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1.
Precise GPS Positioning by Applying Ionospheric Corrections from an Active Control Network 总被引：2，自引：1，他引：1
In this article, initial results are presented of a method to improve fast carrier phase ambiguity resolution over longer
baselines (with lengths up to about 200 km). The ionospheric delays in the global positioning system (GPS) data of these long
baselines mainly hamper successful integer ambiguity resolution, a prerequisite to obtain precise positions within very short
observation time spans.
A way to correct the data for significant ionospheric effects is to have a GPS user operate within an active or permanently
operating network use ionospheric estimates from this network. A simple way to do so is to interpolate these ionospheric estimates
based on the expected spatial behaviour of the ionospheric delays. In this article such a technique is demonstrated for the
Dutch Active Control Network (AGRS.NL). One hour of data is used from 4 of the 5 reference stations to obtain very precise
ionospheric corrections after fixing of the integer ambiguities within this network. This is no problem because of the relatively
long observation time span and known positions of the stations of the AGRS.NL. Next these interpolated corrections are used
to correct the GPS data from the fifth station for its ionospheric effects. Initial conclusions about the performance of this
technique are drawn in terms of improvement of integer ambiguity resolution for this baseline. ? 1999 John Wiley & Sons, Inc. 相似文献
2.
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
3.
顾及GEO卫星约束的长距离BDS三频整周模糊度解算 总被引：1，自引：0，他引：1
长距离BDS三频载波相位整周模糊度解算受大气误差残余的影响较大,GEO卫星相对于地球静止也非常不利于载波相位整周模糊度的解算。利用GEO卫星的信号传播路径相对较稳定、大气延迟误差的影响不随卫星空间位置变化的特点,对GEO卫星进行更符合实际情况的大气延迟误差约束研究。利用GEO卫星B2和B3载波相位整周模糊度线性关系,降低测站差分电离层延迟误差残余对模糊度备选值的影响,进行B2和B3载波相位整周模糊度备选值的选择。通过三频载波相位整周模糊度间不包含观测误差影响的线性关系对模糊度备选值组合进行检测,并对模糊度搜索空间进行约束。利用历元间GEO卫星的模糊度备选值判断历元间电离层延迟误差残余的变化,对GEO卫星的参数估计进行更符合实际情况的约束。研究了顾及GEO卫星实际大气延迟变化和整周模糊度约束的长距离BDS三频载波相位整周模糊度解算方法。提出了利用历元间模糊度备选值确定电离层延迟约束值的方法,对GEO卫星历元间随机游走的约束值进行符合实际情况的调整。试验结果表明,本文的方法能够提高三频载波相位整周模糊度解算的效率和测站位置的精度。 相似文献
4.
准确固定非差模糊度是利用相位观测量获取高精度电离层延迟的关键。三频观测条件下常规的处理策略需依次固定超宽巷、宽巷以及窄巷模糊度,通常利用MW（melbourne-wubbena）组合解算宽巷模糊度时易受到码硬件延迟和观测噪声的影响而固定错误。利用北斗三频数据和GIM（grid ionosphenimap）产品,通过固定的超宽巷模糊度以及构造相位无几何组合解算宽巷模糊度,进而重构得到高精度电离层延迟,并且分离了码硬件延迟总量。结果表明,GIM模型辅助条件下宽巷模糊度固定成功率能达到100%,且消除了系统性偏差;电离层重构值与GIM模型改正值存在约1 m的差异,等效精度约6TECU;分离的码硬件延迟变化平稳,标准偏差不超过0.3 m。 相似文献
5.
单基站中长基线动态相对定位受到大气残余误差影响,无法快速固定整周模糊度,定位精度和可靠性不如短基线场景。在航空测量场景下,流动站与基准站之间的基线由短到长变化,利用短基线场景下固定的整周模糊度反算得到高精度的电离层延迟量,并对其进行建模预报。随着基线变长,利用预报的电离层延迟约束中长基线定位模型,实现快速模糊度固定。本文分析了动态长基线情形下的电离层延迟的时变特性,采用滑动窗口进行电离层建模预报,讨论了该方法在航空测量实际作业中的实施条件、定位精度及模糊度固定情况。实测机载数据的解算结果表明,使用该方法,当测量载体出发阶段处于短基线场景下,单基站相对定位结果就可以达到接近100%的模糊度固定率,且定位精度保持在厘米级,显著减小了航空测量任务的作业成本。 相似文献
6.
北斗卫星系统(BDS)能全星座播发三频信号,可通过线性组合构成不同虚拟观测量,有利于模糊度解算等,文中采用北斗三频中长基线实测数据进行差分定位,首先使用宽巷模糊度和电离层无关组合进行B3频段窄巷模糊度解算,在此基础上提出利用相邻历元B3频段窄巷模糊度构建卡尔曼滤波新息向量,通过新息向量内积RMS值很容易分析出窄巷模糊度的误差对滤波性能的影响,并结合滤波发散条件进行相关卫星历元挑选,实验最终得到中长基线厘米级定位精度并有效缩短首次收敛时间和提高固定率,对促进北斗高精度定位有着现实意义。 相似文献
7.
针对常规实时动态（RTK）定位技术中长基线初始化时间较长、定位结果不稳定的问题,提出了一种基于部分模糊度固定策略的BDS/GPS宽巷卡尔曼滤波RTK定位方法,从充分发挥宽巷观测值波长较长和宽巷模糊度易于固定的优势,避免低高度角卫星对模糊度解算的影响,从而提高中长基线情况下的模糊度固定率. 同时采用附加宽巷模糊度参数的卡尔曼滤波方法计算浮点解,以固定高于设置模糊度解算截止高度角的卫星进行定位,并解算电离层活动较剧烈的25~76 km的中长基线. 通过3组试验,结果表明,BDS/GPS双系统联合定位宽巷模糊度固定率均接近100%,76 km基线模糊度固定率达到99.9%,定位精度达到厘米级或准厘米级. 相似文献
8.
The reliability of the classical geometry- and ionospheric-free (GIF) three-carrier ambiguity resolution (TCAR) degrades when applied to long baselines of hundreds of kilometers. To overcome this deficiency, we propose two new models, which are used sequentially to resolve wide-lane (WL) and narrow-lane (NL) ambiguities and form a stepwise ambiguity resolution (AR) strategy. In the first model, after a successful extra-wide-lane AR, the pseudorange and phase observations are combined to estimate WL ambiguities, in which the residual ionospheric delays and geometry effects are eliminated. In the second model, using the resolved ambiguities from the first step, the two WL ambiguities are combined to remove ionospheric and geometry effects. The unknown coefficients in the two models are determined in such that they minimize the formal errors in the ambiguity estimates to optimize the ambiguity estimation. Using experimental BeiDou triple-frequency observations, we evaluate our method and identify three advantages. First, the two models use double-differenced phase observations that are not differences across frequency. Second, the two models are entirely free from ionospheric delay and geometry effects. Third, the unknown estimates in the two models satisfy the minimum noise condition, which makes the formal errors in the float NL ambiguity estimates much lower than those obtained with common GIF TCAR methods, thereby directly and significantly increasing the success rate of AR compared to the cascaded integer resolution method and two other GIF combinations. 相似文献
9.
An approach for instantaneous ambiguity resolution for medium- to long-range multiple reference station networks 总被引：2，自引：2，他引：2
G. Hu D. A. Abbey N. Castleden W. E. Featherstone C. Earls O. Ovstedal D. Weihing 《GPS Solutions》2005,9(1):1-11
Integer ambiguity resolution (AR) is a prerequisite for all high-precision (centimetre level) GPS applications that utilise multiple reference station (MRS) networks. However, due to the presence of distance-dependent GPS errors, notably atmospheric refraction, AR across the network is difficult on an epoch-by-epoch basis, especially for medium- to long-range (typically 30–130 km as used here) MRS networks. This paper presents an approach for medium- to long-range instantaneous AR for MRS networks, based on an ionosphere-weighted observation model and network geometry constraints, along with a multiple ambiguity validation test procedure. The performance of the proposed method was demonstrated through two case-study examples from Australia and Norway. Our test results show that the instantaneous AR success rate varied from 93% (131 km baseline) to 98% (35 km baseline). It is also shown that the adopted high-precision prediction models for the double-difference (DD) ionospheric delay and residual tropospheric zenith delay (RTZD) are of benefit to the high success rate of the network AR. Due to its epoch-by-epoch nature, the proposed approach is insensitive to cycle-slips, rising or setting satellites, or loss-of-lock. 相似文献
10.
北斗中长基线三频模糊度解算的自适应抗差滤波算法 总被引：1，自引：1，他引：0
针对经典TCAR(three carrier ambiguity resolution)算法受电离层延迟及测量噪声的影响,在中长基线下难以正确固定模糊度的问题,提出一种顾及电离层延迟影响并具有良好自适应抗差特性的改进TCAR算法。在无几何TCAR模型的基础上,通过对模糊度固定的超宽巷进行线性组合得到电离层延迟,再求解宽巷模糊度,通过构造最优组合观测量后用自适应抗差滤波求解窄巷模糊度,以提高窄巷模糊度固定正确率,减小粗差的不利影响。试验结果表明,改进TCAR算法可保证较高的宽巷模糊度固定正确率,有效提高了窄巷模糊度固定正确率,并具有良好抵抗粗差的能力。 相似文献
11.
Single-epoch relative GPS positioning has many advantages, especially for monitoring dynamic targets. In this technique, errors occurring in previous epochs cannot affect the position accuracy at the current epoch, but careful processing is required, and resolving carrier phase ambiguities is essential. Statistical ambiguity resolution functions have been used to determine the best values of these ambiguities. The function inputs include as a minimum the known base station position, the approximate roving antenna “seed” position, and the dual-frequency carrier phase measurements from both receivers. We investigate different solutions to find the ambiguity function inputs that achieve the highest ambiguity resolution success rate. First, we address the rover seed position. A regionally filtered undifferenced pseudorange coordinate solution proves better than a double-differenced one. Multipath errors approximately repeat themselves every sidereal day in the case of static or quasi-static antennas; applying a sidereal filter to the pseudorange-derived positions mitigates their effects. Second, we address the relative carrier phase measurements, which for medium to long baselines are significantly affected by ionospheric propagation errors imperfectly removed during differencing. In addition to the International GNSS Service ionospheric model, we generate a local pseudorange-based ionospheric correction. Applying this correction improves the quality of the phase measurements, leading to more successful ambiguity resolution. Temporally smoothing the correction by means of a Kalman filter further improves the phase measurements. For baselines in the range 60–120 km, the mean absolute deviation of single-epoch coordinates improves to 10–20 cm, from 30–50 cm in the default case. 相似文献
12.
虽然TCAR能够实现短基线三频模糊度单历元解算,但由于电离层延迟及观测噪声等的影响,中长基线三频模糊度快速解算仍然是导航定位的一大难点。本文提出了一种新的无几何无电离层三频模糊度解算方法。该方法通过对伪距观测值赋予不同的权重,辅助宽巷及窄巷消除电离层残差的影响,使宽巷及窄巷求解只受观测噪声的影响;然后通过多历元的平滑获取宽巷及窄巷模糊度值。通过实测BDS三频长基线数据表明,相比经典TCAR算法,该方法可大大改善中长基线模糊度的求解精度,经过数据平滑并验证基本可以实现中长基线模糊度的快速解算。 相似文献
13.
14.
通过引入北斗星上多径参数,量化了北斗星上多径对宽巷模糊度解算的影响;从理论上分析了该影响量在非差、单差和双差条件下的特性,并采用零基线、短基线和长基线3组实测数据进行了分析与验证。结果表明:星上多径对非差宽巷模糊度估值的影响在三类卫星上表现出不同的特性,在MEO卫星上最大,可达1周;星间单差无法消除星上多径偏差影响,进而PPP宽巷模糊度的解算将受到影响;星上多径不会对零基线双差宽巷模糊度解算造成影响,对短基线双差宽巷模糊度解算的影响也可忽略,但长基线双差宽巷模糊度解算则受严重影响;星上多径会导致长基线双差宽巷模糊度平滑收敛缓慢,经改正后模糊度固定成功率能够显著提高,单历元取整成功率从52.7%提升到61.4%,平滑20个历元模糊度固定成功率即可从68.4%提升到95.5%。 相似文献
15.
BDS网络RTK参考站三频整周模糊度解算方法 总被引：1，自引：1，他引：0
北斗卫星导航系统是目前唯一一个全星座提供三频观测数据的卫星导航定位系统,三频观测值有助于载波相位整周模糊度的快速、准确固定。本文提出了一种BDS网络RTK参考站三频整周模糊度解算方法。首先利用B2、B3频率的观测值及严格的模糊度固定标准确定超宽巷整周模糊度,将固定的超宽巷整周模糊度与其他宽巷整周模糊度的线性关系作为约束条件,然后估计宽巷整周模糊度、相对天顶对流层延迟误差和电离层延迟误差,并搜索确定宽巷整周模糊度。利用固定的宽巷整周模糊度与三频载波相位整周模糊度的整数线性关系,将线性关系加入载波相位整周模糊度参数估计观测模型中,然后确定载波相位整周模糊度。使用实测的CORS网BDS三频观测数据进行算法验证,结果表明,该方法可正确有效地实现参考站间三频载波相位整周模糊度的快速解算。 相似文献
16.
北斗卫星提供3种频率载波信号,极大地推动了利用载波对用户位置和速度信息进行高精度计算方法研究。本文重点研究基于北斗卫星三频信号的载波相位模糊度解算CIR方法,通过使用函数极限的原理推导载波组合,为算法提供了理论基础;分析每一步的误差传递,选取优秀的伪距组合、相位组合,并处理数据验证算法的可行性。在短基线向量前提下,双差中忽略大气延迟的影响,验证了本文提出的几种载波组合的计算模糊度的可行性。 相似文献
17.
针对北斗三号新的三频观测值,通过分析BDS-3三频线性组合观测值特性,选取高质量组合观测值,采用无几何相关GF(Geometry-Free)模型和无几何无电离层相关GIF(Geometry-Ionospheric-Free)模型分别对实测BDS-3卫星数据进行单历元三频相位模糊度解算TCAR(Triple-freque... 相似文献
18.
提出部分模糊度固定的加权电离层模型提高大范围全球卫星导航系统(GNSS)航空定位的精度、可靠性及连续性.该方法的主要思路包括:自适应调整大气扰动等误差影响以实现短基线与长基线两类解算模式之间的灵活切换;施加虚拟电离层观测约束信息,提高基线动态定位的浮点解精度;采用部分模糊度固定方法有效挖掘若干模糊度参数的整周约束.试验表明,提出的方法可提高模糊固定效率与定位精度,克服传统方法有效观测信息利用率不足、定位精度较差、可靠性不高以及连续性较差的问题.实验结果表明,部分模糊度固定算法可在2 min内固定95%以上宽巷模糊度解算与80%以上窄巷模糊度,约20 min后可固定所有模糊度. 相似文献
19.
首先阐述了多频观测数据解算模糊度时所用到的矩阵转换的一些方法,讨论了由矩阵变换方法和CAR方法可以引申出的模糊度解算方法,指出TCAR/MCAR方法模糊度解算精度低的原因并改进,对短基线利用TCAR/MCAR方法进行模糊度解算,并与矩阵变换法做了比较。 相似文献
20.
Assessment of correct fixing rate for precise point positioning ambiguity resolution on a global scale 总被引：3，自引：1，他引：2
Ambiguity resolution (AR) for a single receiver has been a popular topic in Global Positioning System (GPS) recently. Ambiguity-resolution methods for precise point positioning (PPP) have been well documented in recent years, demonstrating that it can improve the accuracy of PPP. However, users are often concerned about the reliability of ambiguity-fixed PPP solution in practical applications. If ambiguities are fixed to wrong integers, large errors would be introduced into position estimates. In this paper, we aim to assess the correct fixing rate (CFR), i.e., number of ambiguities correctly fixing to the total number of ambiguities correctly and incorrectly fixing, for PPP user ambiguity resolution on a global scale. A practical procedure is presented to evaluate the CFR of PPP user ambiguity resolution. GPS data of the first 3 days in each month of 2010 from about 390 IGS stations are used for experiments. Firstly, we use GPS data collected from about 320 IGS stations to estimate global single-differenced (SD) wide-lane and narrow-lane satellite uncalibrated phase delays (UPDs). The quality of UPDs is evaluated. We found that wide-lane UPD estimates have a rather small standard deviation (Std) between 0.003 and 0.004 cycles while most of Std of narrow-lane estimates are from 0.01 to 0.02 cycles. Secondly, many experiments have been conducted to investigate the CFR of integer ambiguity resolution we can achieve under different conditions, including reference station density, observation session length and the ionospheric activity. The results show that the CFR of PPP can exceed 98.0 % with only 1 h of observations for most user stations. No obvious correlation between the CFR and the reference station density is found. Therefore, nearly homogeneous CFR can be achieved in PPP AR for global users. At user end, higher CFR could be achieved with longer observations. The average CFR for 30-min, 1-h, 2-h and 4-h observation is 92.3, 98.2, 99.5 and 99.7 %, respectively. In order to get acceptable CFR, 1 h is a recommended minimum observation time. Furthermore, the CFR of PPP can be affected by diurnal variation and geomagnetic latitude variation in the ionosphere. During one day at the hours when rapid ionospheric variations occur or in low geomagnetic latitude regions where equatorial electron density irregularities are produced relatively frequently, a significant degradation of the CFR is demonstrated. 相似文献