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.     

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

Foracertainionosphericregion,duetomanyfactorsespeciallytheinvisiblesolarradiation,thechangelawofthetotalelectroncontent(TEC)isdifferentindaytimeandnighttime.ThecorrespondingmathematicalexpressionsofTECshouldalsobedifferent.Therefore,whenusingGPStomodelpreciseionosphericdelay,oneofthecriticalfactorsistoexactlydistinguishtheionosphericdaytimeandnighttimeandreasonablydescribetheTECchangecharacteristicsofthedifferentperiodsattheionosphericpiercepoint(IPP).Inthepast,inthefieldsofGPSresearcha…     

Variation properties of ionospheric eclipse factor and ionospheric influence factor

The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal an d spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay bas ed on the above variation properties is also analysed.     

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 ...     

Preliminary results and analyses of using IGS GPS data to determine global ionospheric TEC

Using the spherical harmonic (SH) function model and the dual frequency GPS data of 139 International GPS Service (IGS) stations for July 15 of 2000, the global ionospheric total electron content (TEC) is calculated and the basic method is investigated. Here, preliminary results are reported and the problems and difficulties to be solved for using GPS data to determine the global ionospheric TEC are discussed.     

Models and methods for precise determination of ionospheric delay using GPS

The basic principles and methods for precisely determining ionospheric delays in GPS observations are introduced and discussed. Various methods and models for fitting ionospheric delays based on GPS are compared and analyzed, and applications of the methods and models to the research and engineering are summarized.     

Models and methods for precise determination of ionospheric delay using GPS

The basic principles and methods for precisely determining ionospheric delays in GPS observations are introduced and discussed. Various methods and models for fitting ionospheric delays based on GPS are compared and analyzed, and applications of the methods and models to the research and engineering are summarized.     

Ionospheric responses to a total solar eclipse deduced by the GPS beacon observations

The total electron content (TEC) data during the total eclipse of March 9, 1997 were collected, which were observed by means of nine GPS receivers located at the eastern Asia. The responses of total TEC to the eclipse were analyzed. The results show that: 1) the eclipse led to apparent decrement in TEC that lasted for six to eight hours; 2) the maximum decrement occurred after the middle of the eclipse with time-delays varying from twenty minutes to about three hours; 3) the maximum absolute deviations of TEC on the eclipse day do not show a simple and consistent relationship to the maximum solar obscuration. Foundation item: Supported by the National Natural Science Foundation of China(49684002) Biography: CHEN An-hua (1976-), female, Master candidate. Research interests: studying ionosphere by GPS beacons.     

Storm-time ionospheric disturbances monitored by GPS beacon measurements

The Total Electron Content (TEC) during three great storms, from April to August 2000, was collected by means of a GPS receiver located in Jingzhou (30.4° N, 112.2° E). The time-latitude-dependent features of ionospheric storms are identified using TEC difference images based on the deviations of TEC during storm relative to quiet time. The responses of ionospheric TEC to magnetic storms were analyzed. The results show that: 1) In middle and low latitude, ionospheric storms effects are more apparent in local day time than at night: 2) Ionospheric storm effects are more dominant near the hump of the equatorial anomaly region than in other regions of TEC measurements; 3) The positive effects during the main phase of ionospheric storm may be caused by electric fields in low latitude; 4) During the recovery period of ionospheric storm, the negative phase of storm may be due to the perturbation of the neutral gas composition. Foundation item: Supported by the National Natural Science Foundation of China (49984001) Biography: Pei Xiao-hong (1977-), male, Master candidate, research direction: studying ionosphere on GPS beacons.     

我国中低纬地区GPS定位中的电离层二阶项延迟影响分析与研究

基于消除电离层一阶项延迟的双频载波相位Lc线性组合观测量,利用中国地壳运动观测网络以及国际IGS（International GNSS Service）提供的6个跟踪站连续15天的观测数据,初步分析和研究了电离层二阶项延迟对我国中低纬地区全球定位系统（Global Positioning System,GPS）定位结果的影响.研究结果表明,在电离层二阶项延迟影响下,我国中低纬地区GPS定位结果呈普遍规律性南移的现象,且各地区南偏趋势差异甚微.     

Analysis of ionospheric anomalies before the 2011 <Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> 9.0 Japan earthquake

On March 11, 2011, a large earthquake of Mw=9.0 occurred near the east coast of Honshu, Japan. This paper investigates preearthquake ionospheric anomalies during the earthquake period, using data from global navigation satellite systems and ionosonde stations near the epicenter. A clear anomaly that occurred on March 8 lasted 6 hours. Eliminating ionospheric anomalies that may have been caused by solar activities and magnetic storms, we believe that a positive anomaly on March 8 was very possibly an ionospheric precursor. The affected ionospheric area on March 8, which is evident on a vertical total electron content distribution map, extended to 50° in longitude and 20° in latitude, with length ratio approximately 3:1. The anomaly peak arose from 15:00-19:00 LT, and its location did not coincide with the vertical projection of the epicenter, but was instead to its south. Corresponding ionospheric anomalies are also observed in the magnetically conjugated region. There were no obvious ionospheric anomalies in other parts of the world. To analyze changes in the ionospheric anomaly, computerized ionospheric tomography technology was used to invert the spatial and temporal distribution of electron density in the ionosphere. The ionospheric anomaly on March 8, 2011 is suggested to be an ionospheric precursor of the March 11 earthquake in Japan.     

GPS信号的码相位交错捕获方法

为了使全球定位系统(GPS)接收机的信号捕获搜索过程更加有效,在传统捕获方法的基础上进行了改进,提出一种新的捕获方法。通过分析传统捕获方法的性能,在几何上对捕获点的分布进行了优化设计,并对其捕获性能进行了分析比较。新算法可以在捕获相关峰平均衰减值相同的情况下,增加捕获分格的面积,减少整个搜索区域的捕获时间。仿真结果表明:该方法在平均衰减性能和最大衰减性能方面都优于传统捕获方法,且衰减值分布均匀,捕获性能更加稳定。     

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.     

Study of the ionospheric TEC using GPS during the large solar flare burst on Nov. 6, 1997

Using the data from 15 global positioning system (GPS) stations scattered between 28° N—45° N and 90° W—77° E we obtained the total electron content (TEC) variations with time during a large solar flare. The results indicated that the flare makes the TEC of ionosphere increasing in a large spatial area. The amounts of the TEC enhancement are mainly determined by the local time of subionospheric point, and the largest TEC enhancement is about 2.5 TECU. It is also concluded that the TEC enhancement is not symmetrical about the local noon time, the TEC enhancement values during morning hours are larger than those of the afternoon hours.     

基于联邦Kalman滤波的Wi-Fi/GPS车辆组合定位系统

针对全球卫星定位系统(GPS)在密集城市地带、隧道、室内停车场等环境下不可用及Wi-Fi定位精度不足的问题,提出了一种Wi-Fi/GPS组合定位系统.该系统基于联邦Kalman滤波器,先通过两个并行的局部滤波器获得Wi-Fi、GPS定位子系统的局部最优估计,再由主滤波器融合得到最优全局估计.仿真结果表明:较之单独使用G...     

高层建筑动态变形的GPS监测技术

介绍了利用GPS技术测量高层建筑变形的原理及试验模拟与监测过程;重点阐述了GPS动态特征模拟数学模型及不同外界环境条件下试验数据的采集及分析过程;通过对试验数据的分析处理,阐明了GPS技术在高层建筑动态变形监测中应用的可行性,指出了将GPS技术和自动分析及控制技术结合后在工程测量领域具有广泛应用前景。     

基于通用相关器的高动态GPS信号并行快速捕获

高动态全球定位系统(GPS)信号的快速捕获是GPS接收机的关键技术之一,然而现有算法难以兼顾捕获速度和硬件成本。该文研究在低成本通用GPS器件上实现快速捕获算法。对高动态GPS信号的并行捕获方法基于商用GPS系列芯片GP4000进行了改进,通过扩大算法频率搜索步长提高搜索效率。对该算法进行仿真验算并利用接收的GPS卫星信号进行实测。结果表明:改进算法可以有效地扩大GPS接收机频率搜索步长,提高接收到的卫星信号的质量,同时缩短卫星信号的搜索时间。     

一种基于频率补偿的GPS位同步方法

针对GPS接收机在跟踪过程中由频率误差引起的位同步概率下降问题,提出了一种基于频率补偿的GPS位同步方法.分析了环路中频率误差引起相干积分累加值衰减的机理,利用不同频率的复信号分别对相干积分结果进行补偿,计算出20个候选位置的值,最大值对应的位置即为数据边界位置.该方法有效减少了由频率误差导致的相干累加损耗,提高了位同步的概率.在弱信号情况下,使用非相干积分方法可进一步提高信号增益和位同步概率.与其他位同步方法相比,所提方法可容忍更大的频率误差,即使跟踪环路处于失锁状态也能准确实现位同步,且在频率误差小于25 Hz的情况下表现出更优的位同步性能.     

基于时钟偏差模型的GPS不完整星座定位方法

为使GPS接收机在卫星星座不完整情况下仍能定位,提出采用接收机时钟偏差模型辅助接收机定位的方法.将模型预测的时钟偏差引入伪距线性化定位解算方程中,保证了在GPS星座不完整时仍能给出接收机的位置.基于GPS实测数据的验证分析表明,该方法的定位精度在标准误差范围内.同时,该方法具有计算简单、有效可行的特点,可以方便地嵌入到GPS接收机中.     

GPS非差数据周跳探测的TECR-MW综合法

针对电离层总电子含量变化率(TECR)方法和双频码相组合(MW)方法探测周跳各自的局限性,综合利用TECR法和MW法进行周跳探测。首先采用TECR法探测周跳,然后用MW法进行第2次探测,最后综合电离层TECR法和MW法的宽巷模糊度探测L₁频率和L₂频率上发生的周跳。这种综合探测法不受接收机与卫星间的几何距离、接收机钟差和卫星钟差、电离层折射的影响。采用实测数据进行试验,结果表明,综合利用TECR法与MW法探测GPS周跳比采用单一方法探测周跳更加有效、可靠。