In December of 2019,a novel coronavirus(2019-nCoV)emerged in Wuhan China,which was later named COVID-19(1).It quickly spread and as of February 11,2020,there were 38,800 laboratoryconfirmed cases,16,067 suspected case...In December of 2019,a novel coronavirus(2019-nCoV)emerged in Wuhan China,which was later named COVID-19(1).It quickly spread and as of February 11,2020,there were 38,800 laboratoryconfirmed cases,16,067 suspected cases,and 1,113 attributable deaths that have affected all provinciallevel administrative divisions(PLADs)of China's Mainland(2).The first confirmed COVID-19 case in Shenyang City,the capital of Liaoning Province,occurred on January 22,2020,with a total of 9 confirmed cases by January 29,2020.Of these cases,4 were clustered in one family.Shenyang CDC immediately launched an investigation to determine routes of transmission,scale of the outbreak,and evidence for epidemic control.展开更多
Precise point positioning(PPP)is famous for its capability of high-precision positioning with just one station as long as the receiver can receive global navigation satellite system(GNSS)signals.With the rapid develop...Precise point positioning(PPP)is famous for its capability of high-precision positioning with just one station as long as the receiver can receive global navigation satellite system(GNSS)signals.With the rapid development of BDS and Galileo,the number of available satellites for positioning has increased significantly.In addition,GPS III,GLONASS-K,BDS,and Galileo satellites can transmit triple-frequency signals.The potentials of multi-constellation GNSS PPP requires further analysis on a global scale.Therefore,we selected 96 multi-GNSS experiment(MGEX)stations with a global distribution and used 1 week’s data to assess the PPP performance.The results show that the PPP based on multi-frequency raw observations with spatial and temporal constraints has better performance than PPP using dual-frequency ionospheric-free observations.The main contribution of multi-constellation GNSS PPP is to shorten the convergence time.The convergence time for GPS PPP is approximately 40 min,which can be shortened to less than 20 min in multi-GNSS PPP.After convergence,the positioning accuracy of multi-GNSS PPP is improved by 0.5 to 1.0 cm compared with GPS or GLONASS PPP.The positioning accuracy of multi-GNSS could be further improved in the future with the BDS and Galileo precise products of orbits,clock and phase center offset/variation.展开更多
文摘In December of 2019,a novel coronavirus(2019-nCoV)emerged in Wuhan China,which was later named COVID-19(1).It quickly spread and as of February 11,2020,there were 38,800 laboratoryconfirmed cases,16,067 suspected cases,and 1,113 attributable deaths that have affected all provinciallevel administrative divisions(PLADs)of China's Mainland(2).The first confirmed COVID-19 case in Shenyang City,the capital of Liaoning Province,occurred on January 22,2020,with a total of 9 confirmed cases by January 29,2020.Of these cases,4 were clustered in one family.Shenyang CDC immediately launched an investigation to determine routes of transmission,scale of the outbreak,and evidence for epidemic control.
基金China Scholarship Council(CSC).Under the foundation of CSC,the first author was given the opportunity to study at the University of Nottingham,UK to complete this research with Prof.Meng and Prof.Jiang.
文摘Precise point positioning(PPP)is famous for its capability of high-precision positioning with just one station as long as the receiver can receive global navigation satellite system(GNSS)signals.With the rapid development of BDS and Galileo,the number of available satellites for positioning has increased significantly.In addition,GPS III,GLONASS-K,BDS,and Galileo satellites can transmit triple-frequency signals.The potentials of multi-constellation GNSS PPP requires further analysis on a global scale.Therefore,we selected 96 multi-GNSS experiment(MGEX)stations with a global distribution and used 1 week’s data to assess the PPP performance.The results show that the PPP based on multi-frequency raw observations with spatial and temporal constraints has better performance than PPP using dual-frequency ionospheric-free observations.The main contribution of multi-constellation GNSS PPP is to shorten the convergence time.The convergence time for GPS PPP is approximately 40 min,which can be shortened to less than 20 min in multi-GNSS PPP.After convergence,the positioning accuracy of multi-GNSS PPP is improved by 0.5 to 1.0 cm compared with GPS or GLONASS PPP.The positioning accuracy of multi-GNSS could be further improved in the future with the BDS and Galileo precise products of orbits,clock and phase center offset/variation.
