector retrieval errors from polarimetric radiometer measurements. We focus on wind direction errors due to ambiguous solutions. 相似文献
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WEI Erhu LIU Jingnan SHI Chuang 《地球空间信息科学学报》2007,10(1):12-16
The meaning to research the potential of VLBI for geodetic applications is summarized. And the observation models and their related parameters of geodetic interest are investigated. Then, the principle and method of using the random model in VLBI data processing are investigated. With the world wide VLBI data from 2000-2004, the conditions to compute the parameters of geodetic interest are introduced, and so are the computing methods and processes. And the computed results of the parameters of geodetic interest are analyzed. 相似文献