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An Evaluation of the Practicability of Current Mapping Functions using Ray-traced Delays from JMA Mesoscale Numerical Weather Data. (1) Ichikawa R., (1) T. Hobiger, (1) Koyama Y., and (1), (2) Kondo T. (1) National Institute of Information and Communications Technology (NICT), Japan - PowerPoint PPT Presentation
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008
An Evaluation of the Practicability of CurAn Evaluation of the Practicability of Current Mapping Functions using Ray-tracerent Mapping Functions using Ray-traced Delays from JMA Mesoscale Numericd Delays from JMA Mesoscale Numeric
al Weather Dataal Weather Data
(1)(1) Ichikawa R., Ichikawa R., (1)(1)T. Hobiger,T. Hobiger, (1)(1) Koyama Y., and Koyama Y., and (1), (2)(1), (2) Kondo T. Kondo T.
(1)(1)National Institute of Information and Communications TechnNational Institute of Information and Communications Technology (NICT), Japanology (NICT), Japan
(2)(2) Ajou University, Republic of Korea Ajou University, Republic of Korea
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ContentContent1.1. MotivationMotivation
2.2. KARATKARAT
3.3. Mapping FunctionsMapping Functions
4.4. Position Error SimulationPosition Error Simulation
5.5. PPP Analysis ResultsPPP Analysis Results
6.6. Summary and OutlookSummary and Outlook
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008MotivatiMotivati
ononVLBI
GNSS
Atmosphere
Analysis
DATA Result
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Motivation Motivation (cont’d)(cont’d)
Estimation of Atmospheric Path Estimation of Atmospheric Path Delay by Ray Tracing Technique Delay by Ray Tracing Technique through Numerical Weather through Numerical Weather ModelsModels• Mitigation of Atmospheric Path Delay Mitigation of Atmospheric Path Delay
ErrorErrorGNSS, VLBI, In-SAR, …etc.GNSS, VLBI, In-SAR, …etc.
• Understanding of Position Error Understanding of Position Error Behavior due to Atmospheric Path Behavior due to Atmospheric Path DelayDelay
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008
KARATKARATKAKAshima shima RARAy-tracing y-tracing TToolool
through Numerical Weather Modelsthrough Numerical Weather Models
Kashima
We are here
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008
NumericalWeather
Model
NumericalWeather
Model
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008
NWM from JMANWM from JMA Japan Meteorological Agency (JMA) provides iJapan Meteorological Agency (JMA) provides i
nformation about nformation about • Pressure (Pressure (PP), temperature (), temperature (TT), rel. humidity (which ), rel. humidity (which
allows to calculate partial pressure of water vapoallows to calculate partial pressure of water vapour – ur – PPvv ))
• Refractivity Refractivity NN can be used to compute tropospher can be used to compute troposphere delaye delay
Mesoscale Analysis Data (MANAL data)Mesoscale Analysis Data (MANAL data)• Raster width 10km (≈ 0.1 deg)Raster width 10km (≈ 0.1 deg)• 21 pressure levels up to 10hPa21 pressure levels up to 10hPa• Time resolution: 3 hrsTime resolution: 3 hrs
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008Covered region ofCovered region of
JMA MANAL dataJMA MANAL data
Boundaries=[107˚,157˚]
=[19˚,49˚]
Countries covered:- Japan (100%)- Korea (100%)- Taiwan (100%)- China (partly)
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008Estimated Zenith Total Estimated Zenith Total
Delay using KARATDelay using KARAT
1st-31st of July, 2006Epoch: 1hr
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Mapping Mapping FunctionsFunctions
e
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aa, , bb, and , and cc are are determined bydetermined by
NWMNWM
NMFNMF Niell[1996]Niell[1996] lat, doy, hgtlat, doy, hgt [none][none]
IMFIMF Niell et al.[2001]Niell et al.[2001] NWMNWM NCEPNCEP
GMFGMF Boehm et al.Boehm et al.[2006][2006]
lat, lon, doy, hgtlat, lon, doy, hgt(indirect use of NWM)(indirect use of NWM)
ECMWFECMWF
VMFVMF Boehm and Boehm and Schuh[2004]Schuh[2004] NWMNWM ECMWFECMWF
Typical Mapping Typical Mapping FunctionsFunctions
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008Comparison of Mapping Comparison of Mapping
Functions (Example)Functions (Example)
Accuracy: VMF < GMF << NMF(Boehm and Schuh[2004])
Kashima
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Position Error Position Error Simulation Simulation
using KARATusing KARAT Position Error BehaviorPosition Error Behavior Evaluation of Mapping FunctionsEvaluation of Mapping Functions
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NWM
misfitresidual
misfitresidual
misfitresidual
misfitresidual
Estimated ZWD
gradientvector
positiopositionn
errorerror
Position Error SimulationPosition Error Simulationusing KARATusing KARAT
watervapor
watervapor
watervapor
watervapor
KARATslant delaySlant delay calculated by MF
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Simulated Position Error due to the NeglSimulated Position Error due to the Neglection of Atmospheric Asymmetryection of Atmospheric Asymmetry
IR Images by GMS
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Simulated Position Error: ComparSimulated Position Error: Comparison at Uchinouraison at Uchinoura
GMF only GMF with gradient
2007
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008PPP PPP
AnalysisAnalysis Period: July 1Period: July 1stst – August 31 – August 31stst, 2007, 2007 Whole GEONET Stations Whole GEONET Stations (~1350 stations)(~1350 stations) GPSTools Ver.0.6.3GPSTools Ver.0.6.3(Takasu and Kasai, 2005)(Takasu and Kasai, 2005)
Comparison of Atmospheric Delay CorrectComparison of Atmospheric Delay Correctionsions
1.1. KARAT reduced RINEXKARAT reduced RINEX2.2. GMF with horizontal gradientGMF with horizontal gradient3.3. GMF w/o horizontal gradientGMF w/o horizontal gradient
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008Meteorological Meteorological
ConditionCondition
(JMA ,2007)
Total Precipitation during2nd – 17thof July, 2007
Typhoon #4(MAN-YI)
(JMA ,2007)
Heavy Rain Fall
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008North-South North-South
Repeatability during 2 Repeatability during 2 MonthsMonths
GMF with gradient < KARAT < GMF only
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008East-West Repeatability East-West Repeatability
during 2 Monthsduring 2 Months
GMF with gradient < KARAT < GMF only
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Station Height Station Height Repeatability during 2 Repeatability during 2 MonthsMonths
GMF with gradient ≤ KARAT < GMF only
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Concluding RemarksConcluding Remarks
Position error simulation is Position error simulation is available.available.• large position errors during heavy large position errors during heavy
rain fall eventsrain fall eventsEx. EW: ~15mm, NS: ~20mm, UD: Ex. EW: ~15mm, NS: ~20mm, UD:
~35mm~35mm
KARAT performance for KARAT performance for atmospheric path delay atmospheric path delay correction in PPP analysis is correction in PPP analysis is evaluated.evaluated.• GMF with gradient ≤ KARAT < GMF onlyGMF with gradient ≤ KARAT < GMF only
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OutlookOutlookHigh Spatial and Temporal High Spatial and Temporal
ResolutionResolution• Numerical weather prediction data Numerical weather prediction data
with more fine meshwith more fine meshEx. JMA 5km MANALEx. JMA 5km MANAL
• Improvement of time interpolation Improvement of time interpolation between two NWM epochsbetween two NWM epochsex. To use numerical weather model ex. To use numerical weather model
such as MM5 is one possibilitysuch as MM5 is one possibility
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Thank you Thank you for your for your
attentionattention
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ResultResult
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GNSS2008@Odaiba,TokyoNov. 11-14, 2008Ray-tracingRay-tracing
Once the data slices have Once the data slices have been prepared ray-tracing been prepared ray-tracing can be carried out very can be carried out very efficiently using analytical efficiently using analytical expressions for the expressions for the calculation of calculation of • 3D - intersection points3D - intersection points
with the sliceswith the slices• Delay inside the Delay inside the
segmentssegments• Bending angle due to Bending angle due to
refractivity gradientsrefractivity gradients
Output of total delay,Output of total delay,bending angle and groundbending angle and groundrefractivityrefractivity