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1.
Reducing the draconitic errors in GNSS geodetic products 总被引：2，自引：2，他引：0
C. J. Rodriguez-Solano U. Hugentobler P. Steigenberger M. Bloßfeld M. Fritsche 《Journal of Geodesy》2014,88(6):559-574
Systematic errors at harmonics of the GPS draconitic year have been found in diverse GPS-derived geodetic products like the geocenter $Z$ -component, station coordinates, $Y$ -pole rate and orbits (i.e. orbit overlaps). The GPS draconitic year is the repeat period of the GPS constellation w.r.t. the Sun which is about 351 days. Different error sources have been proposed which could generate these spurious signals at the draconitic harmonics. In this study, we focus on one of these error sources, namely the radiation pressure orbit modeling deficiencies. For this purpose, three GPS+GLONASS solutions of 8 years (2004–2011) were computed which differ only in the solar radiation pressure (SRP) and satellite attitude models. The models employed in the solutions are: (1) the CODE (5-parameter) radiation pressure model widely used within the International GNSS Service community, (2) the adjustable box-wing model for SRP impacting GPS (and GLONASS) satellites, and (3) the adjustable box-wing model upgraded to use non-nominal yaw attitude, specially for satellites in eclipse seasons. When comparing the first solution with the third one we achieved the following in the GNSS geodetic products. Orbits: the draconitic errors in the orbit overlaps are reduced for the GPS satellites in all the harmonics on average 46, 38 and 57 % for the radial, along-track and cross-track components, while for GLONASS satellites they are mainly reduced in the cross-track component by 39 %. Geocenter $Z$ -component: all the odd draconitic harmonics found when the CODE model is used show a very important reduction (almost disappearing with a 92 % average reduction) with the new radiation pressure models. Earth orientation parameters: the draconitic errors are reduced for the $X$ -pole rate and especially for the $Y$ -pole rate by 24 and 50 % respectively. Station coordinates: all the draconitic harmonics (except the 2nd harmonic in the North component) are reduced in the North, East and Height components, with average reductions of 41, 39 and 35 % respectively. This shows, that part of the draconitic errors currently found in GNSS geodetic products are definitely induced by the CODE radiation pressure orbit modeling deficiencies. 相似文献
2.
Anomalous harmonics in the spectra of GPS position estimates 总被引：22，自引：3，他引：19
Prior studies of the power spectra of GPS position time series have found pervasive seasonal signals against a power-law background
of flicker noise plus white noise. Dong et al. (2002) estimated that less than half the observed GPS seasonal power can be explained by redistributions of geophysical fluid mass
loads. Much of the residual variation is probably caused by unidentified GPS technique errors and analysis artifacts. Among
possible mechanisms, Penna and Stewart (2003) have shown how unmodeled analysis errors at tidal frequencies (near 12- and 24-hour periods) can be aliased to longer periods
very efficiently. Signals near fortnightly, semiannual, and annual periods are expected to be most seriously affected. We
have examined spectra for the 167 sites of the International GNSS (Global Navigation Satellite Systems) Service (IGS) network
having more than 200 weekly measurements during 1996.0–2006.0. The non-linear residuals of the weekly IGS solutions that were
included in ITRF2005, the latest version of the International Terrestrial Reference Frame (ITRF), have been used. To improve
the detection of common-mode signals, the normalized spectra of all sites have been stacked, then boxcar smoothed for each
local north (N), east (E), and height (H) component. The stacked, smoothed spectra are very similar for all three components.
Peaks are evident at harmonics of about 1 cycle per year (cpy) up to at least 6 cpy, but the peaks are not all at strictly
1.0 cpy intervals. Based on the 6th harmonic of the N spectrum, which is among the sharpest and largest, and assuming a linear
overtone model, then a common fundamental of 1.040 ± 0.008 cpy can explain all peaks well, together with the expected annual
and semiannual signals. A flicker noise power-law continuum describes the background spectrum down to periods of a few months,
after which the residuals become whiter. Similar sub-seasonal tones are not apparent in the residuals of available satellite
laser ranging (SLR) and very long baseline interferometry (VLBI) sites, which are both an order of magnitude less numerous
and dominated by white noise. There is weak evidence for a few isolated peaks near 1 cpy harmonics in the spectra of geophysical
loadings, but these are much noisier than for GPS positions. Alternative explanations related to the GPS technique are suggested
by the close coincidence of the period of the 1.040 cpy frequency, about 351.2 days, to the “GPS year”; i.e., the interval
required for the constellation to repeat its inertial orientation with respect to the sun. This could indicate that the harmonics
are a type of systematic error related to the satellite orbits. Mechanisms could involve orbit modeling defects or aliasing
of site-dependent positioning biases modulated by the varying satellite geometry. 相似文献
3.
GPS精密定位中的海潮位移改正 总被引：2，自引：0，他引：2
根据海洋负荷潮理论，利用NAO99b全球海潮模型，计算了中国部分IGS站的海潮位移改正，并将海潮位移改正应用到GPS数据处理当中。在GAMIT软件的解算过程中，分别按加入和不加入海潮位移改正，对GPS基线分量和测站坐标分别进行了计算和比较分析。结果表明，海潮位移改正无论是对GPS基线分量还是对测站坐标，都有一定的影响。 相似文献
4.
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
5.
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
6.
Impact of Earth radiation pressure on GPS position estimates 总被引：10，自引：8，他引：2
C. J. Rodriguez-Solano U. Hugentobler P. Steigenberger S. Lutz 《Journal of Geodesy》2012,86(5):309-317
GPS satellite orbits available from the International GNSS Service (IGS) show a consistent radial bias of up to several cm
and a particular pattern in the Satellite Laser Ranging (SLR) residuals, which are suggested to be related to radiation pressure
mismodeling. In addition, orbit-related frequencies were identified in geodetic time series such as apparent geocenter motion
and station displacements derived from GPS tracking data. A potential solution to these discrepancies is the inclusion of
Earth radiation pressure (visible and infrared) modeling in the orbit determination process. This is currently not yet considered
by all analysis centers contributing to the IGS final orbits. The acceleration, accounting for Earth radiation and satellite
models, is introduced in this paper in the computation of a global GPS network (around 200 IGS sites) adopting the analysis
strategies from the Center for Orbit Determination in Europe (CODE). Two solutions covering 9 years (2000–2008) with and without
Earth radiation pressure were computed and form the basis for this study. In previous studies, it has been shown that Earth
radiation pressure has a non-negligible effect on the GPS orbits, mainly in the radial component. In this paper, the effect
on the along-track and cross-track components is studied in more detail. Also in this paper, it is shown that Earth radiation
pressure leads to a change in the estimates of GPS ground station positions, which is systematic over large regions of the
Earth. This observed “deformation” of the Earth is towards North–South and with large scale patterns that repeat six times
per GPS draconitic year (350 days), reaching a magnitude of up to 1 mm. The impact of Earth radiation pressure on the geocenter
and length of day estimates was also investigated, but the effect is found to be less significant as compared to the orbits
and position estimates. 相似文献
7.
The International GNSS Service (IGS) provides Ultra-rapid GPS & GLONASS orbits every 6 h. Each product is composed of 24 h of observed orbits with predicted orbits for the next 24 h. We have studied how the orbit prediction performance varies as a function of the arc length of the fitted observed orbits and the parameterization strategy used to estimate the empirical solar radiation pressure (SRP) effects. To focus on the dynamical aspects of the problem, nearly ideal conditions have been adopted by using IGS Rapid orbits and known earth rotation parameters (ERPs) as observations. Performance was gauged by comparison with Rapid orbits as truth by examining WRMS and median orbit differences over the first 6-h and the full 24-h prediction intervals, as well as the stability of the Helmert frame alignment parameters. Two versions of the extended SRP orbit model developed by the Centre for Orbit Determination in Europe (CODE) were tested. Adjusting all nine SRPs (offsets plus once-per-revolution sines and cosines in each satellite-centered frame direction) for each satellite shows smaller mean sub-daily, scale, and origin translation differences. On the other hand, eliminating the four once-per-revolution SRP parameters in the sun-ward and the solar panel axis directions yields orbit predictions that are much more rotationally stable. We found that observed arc lengths of 40–45 h produce the most stable and accurate predictions during 2010. A combined strategy of rotationally aligning the 9 SRP results to the 5 SRP frame should give optimal predictions with about 13 mm mean WRMS residuals over the first 6 h and 50 mm over 24 h. Actual Ultra-rapid performance will be degraded due to the unavoidable rotational errors from ERP predictions. 相似文献
8.
Stavros A. Melachroinos Jean-Michel Lemoine Paul Tregoning Richard Biancale 《Journal of Geodesy》2009,83(10):915-923
Unmodeled sub-daily ocean S2 tide signals that alias into lower frequencies have been detected in the analysis of gravity recovery and climate experiment
(GRACE) space gravity fields of GRGS. The most significant global S2 aliased signal occurs off the northwest coast of Australia in a shallow continental shelf zone, a region with high tidal
amplitudes at a period of 161 days. The GRACE S2 aliased equivalent water height grids are convolved with Green’s functions to produce GRACE aliased tidal loading (GATL)
vertical displacements. The analysis of hourly global positioning system (GPS) vertical coordinate estimates at permanent
sites in the region confirms the presence of spectral power at the S2 frequency when the same ocean tide model (FES2004) was used. Thus, deficiencies in the FES2004 ocean tide model are detected
both directly and indirectly by the two independent space geodetic techniques. Through simulation, the admittance (ratio of
amplitude of spurious long-wavelength output signal in the GRACE time-series to amplitude of unmodeled periodic signals) of
the GRACE unmodeled S2 tidal signals, aliased to a 161-day period, is found to have a global average close to 100%, although with substantial spatial
variation. Comparing GATL with unmodeled S2 tidal sub-daily signals in the vertical GPS time-series in the region of Broome in NW Australia suggests an admittance of
110–130%. 相似文献
9.
Different types of GPS clock and orbit data provided by the International GPS Service (IGS) have been used to assess the accuracy
of rapid orbit determination for satellites in low Earth orbit (LEO) using spaceborne GPS measurements. To avoid the need
for reference measurements from ground-based reference receivers, the analysis is based on an undifferenced processing of
GPS code and carrier-phase measurements. Special attention is therefore given to the quality of GPS clock data that directly
affects the resulting orbit determination accuracy. Interpolation of clock data from the available 15 min grid points is identified
as a limiting factor in the use of IGS ultra-rapid ephemerides. Despite this restriction, a 10-cm orbit determination accuracy
can be obtained with these products data as demonstrated for the GRACE-B spacecraft during selected data arcs between 2002
and 2004. This performance may be compared with a 5-cm orbit determination accuracy achievable with IGS rapid and final products
using 5 min clock samples. For improved accuracy, high-rate (30 s) clock solutions are recommended that are presently only
available from individual IGS centers. Likewise, a reduced latency and more frequent updates of IGS ultra-rapid ephemerides
are desirable to meet the requirements of upcoming satellite missions for near real-time and precise orbit determination. 相似文献
10.
精密卫星钟差加密方法及其对星载GPS低轨卫星定轨精度影响 总被引：7，自引：0，他引：7
韩保民 《武汉大学学报(信息科学版)》2006,31(12):1075-1078
系统分析、比较了几种精密卫星钟差加密方法，研究了利用全球分布的IGS永久跟踪站的GPS观测数据估计高采样率卫星钟差参数的原理与方法，并将各种卫星钟差加密方法得到的结果与IGS数据分析中心估计的卫星钟差结果相比较。最后将不同加密方法得出的精密卫星钟差结果用于基于星载GPS双频非差观测值的CHAMP低轨卫星的定轨，并将不同方法得到的定轨精度进行比较。结果表明，利用地面跟踪站的GPS观测数据，可高精度、高密度地估计GPS卫星钟差，估计精度可达0．1～0．5ns。经地面GPS跟踪站数据估计的GPS卫星钟差，应用于基于PPP方法的低轨卫星定轨，其定轨精度在10cm以内。 相似文献
11.
由星载GPS双差相位数据进行CHAMP卫星动力学定轨 总被引：1，自引：0，他引：1
为了确定CHAMP卫星的轨道，由星载GPS数据和IGS跟踪站的GPS数据构造星地相位双差观测量，利用EOP、SGO、时间等数据，对GPS数据进行预处理，包括钟差改正、模糊度解算和周跳探测、卫星姿态改正、天线偏差和相位中心改正等，采用CHAMP卫星受力摄动模型，根据动力学原理，对CHAMP卫星进行实际定轨。与德国GFZ定轨结果PSO相比，本方法定轨结果径向精度为0．2857m。对于1d的重叠轨道，径向轨道差异的RMS为0．0958m。对于轨道端点比较，径向轨道差异平均为0．0666m。 相似文献
12.
针对IGS实时数据流产品,该文开展了实时精密单点定位技术在远海实时GPS验潮中的应用研究。对RTS改正的实时精密卫星轨道和钟差进行了精度验证和分析,给出了实时精密单点定位的数据处理策略以及实时GPS验潮的基本流程;组织和实施了渤海湾船载GPS验潮试验,以压力式验潮仪数据为参考,对远距离实时GPS潮汐测量结果进行了精度分析。结果表明:以IGS最终卫星轨道和钟差产品为参考,实时数据流产品实时精密卫星轨道在X、Y、Z方向的精度均优于3cm,卫星钟差的精度优于0.15ns;采用傅里叶低通滤波方法,消除波浪对潮汐观测的影响,进一步提取潮位信息。在忽略船体姿态改正的情况下,实时精密单点定位验潮相对于压力式验潮仪结果的最大偏差优于20cm,RMS达到7.5cm。 相似文献
13.
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
14.
Analysis of the first year of Earth rotation parameters with a sub-daily resolution gained at the CODE processing center of the IGS 总被引：4，自引：4，他引：0
The solutions of the CODE Analysis Center submitted to the IGS, the International Global Position System (GPS) Service for
Geodynamics, are based on three days of observation of about 80–100 stations of the IGS network. The Earth rotation parameters
(ERPs) are assumed to vary linearly over the three days with respect to an a priori model. Continuity at the day boundaries
as well as the continuity of the first derivatives are enforced by constraints. Since early April 1995 CODE has calculated
a new ERP series with an increased time resolution of 2 hours. Again continuity is enforced at the 2-hours-interval boundaries.
The analysis method is described, particularly how to deal with retrograde diurnal terms in the ERP series which may not be estimated with satellite geodetic methods. The results obtained from the first year of data covered by the time series
(time interval from 4 April 1995 to 30 June 1996) are also discussed. The series is relatively homogeneous in the sense of
the used orbit model and the a priori model for the ERPs. The largest source of excitation at daily and sub-daily periods
is likely to be the effect of the ocean tides. There is good agreement between the present results and Topex/Poseidon ocean
tide models, as well as with models based on Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data.
Non-oceanic periodic variations are also observed in the series. Their origin is most probably a consequence of the GPS solution
strategy; other possible sources are the atmospheric tides.
Received: 13 July 1999 / Accepted: 21 March 2000 相似文献
15.
GPS形变监测网基线处理中系统误差的分析 总被引：18，自引：3，他引：18
分析了高精度GPS形变监测网基线处理中系统误差产生的原因，分类及其对基线处理的影响，并在此基础上提出消除和削弱这些系统误差影响的一些原则和算法。 相似文献
16.
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
17.
针对传统事后精密单点定位技术的时间延迟问题,该文基于IGS RTS实时数据流产品,开展了实时精密单点定位技术在远海实时GPS验潮中的应用研究.对RTS改正的实时精密卫星轨道和钟差进行了精度验证和分析,给出了RT-PPP的数据处理策略以及实时GPS验潮的基本流程;组织和实施了渤海湾船载GPS验潮试验,以压力式验潮仪数据为参考,对远距离实时GPS潮汐测量结果进行了精度分析.结果表明:①以IGS最终卫星轨道和钟差产品为参考,RTS实时精密卫星轨道在X、y、Z方向的精度(RMS)均优于3 cm,卫星钟差的精度优于0.15 ns;②采用傅里叶低通滤波方法,消除波浪对潮汐观测的影响,进一步提取潮位信息.在忽略船体姿态改正的情况下,实时精密单点定位验潮相对于压力式验潮仪结果的最大偏差优于20 cm,RMS达到7.5 cm. 相似文献
18.
EOP预报误差对导航卫星轨道预报的影响分析 总被引：1，自引：0，他引：1
导航卫星轨道预报是利用精密定轨结果在惯性系下进行轨道外推,再将外推得到的惯性系轨道转换为地固系轨道,然后生成卫星星历数据。由于坐标系转换时使用的是带有误差的地球定向参数（EOP：Earth Orientation Parameters）预报值,转换结果会产生误差,进而影响轨道预报结果的精度。分析了EOP快速预报产品公报A的预报精度,研究了参数预报误差对轨道预报精度的影响。结果表明,对于利用GPS精密星历外推模拟得到的卫星轨道而言,EOP预报1天引起的轨道预报误差大致分布在0．232±0．183m,参数预报7天引起的轨道预报误差大致分布在0．438±0．356m。 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