BDS与GPS数据解算地球自转参数精度分析北大核心CSCD

针对我国利用BDS数据自主确定地球自转参数(ERP)时,需对其精度进行验证和分析的问题,该文利用我国境内及周边的GPS基准站数据以及MEGX网BDS数据进行ERP解算,对解算结果进行精度对比和分析。解算结果表明:利用BDS数据解算的ERP,在X方向极移和国际地球自转服务(IERS)公布值差值的RMS为0.6576mas,Y方向极移差值的RMS为1.0324mas,UT1-UTC差值的RMS为0.0853ms;利用GPS数据解算ERP,在x方向极移差值的RMS为0.4516mas,Y方向极移差值的RMS为0.5475mas,精度明显比利用BDS数据解算的要高,UT1-UTC差值的RMS为0.2153ms,比利用BDS数据解算的精度差。利用两种技术解算ERP发现极移参数存在明显的系统性误差,而UT1-UTC值不存在明显的系统性误差。结果表明,利用BDS技术确定地球自转参数精度虽然比GPS要差,但较之前成果有了很大提高。     

VLBI和GPS观测联合解算地球自转参数和日长变化

利用GAMIT软件处理了2005年9月、2006年1月和2月每天17个IGS国际GNSS服务(International GNSS Service, IGS)站的GPS观测数据,获得了地球自转参数(Earth rotation parameter, ERP)和日长变化(ΔLOD),并与IGS综合解进行了对比。利用OCCAM 6.2软件处理了相同时间内的甚长基线干涉测量(very long baseline interferometry,VLBI)观测数据,将解算结果与国际VLBI服务(International VLBI Service, IVS)结果进行了对比。分别采用基于内符合精度和IERS 08C04序列的定权方法对VLBI解算结果与GPS解算结果进行了加权平均,获得了VLBI和GPS技术对ERP和ΔLOD的协议结果。研究结果表明,VLBI解算结果与采用的插值方法有较大的关系,基于IERS 08C04序列的加权平均方法达到了利用VLBI解算结果对GPS解算结果进行修正的目的。VLBI和GPS技术的联合弥补了VLBI观测数据密度不够和GPS解算结果不稳定的缺陷,使解算结果的稳定性和可靠性有所提高。     

测站数目及分布对地球自转参数解算精度的影响

为研究GPS数据解算地球自转参数(ERP)精度受测站数目及分布均衡性影响规律的问题,该文利用全球国际GNSS服务(IGS)站提供的GPS数据,设置不同测站数、不同测站分布均衡程度的解算策略,通过对比不同策略下ERP解算精度,来研究测站数目和均衡程度对ERP解算过程中的影响规律。结果表明,考虑到解算效率的情况下,测站数目选择40个时能达到最佳效果,此时极移在x方向的RMS值为0.223 081 mas,在y方向的RMS值为0.186 941 mas;对于测站分布均衡性,该文提出用观测网的网重心坐标转换为大地坐标作为评价指标,当网重心越接近地心,解算精度越高。研究成果表明在利用GPS数据解算ERP参数时,选择适当数目的测站以及分布均衡性好的解算策略可以提高解算效率及精度。     

近三年VLBI观测的数据处理及分析

介绍了标准NGS数据格式与IVS(international VLBI service for geodesy and astrometry)网站公布的新格式之间的差异,将2005~2007年的VLBI数据进行了格式转换,利用由挪威大地测量研究所和澳大利亚地球科学研究所共同开发的OCCAM 6.2软件解算出大地测量参数(Xp,Yp,UT1-UTC、dψ,dε),并在解算过程中,将两种不同的UT1内插模型进行了对比,同时还将解算结果与IERS网站公布的数据进行了对比。     

基于GAMIT10.61的高精度GPS／BDS数据处理及精度对比分析

本文利用GAMIT10.61软件对重庆8个CORS站GPS数据和BDS数据进行处理,并从基线重复性、单日解时间序列、联合解平差等三个方面对GPS和BDS解算结果进行对比分析.结果表明,GPS解算结果整体优于BDS,且单BDS解与单GPS解在水平方向差值小于0.7 cm,高程方向差值在1～3 cm;基于GAMIT 10.61的BDS基线解算重复性在南北方向上1.39 mm+0.205 mm×10?-8 ,东西方向上为3.10 mm+0.252×10-8 ,高程方向上为7.81 mm+2.001×10-8,基线长度方向上2.13 mm+0.384×10-8,解算精度能满足高精度数据处理要求.      

BDS精密相对定位精度的GAMIT分析北大核心CSCD

为了验证GAMIT用于BDS精密相对定位的可靠性与精度,该文以BDS短基线和长基线实测数据,基于GAMIT软件的不同解算策略进行BDS精密相对定位实验。由实验结果可知,GAMIT用于BDS短基线解算,相对于GPS在水平方向基线分量差值优于3mm,在高程方向基线分量差值优于3mm;GAMIT用于BDS长基线解算,相对于GPS在水平方向的基线分量差值优于6mm,在高程方向基线分量差值优于1.3cm。研究结果表明,GAMIT可用于BDS的精密定位解算且精度较高。     

利用GLOBK实现GPS周综合解

介绍了利用GLOBK实现GPS周综合解的基本原理和详细步骤,给出了实际计算结果与IGS计算结果的比较.从比较结果可以看出,两者卫星星历的RMS最大值为22.7mm;ERP的pole参数的X和Y方向的STD分别为0.018 mas和0.019 mas,LOD参数的STD为0.006 ms.     

基于MGEX站多系统GNSS反演大气可降水量精度评估

2020年6月北斗卫星导航系统(BDS)完成全面组网,为分析其解算水汽信息的精度,选用15个MGEX (Multi-GNSS Experiment)测站2021年10月至11月的观测数据进行水汽反演. 利用GAMIT软件分别解算BDS、GPS、Galileo和GLONASS的观测数据,将得到的对流层天顶延迟(ZTD)与国际GNSS服务(IGS)发布的结果进行对比,并将解算的大气可降水量(PWV)分别与探空数据、ERA5数据计算得到的PWV对比. 实验结果表明:截止高度角设置为5°时,4个卫星系统估计的ZTD均方根 (RMS)均小于13 mm,GPS-PWV、BDS-PWV、Galileo-PWV、GLONASS-PWV与无线电探空可降水量(RS-PWV)相比,RMS平均值分别为2.25 mm、2.46 mm、2.52 mm和2.84 mm,RMS均小于3 mm;与ERA5-PWV相比,RMS平均值分别为1.63 mm、1.86 mm、1.76 mm和1.99 mm,RMS均小于2 mm. GPS探测水汽的精度最高,BDS探测水汽的精度低于GPS和Galileo,高于GLONASS,均满足气象学应用需求.      

GAMIT(10.7)用于GLONASS/BDS精密相对定位性能测试与分析

2018年6月GAMIT发布了10.7版本,此版本新增加了GLONASS系统。文中首先介绍新版本GAMIT(10.7)的特点和功能,详细讨论分析了GAMIT(10.7)解算结果的可靠性及精度评价指标。为了验证GAMIT(10.7)对GLONASS/BDS的精密相对定位的可靠性及精度,使用HKCORS的数据分别对GPS,GLONASS,BDS进行解算。从NRMS,RMS、模糊度固定率方面详细分析解算可靠性;从实验结果可知,GLONASS和BDS相对于GPS在平面及高程方向的差值均在mm级,相对精度达到10~(-8)量级,由此证明GAMIT(10.7)可用于GLONASS和BDS的精密相对定位并且精度比较可靠。     

利用2008年VLBI观测数据进行EOP参数的解算与分析

利用2008年的VLBI观测数据解算出了EOP参数,并在其精度的内外符合方面进行了分析。此外,还集中解算了CONT08的VLBI数据,并将解算出的EOP参数精度分别与IVS和IERS网站公布的精度进行了对比分析。     

IGS Earth Rotation Parameters

Since its official start in January 1994, the International GPS Service (IGS) has been distributing, as part of its product combination, two distinct Earth rotation parameter (ERP) series: the IGS Rapid series and the IGS Final series. Initially, the IGS Rapid ERP values were interpolations of the International Earth Rotation Service (IERS) Bulletin A, whereas the IGS Final ERP series was based on the IERS Bulletin B. Since June 1996, the IGS has been generating its own Final ERP series consistent with the IGS combined orbit products and based on weighted means of individual IGS analysis center (AC) solutions. At first, only the polar motion (PM) coordinates and their rates were combined. Length of Day (LOD) and Universal Time (UT) solutions, also based on separate weighted mean combinations, followed in March 1997. Currently, the IGS Rapid and Final combinations are produced and made available within 17 hours and 11 days, respectively, after the last observation. Both IGS and the best AC series are consistent and precise at the 0.1-milliarcsecond (mas) level for PM and at about 30 μs for LOD. Biases in some AC solutions may exceed these consistency levels. Comparisons of both IGS ERP series with external standards, such as the IERS multitechnique Bulletins and atmospheric angular momentum series, confirm the estimated precisions. ? 1999 John Wiley & Sons, Inc.     

Assessment of periodic sub-diurnal Earth rotation variations at tidal frequencies through transformation of VLBI normal equation systems

We present an empirical model for periodic variations of diurnal and sub-diurnal Earth rotation parameters (ERPs) that was derived based on the transformation of normal equation (NEQ) systems of Very Long Baseline Interferometry (VLBI) observing sessions. NEQ systems that contain highly resolved polar motion and UT1-TAI with a temporal resolution of 15 min were generated and then transformed to the coefficients of the tidal ERP model to be solved for. To investigate the quality of this model, comparisons with empirical models from the Global Positioning System (GPS), another VLBI model and the model adopted by the conventions of the International Earth Rotation and Reference Systems Service (IERS) were performed. The absolute coefficients of these models agree almost completely within 7.5 μ as in polar motion and 0.5 μs in UT1-TAI. Several bigger differences exist, which are discussed in this paper. To be able to compare the model estimates with results of the continuous VLBI campaigns, where signals with periods of 8 and 6 h were detected, terms in the ter- and quarter-diurnal band were included in the tidal ERP model. Unfortunately, almost no common features with the results of continuous VLBI campaigns or ERP predictions in these tidal bands can be seen.     

GGOS-D: homogeneous reprocessing and rigorous combination of space geodetic observations

In preparation of activities planned for the realization of the Global Geodetic Observing System (GGOS), a group of German scientists has carried out a study under the acronym GGOS-D which closely resembles the ideas behind the GGOS initiative. The objective of the GGOS-D project was the investigation of the methodological and information-technological realization of a global geodetic-geophysical observing system and especially the integration and combination of the space geodetic observations. In the course of this project, highly consistent time series of GPS, VLBI, and SLR results were generated based on common state-of-the-art standards for modeling and parameterization. These series were then combined to consistently and accurately compute a Terrestrial Reference Frame (TRF). This TRF was subsequently used as the basis to produce time series of station coordinates, Earth orientation, and troposphere parameters. In this publication, we present results of processing algorithms and strategies for the integration of the space-geodetic observations which had been developed in the project GGOS-D serving as a prototype or a small and limited version of the data handling and processing part of a global geodetic observing system. From a comparison of the GGOS-D terrestrial reference frame results and the ITRF2005, the accuracy of the datum parameters is about 5?C7?mm for the positions and 1.0?C1.5?mm/year for the rates. The residuals of the station positions are about 3?mm and between 0.5 and 1.0?mm/year for the station velocities. Applying the GGOS-D TRF, the offset of the polar motion time series from GPS and VLBI is reduced to 50 ??as (equivalent to 1.5?mm at the Earth??s surface). With respect to troposphere parameter time series, the offset of the estimates of total zenith delays from co-located VLBI and GPS observations for most stations in this study is smaller than 1.5?mm. The combined polar motion components show a significantly better WRMS agreement with the IERS 05C04 series (96.0/96.0???as) than VLBI (109.0/100.7???as) or GPS (98.0/99.5???as) alone. The time series of the estimated parameters have not yet been combined and exploited to the extent that would be possible. However, the results presented here demonstrate that the experiences made by the GGOS-D project are very valuable for similar developments on an international level as part of the GGOS development.     

利用2006—2015年VLBI数据进行地球定向参数解算与分析

目前正处在下一代甚长基线干涉测量（very long baseline interferometry,VLBI）系统的建设时期。利用维也纳VLBI与卫星软件（Vienna VLBI and satellite software,VieVS）解算了2006—2015年的VLBI数据,得到了10 a的地球定向参数（Earth orientation parameters,EOP）时间序列,并与国际地球自转服务机构的结果进行了对比。利用解算结果得到了10 a的日长变化时间序列,通过傅里叶分析得出了日长变化的短周期、半月周期、月周期、半年周期和周年周期,同时还分析得到了极移序列中的周年项和张德勒周期项以及章动改正序列中的自由核章动项。此次解算工作可为武汉大学卫星台站日后的VLBI数据解析积累一定的经验。     

Radio source instability in VLBI analysis

The source position time-series for many of the frequently observed radio sources in the NASA geodetic very long baseline interferometry (VLBI) program show systematic linear and non-linear variations of as much as 0.5 mas (milli-arc-seconds) to 1.0 mas, due mainly to source structure changes. In standard terrestrial reference frame (TRF) geodetic solutions, it is a common practice to only estimate a global source position for each source over the entire history of VLBI observing sessions. If apparent source position variations are not modeled, they produce corresponding systematic variations in estimated Earth orientation parameters (EOPs) at the level of 0.02–0.04 mas in nutation and 0.01–0.02 mas in polar motion. We examine the stability of position time-series of the 107 radio sources in the current NASA geodetic source catalog since these sources have relatively dense observing histories from which it is possible to detect systematic variations. We consider different strategies for handling source instabilities where we (1) estimate the positions of unstable sources for each session they are observed, or (2) estimate spline parameters or rate parameters for sources chosen to fit the specific variation seen in the position-time series. We found that some strategies improve VLBI EOP accuracy by reducing the biases and weighted root mean square differences between measurements from independent VLBI networks operating simultaneously. We discuss the problem of identifying frequently observed unstable sources and how to identify new sources to replace these unstable sources in the NASA VLBI geodetic source catalog.     

基于Kalman滤波的大规模GNSS网参数估计方法

针对传统方法存在的缺陷,研究了利用Kalman滤波技术进行大规模GNSS网参数（主要包括测站位置参数、卫星轨道参数及极移参数）估计的理论方法与关键技术,并利用40个全球均匀分布的IGS站多天的观测数据对理论成果进行了验证。结果表明,本文估计得到的测站位置参数与IGS结果各分量较差的RMS值分别为0.85、1.1、1.21 cm,得到的卫星轨道参数外推1 h后与IGS最终星历各分量较差的RMS值分别为9.8、8.6、7.2 cm,得到的极移参数与IERS结果的较差基本在1 mas之内;该方法具有较高的估值精度,可有效地用于GNSS网各类参数的估计。     

利用LS_AR模型对极移参数的中长期预报

为了满足深空探测器自主导航定位对极移参数中长期预报的需求,阐述了基于LS_AR模型的极移参数中长期预报和精度评定的原理,提出了4种改进方案对LS_AR模型的构建进行优化,并利用IERS提供的1990～1996年的极移参数的时间序列检验4种优化方案,得到了最优的预报模型,在400 d跨度上,其预报结果的平均绝对误差比未优化的模型小3 mas左右。     

Polar motion modeling,analysis, and prediction with time dependent harmonic coefficients

A time dependent amplitude model was proposed for the analysis and prediction of polar motion time series. The formulation was implemented to analyze part of the new combined solution, EOP (IERS) C 04, daily polar motion time series of 14 years length using a statistical model with first order autoregressive disturbances. A new solution approach, where the serial correlations of the disturbances are eliminated by sequentially differencing the measurements, was used to estimate the model parameters using weighted least squares. The new model parsimoniously represents the 14-year time series with 0.5 mas rms fit, close to the reported 0.1 mas observed pole position precisions for the x and y components. The model can also predict 6 months into the future with less than 4 mas rms prediction error for both polar motion components, and down to sub mas for one-step ahead prediction as validated using a set of daily time series data that are not used in the estimation. This study is dedicated to the memory of Prof. Urho Uotila (1923–2006) whose teaching of “Adjustment Computations” over the years influenced so much, so many of us who had the privilege of being his students.     

7个月周期极移的非线性动力机制

从滞弹性阻尼形变摄动造成CW频率调制假设出发,对CW的共振激发模型加上了参数的时变调制,变成了参数共振模型。经正演计算发现,参数共振模型完全符合CW的实际,表明滞弹性阻尼形变摄动造成频率的3%调制,进一步使得CW振幅调制可达70%以上。这一参数共振模型是一个非线性动力系统,在非线性情况下,运动将发生分岔,即多解。