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

1. 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 (2) Ajou University, Republic of Korea

2. Content • Motivation • KARAT • Mapping Functions • Position Error Simulation • PPP Analysis Results • Summary and Outlook

3. Motivation VLBI Atmosphere GNSS Analysis Result DATA

4. Motivation (cont’d) • Estimation of Atmospheric Path Delay by Ray Tracing Technique through Numerical Weather Models • Mitigation of Atmospheric Path Delay Error • GNSS, VLBI, In-SAR, …etc. • Understanding of Position Error Behavior due to Atmospheric Path Delay

5. Kashima We are here KARATKAshima RAy-tracing Toolthrough Numerical Weather Models

6. Numerical Weather Model

7. NWM from JMA • Japan Meteorological Agency (JMA) provides information about • Pressure (P), temperature (T), rel. humidity (which allows to calculate partial pressure of water vapour – Pv) • Refractivity N can be used to compute troposphere delay • Mesoscale Analysis Data (MANAL data) • Raster width 10km (≈ 0.1 deg) • 21 pressure levels up to 10hPa • Time resolution: 3 hrs

8. Covered region ofJMA MANAL data • Boundaries • l=[107˚,157˚] • f=[19˚,49˚] • Countries covered: • Japan (100%) • Korea (100%) • Taiwan (100%) • China (partly)

9. Estimated Zenith Total Delay using KARAT 1st-31st of July, 2006 Epoch: 1hr

10. e Mapping Functions

11. Typical Mapping Functions

12. Comparison of Mapping Functions (Example) Kashima Accuracy: VMF < GMF << NMF (Boehm and Schuh[2004])

13. Position Error Simulation using KARAT • Position Error Behavior • Evaluation of Mapping Functions

14. misfit residual misfit residual misfit residual misfit residual KARAT slant delay Slant delay calculated by MF Position Error Simulationusing KARAT gradient vector Estimated ZWD water vapor water vapor water vapor water vapor NWM position error

15. Simulated Position Error due to the Neglection of Atmospheric Asymmetry IR Images by GMS

16. Simulated Position Error: Comparison at Uchinoura GMF only GMF with gradient 2007

17. PPP Analysis • Period: July 1st – August 31st, 2007 • Whole GEONET Stations (~1350 stations) • GPSTools Ver.0.6.3(Takasu and Kasai, 2005) • Comparison of Atmospheric Delay Corrections • KARAT reduced RINEX • GMF with horizontal gradient • GMF w/o horizontal gradient

18. Meteorological Condition Typhoon #4 (MAN-YI) Total Precipitation during 2nd – 17thof July, 2007 Heavy Rain Fall (JMA ,2007) (JMA ,2007)

19. North-South Repeatability during 2 Months GMF with gradient < KARAT < GMF only

20. East-West Repeatability during 2 Months GMF with gradient < KARAT < GMF only

21. Station Height Repeatability during 2 Months GMF with gradient ≤ KARAT < GMF only

22. Concluding Remarks • Position error simulation is available. • large position errors during heavy rain fall events • Ex. EW: ~15mm, NS: ~20mm, UD: ~35mm • KARAT performance for atmospheric path delay correction in PPP analysis is evaluated. • GMF with gradient ≤ KARAT < GMF only

23. Outlook • High Spatial and Temporal Resolution • Numerical weather prediction data with more fine mesh • Ex. JMA 5km MANAL • Improvement of time interpolation between two NWM epochs • ex. To use numerical weather model such as MM5 is one possibility

24. Thank you for your attention

26. Result

27. Ray-tracing • Once the data slices have been prepared ray-tracing can be carried out very efficiently using analytical expressions for the calculation of • 3D - intersection points with the slices • Delay inside the segments • Bending angle due to refractivity gradients • Output of total delay, bending angle and ground refractivity