(1) Ichikawa R., (1) T. Hobiger, (1) Koyama Y., and (1), (2) Kondo T

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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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KARATKARATKAKAshima shima RARAy-tracing y-tracing TToolool

through Numerical Weather Modelsthrough Numerical Weather Models

Kashima

We are here

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NumericalWeather

Model

NumericalWeather

Model

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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

Documents

(1) Ichikawa R., (1) T. Hobiger, (1) Koyama Y., and (1), (2) Kondo T