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AnEvalua)onofReal-TimeTroposphereProductsBasedonmul)-
GNSSPrecisePointPosi)oningNormanTeferle1,WenwuDing1,2,Kamil
Kaźmierski3,DenisLaurichesse4,YunbinYuan2
1)UniversityofLuxembourg,Luxembourg2)StateKeyLaboratoryofGeodesyandEarth’sDynamics,Wuhan,China
3)WroclawUniversityofEnvironmentalandLifeSciences,Wroclaw,Poland4)CentreNa<onald’EtudesSpa<ales,Toulouse,France
COST ES1206 Workshop, 21-23 February 2017, ESTEC, Noordwijk, The Netherlands
Overview
• Motivation • Previous results of real-time (RT) Precise Point Positioning (PPP) zenith total delay (ZTD) estimates
• Evaluation of RT PPP ZTD estimates from PPP-Wizard
• Results • Conclusions
GNSSMeteorology
• Assimila)on of GNSS-derived Zenith Total Delay (ZTD) inNumericalWeatherPredic)on(NWP)models– Hasareportedposi)veimpactonweatherforecas)ng– Isinprac)ceatvariousmeteorologicalins)tu)ons
• Low-latencyZTDes)matesareneededforhighupdate-rateNWPmodelsusedfornow-cas)ng
• Meteorologyuserrequirementsfornow-cas)ng(TOUGH,2004):
IntegratedWaterVapour(IWV)
Target Threshold
HorizontalDomain EuropetoNa)onal
Repe;;onCycle 5min 1hour
Integra;onTime MIN(5min,repcycle)
Rela;veAccuracy 1kg/m2 5kg/m2
Timeliness 5min 30min
GNSSMeteorology
• Assimila)on of GNSS-derived Zenith Total Delay (ZTD) inNumericalWeatherPredic)on(NWP)models– Hasareportedposi)veimpactonweatherforecas)ng– Isinprac)ceatvariousmeteorologicalins)tu)ons
• Low-latencyZTDes)matesareneededforhighupdate-rateNWPmodelsusedfornow-cas)ng
• Meteorologyuserrequirementsfornow-cas)ng(TOUGH,2004):
IntegratedWaterVapour(IWV)
Target Threshold
HorizontalDomain EuropetoNa)onal
Repe;;onCycle 5min 1hour
Integra;onTime MIN(5min,repcycle)
Rela;veAccuracy 1kg/m2 5kg/m2
Timeliness 5min 30min
≈ 6 mm, 30 mm in ZTD
GNSSMeteorology
• Assimila)on of GNSS-derived Zenith Total Delay (ZTD) inNumericalWeatherPredic)on(NWP)models– Hasareportedposi)veimpactonweatherforecas)ng– Isinprac)ceatvariousmeteorologicalins)tu)ons
• Low-latencyZTDes)matesareneededforhighupdate-rateNWPmodelsusedfornow-cas)ng
• Meteorologyuserrequirementsfornow-cas)ng(TOUGH,2004):
IntegratedWaterVapour(IWV)
Target Threshold
HorizontalDomain EuropetoNa)onal
Repe;;onCycle 5min 1hour
Integra;onTime MIN(5min,repcycle)
Rela;veAccuracy 1kg/m2 5kg/m2
Timeliness 5min 30min
Mo)va)onforreal-)meprocessing
RTZTDProcessingSystemsatUL• In2014weevaluated
severalRTso]warepackages(BNC,PPP-Wizard,G-nut/Tefnut),seeAhmedetal.(2016)
• SinceJune2015wecontributedtotheGNSS4SWECRTCampaignwith2solu)onsbasedonBNC
• InJuly2015westartedmodifica)onsofPPP-Wizard
• SinceSeptember2015wepredominantlyworkedwiththePPP-Wizard.
26
Table 7 Biases in RT-PPP ZTD solutions to IGFT
Solution Mean [cm] STD [cm] RMS [cm]
BN01 3.17 4.61 6.04
BN02 0.46 2.72 2.92
PWFL 6.81 2.42 14.96
GN01 1.16 0.82 1.43
GN02 1.11 0.80 1.38
RTZTDProcessingSystemsatUL
26
Table 7 Biases in RT-PPP ZTD solutions to IGFT
Solution Mean [cm] STD [cm] RMS [cm]
BN01 3.17 4.61 6.04
BN02 0.46 2.72 2.92
PWFL 6.81 2.42 14.96
GN01 1.16 0.82 1.43
GN02 1.11 0.80 1.38
Largely due to no PCO corrections In PPP-Wizard
• In2014weevaluatedseveralRTso]warepackages(BNC,PPP-Wizard,G-nut/Tefnut),seeAhmedetal.(2016)
• SinceJune2015wecontributedtotheGNSS4SWECRTCampaignwith2solu)onsbasedonBNC
• InJuly2015westartedmodifica)onsofPPP-Wizard
• SinceSeptember2015wepredominantlyworkedwiththePPP-Wizard.
PPP-WizardModifica)onsPPP-WizarddevelopedbyCNES• GPS/GLONASS/Galileoobserva)ons• Real-)meproductsfromCNESCLK93,includingsatelliteorbit,clockand
code/phasebiases• PPPambiguityresolu)on(GPSonly)[zero-differenceambiguity
resolu)on]Modifica;ons• ApplyAntennaReferencePoint(ARP)correc)onfromigs08.atx• ApplyreceiverPCO+PCVcorrec)onfromigs08.atx• Solidearth)de+ocean)deloadingcorrec)on(FES2004)• ZTD(GPTandSaastamoinen)+ZWD(modeledasrandomwalkprocess)• TroposphereMappingFunc)on(GMF)• Eleva)ondependentweigh)ngstrategy(Q=1/cos(zen)**2)
September2015Analysis(Dingetal.,2015)
• Real-)mestreamofmul)-GNSSobserva)onsfromIGS/MGEX
• Real-)meproductsfromCNESCLK93,includingsatelliteorbit,clockandcode/phasebiases
• Eleva)oncut-off:7degrees;processinginterval
• Acon)nuousanalysisofthreeweeks(16/08/2015-05/09/2015)isconducted
• AppliedCODEtroposphericproductsasreferenceforaccuracyevalua)on
• Thefirst1hourofeachini)aliza)onprocesswasignoredintheaccuracyevalua)on
September2015Results:MeanRMSofZWDDifferences
GLO-only Float amb
GPS-only Float amb
GPS-only Fix amb
GPS/GLO Float amb
GPS/GLO/Galileo Fix amb
(Ding et al., 2015)
Spring2016Analysis(Dingetal.,2016)
• Real-)mestreamofmul)-GNSSobserva)onsfromIGS/MGEX
• Real-)meproductsfromCNESCLK93,includingsatelliteorbit,clockandcode/phasebiases(GPS,GlonassandGalileo)
• Eleva)oncut-off:7degrees;processinginterval5s
• Acon)nuousanalysisof1Month(14/02/2016-14/03/2016)isconducted
• Rela)veevalua)onwithCODEandUSNOfinaltroposphericproducts
• Externalevalua)onwithintegratedZTDfromradiosondeprofiles
Real-TimeCampaign2016
20 Global IGS/MGEX Stations: Stations (GPS, Glonass, Galileo) Stations (GPS, Glonass) 13 are close to radiosonde sites
RTSatelliteTrackingatBRST(ExampleforDOY45,2016)
At least 6 GPS and 4 GLONASS satellites were tracked and on average 9 and 7, respectively. For Galileo a maximum of 4 satellites were observed.
RT-PPPZTDSolu)ons
• GPS-only,Glonass-onlyandGPS+Glonass+Galileosolu)ons
• Floatandfixedambiguitysolu)ons
RTZTDforBRST(Example,DOY45,2016)
All data processing modes during the two hours of DOY 45, 2016
Ini)aliza)onTimesforBRST All data processing modes for DOYs 45-75
Forced re-initialization every two hours
AverageIni)aliza)onTimes
All data processing modes, all stations
Solu;on AverageTime[min]
GFLT 10,2
GFIX 9,7
MFLT 8,9
MFIX 8,5
ExampleRTZTDErrorforBRSTwrt final troposphere products from USNO
MeanBiasesandSDofRTZTDwrtUSNO
All biases and SDs are <10mm except for those for RFLT.
AccuracySta)s)csofRTZTDwrtCODEandUSNOFinalProducts
• Sta)s)csforbothbenchmarkproductsaresimilar,withCODEslightlyberer
• RMSofGlonass-onlysolu)onistheworstandofM-GNSSwithambigui)esfixedisbest.
Radiosonde(RS)Observa)ons
• At13Sta)onsitwaspossibletocomparetoRSobserva)ons
• ThesewereobtainedfromtheNa)onalOceanicandAtmosphericAdministra)on(NOAA)EarthSystemResearchLaboratory(ESRL)RSdatabase(hrp://esrl.noaa.gov/raobs/)
• IntegratedZTDsfromRSprofileswerecalculatedusingthemethodinHaaseetal.[2003]withoutlierdetec)onapplied(DousaandBennir,2013)
RTZTDDifferenceswrtZTDfromRSobserva)onsatWTZR
All differences are generally within ±4 cm. RFLT is worst while the STD of the others is about 9 mm.
STDofRTZTDErrorswrtRSObserva)ons
All stations (13) and all data processing modes
Conclusions• WehavebrieflypresentedtheRTPPPZTDprocessingsystemsatUL
– Contribu)onstoGNSS4SWECRTdemonstra)oncampaign– NewRTsystembasedonamodifiedPPP-Wizard
• FortheRTsystemusingPPP-Wizardwefindfora1-Monthcomparison:– Convergence,theresultsrevealthatanaverageini)aliza)on)meof22min
and10minrespec)velybasedonGLONASS-onlyandGPS-onlyobserva)onsisrequired.Theini)aliza)onprocesscanbeacceleratedbybothRTPPPambiguityresolu)onandu)lizingGNSSobserva)ons,wherebythelarer(observinggeometry)ismoreeffec)ve(8,4min).
– Accuracy,theresultsrevealthatallprocessingsystemscanfulfilltheuserrequirementsfornow-cas)ng,however,
– theaccuracyisimprovedmoreeffec)velythroughambiguityresolu)onratherthanusingmul)pleGNSS.ThismightbeduetothelowerqualityoftheGlonassproductsandtheweigh)ngstrategy.
– ThebestaccuracyisachievedfortheMFIXsolu)onwithanRMSofapprox.8mm.
Thankyouforyouraren)onandforyourcollabora)on!
ReferencesAhmedF,VáclavovicP,TeferleFN,DoušaJ,BingleyRMandLaurichesseD(2016).Compara)veanalysisofreal-)meprecisepointposi)oningzenithtotaldelayes)mates.GPSSolu)on,20(2),187-199.DingW,AhmedF,Teferle,FN,Laurichesse,D,Abraha,KE(2015).AnEvalua)onofMul)-GNSSZenithTroposphericDelayProductsbasedonReal-)meSatelliteProducts.5thInterna)onalColloquiumScien)ficandFundamentalAspectsoftheGalileoProgramme,Braunschweig,Germany,October27–29.DingW.,Teferle,FN,Kaźmierski,K,Laurichesse,D,Yuan,Y(2017).Anevalua)onofreal-)metropospherees)ma)onbasedonGNSSprecisepointposi)oning,manuscriptinreview.AcknowledgementsThisprojectispartlyfundedbytheFondsNa<onaldelaRecherche,Luxembourg(ReferenceNo.6823109)andtheNa<onalNaturalScienceFounda<onofChina(GrantNo.41404017).WealsoacknowledgetheCOSTAc)onES1206anditscommunityfordiscussions,collabora)onsandtravelfunds,andarethankfultoBKGfortheirBNCso]ware,theIGSforreal-)meGNSSdataandproducts,andNOAAESRLfortheRSobserva)ons.
Contribu)onstoGNSS4SWECWG1RTCampaign
• UniversityofLuxembourg(UL)providedtwoRT-PPPsolu)ons– Solu)onbasedonGPSobserva)onsonly– Solu)onbasedonGPS+GLONASSobserva)ons
• Processingso]ware:BKGNtripClient(BNC)v2.11
• Discon)nuedduetopoorperformanceanddevelopmentofnewsystembasedonamodifiedPPP-Wizard
Real-TimeSolu;on: ULXG ULXR
ProcessingStrategy PPP PPP
Observa;onsUsed GPSOnly GPS+GLONASS
ProcessingEngine BNC2.11 BNC2.11
InputRawData Real-)mestreams(RTCM3)
Real-)mestreams(RTCM3)
InputClockStream IGS03(IGS) IGS03(IGS)
InputEphemerisStream RTCM3EPH(IGS) RTCM3EPH(IGS)
AmbiguityResolu;on No No