Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position ac...Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).展开更多
北斗三号全球卫星导航系统(BDS-3)于2020年7月31日正式开通,其空间段服务能力是决定系统整体性能表现的重要因素.本文对广播轨道、广播钟差、空间信号测距误差、广播电离层精度的评估计算方法进行了分析,分别以GFZ(German Research Cent...北斗三号全球卫星导航系统(BDS-3)于2020年7月31日正式开通,其空间段服务能力是决定系统整体性能表现的重要因素.本文对广播轨道、广播钟差、空间信号测距误差、广播电离层精度的评估计算方法进行了分析,分别以GFZ(German Research Centre for Geosciences)和iGMAS(International GNSS Monitoring and Assessment System)的最终产品为参考基准,对系统从2020年正式开通至2025年的变化情况进行了评估分析.研究表明, BDS-3广播轨道精度呈现明显的卫星类型相关性, MEO卫星高于IGSO卫星,与GFZ产品和iGMAS产品相比,径向、切向、法向95%的RMS值均得到不同程度地改善;广播钟差误差与SISRE(Signal-InSpace Range Error) 95%的RMS值则提升了分米级的精度;电离层模型误差方面,在评估周期内, Klobuchar模型的VTEC值分布范围相对较广,低VTEC区间BDGIM模型的频次分布更为集中;与CODE和iGMAS电离层产品相比,在太阳活动极小期的2020年BDGIM(Beidou Global Lonospheric Delay Correction Model)模型VTEC平均RMS值优于Klobuchar模型,而在太阳活动极大期的2025年两模型的VTEC平均RMS值均呈上升的趋势,且BDGIM模型的稳定性更强.展开更多
文摘Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).
文摘北斗三号全球卫星导航系统(BDS-3)于2020年7月31日正式开通,其空间段服务能力是决定系统整体性能表现的重要因素.本文对广播轨道、广播钟差、空间信号测距误差、广播电离层精度的评估计算方法进行了分析,分别以GFZ(German Research Centre for Geosciences)和iGMAS(International GNSS Monitoring and Assessment System)的最终产品为参考基准,对系统从2020年正式开通至2025年的变化情况进行了评估分析.研究表明, BDS-3广播轨道精度呈现明显的卫星类型相关性, MEO卫星高于IGSO卫星,与GFZ产品和iGMAS产品相比,径向、切向、法向95%的RMS值均得到不同程度地改善;广播钟差误差与SISRE(Signal-InSpace Range Error) 95%的RMS值则提升了分米级的精度;电离层模型误差方面,在评估周期内, Klobuchar模型的VTEC值分布范围相对较广,低VTEC区间BDGIM模型的频次分布更为集中;与CODE和iGMAS电离层产品相比,在太阳活动极小期的2020年BDGIM(Beidou Global Lonospheric Delay Correction Model)模型VTEC平均RMS值优于Klobuchar模型,而在太阳活动极大期的2025年两模型的VTEC平均RMS值均呈上升的趋势,且BDGIM模型的稳定性更强.
