基于北斗三频的BDS/GPS宽巷模糊度逐级单历元固定方法

利用北斗三频超宽巷模糊度波长较长易于固定的优势,提出一种基于北斗三频的BDS/GPS宽巷模糊度逐级单历元固定方法。首先利用载波和伪距组合固定BDS(0,-1,1)和(1,4,-5)两个超宽巷模糊度,根据固定后的超宽巷模糊度变换得到BDS宽巷模糊度(1,-1,0),然后将BDS宽巷模糊度作为约束条件与GPS宽巷观测方程联立得到GPS宽巷模糊度浮点解和其方差协方差阵,最后采用LAMBDA算法实现GPS宽巷模糊度的固定。实验结果表明,BDS超宽巷组合可实现100%固定,采用BDS约束GPS宽巷模糊度固定时ratio值均大于2,大于5的占97.8%以上,因此文中提出的方法可实现BDS/GPS双系统宽巷模糊度单历元固定,有效提升GNSS模糊度解算的时效性。     

现代化GPS信号的宽巷组合及其求解模糊度研究

结合GPS现代化计划的主要方面，即增加第3信号L5，给出了新的信号L5和L2载波组性组合的数学模型，重点对宽巷线性组合进行了研究，分别模拟计算并比较L5和L2以及L5和L1载波宽巷线性组合结果，最后利用宽巷组合求解模糊度，并得出结论。     

一种改进的宽巷引导整周模糊度固定算法

一般卫星导航接收机的伪距测量误差大于宽巷波长。根据宽巷引导模型,直接使用双差伪距取整固定双差宽巷整周模糊度有很大概率会产生一周固定错误。基于此,提出了一种改进的宽巷引导整周模糊度固定算法,针对宽巷整周模糊度一周固定错误进行探测和修复。利用整周模糊度为整数的特质构造理论探测量,并将该探测量与载噪比所确定的门限相比较,判断是否出现宽巷整周模糊度一周固定错误;利用双差整周模糊度自由度为3的特点,修复错误宽巷整周模糊度。对该算法在高斯噪声条件下的可行性进行了理论分析,结果表明正常载噪比的观测数据均可分辨出一周宽巷整周模糊度的估计错误。同时,分析了考虑多径等误差后该算法所能接受的载波相位最大误差。计算了不同伪距误差下宽巷整周模糊度一周固定错误出现的概率。使用GPS实测短基线数据对算法进行验证,该算法可将基于宽巷引导的整周模糊度固定算法的固定率从原来的只有不到1/3提升至接近100%。     

基于BDS/GPS组合定位的部分模糊度固定效果分析

多系统组合有利于提高卫星导航定位的精度及可靠性,然而对于载波差分定位由于模糊度维数的陡增、观测噪声、大气残余误差等原因用传统的Lambda方法很难得到所有模糊度的固定解,采用部分模糊度方法固定最优的模糊度子集则相对容易。总结了现有的部分模糊度固定方法,分析了不同方法的特点,并用实测数据分析了BDS/GPS组合动态定位时部分模糊度固定的效果。实验结果表明,部分模糊度方法可以显著提高模糊度固定时的成功率及Ratio值,并且可以缩短RTK定位时的初始化时间,加快坐标的收敛速度,提高组合系统动态定位结果的精度。     

一种基于多频模糊度快速解算方法的BDS/GPS中长基线RTK定位模型

随着全球卫星导航系统（global navigation satellite system,GNSS）进入多系统时代,空中导航卫星的可见卫星数不断增加,中国北斗卫星导航系统（BeiDou navigation satellite system,BDS）已开始面向用户提供三频导航信号,这都有利于改善单历元实时动态定位（real-time kinematic,RTK）的精度和可靠性。中长基线单历元RTK通常采用电离层无关组合算法,但是该方法将观测噪声进行了放大,模糊度固定成功率随着基线长度的增加而明显降低。提出一种BDS/GPS（global positioning system）中长基线单历元多频RTK定位算法,先以较高成功率快速固定BDS的两个超宽巷模糊度,继而通过简单变换得到BDS宽巷模糊度,然后将其辅助提高GPS宽巷模糊度固定成功率,最后采用将电离层延迟误差参数化的策略以提高BDS/GPS窄巷模糊度固定成功率。结合实测数据进行验证分析,结果表明本文算法是可行的。     

基于宽巷/窄巷法的星载GPS相位数据的模糊度解算和周跳探测

星载GPS技术是卫星精密定轨及其任务顺利执行的关键,而模糊度和周跳问题是星载GPS相位数据应用的难题。本文利用宽巷/窄巷法对星载GPS相位数据进行模糊度计算和周跳探测,给出了模糊度计算和周跳探测的计算公式和解算步骤。利用宽巷/窄巷法对CHAMP卫星实际星载GPS数据进行了处理,结果表明该方法是可行的,同时由于卫星的高速运动,星载GPS数据的模糊度解算和周跳探测难度也较大。     

一种GPS整周模糊度单历元解算方法

仅利用单历元的载波相位观测值进行整周模糊度解算,观测方程秩亏,给单历元模糊度解算带来很大困难.因此,本文提出一种单历元确定GPS整周模糊度的方法.利用单历元测码伪距观测值和双频载波相位观测值组成双差观测方程,根据方差矩阵对宽巷模糊度进行分组,采用基于LABMDA方法的逐步解算方法来确定双差相位观测值的宽巷模糊度.确定宽...     

GPS/BDS接收机端系统偏差稳定性对整周模糊度固定的影响

GNSS接收机端的UPD与接收到的信号频率有关,这导致GPS和BDS系统间的双差模糊度不具有整数特性,为了恢复其整数特性,两系统间的系统偏差需要进行估计或改正。在顾及GPS和BDS之间的时间系统、坐标系统和频率间偏差的基础上,推导出GPS/BDS系统偏差计算模型,并利用不同实验对系统偏差的稳定性进行验证。实验结果表明,不同品牌接收机在GPS/BDS系统偏差方面在一定条件下均具有稳定性;天线类型和天线连接线长度没有对GPS/BDS系统偏差产生显著影响。加入系统偏差改正的GPS/BDS紧组合定位在恶劣环境下表现良好,可将模糊度固定平均所需时间缩短33%,模糊度固定成功率提高31%。     

GPS/BDS接收机端系统偏差实时估计方法

针对GPS-BDS系统偏差会导致GPS和BDS系统间的混合双差模糊度不具有整数特性,且其不完全稳定的问题,该文提出一种GPS/BDS系统偏差实时在线估计方法。通过将双差模糊度以单差模糊度之差的形式进行求解,然后再将以周为单位的单差模糊度投影为双差模糊度,以此消除GPS和BDS不同波长的影响;在此基础上,采用Kalman滤波对系统偏差进行实时动态估计。实验结果表明,该方法采用较少历元的观测数据便可使系统偏差收敛,并且收敛后十分稳定,可以将其作为校正参数;加入系统偏差改正的GPS/BDS紧组合定位在恶劣环境下表现良好,可将模糊度固定平均所需时间缩短29%,模糊度固定成功率提高45%。     

基于部分模糊度解算的BDS/GPS组合RTK算法

GNSS多频率组合RTK定位逐步进入实际应用,存在模糊度维数增多、搜索空间增大,导致模糊度搜索运算量增大及模糊度固定效率低等问题。文中提出一种多星座部分模糊度解算算法,该算法综合考虑卫星高度角、模糊度固定成功率及Ratio值来筛选卫星进行模糊度解算。通过一组动态跑车实验分析表明:相比于全模糊度解算(FAR),部分模糊度解算(PAR)可以有效地提高BDS/GPS组合RTK的模糊度固定率,其模糊度固定率从79.9%(FAR)提高到99.1%(PAR),且PAR算法定位结果可靠性更高。     

Reliable partial ambiguity resolution for single-frequency GPS/BDS and INS integration

GPS Solutions - Correctly fixing carrier phase integer ambiguities is a prerequisite to achieve high-precision positioning solutions from global navigation satellite system (GNSS). However, for the...     

Reliable single-epoch ambiguity resolution for short baselines using combined GPS/BeiDou system

GNSS single-epoch real-time kinematic (RTK) positioning depends on correct ambiguity resolution. If the number of observed satellites in a single epoch is insufficient, which often happens with a standalone GNSS system, the ambiguity resolution is difficult to achieve. China’s BeiDou Navigation Satellite System has been providing continuous passive positioning, navigation and timing services since December 27, 2012, covering China and the surrounding area. This new system will increase the number of satellites in view and will have a significant effect on successful ambiguity resolution. Since the BeiDou system is similar to GPS, the procedure of data processing is easier than that for the Russian GLONASS system. We briefly introduce the time and the coordinate system of BeiDou and also the BeiDou satellite visibility in China, followed by the discussion on the combined GPS/BeiDou single-epoch algorithm. Experiments were conducted and are presented here, in which the GPS/BeiDou dual-frequency static data were collected in Wuhan with the baseline distance varying from 5 to 13 km, and processed in separate and combined modes. The results indicate that, compared to a standalone GPS or BeiDou system, the combined GNSS system can increase the successful ambiguity fixing rate for single epochs and can also improve the precision of short baselines determination.     

Performance analysis of triple-frequency ambiguity resolution with BeiDou observations

We investigate triple-frequency ambiguity resolution performance using real BeiDou data. We test four ambiguity resolution (AR) methods which are applicable to triple-frequency observations. These are least squares ambiguity decorrelation adjustment (LAMBDA), GF-TCAR (geometry-free three-carrier ambiguity resolution), GB-TCAR (geometry-based three-carrier ambiguity resolution) and GIF-TCAR (three-carrier ambiguity resolution based on the geometry-free and ionospheric-free combination). A comparison between LAMBDA, GF-TCAR and GB-TCAR was conducted over three short baselines and two medium baselines. The results indicated that LAMBDA is optimal in both short baseline and medium baseline cases. However, the performances of GB-TCAR and LAMBDA differ slightly for short baselines. Compared with GF-TCAR, which uses the geometry-free model, the GB-TCAR using the geometry-based model improves the AR performance significantly. Compared with dual-frequency observations, the LAMBDA AR results show a significant improvement when using triple-frequency observations over short baselines. The performance of GIF-TCAR is evaluated using multi-epoch observations. The results indicated that multi-path errors on carrier phases will have a significant influence on GIF-TCAR AR results, which leads to different GIF-TCAR AR performance for different type of satellites. For GEO (Geostationary Orbit) satellites, the ambiguities can barely be correctly fixed because the multi-path errors on carrier phases are very systematic. For IGSO (Inclined Geosynchronous Orbit) and MEO (Medium Earth Orbit) satellites, when the elevation cutoff angle is set as 30°, several tens to several hundreds of epochs are needed for correctly fixing the narrow lane ambiguities. The comparison of positioning performance between dual-frequency observations and triple-frequency observations was also conducted. The results indicated that a minor improvement can be achieved by using triple-frequency observations compared with using dual-frequency observations.     

长距离GPS/BDS参考站网多频载波相位整周模糊度解算方法

长距离网络RTK是实现GPS/BDS高精度实时定位的主要手段之一,其核心是长距离参考站网GPS/BDS整周模糊度的快速准确确定。本文提出了一种长距离GPS/BDS参考站网载波相位整周模糊度解算方法,首先利用GPS双频观测数据计算和确定宽巷整周模糊度,同时利用BDS的B2、B3频率观测值确定超宽巷整周模糊度。然后建立GPS载波相位整周模糊度和大气延迟误差的参数估计模型,附加双差宽巷整周模糊度的约束,解算双差载波相位整周模糊度,并建立参考站网大气延迟误差的空间相关模型。根据B2、B3频率的超宽巷整周模糊度建立包含大气误差参数的载波相位整周模糊度解算模型,利用大气延迟误差空间相关模型约束BDS双差载波相位整周模糊度的解算。克服了传统的使用无电离层组合值解算整周模糊度的不利影响。采用实测长距离CORS网GPS、BDS多频观测数据进行算法验证,试验结果证明该方法可实现长距离参考站网GPS/BDS载波相位整周模糊度的准确固定。     

Single receiver phase ambiguity resolution with GPS data

Global positioning system (GPS) data processing algorithms typically improve positioning solution accuracy by fixing double-differenced phase bias ambiguities to integer values. These “double-difference ambiguity resolution” methods usually invoke linear combinations of GPS carrier phase bias estimates from pairs of transmitters and pairs of receivers, and traditionally require simultaneous measurements from at least two receivers. However, many GPS users point position a single local receiver, based on publicly available solutions for GPS orbits and clocks. These users cannot form double differences. We present an ambiguity resolution algorithm that improves solution accuracy for single receiver point-positioning users. The algorithm processes dual- frequency GPS data from a single receiver together with wide-lane and phase bias estimates from the global network of GPS receivers that were used to generate the orbit and clock solutions for the GPS satellites. We constrain (rather than fix) linear combinations of local phase biases to improve compatibility with global phase bias estimates. For this precise point positioning, no other receiver data are required. When tested, our algorithm significantly improved repeatability of daily estimates of ground receiver positions, most notably in the east component by approximately 30% with respect to the nominal case wherein the carrier biases are estimated as real values. In this “static” test for terrestrial receiver positions, we achieved daily repeatability of 1.9, 2.1 and 6.0 mm in the east, north and vertical (ENV) components, respectively. For kinematic solutions, ENV repeatability is 7.7, 8.4, and 11.7 mm, respectively, representing improvements of 22, 8, and 14% with respect to the nominal. Results from precise orbit determination of the twin GRACE satellites demonstrated that the inter-satellite baseline accuracy improved by a factor of three, from 6 to 2 mm up to a long-term bias. Jason-2/Ocean Surface Topography Mission precise orbit determination tests results implied radial orbit accuracy significantly below the 10 mm level. Stability of time transfer, in low-Earth orbit, improved from 40 to 7 ps. We produced these results by applying this algorithm within the Jet Propulsion Laboratory’s (JPL’s) GIPSY/OASIS software package and using JPL’s orbit and clock products for the GPS constellation. These products now include a record of the wide-lane and phase bias estimates from the underlying global network of GPS stations. This implies that all GIPSY–OASIS positioning users can now benefit from this capability to perform single-receiver ambiguity resolution.     

0.99999999 confidence ambiguity resolution with GPS and Galileo

In this short contribution it is demonstrated how integer carrier phase cycle ambiguity resolution will perform in near future, when the US GPS gets modernized and the European Galileo becomes operational. The capability of ambiguity resolution is analyzed in the context of precise differential positioning over short, medium and long distances. Starting from dual-frequency operation with GPS at present, particularly augmenting the number of satellites turns out to have beneficial consequences on the capability of correctly resolving the ambiguities. With a 'double' constellation, on short baselines, the confidence of the integer ambiguity solution increases to a level of 0.99999999 or beyond. Electronic Publication     

Multi-GNSS phase delay estimation and PPP ambiguity resolution: GPS,BDS, GLONASS,Galileo

This paper focuses on the precise point positioning (PPP) ambiguity resolution (AR) using the observations acquired from four systems: GPS, BDS, GLONASS, and Galileo (GCRE). A GCRE four-system uncalibrated phase delay (UPD) estimation model and multi-GNSS undifferenced PPP AR method were developed in order to utilize the observations from all systems. For UPD estimation, the GCRE-combined PPP solutions of the globally distributed MGEX and IGS stations are performed to obtain four-system float ambiguities and then UPDs of GCRE satellites can be precisely estimated from these ambiguities. The quality of UPD products in terms of temporal stability and residual distributions is investigated for GPS, BDS, GLONASS, and Galileo satellites, respectively. The BDS satellite-induced code biases were corrected for GEO, IGSO, and MEO satellites before the UPD estimation. The UPD results of global and regional networks were also evaluated for Galileo and BDS, respectively. As a result of the frequency-division multiple-access strategy of GLONASS, the UPD estimation was performed using a network of homogeneous receivers including three commonly used GNSS receivers (TRIMBLE NETR9, JAVAD TRE_G3TH DELTA, and LEICA). Data recorded from 140 MGEX and IGS stations for a 30-day period in January in 2017 were used to validate the proposed GCRE UPD estimation and multi-GNSS dual-frequency PPP AR. Our results show that GCRE four-system PPP AR enables the fastest time to first fix (TTFF) solutions and the highest accuracy for all three coordinate components compared to the single and dual system. An average TTFF of 9.21 min with \(7{^{\circ }}\) cutoff elevation angle can be achieved for GCRE PPP AR, which is much shorter than that of GPS (18.07 min), GR (12.10 min), GE (15.36 min) and GC (13.21 min). With observations length of 10 min, the positioning accuracy of the GCRE fixed solution is 1.84, 1.11, and 1.53 cm, while the GPS-only result is 2.25, 1.29, and 9.73 cm for the east, north, and vertical components, respectively. When the cutoff elevation angle is increased to \(30{^{\circ }}\), the GPS-only PPP AR results are very unreliable, while 13.44 min of TTFF is still achievable for GCRE four-system solutions.