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1.
Observations on Navy navigation satellites made by thirteen Doppler receiving stations have been used to determine the position
of the earth's pole daily for a six month period of time. A precision of one meter has been obtained on the basis of forty-eight
hours of observations on one satellite. No bias is apparant between computations based on different satellites, but differences
of about a meter exist with respect to values published by the Bureau International de l'Heure on the basis of astronomical
observations. 相似文献
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R. J. Anderle 《Journal of Geodesy》1976,50(1):43-77
Doppler observations of Navy Navigation Satellites have been used to strengthen and extend many terrestrial geodetic networks.
The main sources of errors in positions determined from these observations are random error of observations, random and systematic
errors in satellite positions due to uncertainties in the gravity field, and biases in the coordinate system in which the
satellite ephemeris is given.
Effects of uncertainties in the gravity field on station coordinates computed with respect to a precise satellite ephemeris
are reduced to about 70 cm after 20 satellite passes are observed, but systematic effects prevent assurance that additional
observations will improve the accuracy further. A one part per million reduction in scale must be applied to positions computed
with the ephemeris to obtain agreement with terrestrial and other precise determinations of scale. The origin of the system
is coincident with the center of mass of the earth to 1 m accuracy but the polar axis may be tilted three to five meters at
the earth's surface with respect to coordinate systems upon which star catalogues are based. 相似文献
3.
R. J. Anderle 《Journal of Geodesy》1976,50(4):377-390
Doppler observations of Navy Navigation Satellites have been used to comput pole positions on a daily basis since 1969. Limited
computations have been performed using data on file for the period 1964–1969. Results of recent computations give a standard
error in pole position based on 48 hours of Doppler observations of 7 cm. However, effects of errors in the orbit due to uncertainties
in the gravity field prevent the attainment of this precision; the standard deviation of pole position for this time span
is 60 cm, giving a standard error for a five day mean based on observations of two satellites of 25 cm. 相似文献
4.
不同于当前广泛使用的空域法、时域法、直接解法,本文尝试采用Torus方法处理GOCE实测数据,利用71 d的GOCE卫星引力梯度数据反演了200阶次GOCE地球重力场模型,实现了对参考模型的精化。首先,采用Butterworth零相移滤波方法加移去—恢复技术,处理引力梯度观测值中的有色噪声,并利用泰勒级数展开和Kriging方法对GOCE卫星引力梯度数据进行归算和格网化,计算得到了名义轨道上格网点处的引力梯度数据。然后,利用2D-FFT技术和块对角最小二乘方法处理名义轨道上数据,获得了200阶次的GOCE地球重力场模型GOCE_Torus。利用中国和美国的GPS/水准数据进行外部检核结果说明,GOCE_Torus与ESA发布的同期模型的精度相当;GOCE_Torus模型与200阶次的EGM2008模型相比,在美国区域精度相当,但在中国区域精度提高了4.6 cm,这充分体现了GOCE卫星观测数据对地面重力稀疏区的贡献。Torus方法拥有快速高精度反演卫星重力场模型的优势,可以在重力梯度卫星的设计、误差分析及在轨快速评估等方面得到充分应用。 相似文献
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The optical astrometric data of the years 1962–1982 have been reduced once again at the Bureau International de l’Heure (BIH) in order to redetermine the Earth Rotation Parameters (ERP). This new reduction is based on serie largely revised by the stations since their use in the operational work of theBIH, and on some series which were not available previously.
A total of 113 stations is considered, totaling nearly 500,000 measurements of time or latitude. TheERP are determined at five-day intervals.
A new approach is developed: the catalog and local errors are analysed and corrected as group unknowns, which values are adjusted
together with the main unknowns.
The results obtained in the new reduction are compared to other series obtained by astrometry and space geodesy. 相似文献
7.
Doppler tracking of artificial satellites has been applied to determine the pole components through an experiment called MEDOC.
In addition to developing scientific aspects dealing with polar motion, it is proposed to promote new observational techniques
and to investigate the possibility of operating an international permanent service.
So far, nearly two years of bi-daily solutions have been derived. Each improvement of computational procedures, data processing
and station component determination has contributed to better precision in the computed pole positions.
MEDOC pole coordinate solutions show good agreement with DMA and BIH global solutions corrected for annual terms. Differences
of the smoothed values are less than one meter for both components.
The MEDOC experiment was initiated by the GRGS (Groupe de Recherches de Géodésie Spatiale) and took place in 1977 and 1978.
The experiment as presently organized will continue up to 1980. Future improvements are still foreseen by increasing the number
of observing sites and refinement of the force models, but already international involvement is taking place in the MEDOC
experiment. 相似文献
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目前可遥感反演的海上风能参量主要为平均风速和平均风功率密度,缺乏对风能方向性参量的反演。本文建立了以风向频率、风能密度方向分布为核心的风能方向性参量体系及相应的反演方法,使用2007年—2016年ASCAT星载散射计观测数据进行了反演实验,并利用海上现场观测数据对反演结果进行比较验证,通过理论分析和模拟实验对反演方法的数据量需求和误差传递进行了分析。结果表明,90%的反演结果通过了所有的同一性检验,验证了其有效性和准确性;风向频率和风能密度方向分布准确反演所需的最小数据量分别为350条和800条;遥感反演的风速风向数据的误差使得最终反演的风能方向性参量趋于离散,真实的风能方向分布越集中,对其影响越敏感。 相似文献
11.
J. Neumeyer F. Barthelmes O. Dierks F. Flechtner M. Harnisch G. Harnisch J. Hinderer Y. Imanishi C. Kroner B. Meurers S. Petrovic Ch. Reigber R. Schmidt P. Schwintzer H. -P. Sun H. Virtanen 《Journal of Geodesy》2006,79(10-11):573-585
Gravity recovery and climate experiment (GRACE)-derived temporal gravity variations can be resolved within the μgal (10?8 m/s 2) range, if we restrict the spatial resolution to a half-wavelength of about 1,500 km and the temporal resolution to 1 month. For independent validations, a comparison with ground gravity measurements is of fundamental interest. For this purpose, data from selected superconducting gravimeter (SG) stations forming the Global Geodynamics Project (GGP) network are used. For comparison, GRACE and SG data sets are reduced for the same known gravity effects due to Earth and ocean tides, pole tide and atmosphere. In contrast to GRACE, the SG also measures gravity changes due to load-induced height variations, whereas the satellite-derived models do not contain this effect. For a solid spherical harmonic decomposition of the gravity field, this load effect can be modelled using degree-dependent load Love numbers, and this effect is added to the satellite-derived models. After reduction of the known gravity effects from both data sets, the remaining part can mainly be assumed to represent mass changes in terrestrial water storage. Therefore, gravity variations derived from global hydrological models are applied to verify the SG and GRACE results. Conversely, the hydrology models can be checked by gravity variations determined from GRACE and SG observations. Such a comparison shows quite a good agreement between gravity variation derived from SG, GRACE and hydrology models, which lie within their estimated error limits for most of the studied SG locations. It is shown that the SG gravity variations (point measurements) are representative for a large area within the accuracy, if local gravity effects are removed. The individual discrepancies between SG, GRACE and hydrology models may give hints for further investigations of each data series. 相似文献
12.
Canada has recently faced two geodetic problems. Existing control on land must be rapidly upraged for resource development
and for the coming redefinition of North American networks. Geodetic methods of managing territorial and lease boundaries
in the offshore region are required. A series of developments in Doppler Satellite techniques begun in 1968 have contributed
to the solution of both these problems. Today these developments have resulted in a Canadian-made receiver, permanent Canadian
tracking stations, a primary geodetic network of about 200 Doppler points, major Doppler processing software systems, and
the routine use of Doppler points, major Doppler processing software systems, and the routine use of Doppler positioning for
land surveying, drill rig positioning and precise navigation. The accuracy of Doppler positioning has been improved from 100
m in 1968 to better than 1 m in 1975. These developments have applications in other nations than Canada. 相似文献
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地震的发生会造成巨大的破坏和损失,大地测量技术能观测地震形变和反演地震断层的错动情况,对于减少地震灾害具有非常重要的现实意义。GNSS技术已广泛用于震源参数的反演工作,但对于发生在海域的地震,由于GNSS站点往往位于陆地一侧,导致对断层的约束 能力有限。卫星重力技术因其全天候、全球覆盖、连续性,以及不受地域地形限制等诸多特点,可弥补海洋一侧常规观测不足。联合GNSS和GRACE两种观测手段反演震源机制,可进一步提高反演海域地震的震源参数。为此,论文基于GRACE和GNSS观测的同震和震后形变,联合反演了断层参数和地幔黏滞性系数等,主要成果如下。 相似文献
15.
Characterization of periodic variations in the GPS satellite clocks 总被引:11,自引:7,他引:4
The clock products of the International Global Navigation Satellite Systems (GNSS) Service (IGS) are used to characterize
the timing performance of the GPS satellites. Using 5-min and 30-s observational samples and focusing only on the sub-daily
regime, approximate power-law stochastic processes are found. The Block IIA Rb and Cs clocks obey predominantly random walk
phase (or white frequency) noise processes. The Rb clocks are up to nearly an order of magnitude more stable and show a flicker
phase noise component over intervals shorter than about 100 s. Due to the onboard Time Keeping System in the newer Block IIR
and IIR-M satellites, their Rb clocks behave in a more complex way: as an apparent random walk phase process up to about 100 s
and then changing to flicker phase up to a few thousand seconds. Superposed on this random background, periodic signals have
been detected in all clock types at four harmonic frequencies, n × (2.0029 ± 0.0005) cycles per day (24 h coordinated universal time or UTC), for n = 1, 2, 3, and 4. The equivalent fundamental period is 11.9826 ± 0.0030 h, which surprisingly differs from the reported mean
GPS orbital period of 11.9659 ± 0.0007 h by 60 ± 11 s. We cannot account for this apparent discrepancy but note that a clear
relationship between the periodic signals and the orbital dynamics is evidenced for some satellites by modulations of the
spectral amplitudes with eclipse season. All four harmonics are much smaller for the IIR and IIR-M satellites than for the
older blocks. Awareness of the periodic variations can be used to improve the clock modeling, including for interpolation
of tabulated IGS products for higher-rate GPS positioning and for predictions in real-time applications. This is especially
true for high-accuracy uses, but could also benefit the standard GPS operational products. The observed stochastic properties
of each satellite clock type are used to estimate the growth of interpolation and prediction errors with time interval. 相似文献
16.
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
17.
Methodology for the combination of sub-daily Earth rotation from GPS and VLBI observations 总被引:3,自引:3,他引:0
A combination procedure of Earth orientation parameters from Global Positioning System (GPS) and Very Long Baseline Interferometry
(VLBI) observations was developed on the basis of homogeneous normal equation systems. The emphasis and purpose of the combination
was the determination of sub-daily polar motion (PM) and universal time (UT1) for a long time-span of 13 years. Time series
with an hourly resolution and a model for tidal variations of PM and UT1-TAI (dUT1) were estimated. In both cases, 14-day
nutation corrections were estimated simultaneously with the ERPs. Due to the combination procedure, it was warranted that
the strengths of both techniques were preserved. At the same time, only a minimum of de-correlating or stabilizing constraints
were necessary. Hereby, a PM time series was determined, whose precision is mainly dominated by GPS observations. However,
this setup benefits from the fact that VLBI delivered nutation and dUT1 estimates at the same time. An even bigger enhancement
can be seen for the dUT1 estimation, where the high-frequency variations are provided by GPS, while the long term trend is
defined by VLBI. The estimated combined tidal PM and dUT1 model was predominantly determined from the GPS observations. Overall,
the combined tidal model for the first time completely comprises the geometrical benefits of VLBI and GPS observations. In
terms of root mean squared (RMS) differences, the tidal amplitudes agree with other empirical single-technique tidal models
below 4 μas in PM and 0.25 μs in dUT1. The noise floor of the tidal ERP model was investigated in three ways resulting in about 1 μas for diurnal PM and 0.07 μs for diurnal dUT1 while the semi-diurnal components have a slightly better accuracy. 相似文献
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