低纬电离层闪烁对GPS观测值及其导航定位的影响

电离层闪烁对全球定位系统(GPS)的影响已经被认为是GPS现代化后面临的主要问题.利用低纬地区电离层闪烁监测接收机(18.34°N, 109.62°E)在2012-08-01～31的GPS闪烁数据和观测数据,开展了电离层闪烁对GPS观测值及单点定位的影响研究.研究结果表明,电离层闪烁可以导致GPS卫星信号发生衰减,最大衰减幅度达20 dB-Hz;相比于GPS L1观测值,电离层闪烁对GPS L2影响更大;电离层闪烁可导致周跳的发生,统计表明,每100个强电离层闪烁事件(S_40.5)可以导致21个周跳发生,而100个弱电离层闪烁事件(0.2S_4≤0.5)仅导致6个周跳发生;强电离层闪烁环境下,卫星信号会遭遇失锁现象,从而破坏卫星几何分布结构,导致GPS导航定位性能降低;相比正常的电离层环境,电离层闪烁活跃环境下的GPS单点定位精度降低了23%.     

GPS对流层延迟的历元间差分分析

GPS(Global Positioning System)观测难免受到各种因素的影响,虽然可以通过不同观测组合和改正模型予以消弱,但总有一定的残留误差对定位结果产生影响.基于精密单点定位理论,通过无电离层组合模型、高精度GPS卫星轨道、卫星钟差来削弱电离层延迟误差、轨道误差的影响,以不同采样间隔的观测数据,分析对流层延迟历元间差分结果的特性;分析不同采样间隔观测中,对流层延迟历元间差分值的变化,对流层延迟对历元间差分观测值的影响;残留误差对历元间差分结果、组合观测值的影响;残留误差在时间序列上的变化.     

利用GPS双频观测值实现PPP电离层延迟高阶项改正

给出了利用双频观测值计算L3组合电离层延迟高阶项改正的方法,并与全球电离层延迟文件的改正效果进行对比.利用赤道附近的15个国际全球卫星导航定位系统服务组织(IGS)站的数据进行比较,结果表明:2种方法计算的电离层二阶项延迟互差最大不超过1 cm,三阶项延迟互差最大不超过5 mm;电离层高阶项改正后的观测值精密单点定位(PPP)解算结果N、E、U方向互差平均值分别为0.4、0.5、1.0mm,因此2种改正方法效果在同一水平.     

地面GPS双频非差观测值仿真

本文在系统研究GPS观测模型和各项误差模型的基础上,建立了地面GPS双频非差观测模型,设计了一套较完整的计算仿真程序。误差模型包括钟差、电离层延迟、对流层延迟、相对论效应、地球固体潮等,反映了测量环境条件。根据具体要求可在观测值中添加粗差和周跳,为利用GPS观测值探讨定位方案设计、周跳和粗差探测等问题提供了验证平台。最后,本文利用BERNESE定位软件给出了电离层延迟和对流层延迟分别对单点定位精度影响的实例,实验证明仿真结果与实际情况符合较好。     

WASS电离层网格算法在低纬地区的误差分析

对不同纬度的8个GPS观测台站得到的数据,采用广域增强系统(WASS)电离层网格算法计算了斜向电离层时延,并将计算结果同实际观测值之间的差别进行了统计分析.结果表明:在中高纬地区,WASS电离层网格算法的精度很高,但是在纬度较低的地区存在着较大的误差,产生这种误差的原因是由于低纬电离层中的电子浓度较大并且存在较大的经向梯度变化.为了减少这种误差,可以在低纬地区增加广域基准站的数量、缩小电离层单元网格的尺度等方法.     

电离层对GPS测量的影响

GPS作为一种无线电导航系统,受到很多误差源的影响,即:卫星轨道误差、卫星钟差、电离层延迟误差、对流层延迟误差、多路径误差、接收机钟差和测量噪声等误差。其中,自从SA(Selected Availability)于2000年5月1日取消以后,电离层误差是最大的一项误差。电离层延迟对GPS定位的影响结果,主要体现在定位精度的降低和定位方法的限制等方面。电离层使接收到的GPS信号产生延迟,从几米到百米以上。如果不考虑这种影响,就会严重降低GPS定位和授时的精度。因此,电离层误差是GPS测量中的主要误差源,必须加以改正。本文介绍了电离层对GPS定位的影响,包括码群延迟(即绝对测距误差)、载波相位超前(即相对测距误差)、多普勒时延(即距速误差)以及信号衰减(即振幅闪烁),并论述了影响电离层密度的因素。     

磁暴对GPS硬件延迟影响的研究

根据不同纬度的4个GPS台站的数据,采用6系数二次曲面模型对磁暴期间GPS系统的硬件延迟的波动进行了研究,结果表明:在纬度较低的地区,由于电离层中的电子浓度较大并且存在较大的经向梯度变化,磁暴期间计算出的硬件延迟存在着较大的波动.因此,对GPS系统硬件延迟的估算应尽量选择中高纬地区台站的数据并且避免使用磁暴发生期间的数据.     

利用GPS观测值反演电离层总电子含量的时空变化

为了便于电离层总电子含量时空变化的研究,利用区域电离层模型获得了GPS系统硬件延迟,从而进一步获取了绝对电离层总电子含量值.利用北京IGS站的GPS观测数据分别计算了2000年至2004年各个不同季节的总电子含量,经比较发现,电离层总电子含量表现出明显的季节性变化.利用中国地壳观测网络25个测站的观测数据计算发现,电离层总电子含量空间变化幅度大,在低纬度地区总电子含量值相对较大,而在中纬度地区相对较小.     

影响GPS测量的电离层延迟模型研究

GPS作为一种无线电导航系统,受到很多误差源的影响,如:卫星轨道误差、卫星钟差、电离层延迟误差、对流层延迟误差、多路径误差、接收机钟差和测量噪声等误差。其中,自从SA(Selected Availability)于2000年5月1日取消以后,电离层误差是最大的一项误差。为了消除电离层延迟的影响,GPS导航定位中采用了双频改正法、利用电离层延迟的空间相关性差分以及各种电离层模型来削弱其影响。本文探讨了常用的修正GPS电离层延迟的模型和经验改正公式:Bent模型,IRI模型,Klubuchar模型,双频改正法等,并详细论述了如何利用双频观测值建立电离层模型。     

一种实时双频电离层修正方法

电离层延迟是影响GPS绝对定位的重要因素。比较常用的电离层延迟修正方法有模型方法和双频方法。模型方法和使用双频码伪距的方法精度有限。使用双频载波相位进行电离层延迟计算需要求解整周模糊度,计算复杂。本文提出了一种同时使用GPS双频码和载波观测量进行电离层误差修正的方法。使用卫星信号模拟器生成信号并用接收机实时接收,用此方法计算出电离层延迟值,并与真值进行比较,计算误差为厘米级。最后,接收真实卫星信号并计算了真实电离层延迟,并与使用Klobuchar模型方法计算出的电离层延迟进行了比较。     

Model analysis method (MAM) on the effect of the second-order ionospheric delay on GPS positioning solution

In this paper,we develop an approach to study the effect of second-order ionospheric delay on GPS positioning based on the ionosphere-free combination (abbreviated to Lc) of GPS dual-frequency carrier phase observables,in which the first-order ionospheric delay has been eliminated.GPS data from IGS WUHN tracking station during April 9 23,2003 is used to perform the above approach,and results show that the second-order ionospheric delay in GPS so-called ionosphere-free observables will result in the regular ...     

Novel algorithms for GPS network RTK

This paper gives some new algorithms for GPS Network RTK. The whole algorithms are based on the Double-Difference (DD) using single epoch of GPSdata. So cycle-slips and loss-of-locks of GPS satelliteare avoided. And the time of Network RTK systems tart-up and positioning is shortest, only one epoch.These algorithms need no ionospheric or troposhperic correction models. The combined bias of rover station is directly estimated and corrected by observations of reference stations of network. Hence, the algorithms are no delay, and are the really and truly real-time difference and positioning. Compared with other algorithms, they can synchronously eliminate orbital bias, ionosphere delay, troposphere delay and otherbiases of positioning correlated with distance to great degree. There are little residual high order biases and measurement noise in DD observation equation of rover station after difference correction, so RTK positioning of network with the algorithms can perform wider and more equably.     

一种全球定位系统卫星C/A信号通道绝对时延标定算法

为了精密测量全球定位系统（GPS）卫星C/A（Coarse/Acquisition）信号发射通道时延,提出了一种采用数字信号处理技术的标定算法.对GPS卫星输出的C/A导航信号和时间保持系统的Z计数脉冲进行双通道同步采样,在数字域完成C/A信号预处理后,进行多速率数字信号处理,获取C/A信号中伪随机码起始点;结合Z计数脉冲信号样本数据的处理结果,计算得到C/A信号发射通道的绝对时延.采样率为10 GHz时算法标定结果的不确定度低于0.2 ns.

     

GPS接收机的定位误差分析

基于Superstar Ⅱ GPS接收机和MATLAB实验平台,实现了所有星座误差及信道误差的修正.重点分析了卫星钟差、电离层误差、对流层误差、地球自转效应等误差及修正方法.参照IGS精密星历,利用Klobuchar模型,电离层误差修正掉约14 m;利用高度角模型,对流层误差平均修正掉4.05 m;地球旋转效应误差最大修正掉约30 m;卫星钟差修正后不超过3.1 m.实验结果最终定位精度17 m,验证了误差修正方法的正确性,为今后进行的GPS接收机研制工作积累了经验.     

Ionospheric eclipse factor method (IEFM) for determining the ionospheric delay using GPS data

By establishing the ionospheric eclipse factor (IEF) λ of the ionospheric pierce point (IPP) and its ionospheric influence factor (IFF) λ, and combining λ, λ with t of IPP, a new method of modeling high-precision ionospheric delay using GPS data-ionospheric eclipse factor method (IEFM)-is presented in this paper. The IEFM can effectively select the proper ionospheric models to model the total electron content (TEC) with different changes corresponding to annual, seasonal and diurnal variations. Initial experimental results show that the correction precision of ionospheric delay modeled by the IEFM seems to be close to that of using L3 GPS observations to directly correct the corresponding ionospheric delay.     

Performance analysis of a 3D ionosphere tomographic model

A 3D high precision ionospheric model is developed based on tomography technique. This tomographic model employs GPS data observed by an operational network of dual-frequency GPS receivers. The methodology of developing a 3D ionospheric tomography model is briefly summarized. However emphasis is put on the analysis and evaluation of the accuracy variation of 3D ionosphere modeling with respect to the change of GPS data cutoff angle.Three typical cutoff angle values (15°, 20° and 25°) are tested. For each testing cutoff angle, the performances of the3D ionospheric model constructed using tomography technique are assessed by calibrating the model predicted ionospheric TEC with the GPS measured TEC and by employing the model predicted TEC to a practical GPS positioning application single point positioning (SPP).Test results indicate the 3D model predicted VTEC has about 0.4 TECU improvement in accuracy when cutoff angle rises from 15° to 20°. However, no apparent improvement is found from 20° to 25°. The model's improvement is also validated by the better SPP accuracy of 3D model than its counterpart-dual frequency model in the 20° and 25° cases.     

基于分片线性插值的北斗格网电离层延迟问题研究

为了增强定位精度,需不断提高电离层延迟模型精度,格网电离层模型由于修正效果佳而被广泛应用。针对格网模型构建过程中网格节点处电离层延迟的插值问题,提出了分片线性插值法计算用户端穿透点的电离层延迟。基于格网模型的特征,在同一模型中应用不同的插值算法进行电离层延迟误差的对比,并检验格网电离层垂直延迟修正误差(GIVE)。结果表明,使用分片线性插值法计算的穿透点电离层延迟值更接近于实测数据,GIVE值更小,从而验证了该插值方法计算用户端穿透点的电离层延迟的高准确度。     

Development of an ionospheric scintillation monitor using single frequency GPS receiver

Besides their intended use in radio navigation, global positioning system (GPS) satellite signals provide convenient radio beacons for ionospheric studies. Among other propagation phenomena, the ionosphere affects GPS signal propagation through amplitude scintillations that develop after radio waves propagation through ionospheric electron density irregularities. This paper outlines the design, testing, and results of a specialized GPS receiver to monitorL-band scintillations. The scintillation monitor system consists of a commercial GPS receiver development kit with its software designed to log signal strength and carrier phase from up to 12 channels at one sample per second rate. Other prime features of the monitor include the data compression transmission and processing. Here is the fact that they are inexpensive and compact and therefore can be readily proliferated. Foundation item: Supported by the National Natural Science Foundation of China (No. 49984001) Biography: Shu Di-fei (1973-), male, Master candidate, research direction: studying ionosphere on GPS beacons.     

A generalized trigonometric series function model for determining ionospheric delay

A generalized trigonometric series function (GTSF) model, with an adjustable number of parameters, is proposed and analyzed to study ionosphere by using GPS, especially to provide ionospheric delay correction for single frequency GPS users. The preliminary results show that, in comparison with the trigonometric series function (TSF) model and the polynomial (POLY) model, the GTSF model can more precisely describe the ionospheric variation and more efficiently provide the ionospheric correction when GPS data are used to investigate or extract the earth's ionospheric total electron content. It is also shown that the GTSF model can further improve the precision and accuracy of modeling local ionospheric delays.