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1.
差分码偏差(DCB)作为电离层建模和导航定位中一项重要的误差源,对其进行估计求解至关重要.为提高北斗卫星导航系统(BDS) DCB估计和电离层建模精度,提出了一种综合高度角、卫地距和测站纬度多因素的随机模型,并对比分析了不同随机模型对BDS DCB估计和电离层垂直总电子含量(VTEC)建模精度的影响.结果表明：不同随机模型对卫星端DCB解算产生约0.2 ns差异.相较于高度角随机模型,采用高度角、卫地距组合模型测站DCB估计精度平均提高0.13 ns,电离层建模精度提高了约0.2 TECU.新提出的随机模型,在低纬度测站DCB解算精度上差于高度角模型和高度角、卫地距组合模型,但在高纬度测站DCB解算结果上更优,且对电离层VTEC建模精度提升效果明显,与前两种随机模型相比分别提升了0.88 TECU和0.68TECU. 相似文献
2.
Minimal detectable biases of GPS data 总被引：4，自引：1，他引：3
P. J. G. Teunissen 《Journal of Geodesy》1998,72(4):236-244
In this contribution closed-form expressions are given for the minimal detectable biases of single- and dual-frequency pseudo-range
and carrier-phase data. They are given for three different single-baseline models. These are the geometry-free model and two
variants of the geometry-based model, namely the roving and stationary variants. The baselines are considered to be sufficiently
short such that orbital uncertainties in the fixed orbits and residual ionospheric and tropospheric delays can be assumed
absent. The stochastic model used is one that permits cross-correlation and the use of different variances for individual
GPS observables, including the possibility to weigh the observables in dependence on which satellite is tracked.
Received: 23 April 1997 / Accepted: 27 October 1997 相似文献
3.
Baocheng Zhang Peter J. G. Teunissen Yunbin Yuan Hongxing Zhang Min Li 《Journal of Geodesy》2018,92(4):401-413
Vertical total electron content (VTEC) parameters estimated using global navigation satellite system (GNSS) data are of great interest for ionosphere sensing. Satellite differential code biases (SDCBs) account for one source of error which, if left uncorrected, can deteriorate performance of positioning, timing and other applications. The customary approach to estimate VTEC along with SDCBs from dual-frequency GNSS data, hereinafter referred to as DF approach, consists of two sequential steps. The first step seeks to retrieve ionospheric observables through the carrier-to-code leveling technique. This observable, related to the slant total electron content (STEC) along the satellite–receiver line-of-sight, is biased also by the SDCBs and the receiver differential code biases (RDCBs). By means of thin-layer ionospheric model, in the second step one is able to isolate the VTEC, the SDCBs and the RDCBs from the ionospheric observables. In this work, we present a single-frequency (SF) approach, enabling the joint estimation of VTEC and SDCBs using low-cost receivers; this approach is also based on two steps and it differs from the DF approach only in the first step, where we turn to the precise point positioning technique to retrieve from the single-frequency GNSS data the ionospheric observables, interpreted as the combination of the STEC, the SDCBs and the biased receiver clocks at the pivot epoch. Our numerical analyses clarify how SF approach performs when being applied to GPS L1 data collected by a single receiver under both calm and disturbed ionospheric conditions. The daily time series of zenith VTEC estimates has an accuracy ranging from a few tenths of a TEC unit (TECU) to approximately 2 TECU. For 73–96% of GPS satellites in view, the daily estimates of SDCBs do not deviate, in absolute value, more than 1 ns from their ground truth values published by the Centre for Orbit Determination in Europe. 相似文献
4.
本文首先回顾了GNSS差分和组合数据处理的起源、特点和应用,并阐述了其在多频多模背景下的局限。然后,引出了非差非组合数据处理的诸多优势,介绍了构建满秩非差非组合函数模型的消秩亏方法。基于该方法,本文系统构建了系列非差非组合PPP-RTK模型,包括伪距加相位和仅用相位两大类。两类模型均考虑不同的大气约束而衍生出电离层加权、浮点和固定3种变体,且所有模型均顾及码分多址和频分多址两类系统。最后,本文测试分析了非差非组合PPP-RTK在无人船、无人机和农机应用中的动态定位性能。试验结果表明,3个场景下的模糊度首次固定时间均在10 s以内,模糊度固定成功率在96%以上,水平定位精度优于2 cm,高程定位精度优于5 cm。在Galileo+GPS+BDS三系统农机定位中,仅用相位PPP-RTK与伪距加相位PPP-RTK定位性能相当。与Galileo+GPS双系统定位相比,三系统PPP-RTK将模糊度首次固定时间从几百秒缩短至几秒,模糊度固定成功率从85%左右提升至99%以上,定位精度提升了30%左右。 相似文献
5.
On the GPS widelane and its decorrelating property 总被引：2，自引：1，他引：2
P. J. G. Teunissen 《Journal of Geodesy》1997,71(9):577-587
In this contribution we consider the popular widelaning technique from the viewpoint of ambiguity decorrelation. It enables
us to cast the technique into the framework of the least-squares ambiguity decorrelation adjustment (LAMBDA) and to analyse
its relative merits. In doing so, we will provide answers to the following three questions. Does the widelane decorrelate?
Does it explicitly appear in the automated transformation step of the LAMBDA method? Can one do better than the widelane?
It is shown that all three questions can be answered in the affirmative. This holds true for the ionosphere-fixed case, the
ionosphere-float case, as well as for the ionosphere-weighted case.
Received: 11 November 1996 / Accepted: 23 April 1997 相似文献
6.
As a first step towards studying the ionosphere with the global navigation satellite system (GNSS), leveling the phase to the code geometry-free observations on an arc-by-arc basis yields the ionospheric observables, interpreted as a combination of slant total electron content along with satellite and receiver differential code biases (DCB). The leveling errors in the ionospheric observables may arise during this procedure, which, according to previous studies by other researchers, are due to the combined effects of the code multipath and the intra-day variability in the receiver DCB. In this paper we further identify the short-term temporal variations of receiver differential phase biases (DPB) as another possible cause of leveling errors. Our investigation starts by the development of a method to epoch-wise estimate between-receiver DPB (BR-DPB) employing (inter-receiver) single-differenced, phase-only GNSS observations collected from a pair of receivers creating a zero or short baseline. The key issue for this method is to get rid of the possible discontinuities in the epoch-wise BR-DPB estimates, occurring when satellite assigned as pivot changes. Our numerical tests, carried out using Global Positioning System (GPS, US GNSS) and BeiDou Navigation Satellite System (BDS, Chinese GNSS) observations sampled every 30 s by a dedicatedly selected set of zero and short baselines, suggest two major findings. First, epoch-wise BR-DPB estimates can exhibit remarkable variability over a rather short period of time (e.g. 6 cm over 3 h), thus significant from a statistical point of view. Second, a dominant factor driving this variability is the changes of ambient temperature, instead of the un-modelled phase multipath. 相似文献
7.
在北斗导航卫星伪距码偏差特性分析的基础上,建立了倾斜地球同步轨道卫星（IGSO）和中轨卫星（MEO）的伪距码偏差多项式改正模型;并利用星间单差宽巷小数周一致性,分析建立北斗地球同步轨道卫星（GEO）卫星伪距码偏差改正模型。采用武汉大学北斗试验网、中国陆态网络和MGEX网不同位置、不同类型接收机观测数据进行分析验证,结果表明,北斗卫星伪距码偏差特性与观测值频率、卫星类型相关,所有GEO和IGSO卫星变化规律相同,所有MEO卫星变化规律相同,与接收机类型、测站位置和观测时间无关,偏差值大小随卫星高度角变化,其变化规律稳定,可以采用建立的两类改正模型（GEO/IGSO和MEO）进行修正。通过偏差修正后的伪距无电离层组合的残差、双频SPP以及单频PPP三个方面验证了伪距码偏差改正模型的正确性。 相似文献
8.
GNSS observables for ionospheric estimation are commonly based on carrier-to-code leveling (CCL) and precise point positioning (PPP) methods. The CCL method is a geometry-free method which uses carrier phase to level pseudorange observation for decreasing multipath error and observation noise. However, the ionospheric observable based on the CCL has been proven to be affected by leveling errors. The leveling errors are caused by pseudorange multipath and intraday variation of receiver DCB. To obtain more accurate ionospheric observable, the PPP method takes advantage of precise satellite-to-ground range for retrieving slant total electron content and is less affected by the leveling errors. Previous studies have only proven that the ionospheric observables extracted by the two methods are affected by the leveling errors. The influence on ionospheric observable by the pseudorange inter-receiver satellite bias (IRSB) of the receiver has not been taken into consideration. Also, the magnitude of the differences between the ionospheric observables extracted by the two methods has also not been given. In this work, three methods, namely, the CCL, the conventional ionospheric-free PPP method which uses the ionospheric-free Hatch–Melbourne–Wubbena (HMW) function, and the University of Calgary (UOFC) PPP method, are selected to analyze and compare the differences of ionospheric observables and the global ionospheric maps, using a large number of measured data from international GNSS service global stations. Experimental results show that the accuracy of ionospheric observables obtained by the three methods is not only related to the leveling error, but also pseudorange IRSB. The IRSB of the receiver exerts a major effect on the ionospheric observables obtained by the CCL method and a minor effect on the ionospheric observables obtained by the HMW and UOFC methods. The accuracies in the latter case are similar and superior to those obtained by the CCL. The differences of the ionospheric observables obtained by the CCL and UOFC methods, or the CCL and HMW methods, are at decimeter level, whereas the difference of the ionospheric observables obtained by the UOFC and HMW methods is at centimeter level. The UOFC method presented the highest single-frequency pseudorange positioning accuracy using estimated global ionospheric products, followed by the HMW and the CCL methods which presented the lowest positioning accuracy. 相似文献
9.
A performance comparison of single and dual frequency GPS ambiguity resolution strategies 总被引：1，自引：1，他引：0
The impact of observation selection, observation combination and model parameterization on GPS carrier phase ambiguity resolution and position accuracy under operational conditions is investigated. The impact of an ionospheric bias for a generic linear combination of L1 and L2 measurements is assessed and the results are used to clearly outline the desirable characteristics for improving ambiguity resolution versus positioning accuracy performance. Ambiguity resolution performance and position accuracy are shown for widelane (WL), L1-only, and ionospheric-free (IF) combinations. Several techniques for dealing with the ionospheric bias are also presented and compared, including stochastic ionospheric modelling. Multiple carrier phase combination solutions estimated in the same filter are also compared. The concept of an optimal processing strategy—in terms of both reliable ambiguity resolution and high accuracy positions—is presented. In total, eight strategies, which vary in observables and parameters, are tested on several datasets ranging from 13 km to 43 km. 相似文献
10.
Is the long-term variation of the estimated GPS differential code biases associated with ionospheric variability? 总被引：1，自引：0，他引：1
The global positioning system (GPS) differential code biases (DCB) provided by the International GNSS Service (IGS) show solar-cycle-like variation during 2002–2013. This study is to examine whether this variation of the GPS DCBs is associated with ionospheric variability. The GPS observations from low earth orbit (LEO) satellites including CHAMP, GRACE and Jason-1 are used to address this issue. The GPS DCBs estimated from the LEO-based observations at different orbit altitudes show a similar tendency as the IGS DCBs. However, this solar-cycle-like dependency is eliminated when the DCBs of 13 continuously operating GPS satellites are constrained to zero-mean. Our results thus revealed that ionospheric variation is not responsible for the long-term variation of the GPS DCBs. Instead, it is attributed to the GPS satellite replacement with different satellite types and the zero-mean condition imposed on all satellite DCBs. 相似文献
11.
Processing of data from global navigation satellite systems (GNSS), such as GPS, GLONASS and Galileo, can be considerably impeded by disturbances in the ionosphere. Cycle-slip detection and correction thus becomes a crucial component of robust software. Still, dealing with ionospheric cycle slips is not trivial due to scintillation effects in both the phase and the amplitude of the signals. In this contribution, a geometry-based approach with rigorous handling of the ionosphere is presented. A detailed analysis of the cycle-slip correction process is also tackled by examining its dependence on phase and code noise, non-dispersive effects and, of course, the ionosphere. The importance of stochastic modeling in validating the integer cycle-slip candidates is emphasized and illustrated through simulations. By examining the relationship between ionospheric bias and ionospheric constraint, it is shown that there is a limit in the magnitude of ionospheric delay variation that can be handled by the cycle-slip correction process. Those concepts are applied to GNSS data collected by stations in northern Canada, and show that enhanced cycle-slip detection can lead to decimeter-level improvements in the accuracy of kinematic PPP solutions with a 30-s sampling interval. Cycle-slip correction associated with ionospheric delay variations exceeding 50 cm is also demonstrated, although there are risks with such a procedure and these are pointed out. 相似文献
12.
13.
The Global Positioning System (GPS) satellite differential code bias (DCB) should be precisely calibrated when obtaining ionospheric slant total electron content (TEC). So far, it is ground-based GPS observations that have been used to estimate GPS satellite DCB. With the increased Low Earth Orbit (LEO) missions in the near future, the real-time satellite DCB estimation is a crucial factor in real-time LEO GPS data applications. One alternative way is estimating GPS DCB based on the LEO observations themselves, instead of using ground observations. We propose an approach to estimate the satellite DCB based on Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) and Challenging Minisatellite Payload (CHAMP) GPS observations during the years 2002–2012. The results have been validated through comparisons with those issued by Center for Orbit Determination in Europe (CODE). The evaluations indicate that: The approach can estimate satellite DCB in a reasonable way; the DCB estimated based on CHAMP observations is much better than those on COSMIC observations; the accuracy and precision of DCB show a possible dependency on the ionospheric ionization level. This method is significance for the real-time processing of LEO-based GNSS TEC data from the perspective of real-time applications. 相似文献
14.
通过MGEX观测网CUT0测站连续10天的观测数据,采用零基线单差模型方法求解单差残差序列,并推导出北斗GEO／IGSO／MEO卫星观测值噪声。统计观测值噪声随高度角变化的情况,采用最小二乘拟合的方法建立精化的高度角随机模型。结果表明:北斗三类卫星的观测精度略有差别,精度从高到低依次为MEO、IGSO、GEO;B1频率相位观测精度约为伪距的129倍,B2频率约为118倍;北斗卫星伪距观测值的精度要稍优于GPS,相位观测值的精度与GPS相当。最后,基线测试结果表明,精化后的随机模型提高了单历元动态定位的精度,平均点位精度提高了42.1％,N、E、U方向各分量RMS改善的百分比分别为:31.6％、15.3％、31.4％。 相似文献
15.
利用非组合精密单点定位技术确定斜向电离层总电子含量和站星差分码偏差 总被引：3，自引：0，他引：3
联合双频GPS数据,利用相位平滑伪距算法,可得到包含斜向电离层总电子含量（slant total electron content,sTEC）、测站和卫星差分码偏差（differential code bias,DCB）的电离层观测值（称之为＂平滑伪距电离层观测值＂）,常应用于与电离层有关的研究。然而,平滑伪距电离层观测值易受平滑弧段长度和与测站有关的误差影响。提出一种新算法：利用非组合精密单点定位技术（precise point positioning,PPP）计算电离层观测值（称之为＂PPP电离层观测值＂）,进而估计sTEC和站星DCB。基于短基线试验,先用一台接收机按上述两种方法估计sTEC,用于改正另一接收机观测值的电离层延迟以实施单频PPP,结果表明,利用PPP电离层观测值得到的sTEC精度较高,定位结果的可靠性较强。随后,选取全球分布的8个IGS（internationalGNSS service）连续跟踪站2009年1月内某四天的观测数据,利用上述两种电离层观测值计算所有卫星的DCB,并将计算结果与CODE发布的月平均值进行比较,其中,平滑伪距电离层观测值的卫星DCB估值与CODE（Centre for Orbit Deter mination in Europe）发布值的差别较大,部分卫星甚至可达0.2～0.3 ns,而PPP电离层观测值而言,绝大多数卫星对应的差异均在0.1 ns以内。 相似文献
16.
Ionospheric disturbances present a considerable hazard to single-frequency satellite navigation systems for airborne users. We discuss our implementation of three ionospheric threat models in the DLR “multi-output advanced signal test environment for receivers” global navigation satellite system simulator, which is based on Spirent GSS 7780/7790 signal generator. These threat models include the standard front-based threat model developed for the integrity assessment of ground-based augmentation systems (GBAS), a simplified plasma bubble model, and ionospheric scintillation, which can be combined with either of the two previously mentioned models. These effects can now straightforwardly be simulated at the German Aerospace Center’s research facilities. As an example, we simulate a GBAS ground facility with code–carrier divergence monitoring, affected by an ionospheric front, and we show the results of a simulation with coincidental occurrence of a plasma bubble and scintillation with an S 4 index of 0.4. 相似文献
17.
Improving the GNSS positioning stochastic model in the presence of ionospheric scintillation 总被引：1，自引：0，他引：1
M. Aquino J. F. G. Monico A. H. Dodson H. Marques G. De Franceschi L. Alfonsi V. Romano M. Andreotti 《Journal of Geodesy》2009,83(10):953-966
Ionospheric scintillations are caused by time- varying electron density irregularities in the ionosphere, occurring more often
at equatorial and high latitudes. This paper focuses exclusively on experiments undertaken in Europe, at geographic latitudes
between ~50°N and ~80°N, where a network of GPS receivers capable of monitoring Total Electron Content and ionospheric scintillation parameters was
deployed. The widely used ionospheric scintillation indices S4 and sj{\sigma_{\varphi}} represent a practical measure of the intensity of amplitude and phase scintillation affecting GNSS receivers. However, they
do not provide sufficient information regarding the actual tracking errors that degrade GNSS receiver performance. Suitable
receiver tracking models, sensitive to ionospheric scintillation, allow the computation of the variance of the output error
of the receiver PLL (Phase Locked Loop) and DLL (Delay Locked Loop), which expresses the quality of the range measurements
used by the receiver to calculate user position. The ability of such models of incorporating phase and amplitude scintillation
effects into the variance of these tracking errors underpins our proposed method of applying relative weights to measurements
from different satellites. That gives the least squares stochastic model used for position computation a more realistic representation,
vis-a-vis the otherwise ‘equal weights’ model. For pseudorange processing, relative weights were com- puted, so that a ‘scintillation-mitigated’
solution could be performed and compared to the (non-mitigated) ‘equal weights’ solution. An improvement between 17 and 38%
in height accuracy was achieved when an epoch by epoch differential solution was computed over baselines ranging from 1 to
750 km. The method was then compared with alternative approaches that can be used to improve the least squares stochastic
model such as weighting according to satellite elevation angle and by the inverse of the square of the standard deviation
of the code/carrier divergence (sigma CCDiv). The influence of multipath effects on the proposed mitigation approach is also
discussed. With the use of high rate scintillation data in addition to the scintillation indices a carrier phase based mitigated
solution was also implemented and compared with the conventional solution. During a period of occurrence of high phase scintillation
it was observed that problems related to ambiguity resolution can be reduced by the use of the proposed mitigated solution. 相似文献
18.
针对现有全球卫星导航系统性能评估无规范的评估标准问题,该文提出了以统一模型和算法为评估体系的方法,较详细的评估了全球卫星导航系统公开服务信号的基本性能,主要评估了空间信号误差、广播电离层模型改正效率及伪距单点定位精度等。结果表明:空间信号误差方面,伽利略最优、GPS和北斗三号相当;广播电离层模型方面,北斗全球广播电离层模型改正效果最优,GPSK8与NeQuick模型在低中纬度改正效果相当,北斗区域电离层模型在其服务区内具有较高改正效果;定位方面,北斗、GPS和伽利略静态伪距单点定位的三维位置均方根误差优于5m,格洛纳斯优于10 m;动态伪距单点定位方面,北斗在中国境内定位精度最高;基于统一评估体系下,可以直观对比得到目前各卫星导航系统的性能差异,同时也为后续的建设提供相应的参考。 相似文献
19.
The Global Navigation Satellite System presents a plausible and cost-effective way of computing the total electron content (TEC). But TEC estimated value could be seriously affected by the differential code biases (DCB) of frequency-dependent satellites and receivers. Unlike GPS and other satellite systems, GLONASS adopts a frequency-division multiplexing access mode to distinguish different satellites. This strategy leads to different wavelengths and inter-frequency biases (IFBs) for both pseudo-range and carrier phase observations, whose impacts are rarely considered in ionospheric modeling. We obtained observations from four groups of co-stations to analyze the characteristics of the GLONASS receiver P1P2 pseudo-range IFB with a double-difference method. The results showed that the GLONASS P1P2 pseudo-range IFB remained stable for a period of time and could catch up to several meters, which cannot be absorbed by the receiver DCB during ionospheric modeling. Given the characteristics of the GLONASS P1P2 pseudo-range IFB, we proposed a two-step ionosphere modeling method with the priori IFB information. The experimental analysis showed that the new algorithm can effectively eliminate the adverse effects on ionospheric model and hardware delay parameters estimation in different space environments. During high solar activity period, compared to the traditional GPS + GLONASS modeling algorithm, the absolute average deviation of TEC decreased from 2.17 to 2.07 TECu (TEC unit); simultaneously, the average RMS of GPS satellite DCB decreased from 0.225 to 0.219 ns, and the average deviation of GLONASS satellite DCB decreased from 0.253 to 0.113 ns with a great improvement in over 55%. 相似文献
20.
组合GPS／GLONASS精密定位的观测值随机模型 总被引：1，自引：0，他引：1
为了获得组合GPS／GLONASS精密定位结果，该文从理论和数值实例两方面分析了研究组合GPS／GLONASS观测值随机模型的重要性，提出了两种利用观测值的误差残差估计随机模型的方法，即验后估计法和方差－协方差迭代法。理论和数值结果表明，这两种随机模型估计方法与采用经验随机模型相比，可以提高整周模糊度解算的可靠性和定位精度，所提出的观测值随机模型估计方法理论上更严格，实践上可行，并建议采用方差－协方差迭代法估计组合GPS／GLONASS精密定位的观测值随机模型。 相似文献