The tropospheric delay is a significant error source in Global Navigation Satellite System(GNSS)positioning and navigation.It is usually projected into zenith direction by using a mapping function.It is particularly i...The tropospheric delay is a significant error source in Global Navigation Satellite System(GNSS)positioning and navigation.It is usually projected into zenith direction by using a mapping function.It is particularly important to establish a model that can provide stable and accurate Zenith Tropospheric Delay(ZTD).Because of the regional accuracy difference and poor stability of the traditional ZTD models,this paper proposed two methods to refine the Hopfield and Saastamoinen ZTD models.One is by adding annual and semi-annual periodic terms and the other is based on Back-Propagation Artificial Neutral Network(BP-ANN).Using 5-year data from 2011 to 2015 collected at 67 GNSS reference stations in China and its surrounding regions,the four refined models were constructed.The tropospheric products at these GNSS stations were derived from the site-wise Vienna Mapping Function 1(VMP1).The spatial analysis,temporal analysis,and residual distribution analysis for all the six models were conducted using the data from 2016 to 2017.The results show that the refined models can effectively improve the accuracy compared with the traditional models.For the Hopfield model,the improvement for the Root Mean Square Error(RMSE)and bias reached 24.5/49.7 and 34.0/52.8 mm,respectively.These values became 8.8/26.7 and 14.7/28.8 mm when the Saastamoinen model was refined using the two methods.This exploration is conducive to GNSS navigation and positioning and GNSS meteorology by providing more accurate tropospheric prior information.展开更多
The last satellite of BeiDou Navigation Satellite System with Global Coverage(BDS-3)constellation was successfully launched on June 23rd,2020,and the entire system began to provide Positioning,Navigation,and Timing(PN...The last satellite of BeiDou Navigation Satellite System with Global Coverage(BDS-3)constellation was successfully launched on June 23rd,2020,and the entire system began to provide Positioning,Navigation,and Timing(PNT)services worldwide.We evaluated the performance of location services using BDS with a smartphone that can track the Global Navigation Satellite System(GNSS)satellites in Nottingham,UK.The static and kinematic experiments were conducted in an open meadow and a lakeside route covered by trees,respectively.Experimental results show that BDS has good visibility,and its overall signal carrier-to-noise density ratio(C/N0)is comparable to that of Global Positioning System(GPS).The average C/N0 of BDS-3 satellites with elevation angles above 45°on B1 band is the highest among all systems,reaching 40.0 dB·Hz.The noise level of the BDS pseudorange measurements is within 0.5 m,and it has a good consistency among satellites.In the static experiment,the standard deviations of BDS position-ing in the east,north and up directions are 1.09,1.16,and 3.02 m,respectively,and the R95 value of the horizontal position is 2.88 m.In harsh environments,the number of BDS satellites tracked by the smartphone is susceptible to environmental factors.The bias Root Mean Squares(RMS)in the three directions of the whole kinematic positioning are 6.83,6.68,11.67 m,in which the positioning bias RMS values in a semi-open environment are only 2.81,1.11,3.29 m.Furthermore,the inclusion of BDS in multiple GNSS systems can significantly improve the positioning precision.This study intends to provide a reference for the further improvements of BDS global PNT services,particularly for Location-Based Services(LBS).展开更多
基金the Fundamental Research Funds for the Central Universities(No.2021XJDC01)the State Key Laboratory of Resources and Environmental Information System,the Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan University(No.19-02-08)+1 种基金the Guangxi Key Laboratory of Spatial Information and Geomatics(No.19-050-11-01)the National Natural Science Foundation of China(Nos.41804038,42001368).
文摘The tropospheric delay is a significant error source in Global Navigation Satellite System(GNSS)positioning and navigation.It is usually projected into zenith direction by using a mapping function.It is particularly important to establish a model that can provide stable and accurate Zenith Tropospheric Delay(ZTD).Because of the regional accuracy difference and poor stability of the traditional ZTD models,this paper proposed two methods to refine the Hopfield and Saastamoinen ZTD models.One is by adding annual and semi-annual periodic terms and the other is based on Back-Propagation Artificial Neutral Network(BP-ANN).Using 5-year data from 2011 to 2015 collected at 67 GNSS reference stations in China and its surrounding regions,the four refined models were constructed.The tropospheric products at these GNSS stations were derived from the site-wise Vienna Mapping Function 1(VMP1).The spatial analysis,temporal analysis,and residual distribution analysis for all the six models were conducted using the data from 2016 to 2017.The results show that the refined models can effectively improve the accuracy compared with the traditional models.For the Hopfield model,the improvement for the Root Mean Square Error(RMSE)and bias reached 24.5/49.7 and 34.0/52.8 mm,respectively.These values became 8.8/26.7 and 14.7/28.8 mm when the Saastamoinen model was refined using the two methods.This exploration is conducive to GNSS navigation and positioning and GNSS meteorology by providing more accurate tropospheric prior information.
基金the National Natural Science Foundation of China(41774027)the National Key Research and Development Program(2016YFB0502101)+1 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX19_0067)the CoDRIVE demonstration project funded under the European Space Agency’s Business Applications initiatives(ESA CoDRIVE Contract Number:4000126688/19/NL/FGL).
文摘The last satellite of BeiDou Navigation Satellite System with Global Coverage(BDS-3)constellation was successfully launched on June 23rd,2020,and the entire system began to provide Positioning,Navigation,and Timing(PNT)services worldwide.We evaluated the performance of location services using BDS with a smartphone that can track the Global Navigation Satellite System(GNSS)satellites in Nottingham,UK.The static and kinematic experiments were conducted in an open meadow and a lakeside route covered by trees,respectively.Experimental results show that BDS has good visibility,and its overall signal carrier-to-noise density ratio(C/N0)is comparable to that of Global Positioning System(GPS).The average C/N0 of BDS-3 satellites with elevation angles above 45°on B1 band is the highest among all systems,reaching 40.0 dB·Hz.The noise level of the BDS pseudorange measurements is within 0.5 m,and it has a good consistency among satellites.In the static experiment,the standard deviations of BDS position-ing in the east,north and up directions are 1.09,1.16,and 3.02 m,respectively,and the R95 value of the horizontal position is 2.88 m.In harsh environments,the number of BDS satellites tracked by the smartphone is susceptible to environmental factors.The bias Root Mean Squares(RMS)in the three directions of the whole kinematic positioning are 6.83,6.68,11.67 m,in which the positioning bias RMS values in a semi-open environment are only 2.81,1.11,3.29 m.Furthermore,the inclusion of BDS in multiple GNSS systems can significantly improve the positioning precision.This study intends to provide a reference for the further improvements of BDS global PNT services,particularly for Location-Based Services(LBS).
