Modeling and Prediction of Inter-System Bias for GPS/BDS-2/BDS-3 Combined Precision Point Positioning

The combination of Precision Point Positioning(PPP)with Multi-Global Navigation Satellite System(MultiGNSS),called MGPPP,can improve the positioning precision and shorten the convergence time more effectively than the combination of PPP with only the BeiDou Navigation Satellite System(BDS).However,the Inter-System Bias(ISB)measurement of Multi-GNSS,including the time system offset,the coordinate system difference,and the inter-system hardware delay bias,must be considered for Multi-GNSS data fusion processing.The detected ISB can be well modeled and predicted by using a quadratic model(QM),an autoregressive integrated moving average model(ARIMA),as well as the sliding window strategy(SW).In this study,the experimental results indicate that there is no apparent difference in the ISB between BDS-2 and BDS-3 observations if B1I/B3I signals are used.However,an obvious difference in ISB can be found between BDS-2 and BDS-3 observations if B1I/B3I and B1C/B2a signals are used.Meanwhile,the precision of the Predicted ISB(PISB)on the next day of all stations is about 0.1−0.6 ns.Besides,to effectively utilize the PISB,a new strategy for predicting the PISB for MGPPP is proposed.In the proposed strategy,the PISB is used by adding two virtual observation equations,and an adaptive factor is adopted to balance the contribution of the Observed ISB(OISB)and the PISB to the final estimations of ISB.To validate the effectiveness of the proposed method,some experimental schemes are designed and tested under different satellite availability conditions.The results indicate that in open sky environment,the selective utilization of the PISB achieves almost the same positioning precision of MGPPP as the direct utilization of the PISB,but the convergence time of MGPPP is reduced by 7.1%at most in the north(N),east(E),and up(U)components.In the blocked sky environment,the selective utilization of the PISB contributes to more significant improvement of the positioning precision and convergence time than that in the open sky environment.Compared with the direct utilization of the PISB,the selective utilization of the PISB improves the positioning precision and convergence time by 6.7%and 12.7%at most in the N,E,and U components,respectively.

Reference satellite selection method for GNSS high-precision relative positioning

Selecting the optimal reference satellite is an important component of high-precision relat/ve positioning because the reference satellite directly influences the strength of the normal equation. The reference satellite selection methods based on elevation and positional dilution of precision （PDOP） value were compared. Results show that all the above methods cannot select the optimal reference satellite. We introduce condition number of the design matrix in the reference satellite selection method to improve structure of the normal equation, because condition number can indicate the ill condition of the normal equation. The experimental results show that the new method can improve positioning accuracy and reliability in precise relative positioning.

GNSS/Pseudolites导航定位中的伪卫星优化模型研究

针对GNSS/Pseudolites组合系统的伪卫星优化布设问题,指出了多指标评价体系下的GNSS系统中伪卫星加入的必要性,构建了基于方位角、高度角及观测历元的多指标评价体系四维模型,并通过实测数据进行实验分析,结果表明:伪卫星的加入所带来的可见卫星个数及低高度角处信息的变化可有效地增强系统的可靠性,提高了系统的定位精度;全景显示下的PDOP值与内可靠性值的最优区域变化相似但分布不同;PDOP、内可靠性、耗资等多因素约束的综合定权可有效协调各个指标,为选择最优系统提供可靠依据并在全景显示下有效地解决伪卫星优化GNSS系统的高效选址问题。

Impact Analysis of Solar Irradiance Change on Precision Orbit Determination of Navigation Satellites

Solar radiation pressure is the main driving force and error source for precision orbit determination of navigation satellites.It is proportional to the solar irradiance,which is the"sun constant".In regular calculation,the"solar constant"is regard as a constant.However,due to the existence of sunspots,flares,etc.,the solar constant is not fixed,the change in the year is about 1%.To investigate the variation of solar irradiance,we use interpolation and average segment modeling of total solar irradiance data of SORCE,establishing variance solar radiation pressure(VARSRP)model and average solar radiation pressure(AVESRP)model based on the built solar pressure model(SRPM)(constant model).According to observation data of global positioning system(GPS)and Beidou system(BDS)in 2015 and comparing the solar pressure acceleration of VARSRP,AVESRP and SRPM,the magnitude of change can reach 10-10 m/s^2.In addition,according to the satellite precise orbit determination,for GPS satellites,the results of VARSRP and AVESRP are slightly smaller than those of the SRPM model,and the improvement is between 0.1 to 0.5 mm.For geosynchronous orbit(GEO)satellites of BDS,The AVESRP and VARSRP have an improvement of 3.5 mm and 4.0 mm,respectively,based on overlapping arc,and SLR check results show the AVESRP model and the VARSRP model is improved by 2.3 mm and 3.5 mm,respectively.Moreover,the change of inclined geosynchronous orbit(IGSO)satellites and medium earth orbit(MEO)satellites is relatively small,and the improvement is smaller than 0.5 mm.

Precision Analysis and Parameter Inversion in the Stepwise Deployment of a Mixed Constellation

Along with the planning and implementation of the COMPASS satellite navigation system, first as a regional then a global system, there is a need to probe into the positioning performance of the mixed constellation in the stepwise deployment scheme. Both the increase in the number of the MEO satellites in the constellation and the decrease in the user equivalent ranging error of the GEO satellites will improve the overall positioning performance of the system. Using the weighted dilution of precision as the evaluation criterion, we study the theoretical relationship between the internal parameters and the positioning precision during the evolution of the system. On one hand, the influence of each factor on the positioning performance is quantitatively analyzed under the circumstances of various constellation deployment schemes and user types. On the other hand, for given positioning performance indices, simulations are carried out to present the inversion of parameters. Our conclusions provide useful suggestions to the system design and stepwise deployment scheme of satellites.

New Regional Satellite Positioning Constellation Scheme Discussion

The characteristics of present “Beidou” satellite positioning system are analyzed. In order to perfect our country regional satellite positioning system, the idea of “Beidou” geosychronous earth orbit （GEO） satellites combined with some middle earth orbit （MEO） satellites constellation is put forward. The details of general satellite constellation optimized method are described, using this method the multiple positioning constellation design results are gained. And those results belong to two type of sehems, one is 2 GEO plus some MEO satellites and the other is 3 GEO plus some MEO satellites. Through simulation and comparison, among those multiple design results, final optimized regional positioning constellation is given. In order to check the chosen constellation cover performance, the position dilution of preeision（PDOP） is calculated, and with ,satellite constellation simulation software Satlab many coverage performances of the chosen constellation substellar point track, elevation, azimuth and visible satellites number changing situation are also simulated.

Global precision analysis of carrier phase relative positioning in BeiDou navigation satellite system and United States global positioning system

In this paper, we derived a high-efficiency formula for calculating the precision of carrier phase relative positioning,analyzed the various factors that affect the positioning accuracy using the carrier phase, and proposed the concept of using a frequency dilution of precision to describe the quantitative effect of different frequency combinations on the positioning precision. To this end, we computed and plotted the global spatial distribution map of the relative positioning dilution of precision for single-day solution, half-hour solution, and single-epoch solution of the global positioning system(GPS), regional Beidou navigation satellite system(BDS2), future global Beidou navigation satellite system(BDS3), and their fusion systems.Using processing software with autonomous intellectual property rights(GCN and VENUS/ARSNet), we solved the measurement data and examined the positioning precision of the single-day solution and single-epoch solution of GPS and BDS2.The analysis demonstrated that the B1/B2 frequency positioning precision of BDS2 was better than that of L1/L2 frequency positioning of GPS, but the positioning precision of the BDS2 is worse than that of GPS over most of the service region of the BDS2. Further, the positioning precision of BDS3 is better than that of GPS in the Asia-Pacific region, while it is the opposite in other regions. Based on these conclusions, we put forth some optimization recommendations regarding the signal frequency of the navigation system and GPS measurement standards to serve as references for optimizing the system performance and formulating standards.

Preliminary assessment of the navigation and positioning performance of BeiDou regional navigation satellite system

BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satellites in Inclined Geosynchronous Orbit （IGSO）, and 4 satellites in Medium Earth Orbit （MEO）. In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision （PDOP） value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential position- ing and ambiguity resolution （AR） performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alolae in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accu- racy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.

基于组合圆锥构型的水下声学定位系统布站优化

在水下目标定位中,布站构型的共面约束会导致目标单点定位的几何精度因子(GDOP)理论最小值不能达到。为改善水下布站的观测矩阵,将单圆锥扩展为组合圆锥构型布站模式。然而,传统的优化算法易陷入局部最优且存在收敛效率低等问题。针对以上问题,提出了一种改进的自适应粒子群算法。首先提出了一种有共面约束的水下声学定位系统组合圆锥构型,并证明了所提出的组合圆锥构型具有可叠加性、可旋转性以及GDOP旋转不变性;其次,针对布站优化指标单一的问题,构建了一种基于水下目标全局GDOP的布站优化准则;在此基础上提出了一种基于自适应粒子群的优化算法,并应用于组合圆锥构型下的水下声学定位系统布站优化。所提出的自适应粒子群算法能增强布站的全局最优性,提高算法收敛效率和水下目标的定位精度。

精准时空感知赋能数字经济发展

当前数字经济的发展愈发依赖于精准时空信息,分析了通信导航融合感知网络对实现精准时空感知的作用与挑战,介绍了我国在通导融合研究方面取得的突破性进展,阐述了隐嵌信噪定位技术对5G网络定位性能的提升、异构多网多源融合对定位鲁棒性的保障,对北斗与5G深度融合的增量效应进行了讨论。从精准时空感知如何赋能数字经济发展的角度对通信导航融合网络做出进一步规划。

LEO多星座增强BDS精密单点定位性能评估

针对不同构型的低轨星座(LEO)增强北斗卫星导航系统BDS的精密单点定位PPP性能开展研究。通过IGS高、中、低纬度6测站实测数据、精密轨道及钟差产品,生成BDS、“鸿雁”HY、“微厘空间”CS精密星历、卫星钟差、观测量等实验仿真数据,构建了LEO增强BDS PPP数学模型,实现了BDS、BDS+HY、BDS+CS、BDS+HY+CS不同组合PPP。实验结果表明,在10、60 min静态PPP定位精度以及平均可视卫星数、PDOP值等方面均有不同程度的提升,HY对高纬度KIRU站改善效果显著,收敛时间减至2 min以内,CS对低纬度FAA1站测站收敛时间的提升最大,从46 min 50 s缩短至2 min,HY+CS增强BDS的效果最好,10 min定位精度均能达到毫米级,除FAA1站外其他测站均收敛在1 min以内。

基于GDCORS的北斗终端高精度定位算法实现及性能分析

为了提升广东省卫星导航定位基准服务系统(以下简称“GDCORS”)的社会化应用范围,扩充GDCORS的服务对象,提出了基于时间差分和卡尔曼滤波的实时高精度定位方法,利用该方法开发了高精度定位APP,并且研制了与之配套的外接北斗定位模块,然后基于GDCORS提供的实时差分产品数据使用多种智能手机在广州市内开展了静态和动态定位测试。测试结果表明,提出的高精度定位算法实现了基于手机观测数据的米级北斗伪距差分定位,基于单频外接设备的分米级、基于多频外接设备的厘米级北斗载波相位差分定位,以上基于GDCORS的北斗终端高精度定位算法具备应用推广价值。

BeiDou、Galileo、GLONASS、GPS多系统融合精密单点

随着中国BeiDou系统与欧盟Galileo系统的出现以及俄罗斯GLONASS系统的恢复完善,过去单一的GPS导航卫星系统时代已经逐步过渡为多系统并存且相互兼容的全球性卫星导航系统（multi-constellation global navigation satellite systems,multi-GNSS）时代,多系统GNSS融合精密定位将成为未来GNSS精密定位技术的发展趋势。本文采用GPS、GLONASS、BeiDou、Galileo 4大卫星导航定位系统融合的精密单点定位（precise point positioning,PPP）实测数据,初步研究并分析了4系统融合PPP的定位性能。试验结果表明：在单系统观测几何构型不理想的区域,多系统融合能显著提高PPP的定位精度和收敛速度。4大系统融合的PPP收敛速度相对于单GNSS可提高30%~50%,定位精度可提高10%~30%,特别是对高程方向的贡献更为明显。此外,在卫星截止高度角大于30°的观测环境下,单系统由于可见卫星数不足导致无法连续定位,而多系统融合仍然可以获得PPP定位结果,尤其是水平方向具有较高的定位精度。这对于山区、城市以及遮挡严重的区域具有非常重要的应用价值。

一种信标辅助的北斗伪卫星CPD定位方法

针对北斗伪卫星信号引入室内并在小尺度空间下提供高精度定位的难题,如何在顾及网络建设成本的基础上提升小尺度空间的定位时效性和定位精度是未来室内定位技术中需要解决的重要一环。此处充分结合室内环境下小尺度空间的空间特征,提出一种室内节点信标辅助的北斗伪卫星载波相位差定位方法。该方法首先将传统的大范围指纹构建问题转化为指纹节点的方式,在指纹图谱的基础上提出室内节点信标的概念,通过信标节点实现小尺度空间与周围空间的连接,并对以载噪比和载波相位为基础的信标特征谱构建与处理进行了分析;然后以室内节点信标为基础给出了基于载波相位差的位置估计过程,最后结合粒子群寻优算法提出一种顾及行人特征的位置与速度空间约束下的位置搜索算法。在真实环境下的试验结果表明,通过室内节点信标的辅助在室内环境可以实现动态定位精度优于30 cm、暂停态下的定位精度优于25 cm的定位效果。正常步速运动下算法与惯性导航定位精度相当,同时相比于惯性导航方式具有更宽松的运动姿态条件。在小尺度空间下算法具有更优的适用性。

VLBI观测对转发式测距GEO卫星定轨精度的贡献分析

联合甚长基线干涉测量(very long baseline interferometry,VLBI)时延数据与转发式(orbit determination by transfer tracking,ODTT)测距数据能够有效提高地球静止轨道(geostationary earth orbit,GEO)卫星定轨精度。参照位置精度衰减因子(position dilution of precision,PDOP)的改变,研究不同VLBI基线时延数据与转发式测距数据的联合对GEO卫星定轨精度的改善,可为特定条件下联合观测时VLBI基线的最优选择提供参考。基于中国科学院国家授时中心宽带VLBI系统和转发式测轨系统的实测数据,开展中星12号GEO卫星的定轨试验。试验结果表明定轨精度的提高与PDOP的降低成正相关。相比于转发式单独定轨,联合VLBI系统中的喀什—三亚基线,PDOP降低了3.00,定轨精度提高了11.48%;联合VLBI系统中的吉林—喀什基线,PDOP降低了3.38,定轨精度提高了14.73%;联合VLBI系统中的吉林—三亚基线,PDOP降低了6.90,定轨精度提高了19.75%;联合VLBI系统中的吉林—三亚和吉林—喀什两条基线,PDOP降低了9.94,定轨精度提高了27.23%。

北斗新频点B1C/B2a精密单点定位综合性能

为对比北斗三号卫星导航系统新老信号的定位性能,利用连续两周17个MGEX测站观测数据对BDS-3新频点B1C/B2a消电离层组合精密单点定位(PPP)服务进行全面评估。结果表明,单系统BDS-3 B1C/B2a静态PPP在E、N、U三方向的精度分别为1.3 cm、0.8 cm、1.9 cm,仿动态E、N、U三方向的精度分别为2.6 cm、1.8 cm、4.2 cm;与BDS-3 B1I/B3I组合相比,静态E、N两方向精度相当,U方向提升13.6%,仿动态三方向精度相当,差值在1 mm以内。BDS-3 B1C/B2a静态PPP三维精度40 min可达cm级,仿动态PPP三维精度5 min达到dm级。双系统BDS-3 B1C/B2a+GPS L1/L2静态PPP三维精度20 min达到cm级,仿动态PPP三维精度30 min达到cm级;与双系统BDS-3 B1I/B3I+GPS L1/L2对比,两者定位精度和收敛速度基本一致。综上所述,可以证明B1C/B2a信号的定位性能优于B1I/B3I信号。

BDS-3 PPP-B2b实时精密时间同步方法探讨

针对传统实时精密单点定位(PPP)时间同步方法需要连接互联网,以及对北斗三号全球卫星导航系统(BDS-3)精密单点定位服务信号(PPP-B2b)用于长基线实时时间同步的研究较少的问题,提出一种将PPP-B2b信号用于PPP时间同步的实时时间同步方法:将高精度铷原子钟作为全球卫星导航系统(GNSS)接收机外频标输入,通过GNSS接收机实时接收PPP-B2b改正数,解算接收机钟差并实时调整铷原子钟,输出与时间基准同步的秒脉冲(1PPS)信号,较之传统GNSS接收机输出1PPS有更佳的频率稳定性;设计PPP-B2b时间同步硬件测试平台对提出的PPP-B2b时间同步方法进行测试。结果表明,通过PPP-B2b时间同步方法进行时间传递的精度优于0.2 ns;短基线实测实时时间同步精度优于0.95 ns;卫星模拟器仿短基线精度优于0.87 ns,仿长基线精度优于0.9 ns。

BDS-3 B2b-PPP URA评估精化与播发方法

用户距离精度指数(URAI)作为导航系统定位服务完好性标识,在提供卫星可用性信息的同时,也反映了卫星的轨道钟差精度。本文提出将B2b电文中随轨道改正数播发的URAI信息恢复为用户距离精度(URA),并用于B2bPPP的随机模型构建。对其进行定位性能评估,发现B2b自身播发的URA精度较差。针对该问题,利用分布在中国及周边区域的多个全球卫星导航系统(GNSS)监测站对B2b的URA参数进行重估计。实验结果表明:精化后的URA能显著提升B2b-PPP的服务性能。相比于仅考虑观测噪声和高度角的随机模型,使用精化后的URA作为随机模型,动态和静态定位模式下的收敛时间提升分别达到18.9%、14.5%;收敛后定位精度提升分别达到11.2%、8.9%。在此基础上,进一步结合北斗卫星导航系统(BDS)短报文,提出一种精化后URA的播发方法,结合现有短报文通信效率进一步分析了精化URA的用户使用性能。

基于概率误差的三维室内定位系统最优布站方法

随着智能化、自动化技术的不断发展,室内定位技术的应用场景日益广泛,如何提高室内定位系统的精度和可靠性一直是研究热点。对基站布局进行优化,提升系统整体的定位精度是现有的室内定位系统优化方法之一。对于该方法,现有的研究普遍选择采用其他相似领域的已有方法,主要的两种方法中用于评价卫星共轭的精度稀释因子忽略了基站与标签的距离;作为导弹、惯导系统中落点精度评价因子的概率误差方法没有考虑基站几何结构的影响。对此,提出了一种基于精度稀释因子和概率误差方法的精度评价模型,用于推导三维室内定位系统的最优基站布局,该模型同时考虑了距离和几何结构对室内定位精度的影响,可以很好地应用于室内定位的领域。所提方法在程序模拟和实际定位实验中均取得了优异的效果。在程序模拟中,最优基站布局系统的定位误差均值相比传统四顶角定位系统降低了约14.38%,在实际定位实验中,最优布局的定位精度和效果都得到了显著提升。实验结果验证了精度评价模型的准确性与实用性。所提出的最优基站布局方法在三维室内定位领域具有很高的应用价值和普适性,能够有效提高室内定位系统的精度和效果。

基于北斗高精度定位的铁路巡检技术应用

铁路巡检工作是铁路安全运营工作的重中之重,但是铁路站场内复杂的环境使得常规的卫星导航定位性能大大降低,无法满足巡检工作和数据运营的要求.本文分析了铁路股道形成的轨道峡谷模式下定位场景的特点,分别对使用北斗导航定位实时动态(real-time kinematic,RTK)、连续运行参考站(continuously operating reference stations, CORS)、星基增强系统(satellite-based augmentation system, SBAS)等高精度增强模式进行了分析、实测及精度统计,最后使用了集成多种定位模式的手持北斗高精度定位终端,接入千寻CORS数据,在成都公兴站股道上进行了实地使用与巡检模拟测试.分析结果表明:定位精度有较大提高,高精度定位结果可以满足铁路巡检要求,为下一步开发智能巡检管理系统提供了有益的参考.