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