Tropospheric delay is one of the main sources of measurement error in global navigation satellite systems.It is usually compensated by using an empirical correction model.In this paper,temporal and spatial variations ...Tropospheric delay is one of the main sources of measurement error in global navigation satellite systems.It is usually compensated by using an empirical correction model.In this paper,temporal and spatial variations of the global zenith tropospheric delay(ZTD) are further analyzed by ZTD time series from global International GNSS Service stations and annual ZTDs derived from global National Centers for Environmental Prediction reanalysis data,respectively.A new ZTD correction model,named IGGtrop,is developed based on the characteristics of ZTD.Experimental results show that this new 3D-grid-based model that accommodates longitudinal as well as latitudinal variations of ZTD performs better than latitude-only based models(such as UNB3,EGNOS,and UNB3m).The global average bias and RMS for IGGtrop are about-0.8 cm and 4.0 cm,respectively.Bias values for UNB3,EGNOS,and UNB3m are 2.0,2.0,and 0.7 cm,respectively,and respective RMS values 5.4,5.4,and 5.0 cm.IGGtrop shows much more consistent prediction errors for different areas than EGNOS and UNB3m,In China,the performance of IGGtrop(bias values from-2.0 to 0.4 cm and RMS from 2.1 to 6.4 cm) is clearly superior to those of EGNOS and UNB3m.It is also demonstrated that IGGtrop biases vary little with height,and its RMS values tend to decrease with increasing height.In addition,IGGtrop generally estimates ZTD with greater accuracy than EGNOS and UNB3m in the Southern Hemisphere.展开更多
The International GNSS Service(IGS) final products(ephemeris and clocks-correction) have made the GNSS an indispensable low-cost tool for scientific research, for example sub-daily atmospheric water vapor monitoring. ...The International GNSS Service(IGS) final products(ephemeris and clocks-correction) have made the GNSS an indispensable low-cost tool for scientific research, for example sub-daily atmospheric water vapor monitoring. In this study, we investigate if there is a systematic difference coming from the choice between the Vienna Mapping Function 1(VMF1) and the Global Mapping Function(GMF) for the modeling of Zenith Total Delay(ZTD) estimates, as well as the Integrated Precipitable Water Vapor(IPWV) estimates that are deduced from them. As ZTD estimates cannot be fully separated from coordinate estimates, we also investigated the coordinate repeatability between subsequent measurements.For this purpose, we monitored twelve GNSS stations on a global scale, for each of the three climatic zones(polar, mid-latitudes and tropical), with four stations on each zone. We used an automated processing based on the Bernese GNSS Software Version 5.2 by applying the Precise Point Positioning(PPP)approach, L3 Ionosphere-free linear combination, 7 cutoff elevation angle and 2 h sampling. We noticed an excellent agreement with the ZTD estimates and coordinate repeatability for all the stations w.r.t to CODE(the Center for Orbit Determination in Europe) and USNO(US Naval Observatory) products, except for the Antarctic station(Davis) which shows systematic biases for the GMF related results. As a final step, we investigated the effect of using two mapping functions(VMF1 and GMF) to estimate the IPWV,w.r.t the IPWV estimates provided by the Integrated Global Radiosonde Archive(IGRA). The GPS-derived IPWV estimates are very close to the radiosonde-derived IPWV estimates, except for one station in the tropics(Tahiti).展开更多
Nowadays,China BeiDou Navigation Satellite System(BDS)has been developed well and provided global services with highly precise positioning,navigation and timing(PNT)as well as unique short-message communication,partic...Nowadays,China BeiDou Navigation Satellite System(BDS)has been developed well and provided global services with highly precise positioning,navigation and timing(PNT)as well as unique short-message communication,particularly global system(BDS-3)with higher precision multi-frequency signals.The precise point positioning(PPP)can provide the precise position,receiver clock,and zenith tropospheric delay(ZTD)with a stand-alone receiver compared to the traditional double differenced relative positioning mode,which has been widely used in PNT,geodesy,meteorology and so on.However,it has a lot of challenges for multi-frequency BDS PPP with different strategies and more unknown parameters.In this paper,the detailed PPP models using the single-,dual-,triple-,and quad-frequency BDS observations are presented and evaluated.Firstly,BDS system and PPP method are introduced.Secondly,the stochastic models of time delay bias in BDS-2/BDS-3 PPP including the neglection,random constant,random walk and white noise are presented.Then,three single-frequency,four dual-frequency,four triple-frequency and four quad-frequency BDS PPP models are provided.Finally,the BDS PPP models progress and performances including theoretical comparison of the models,positioning performances,precise time and frequency transfer,ZTD,inter-frequency bias(IFB)and differential code bias(DCB)are presented and evaluated as well as future challenges.The results show that the multi-frequency BDS observations will greatly improve the PPP performances.展开更多
The precise correction of atmospheric zenith tropospheric delay(ZTD)is significant for the Global Navigation Satellite System(GNSS)performance regarding positioning accuracy and convergence time.In the past decades,ma...The precise correction of atmospheric zenith tropospheric delay(ZTD)is significant for the Global Navigation Satellite System(GNSS)performance regarding positioning accuracy and convergence time.In the past decades,many empirical ZTD models based on whether the gridded or scattered ZTD products have been proposed and widely used in the GNSS positioning applications.But there is no comprehensive evaluation of these models for the whole China region,which features complicated topography and climate.In this study,we completely assess the typical empirical models,the IGGtropSH model(gridded,non-meteorology),the SHAtropE model(scattered,non-meteorology),and the GPT3 model(gridded,meteorology)using the Crustal Movement Observation Network of China(CMONOC)network.In general,the results show that the three models share consistent performance with RMSE/bias of 37.45/1.63,37.13/2.20,and 38.27/1.34 mm for the GPT3,SHAtropE and IGGtropSH model,respectively.However,the models had a distinct performance regarding geographical distribution,elevation,seasonal variations,and daily variation.In the southeastern region of China,RMSE values are around 50 mm,which are much higher than that in the western region,approximately 20 mm.The SHAtropE model exhibits better performance for areas with large variations in elevation.The GPT3 model and the IGGtropSH model are more stable across different months,and the SHAtropE model based on the GNSS data exhibits superior performance across various UTC epochs.展开更多
基金supported by the National Natural Science Foundation of China (41104103, 41021003, 40890160 and 41074013)the National Science Fund for Distinguished Young Scholars (40625013)the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Tropospheric delay is one of the main sources of measurement error in global navigation satellite systems.It is usually compensated by using an empirical correction model.In this paper,temporal and spatial variations of the global zenith tropospheric delay(ZTD) are further analyzed by ZTD time series from global International GNSS Service stations and annual ZTDs derived from global National Centers for Environmental Prediction reanalysis data,respectively.A new ZTD correction model,named IGGtrop,is developed based on the characteristics of ZTD.Experimental results show that this new 3D-grid-based model that accommodates longitudinal as well as latitudinal variations of ZTD performs better than latitude-only based models(such as UNB3,EGNOS,and UNB3m).The global average bias and RMS for IGGtrop are about-0.8 cm and 4.0 cm,respectively.Bias values for UNB3,EGNOS,and UNB3m are 2.0,2.0,and 0.7 cm,respectively,and respective RMS values 5.4,5.4,and 5.0 cm.IGGtrop shows much more consistent prediction errors for different areas than EGNOS and UNB3m,In China,the performance of IGGtrop(bias values from-2.0 to 0.4 cm and RMS from 2.1 to 6.4 cm) is clearly superior to those of EGNOS and UNB3m.It is also demonstrated that IGGtrop biases vary little with height,and its RMS values tend to decrease with increasing height.In addition,IGGtrop generally estimates ZTD with greater accuracy than EGNOS and UNB3m in the Southern Hemisphere.
基金the innovation carrier project by Zhejiang provincial science and Technology Department (2017F10008)the French Space Agency (CNES) for their funding, through a DAR grant to the Geodesy Observatory of Tahiti
文摘The International GNSS Service(IGS) final products(ephemeris and clocks-correction) have made the GNSS an indispensable low-cost tool for scientific research, for example sub-daily atmospheric water vapor monitoring. In this study, we investigate if there is a systematic difference coming from the choice between the Vienna Mapping Function 1(VMF1) and the Global Mapping Function(GMF) for the modeling of Zenith Total Delay(ZTD) estimates, as well as the Integrated Precipitable Water Vapor(IPWV) estimates that are deduced from them. As ZTD estimates cannot be fully separated from coordinate estimates, we also investigated the coordinate repeatability between subsequent measurements.For this purpose, we monitored twelve GNSS stations on a global scale, for each of the three climatic zones(polar, mid-latitudes and tropical), with four stations on each zone. We used an automated processing based on the Bernese GNSS Software Version 5.2 by applying the Precise Point Positioning(PPP)approach, L3 Ionosphere-free linear combination, 7 cutoff elevation angle and 2 h sampling. We noticed an excellent agreement with the ZTD estimates and coordinate repeatability for all the stations w.r.t to CODE(the Center for Orbit Determination in Europe) and USNO(US Naval Observatory) products, except for the Antarctic station(Davis) which shows systematic biases for the GMF related results. As a final step, we investigated the effect of using two mapping functions(VMF1 and GMF) to estimate the IPWV,w.r.t the IPWV estimates provided by the Integrated Global Radiosonde Archive(IGRA). The GPS-derived IPWV estimates are very close to the radiosonde-derived IPWV estimates, except for one station in the tropics(Tahiti).
基金the National Natural Science Foundation of China(NSFC)Project(Grant No.41761134092)Jiangsu Province Distinguished Professor Project(Grant No.R2018T20)Startup Foundation for Introducing Talent of NUIST(Grant No.2243141801036).
文摘Nowadays,China BeiDou Navigation Satellite System(BDS)has been developed well and provided global services with highly precise positioning,navigation and timing(PNT)as well as unique short-message communication,particularly global system(BDS-3)with higher precision multi-frequency signals.The precise point positioning(PPP)can provide the precise position,receiver clock,and zenith tropospheric delay(ZTD)with a stand-alone receiver compared to the traditional double differenced relative positioning mode,which has been widely used in PNT,geodesy,meteorology and so on.However,it has a lot of challenges for multi-frequency BDS PPP with different strategies and more unknown parameters.In this paper,the detailed PPP models using the single-,dual-,triple-,and quad-frequency BDS observations are presented and evaluated.Firstly,BDS system and PPP method are introduced.Secondly,the stochastic models of time delay bias in BDS-2/BDS-3 PPP including the neglection,random constant,random walk and white noise are presented.Then,three single-frequency,four dual-frequency,four triple-frequency and four quad-frequency BDS PPP models are provided.Finally,the BDS PPP models progress and performances including theoretical comparison of the models,positioning performances,precise time and frequency transfer,ZTD,inter-frequency bias(IFB)and differential code bias(DCB)are presented and evaluated as well as future challenges.The results show that the multi-frequency BDS observations will greatly improve the PPP performances.
基金supported by the National Natural Science Foundation of China(42204022,52174160,52274169)Open Fund of Hubei Luojia Laboratory(230100031)+2 种基金the Open Fund of State Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing,Wuhan University(23P02)the Fundamental Research Funds for the Central Universities(2023ZKPYDC10)China University of Mining and Technology-Beijing Innovation Training Program for College Students(202302014,202202023)。
文摘The precise correction of atmospheric zenith tropospheric delay(ZTD)is significant for the Global Navigation Satellite System(GNSS)performance regarding positioning accuracy and convergence time.In the past decades,many empirical ZTD models based on whether the gridded or scattered ZTD products have been proposed and widely used in the GNSS positioning applications.But there is no comprehensive evaluation of these models for the whole China region,which features complicated topography and climate.In this study,we completely assess the typical empirical models,the IGGtropSH model(gridded,non-meteorology),the SHAtropE model(scattered,non-meteorology),and the GPT3 model(gridded,meteorology)using the Crustal Movement Observation Network of China(CMONOC)network.In general,the results show that the three models share consistent performance with RMSE/bias of 37.45/1.63,37.13/2.20,and 38.27/1.34 mm for the GPT3,SHAtropE and IGGtropSH model,respectively.However,the models had a distinct performance regarding geographical distribution,elevation,seasonal variations,and daily variation.In the southeastern region of China,RMSE values are around 50 mm,which are much higher than that in the western region,approximately 20 mm.The SHAtropE model exhibits better performance for areas with large variations in elevation.The GPT3 model and the IGGtropSH model are more stable across different months,and the SHAtropE model based on the GNSS data exhibits superior performance across various UTC epochs.
