A GPS/BDS dual-mode positioning algorithm for a train based on CIPSO_EKF

When using global positioning system/BeiDou navigation satellite(GPS/BDS)dual-mode navigation system to locate a train,Kalman filter that is used to calculate train position has to be adjusted according to the features of the dual-mode observation.Due to multipath effect,positioning accuracy of present Kalman filter algorithm is really low.To solve this problem,a chaotic immune-vaccine particle swarm optimization_extended Kalman filter(CIPSO_EKF)algorithm is proposed to improve the output accuracy of the Kalman filter.By chaotic mapping and immunization,the particle swarm algorithm is first optimized,and then the optimized particle swarm algorithm is used to optimize the observation error covariance matrix.The optimal parameters are provided to the EKF,which can effectively reduce the impact of the observation value oscillation caused by multipath effect on positioning accuracy.At the same time,the train positioning results of EKF and CIPSO_EKF algorithms are compared.The eastward position errors and velocity errors show that CIPSO_EKF algorithm has faster convergence speed and higher real-time performance,which can effectively suppress interference and improve positioning accuracy.

Outdoor position estimation based on a combination system of GPS-INS by using UPF

This paper proposes a technique that global positioning system(GPS)combines inertial navigation system(INS)by using unscented particle filter(UPF)to estimate the exact outdoor position.This system can make up for the weak point on position estimation by the merits of GPS and INS.In general,extended Kalman filter(EKF)has been widely used in order to combine GPS with INS.However,UPF can get the position more accurately and correctly than EKF when it is applied to real-system included non-linear,irregular distribution errors.In this paper,the accuracy of UPF is proved through the simulation experiment,using the virtual-data needed for the test.

Remote positioning system based on GPS/GPRS

Considering the need of target positioning,a remote positioning system is designed based on global positioning system(GPS)and general packet radio service(GPRS);The data collection terminal is based on microcontroller unit(MCU)PIC24FV301.It uses GPRS network to create wireless link and transmits GPS source information which is collected by LEA-5H board to monitor center on the Internet.The monitor center obtains the target information through processing and analysis of the calculated data.Actual operation results indicate that the designed system has excellent performance and achieves the goal of the remote location.

GPS的现代化进展及启示

目前的全球定位系统(GPS)相关信息内容多,良莠不齐,导致出现一些二手信息误导读者的问题。该文以GPS官方机构近些年公开发布的相关技术文件为依据,梳理了GPS的现代化发展历程,阐述了导航卫星上新增加的民用信号及军用信号、新一代运行控制系统、新型GPS BlockⅢ/IIIF卫星的特点,介绍了GPS Block IIIF上使用的点波束技术,并提出了几点启示。GPS是世界上第一个建成的全球卫星导航系统(GNSS),全球覆盖程度、软件应用、全球用户数量等指标都处于领先地位,它的很多技术发展方向代表当前的主流趋势。GPS建设过程中的经验教训值得我们借鉴,GPS的发展方向值得我们学习和参考。本文内容可供卫星导航行业相关人员参考。

中国内地GPS坐标时间序列噪声模型特征及其对站点速率影响

为了进一步评估全球定位系统(GPS)时间序列噪声模型水平和垂直速率的大小,及其对误差的影响,选取中国内地227个GPS连续基准站2010—2020年南北、东西和垂直3个方向的坐标时间序列,采用6种噪声模型或噪声组合模型对其进行噪声分析。结果表明,中国内地GPS坐标时间序列噪声模型存在多样性,且部分站点在不同方向的噪声模型也存在差异,主要以一阶高斯马尔可夫+随机漫步噪声(GGMWN)和闪烁噪声+白噪声(FNWN)为主;在100°E附近的GPS站点噪声特性差异最为显著;噪声模型与速率之间的关系分析表明噪声模型对水平向速率的大小和误差影响较小,在现实计算中可不考虑噪声对水平速度的影响,但对垂向速率的大小和误差影响显著;考虑噪声模型可有效提高垂向速率的精度,同时也可能会改变部分站点的垂向运动方向,所以在现实计算中须考虑噪声对垂向速率的影响。

GPS/QZSS在亚太地区实时相对定位性能分析

利用BNC(BKG NTRIP client)传输的实时观测数据,从可见卫星数、位置精度因子(position dilution of precision, PDOP)、多路径效应、信噪比和实时相对定位精度等方面对GPS和QZSS在亚太地区的定位性能进行评估和分析。结果表明,QZSS与GPS组合后,可见卫星数增加,卫星几何构型更好,可提高定位精度的可用性和可靠性;QZSS卫星多路径效应的变化规律与GPS卫星一致,且QZSS卫星各频点的多路径误差大多小于GPS卫星;GPS和QZSS卫星各频点的信噪比随高度角变化趋势基本相同;在N、E、U方向上,GPS/QZSS组合的实时相对定位精度比GPS有所提升。

高频GPS监测的阿拉斯加地震同震形变与震级预估

为了进一步研究2020年阿拉斯加矩震级(MW)7.8地震同震形变获取及震级预估,提出一种高频全球定位系统(GPS)监测的阿拉斯加地震同震形变与震级预估方法:利用双差动态定位方法处理震中周边9个高频GPS测站数据,并解算得到这些测站的三维位移波形;最后获取此次地震引起的同震形变并对震级结果进行预估分析。结果表明,近场GPS测站位移波形变化幅度显著,波动幅度变化不仅受震中距的影响,也可能受破裂断层、地震波传播路径及场地效应等的影响;距震中最近的AC12测站水平地面峰值位移约为40 cm,永久水平位移约为24 cm,垂向抬升约30.6 cm,震中140 km范围内的GPS测站均能够监测到量值大于1 cm的永久水平形变,330 km范围内的GPS测站能够监测到毫米级以上的永久水平形变,除AC12测站与AC45测站外,此次地震造成其余测站明显的永久沉降。这些结果反映出此次地震的震源特征表现为逆冲性质,也可为后续的研究工作提供参考;利用这些高频GPS地面峰值位移(PGD)预估此次地震的震级为7.78,与实际震级基本一致,表明利用高频GPS数据进行强震震级快速预估的可靠性。

复杂环境下结合EMD的GPS-IR水位反演方法

利用法国布雷斯特(Brest)港BRST测站和英国塞文大桥监测系统GNSS双频观测数据,分别在静态和高动态环境下进行GPS-IR水位反演,探究传统GNSS监测系统进行水位反演的可行性与精度.结果表明:L1波段反演精度高于L2波段;在静态场景下,GPS-IR水位反演结果与验潮站数据相关系数大于0.98,在高动态场景下,桥梁GPS-IR水位反演精度稍低.利用经验模态分解(EMD)方法对算法进行改进,提高了在桥梁复杂环境下GPS-IR水位反演结果的精度,均方根误差(RMSE)相比经典方法降低约50%.本文方法提高了GPS-IR技术在不同水域环境下的适用性,在水位监测中具有很好的应用前景.

边坡安全监测GPS-RTK信号的降噪算法研究

全球定位系统实时动态差分技术(global positioning system-real time kinematic, GPS-RTK)是解决路基边坡安全监测问题的重要手段,但GPS-RTK信号易受到多路径误差和共模误差的影响。基于小波变换(wavelet transform, WT)和主成分分析(principal component analysis, PCA)分别可以有效去除多路径误差和共模误差,提出WT-PCA算法去除信号误差。首先设置仿真信号,通过参数调优进一步提高单一算法的降噪效果。其次提出组合算法WT-PCA改进单一算法的缺陷,并与其他组合算法进行对比分析。最后,对十天高速路基边坡的GPS-RTK监测数据进行实例分析。结果表明,WT-PCA算法的信噪比和均方根误差较于WT-VMD优于66%和50%左右,算法可以有效地消除GPS-RTK信号的多路径误差和共模误差影响。提高边坡位移监测信号处理精度,进一步评估边坡结构形变及安全状态。

GPS/BDS组合导航系统的精密单点定位模型

为了改善单卫星导航系统由于卫星数量较少,导致定位误差高的问题,设计全球定位系统(GPS)/北斗卫星导航系统(BDS)组合导航系统的精密单点定位模型:线性组合处理GPS与BDS的伪距和载波相位观测值,并构建GPS/BDS组合导航系统的组合观测值;接下来利用协方差成形自适应卡尔曼滤波方法,对组合导航系统导航过程中的卫星钟差、电离层延迟等误差实施滤波;再利用滤波处理后组合导航系统的广播星历,获取卫星轨道以及钟差;然后利用经验模型修正对流层延迟,获取相位观测值与伪距的综合改正数;最后利用综合改正数修正组合导航系统的观测方程,构建精密单点定位模型。实验结果表明,GPS/BDS组合导航系统采用所构建模型进行精密单点定位,不同方向定位误差均低于10 cm,证明了提出模型的有效性。

GPS/Galileo/BDS-3广播星历精度分析

为了分析当前GPS(Global Positioning System)、Galileo(Galileo Navigation Satellite System)和BDS-3(Beidou Navigation Satellite System with Global Coverage)广播星历的精度,详细分析研究了各种偏差改正及消除方法,并尽可能地消除了系统误差和粗差对评估结果的影响。选取2021-11-01/12-31共61天MGEX(multi-GNSS experiment)发布的多系统混合广播星历与武汉大学分析中心发布的事后精密星历数据进行实验,对GPS、Galileo和BDS-3近期广播星历精度进行对比分析,实验结果表明:3个系统广播星历整体精度由高到低依次是Galileo、BDS-3和GPS,其空间信号测距误差的RMS(root mean square)分别优于0.17、0.25和0.37 m,整体轨道精度的RMS分别优于0.17、0.12和0.25 m,BDS-3广播星历的轨道精度最高,钟差误差的RMS分别优于0.15、0.23和0.27 m,Galileo广播星历的钟差精度最高。对于GPS卫星的广播星历,blockⅢA卫星钟差和轨道精度均优于其他GPS类型卫星。

Weak GPS signal acquisition method based on DBZP

Double block zero padding(DBZP) is a widely used but costly method for weak global positioning system(GPS) signal acquisition in software receivers. To improve the computational efficiency, this paper proposes an algorithm based on the differential DBZP algorithm and the discrete cosine transform(DCT) domain filtering method. The proposed method involves using a differential correlator after the DBZP operation. Subsequently, DCT domain low pass filtering(LPF) and inverse DCT(IDCT) reconstruction are carried out to improve the signal to noise ratio(SNR). The theoretical analysis and simulation results show that the detection algorithm can effectively improve the SNR of the acquired signal and increase the probability of detection under the same false alarm probability.

Hypothesis testing analysis and unknown parameter estimation of GPS signal detection

Hypothesis testing analysis and unknown parameter estimation of both the intermediate frequency(IF) and baseband GPS signal detection are given by using the generalized likelihood ratio test(GLRT) approach,applying the model of GPS signal in white Gaussian noise,It is proved that the test statistic follows central or noncentral F distribution,It is also pointed out that the test statistic is nearly identical to central or noncentral chi-squared distribution because the processing samples are large enough to be considered as infinite in GPS acquisition problem.It is also proved that the probability of false alarm,the probability of detection and the threshold are affected largely when the hypothesis testing refers to the full pseudorandom noise(PRN) code phase and Doppler frequency search space cells instead of each individual cell.The performance of the test statistic is also given with combining the noncoherent integration.

青藏块体东北缘GPS垂向时间序列噪声分析

为了进一步研究青藏块体东北缘全球定位系统(GPS)测站垂向位移序列的最佳噪声模型及对测站垂向速度估计的影响,提出一种青藏块体东北缘GPS垂向时间序列噪声分析方法:选取青藏块体东北缘27个中国大陆构造环境监测网络(CMONOC)GPS测站,利用不同的噪声模型对测站垂向位移时间序列进行噪声分析;并探讨赤池信息准则(AIC)、贝叶斯信息准则(BIC)、时间优化贝叶斯信息准则(BICtp)和修正贝叶斯信息准则(BICc)确定的最优噪声模型之间的差异及对测站垂向速度估计的影响。结果表明,AIC确定的最佳噪声模型主要是广义高斯马尔可夫噪声(GGM)+自回归滑动平均噪声(ARMA1)、GGM+白噪声(WN)和WN+闪烁噪声(FN),分别占总测站数的29.6%、22.2%和18.5%,而BIC、BICtp和BICc准则确定的最佳噪声模型主要为WN+FN,分别占总测站数的74.1%、66.7%和70.4%,其次是GGM,分别占测站数的22.2%、22.2%和14.8%;BIC、BICtp、BICc在确定最佳噪声模型过程中,对GGM+ARMA1和GGM+WN噪声模型的影响较大,并且BICc对随机漫步噪声的敏感程度高于BIC、BICtp;不同信息准则确定的青藏块体东北缘垂向速度及不确定度存在一定的差异,但整体垂向趋势基本相同,西南部测站呈现下降趋势,东北边缘测站呈现上升趋势,但上升或下降的幅度相对较小。

抗差Helmert方差分量估计在GPS/BDS/UWB融合定位中的应用

针对卫星信号受限环境下,全球定位系统(GPS)/北斗卫星导航系统(BDS)组合定位出现较大偏差的问题,引入超宽带(UWB)技术作为定位性能增强技术。GPS/BDS伪距测量值与UWB测距值作为原始观测值,提出了基于抗差赫尔默特(Helmert)方差分量估计的GPS/BDS/UWB融合定位方法,实现合理定权,抵御粗差影响。分别进行了静态实验和动态实验,结果表明:没有粗差情况下,GPS/BDS/UWB融合定位相对于GPS/BDS的定位精度在静态实验和动态实验中均有所提升;引入粗差后,定位结果可抵御粗差,精度提升较为明显。

GPS信号与特性分析的研究

GPS作为一种广泛应用的卫星导航系统,其导航系统的高精度、广覆盖和全天候可用性受到人们的普遍认可。然而,地面GPS接收机是相对脆弱的,容易受到各种环境因素影响,可能会对GPS接收机造成干扰,使其难以或无法正常工作。本文通过对GPS信号的基本原理、调制方式进行了研究,分析了信号特征和C/A码的生成方式,为下一步GPS信号的干扰与抗干扰提供理论和现实意义。

Modeling of Selective Availability for Global Positioning System

To degrade location accuracy for unauthorized GPS users, US government applied Selective Availability (SA) to Global Positioning System (GPS). In this paper we discuss an anti-SAapproach to improve location accuracy which is very important in landing position, and then we derived the SA error by eliminating almost all other errors including ionospheric and tropospheric timedelays and clock errors both in satellites and in receiver, etc. By means of the system identificationtheory, an SA errorl all SA error model with the second-order Gauss-Maukov stochastic process wasderived and simulated. With the selected parameters of the stochastic process) the simulation resultsshow that there is the excellent agreement between the simulated SA error model and that of reallyapplied in GPS system.

Continuous Tracking of GPS Signals with Data Wipe-Off Method

The decentralized pre-filter based vector tracking loop(VTL)configuration with data wipe-off(DWO)method of the Global Positioning System(GPS)receiver is proposed for performance enhancement.It is a challenging task to continuously track the satellites’signals in weak signal environment for the GPS receiver.VTL is a very attractive technique as it can provide tracking capability in signal-challenged environments.In the VTL,each channel will not form a loop independently.On the contrary,the signals in the channels of VTL are shared with each other;the navigation processor in turn predicts the code phases.Thus,the receiver can successfully track signals even the signal strength from individual satellite is weak.The tracking loop based on the pre-filter provides more flexible adjustment to specific environments to reduce noise interference.Therefore,even if the signals from some satellites are very weak the receiver can track them from the navigation results based on the other satellites.The navigation data,which contains information necessary to perform navigation computations,are binary phase-shift keying(BPSK)modulated onto the GPS carrier phase with the bit duration of 20 ms(i.e.,50 bits per second)for the GPS L1 C/A signals.The coherent integration interval can be extended for improved tracking performance in signal-challenged environment.However,tracking accuracy is decreased by possible data bit sign reversal.The DWO algorithm can be employed to remove the data bit in I and Q correlation values so as to avoid energy loss due to bit transitions when the integration interval of the correlator is extended over 20 ms under the low carrier-to-noise ratio(C/No)environments.The proposed method has an advantage to provide continuous tracking of signals and obtain improved navigation performance.Performance evaluation of the tracking capability as well as positioning accuracy will be presented.

Data Wipe-Off Technique for Tracking Weak GPS Signals

In this paper,the data wipe-off(DWO)algorithm is incorporated into the vector tracking loop of the Global Positioning System(GPS)receiver for improving signal tracking performance.The navigation data,which contains information that is necessary to perform navigation computations,are binary phase-shift keying(BPSK)modulated onto the GPS carrier phase with the bit duration of 20 ms(i.e.,50 bits per second).To continuously track the satellite’s signal in weak signal environment,the DWO algorithm on the basis of pre-detection method is adopted to detect data bit sign reversal every 20 ms.Tracking accuracy of a weak GPS signal is decreased by possible data bit sign reversal every 20 ms to the predetection integration time(PIT)or integration interval.To achieve better tracking performance in weak signal environment,the coherent integration interval can be extended.However,increase of the integration interval lead to decrease of the tracking accuracy by possible data bit sign reversal every 20 ms to the integration interval.When the integration interval of the correlator is extended over 20 ms in low C/No levels,the navigation DWO algorithm can be employed to avoid energy loss due to bit transitions.The method presented in this paper has an advantage to continuously estimate the navigation data bit and achieve improved tracking performance.Evaluation of the tracking performance based on the various integration intervals for the vector tracking loop of a GPS receiver will be presented.

基于逐历元相位差分和TEQC的海洋GPS数据质量分析

全球定位系统(GPS)浮标作为海洋观测的重要手段,在海洋监测方面发挥重要作用。本文将以江苏连云港以东海域布放的实验浮标采集的GPS数据为例,使用数据预处理软件(TEQC)从信噪比、多路径和精度因子等角度对GPS浮标数据质量进行分析,引入逐历元相位差分的方法对GPS浮标数据的稳定性和数据质量进行分析。结果显示:GPS L1和L2观测量的信噪比在35~45 dBHz的比例分别占到85.3%和92.1%,与陆地固定站相比,噪声表现相当甚至略优于陆地固定站。L1和L2观测量的多路径效应大部分集中在-0.46~0.46 m和-0.35~0.35 m,与陆地固定站相比,GPS浮标数据的多路径效应略高,GPS浮标观测数据的精度因子比陆地固定站大。从逐历元相位差分的结果来看,GPS浮标的数据稳定性和质量较陆地固定站差,海洋的恶劣环境对GPS观测数据产生了较大影响。