In single-frequency precise-point positioning of a satellite,ionosphere delay is one of the most important factors impacting the accuracy. Because of the instability of the ionosphere and uncertainty of its physical p...In single-frequency precise-point positioning of a satellite,ionosphere delay is one of the most important factors impacting the accuracy. Because of the instability of the ionosphere and uncertainty of its physical properties, the positioning accuracy is seriously limited when using a precision-limited model for correction. In order to reduce the error, we propose to introduce some ionosphere parameter for real-time ionosphere-delay estimation by applying various mapping functions. Through calculation with data from the IGS（ International GPS Service） tracking station and comparison among results of using several different models and mapping functions, the feasibility and effectiveness of the new method are verified.展开更多
Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-fre...Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-frequency receivers. However, user has to consider the resultant positioning accuracy. Since the evolution of low-cost single-frequency (LCSF) receivers is typically cheaper than single-frequency high grade receivers, it is possible to obtain comparable positioning accuracy if the corresponding observables are accurately modelled. In this paper, two LCSF GPS receivers are used to form short baseline. Raw GPS measurements are recorded for several consecutive days. The collected data are used to develop the stochastic model of GPS observables from such receivers. Different functions are tested to determine the best fitting model which is found to be 3 parameters exponential decay function. The new developed model is used to process different data sets and the results are compared against the traditional model. Both results from the newly developed and the traditional models are compared with the reference solution obtained from dual-frequency receiver. It is shown that the newly developed model improves the root-mean-square of the estimated horizontal coordinates by about 10% and improves the root-mean-square of the up component by about 39%.展开更多
Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-referencing around the world. It is estimated that over 75% of all GNSS receivers used globally are single frequency rece...Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-referencing around the world. It is estimated that over 75% of all GNSS receivers used globally are single frequency receivers and users experience positioning error due to the ionosphere. To enable GNSS Single Frequency Precise Point Positioning (SFPPP), accurate a-prior information about the ionosphere is needed. The variation of the ionosphere is larger around the magnetic equator and therefore depends on latitude. It will be expected that SFPPP works better on latitude further from the magnetic equator. This present study aims to investigate the accuracy of some ionospheric error mitigation approaches used in single frequency precise point positioning (SFPPP) at several GNSS station in the new Nigerian GNSS Network (NIGNet) and two IGS sites in the low equatorial African region. This study covers two epochs of observation. The first consists of observation from three consecutive days (GPS week 1638;days 0, 1 and 2) that belongs to a period of low solar activities. The second epoch consists of observation from three consecutive days (GPS week 1647;days 2, 3 and 4) that belongs to a high solar activity and intense geomagnetic conditions. The estimated position for the GNSS stations from dual frequency measurement and their known ITRF solutions were used as a benchmark to assess the accuracy of SFPPP under four conditions i.e., SFPPP without ionospheric correction, SFPPP using final GIM models from the Centre for Orbit Determination in Europe( CODE), SFPPP with Klobuchar model, and SFPPP with a computed (local) model at each station. All computation was done using Leica Geo-office software. The result of the study clearly demonstrates the significance of removing or correcting for the effect of the ionosphere, which can result in up to 7 m displacement. It was recommended that GIMs from different organization should be investigated and also efforts should be towards improvement in algorithms and clock error modeling.展开更多
太阳风暴会造成地球电离层剧烈扰动,影响导航定位性能.本文针对2024-05-08—16太阳风暴期间发生的电离层扰动事件,分析了东、西半球不同纬度台站的电离层总电子含量(total electron content,TEC)、电离层TEC变化率、电离层F_(2)层临界...太阳风暴会造成地球电离层剧烈扰动,影响导航定位性能.本文针对2024-05-08—16太阳风暴期间发生的电离层扰动事件,分析了东、西半球不同纬度台站的电离层总电子含量(total electron content,TEC)、电离层TEC变化率、电离层F_(2)层临界频率、卫星导航单点定位误差等.分析认为:电离层向日面会对X射线耀斑发生响应,但是扰动主要来源是太阳风南向磁场能量注入引起的地磁暴;太阳风暴期间电离层顶部和底部的响应并不是同步的;卫星导航单点定位误差在太阳风暴期间会有明显增大,尤其在垂直方向会增大至±10 m,且在电离层暴恢复相期间会持续存在,并随电离层状态趋于平静呈逐渐减弱趋势.展开更多
基金supported by the National Natural Science Foundation of China(40902081,40774001,40841021)
文摘In single-frequency precise-point positioning of a satellite,ionosphere delay is one of the most important factors impacting the accuracy. Because of the instability of the ionosphere and uncertainty of its physical properties, the positioning accuracy is seriously limited when using a precision-limited model for correction. In order to reduce the error, we propose to introduce some ionosphere parameter for real-time ionosphere-delay estimation by applying various mapping functions. Through calculation with data from the IGS（ International GPS Service） tracking station and comparison among results of using several different models and mapping functions, the feasibility and effectiveness of the new method are verified.
文摘Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-frequency receivers. However, user has to consider the resultant positioning accuracy. Since the evolution of low-cost single-frequency (LCSF) receivers is typically cheaper than single-frequency high grade receivers, it is possible to obtain comparable positioning accuracy if the corresponding observables are accurately modelled. In this paper, two LCSF GPS receivers are used to form short baseline. Raw GPS measurements are recorded for several consecutive days. The collected data are used to develop the stochastic model of GPS observables from such receivers. Different functions are tested to determine the best fitting model which is found to be 3 parameters exponential decay function. The new developed model is used to process different data sets and the results are compared against the traditional model. Both results from the newly developed and the traditional models are compared with the reference solution obtained from dual-frequency receiver. It is shown that the newly developed model improves the root-mean-square of the estimated horizontal coordinates by about 10% and improves the root-mean-square of the up component by about 39%.
文摘Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-referencing around the world. It is estimated that over 75% of all GNSS receivers used globally are single frequency receivers and users experience positioning error due to the ionosphere. To enable GNSS Single Frequency Precise Point Positioning (SFPPP), accurate a-prior information about the ionosphere is needed. The variation of the ionosphere is larger around the magnetic equator and therefore depends on latitude. It will be expected that SFPPP works better on latitude further from the magnetic equator. This present study aims to investigate the accuracy of some ionospheric error mitigation approaches used in single frequency precise point positioning (SFPPP) at several GNSS station in the new Nigerian GNSS Network (NIGNet) and two IGS sites in the low equatorial African region. This study covers two epochs of observation. The first consists of observation from three consecutive days (GPS week 1638;days 0, 1 and 2) that belongs to a period of low solar activities. The second epoch consists of observation from three consecutive days (GPS week 1647;days 2, 3 and 4) that belongs to a high solar activity and intense geomagnetic conditions. The estimated position for the GNSS stations from dual frequency measurement and their known ITRF solutions were used as a benchmark to assess the accuracy of SFPPP under four conditions i.e., SFPPP without ionospheric correction, SFPPP using final GIM models from the Centre for Orbit Determination in Europe( CODE), SFPPP with Klobuchar model, and SFPPP with a computed (local) model at each station. All computation was done using Leica Geo-office software. The result of the study clearly demonstrates the significance of removing or correcting for the effect of the ionosphere, which can result in up to 7 m displacement. It was recommended that GIMs from different organization should be investigated and also efforts should be towards improvement in algorithms and clock error modeling.
文摘太阳风暴会造成地球电离层剧烈扰动,影响导航定位性能.本文针对2024-05-08—16太阳风暴期间发生的电离层扰动事件,分析了东、西半球不同纬度台站的电离层总电子含量(total electron content,TEC)、电离层TEC变化率、电离层F_(2)层临界频率、卫星导航单点定位误差等.分析认为:电离层向日面会对X射线耀斑发生响应,但是扰动主要来源是太阳风南向磁场能量注入引起的地磁暴;太阳风暴期间电离层顶部和底部的响应并不是同步的;卫星导航单点定位误差在太阳风暴期间会有明显增大,尤其在垂直方向会增大至±10 m,且在电离层暴恢复相期间会持续存在,并随电离层状态趋于平静呈逐渐减弱趋势.
文摘电离层延迟可严重制约单频接收机的定位精度.基于此,本文介绍了四种单频接收机常用的电离层延迟改正方法,包括广播电离层改正模型(策略1),顾及太阳位置的变化全球电离层格网产品(Global Ionosphere Map,GIM)时间旋转内插(策略2),GIM投影函数改正(策略3)和半合改正模型(策略4).同时,选择不同太阳活动期,不同纬度的测站验证不同电离层改正方法的单频精密单点定位(single-frequency point positioning,SF-PPP)定位结果偏差.经过对比分析,得到如下结论:1)总体来说,半合改正模型得到的定位效果最佳,其次是使用GIM产品对电离层延迟进行改正,最后是广播电离层模型;2)在不同太阳活动跃期,不同策略在低纬度测站的定位偏差最大,其次是高纬度测站,中纬度测站的定位偏差最小;3)策略2和策略3在不同太阳活动期不同纬度测站的水平定位平差约0.150 m,三维定位偏差约0.700 m;策略4在不同太阳活动期不同纬度测站的水平定位偏差为0.100 m,三维定位偏差为0.500 m.
