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1.
Evaluation of the ITRF2008 GPS vertical velocities using satellite antenna z-offsets 总被引：2，自引：0，他引：2
We develop a method to evaluate the terrestrial reference frame (TRF) scale rate error using Global Positioning System (GPS) satellite antenna phase center offset (APCO) parameters and apply it to ITRF2008. We search for the TRF in which z-APCO parameters have the smallest drift. In order to provide realistic error bars for the z-APCO drifts, we pay attention to model periodic variations and auto-correlated noise processes in the z-APCO time series. We will show that the GPS scale rate with respect to a frame is, as a first approximation, proportional to the estimated mean z-APCO trend if that frame is used to constrain station positions. Thus, an ITRF2008 scale rate error between ?0.27 and ?0.06 mm/yr depending on the GPS analysis center can be estimated, which demonstrates the high quality of the newly constructed ITRF2008. We will also demonstrate that the traditional estimates of the GPS scale rate from 7-parameter similarity transformations are consistent with our newly derived GPS scale rates with respect to ITRF2008 within two sigmas. We find using International GNSS Service (IGS) products that the traditional approach is relevant for scale rate determination even if some of the z-APCO values supplied by the IGS were not simultaneously calibrated. As the scale rate is related to the accuracy of vertical velocities, our estimates supply a conservative evaluation that can be used for error budget computation. 相似文献
2.
Xavier Collilieux Laurent Métivier Zuheir Altamimi Tonie van Dam Jim Ray 《GPS Solutions》2011,15(3):219-231
The International GNSS Service (IGS) contributes to the construction of the International Terrestrial Reference Frame (ITRF)
by submitting time series of station positions and Earth Rotation Parameters (ERP). For the first time, its submission to
the ITRF2008 construction is based on a combination of entirely reprocessed GPS solutions delivered by 11 Analysis Centers
(ACs). We analyze the IGS submission and four of the individual AC contributions in terms of the GNSS frame origin and scale,
station position repeatability and time series seasonal variations. We show here that the GPS Terrestrial Reference Frame
(TRF) origin is consistent with Satellite laser Ranging (SLR) at the centimeter level with a drift lower than 1 mm/year. Although
the scale drift compared to Very Long baseline Interferometry (VLBI) and SLR mean scale is smaller than 0.4 mm/year, we think
that it would be premature to use that information in the ITRF scale definition due to its strong dependence on the GPS satellite
and ground antenna phase center variations. The new position time series also show a better repeatability compared to past
IGS combined products and their annual variations are shown to be more consistent with loading models. The comparison of GPS
station positions and velocities to those of VLBI via local ties in co-located sites demonstrates that the IGS reprocessed
solution submitted to the ITRF2008 is more reliable and precise than any of the past submissions. However, we show that some
of the remaining inconsistencies between GPS and VLBI positioning may be caused by uncalibrated GNSS radomes. 相似文献
3.
IGS contribution to the ITRF 总被引：2，自引：0，他引：2
We examine the contribution of the International GNSS Service (IGS) to the International Terrestrial Reference Frame (ITRF) by evaluating the quality of the incorporated solutions as well as their major role in the ITRF formation. Starting with the ITRF2005, the ITRF is constructed with input data in the form of time series of station positions (weekly for satellite techniques and daily for VLBI) and daily Earth Orientation Parameters. Analysis of time series of station positions is a fundamental first step in the ITRF elaboration, allowing to assess not only the stations behavior, but also the frame parameters and in particular the physical ones, namely the origin and the scale. As it will be seen, given the poor number and distribution of SLR and VLBI co-location sites, the IGS GPS network plays a major role by connecting these two techniques together, given their relevance for the definition of the origin and the scale of the ITRF. Time series analysis of the IGS weekly combined and other individual Analysis Center solutions indicates an internal precision (or repeatability) <2 mm in the horizontal component and <5 mm in the vertical component. Analysis of three AC weekly solutions shows generally poor agreement in origin and scale, with some indication of better agreement when the IGS started to use the absolute model of antenna phase center variations after the GPS week 1400 (November 2006). 相似文献
4.
Ant Sibthorpe Willy Bertiger Shailen D. Desai Bruce Haines Nate Harvey Jan P. Weiss 《Journal of Geodesy》2011,85(8):505-517
The subtle effects of different Global Positioning System (GPS) satellite force models are becoming apparent now that mature
processing strategies are reaching new levels of accuracy and precision. For this paper, we tested several approaches to solar
radiation pressure (SRP) modeling that are commonly used by International GNSS Service (IGS) analysis centers. These include
the GPS Solar Pressure Model (GSPM; Bar-Sever and Kuang in The Interplanetary Network Progress Report 42-160, 2005) and variants of the so-called DYB model (Springer et al. in Adv Space Res 23:673–676, 1999). Our results show that currently observed differences between GPS orbit solutions from the various IGS analysis centers
are in large part explained by differences between their respective approaches to modeling SRP. DYB-based strategies typically
generate orbit solutions that have the smallest differences with respect to the IGS final combined solution, largely because
the DYB approach is most commonly used by the contributing analysis centers. However, various internal and external metrics,
including ambiguity resolution statistics and satellite laser ranging observations, support continued use of the GSPM-based
approach for precise orbit determination of the GPS constellation, at least when using the GIPSY-OASIS software. 相似文献
5.
利用SLR与伪距资料综合定轨 总被引：2，自引：0，他引：2
以GPS伪距为观测量对GPS35卫星进行定轨 ,然后将SLR与GPS伪距资料综合起来进行定轨 ,并将计算的轨道与IGS精密轨道进行了比较 相似文献
6.
A simplified yaw-attitude model for eclipsing GPS satellites 总被引：11，自引：2，他引：9
J. Kouba 《GPS Solutions》2009,13(1):1-12
A simplified yaw-attitude modeling, consistent with Bar-Sever (1996), has been implemented and tested in the NRCan PPP software.
For Block IIR GPS satellite it is possible to model yaw-attitude control during eclipsing periods by using the constant hardware
yaw rate of 0.20°/s. The Block IIR satellites maintain the nominal yaw attitude even during a shadow crossing (Y. E. Bar-Sever,
private communication, 2007), except for the noon and shadow midnight turn maneuvers, both of which can be modeled and last
up to 15 min. Thus, for Block IIR satellites it is possible to maintain continuous satellite clock estimation even during
eclipsing periods. For the Block II/IIA satellites, it is possible to model satisfactorily the noon turns and also shadow
crossing, thanks to the permanent positive yaw bias of 0.5°, implemented in November 1995. However, in order to model the
Block II/IIA shadow crossings, satellite specific yaw rates should be used, either solved for or averaged yaw-rate solutions.
These yaw rates as estimated by the Jet Propulsion Laboratory (JPL) can differ significantly from the nominal hardware values.
The Block II/IIA post-shadow recovery periods, which last about 30 min, should be considered uncertain and cannot be properly
modeled. Data from post-shadow recovery periods should, therefore, not be used in precise global GPS analyses (Bar-Sever 1996). For high-precision applications, it is essential that users implement a yaw-attitude model, which is consistent with the
generation of the satellite clocks. Initial testing and analyses, based on the IGS and AC Final orbits and clocks have revealed
that during eclipsing periods, significant inconsistencies in yaw-attitude modeling still exist amongst the IGS Analyses Centers,
which contribute to the errors of the IGS Final clock combinations. 相似文献
7.
Quality of reprocessed GPS satellite orbits 总被引：4，自引：2，他引：2
Peter Steigenberger Markus Rothacher Mathias Fritsche Axel Rülke Reinhard Dietrich 《Journal of Geodesy》2009,83(3-4):241-248
High-precision Global Positioning System (GPS) satellite orbits are one of the core products of the International GNSS Service (IGS). Since the establishment of the IGS in 1994, the quality and consistency of the IGS orbits has steadily been improved by advances in the modeling of GPS observations. However, due to these model improvements and reference frame changes, the time series of operational orbits are inhomogeneous and inconsistent. This problem can only be overcome by a complete reprocessing starting with the raw observation data. The quality of reprocessed GPS satellite orbits for the time period 1994–2005 will be assessed in this paper. Orbit fits show that the internal consistency of the orbits could be improved by a factor of about two in the early years. Comparisons with the operational IGS orbits show clear discontinuities whenever the reference frame was changed by the IGS. The independent validation with Satellite Laser Ranging (SLR) residuals shows an improvement of up to 30% whereas a systematic bias of 5 cm still persists. 相似文献
8.
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
9.
选取ITRF2008框架下格陵兰岛区域12个GPS站2013年1月-2016年12月期间的日解坐标时间序列作为研究对象，并利用极大似然估计分析地表质量负载改正前后各站点的噪声特性、速度场及周期项振幅。结果表明：站点最优噪声模型主要为白噪声+幂律噪声与白噪声+闪烁噪声，地表质量负载形变修正GPS坐标时序后，明显增加U方向闪烁噪声的成分，平均降低其速度约0.36 mm/a，对水平方向影响较小；同时分别降低高程方向44.1%、14.2%的1 a项、0.5 a项振幅，相反，却增加了水平方向的周期项振幅。 相似文献
10.
11.
Sub-daily alias and draconitic errors in the IGS orbits 总被引：6，自引：2，他引：4
Harmonic signals with a fundamental period near the GPS draconitic year (351.2 days) and overtones up to at least the sixth multiple have been observed in the power spectra of nearly all products of the International GNSS Service (IGS), including station position time series, apparent geocenter motions, orbit jumps between successive days, and midnight discontinuities in earth orientation parameter (EOP) rates. Two main mechanisms have been suggested for the harmonics: mismodeling of orbit dynamics and aliasing of near-sidereal local station multipath effects. Others have studied the propagation of local multipath errors into draconitic position variations, but orbit-related processes have been less examined. We elaborate our earlier analysis of GPS day-boundary orbit discontinuities where we observed some draconitic features as well as prominent spectral bands near 29-, 14-, 9-, and 7-day periods. Finer structures within the sub-seasonal bands fall close to the expected alias frequencies for 24-h sampling of sub-daily EOP tide lines but do not coincide precisely. While once-per-revolution empirical orbit parameters should strongly absorb any sub-daily EOP tide errors due to near-resonance of their respective periods, the observed differences require explanation. This has been done by simulating EOP tidal errors and checking their impact on a long series of estimated daily GPS orbits and EOPs. Indeed, simulated tidal aliases are found to be very similar to the observed IGS orbital features in the sub-seasonal bands. Moreover and unexpectedly, some low draconitic harmonics were also produced, potentially a source for the widespread errors in most IGS products. The results from this study are further evidence for the need of an improved sub-daily EOP tide model. 相似文献
12.
New IGS Station and Satellite Clock Combination 总被引：3，自引：5，他引：3
Following the principles set forth in the Position Paper #3 at the 1998 Darmstadt Analysis Center (AC) Workshop on the new
International GPS Service (IGS) International Terrestrial Reference Frame (ITRF) realization and discussions at the 1999 La
Jolla AC workshop, a new clock combination program was developed. The program allows for the input of both SP3 and the new
clock (RINEX) format (ftp://igsch.jpl.nasa.gov//igscb/data/format/rinex_clock.txt). The main motivation for this new development
is the realization of the goals of the IGS/BIPM timing project. Besides this there is a genuine interest in station clocks
and a need for a higher sampling rate of the IGS clocks (currently limited to 15 min due to the SP3 format). The inclusion
of station clocks should also allow for a better alignment of the individual AC solutions and should enable the realization
of a stable GPS time-scale.
For each input AC clock solution the new clock combination solves and corrects for reference clock errors/instabilities as
well as satellite/station biases, geocenter and station/satellite orbit errors. External station clock calibrations and/or
constraints, such as those resulting from the IGS/BIPM timing pilot project, can be introduced via a subset of the fiducial
timing station set, to facilitate a precise and consistent IGS UTC realization for both station and satellite combined clock
solutions. Furthermore, the new clock combination process enforces strict strict conformity and consistency with the current
and future IGS standards.
The new clock combination maintains orbit/clock consistency at millimeter level, which is comparable to the best AC orbit/clock
solutions. This is demonstrated by static GIPSY precise point positioning tests using GPS week 0995 data for stations in both
Northern and Southern Hemispheres and similar tests with the Bernese software using more recent data from GPS week 1081. ?
2001 John Wiley & Sons, Inc. 相似文献
13.
根据卫星钟固有的特性,即频移、频漂和频漂率以及周期性,提出一种新的拟合方法。新方法首先构造一个合理的钟差模型,该模型包含一个二次多项式和多个周期项。然后利用IGS提供的钟差产品数据,先粗略补充缺失数据,用二次多项式拟合;并对拟合后的残差进行小波分析,作降噪处理;最后通过谱分析,确定其主要的周期项,从而构建出适当的拟合模型,实现精密GPS卫星钟差拟合和预报。多天数据的实验结果表明,采用本文提出的新方法能够有效地对卫星钟差进行拟合和预报,满足不同目的的需求。 相似文献
14.
15.
GPS卫星钟的特性与预报研究 总被引：1，自引：0，他引：1
经实验分析发现:GPS卫星钟差的预报精度与卫星的种类密切相关,最近发射的BLOCK ⅡR和BLOCKIIR-M类卫星比以往的BLOCK ⅡA类卫星要更加稳定,其卫星钟差的预报精度明显较高。直接利用IGS超快速产品和线性模型预报后6小时的卫星钟差,精度在0.5纳秒水平;但一些BLOCK ⅡA类卫星是不稳定的,通过对其预报残差的分析发现:同一颗卫星每天在相同时段用相同的模型去预报其卫星钟差,预报所得的残差呈周期性变化,并且这种周期性变化并不完全重合,还具有一定的随机性。依据这一特性本文构建了一个新的预报模型来实时预报GPS卫星钟差。该模型不仅能预报卫星钟差的总体变化趋势,还能预报残差的周期性变化以及随机项的变化,因此精度更高。预报结果均与IGS发布的最终产品相比,实验显示利用该方法实时预报GPS卫星钟差,预报精度可达0.5纳秒水平。 相似文献
16.
Combining the orbits of the IGS Analysis Centers 总被引：1，自引：0，他引：1
Currently seven Analysis Centers of the International GPS Service for Geodynamics (IGS) are producing daily precise orbits and the corresponding Earth Orientation Parameters (EOP). These individual products are available at several IGS Data Centers (e.g. CDDIS, IGN, SIO, etc.). During 1993 no official IGS orbits were produced, but the routine orbit comparisons by IGS indicated that, after small orientation and scale alignments, the orbit consistency was approaching the 20 cm level (a coordinate RMS), and that some orbit combination should be possible and feasible. An IGS combined orbit could provide a precise and efficient extension of the IERS Terrestrial Reference Frame (ITRF). Another advantage of such a combined orbit would be reliability and precision.Two schemes of orbit combinations are considered here: (a) the first method consists of a weighted averaging process of the earth-fixed satellite positions as produced by the individual Centers; (b) the second method uses the individual IGS orbit files as pseudo-observations in an orbit determination process, where in addition to the initial conditions, different parameter sets may be estimated. Both orbit combination methods have been tested on the January 1993 orbit data sets (GPS weeks 680 and 681) with an impressive agreement at the 5 cm level (coordinate RMS). The quality of the combined orbits is checked by processing a set of continental baselines in two different regions of the globe using different processing softwares. Both types of combined orbits gave similar baseline repeatability of a few ppb in both regions which compared favorably to the best individual orbits in the region. 相似文献
17.
采用了切比雪夫拟合多项式内插IGS精密星历,计算了GPS卫星广播星历轨道误差,比较了其在太阳活动谷值和峰值时的误差,讨论了其与太阳活动状况的关系。 相似文献
18.
The SIRGAS permanent GPS network which is in fact the IGS network densification for the American continent, consists today of more than 200 stations covering the continent and islands. It is currently processed by the IGS RNAAC SIR centre at Deutsches Geodätisches Forschungsinstitut producing weekly free solutions relying on IGS final orbits and EOP that contribute to the ITRF through IGS. By August 2006, the SIRGAS Working Group I had accepted five proposals for experimental processing centers within the region that would collaborate with IGS RNAAC SIR. One of them, Centro de Procesamiento La Plata (CPLat) in Argentina, began processing 60 stations on October 2006. By January 2007 CPLat reached operational capability, delivering weekly free solution SINEX files, with an internal consistency of 1.5 mm average for the horizontal components, and 3 mm in the vertical. Comparisons with IGS global and IGS RNAAC SIR weekly solutions were taken as external consistency indications, showing average RMS residuals of 1.8, 2.4 and 5 mm for the north, east, and vertical component, respectively. Analysis and comparison of adjusted solution time series from CPLat and other processing centers has proved to be highly valuable for solution QC, namely detection and identification of station anomalous behavior or modelling problems. These procedures will ensure the maintenance of the performance specifications for CPLat solutions. Action is being taken in order to guarantee the continuity of this effort beyond the experimental phase. 相似文献
19.
Hiroshi Munekane 《Journal of Geodesy》2013,87(4):393-401
The sub-daily noise in horizontal global positioning system (GPS) kinematic time series arising from monument tilts is quantitatively evaluated using tiltmeter data at GPS stations from the Japanese nationwide global navigation satellite system network. The estimated tilt-induced monument displacements show characteristics that are typical of those caused by thermal tilts of the monuments. The root mean square of the displacements is typically a few millimetres, with notable inter-seasonal variations. The stacked amplitude spectra of the monument displacements have peaks at the tidal bands S1 and S2, and their higher tones. The peaks at the S1 and S2 bands in the amplitude spectra are reduced by 41 and 43 % for the north–south component and 36 and 53 % for the east–west component, respectively, after correcting for the monument displacements. The monument displacements due to the thermal tilts of the monuments may also be a favourable candidate for sub-daily noise at the S1 and S2 bands found in other GPS networks. 相似文献
20.
An assessment of Bernese GPS software precise point positioning using IGS final products for global site velocities 总被引：2，自引：1，他引：2
We assess the use of precise point positioning (PPP) within the Bernese GPS software (BSW) Version 5.0 over the period from
2000 to 2005. In our strategy, we compute a set of daily PPP solutions for international GNSS service (IGS) reference frame
(IGb00) sites by fixing IGS final satellite orbits and clock products, followed by a Helmert transformation of these solutions
into ITRF2000, forming a set of continuous position time series over the entire time span. We assess BSW PPP by comparing
our set of transformation parameters with those produced by the IGS analysis centre coordinator (ACC) and our position time
series with those of the Jet Propulsion Laboratory (JPL) and the Scripps Orbit and Permanent Array Centre at the Scripps Institute
of Oceanography (SIO). The distributions of the north (N), east (E) and up (U) daily position differences are characterized
by means and SD of +2.2 ± 4.8, −0.6 ± 7.9 and +4.8 ± 17.3 mm with respect to JPL, and of +0.1 ± 4.4, −0.1 ± 7.4 and −0.1 ± 11.8 mm
with respect to SIO. Similarly, we find sub-millimetre mean velocity differences and SD for the N, E and U components of 0.9,
1.5 and 2.2 mm/year with JPL, and of 1.2, 1.6 and 2.3 mm/year with SIO. A noise analysis using maximum likelihood estimation
(MLE) shows that when estimating global site velocities from our position time series, the series need to be on average up
to 1.3 times longer than those of JPL and SIO, before an uncertainty of less than 0.5 mm/year is obtained. 相似文献