1. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 1/24 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) Koyama Y., and (1), (2) Kondo T. (1) National Institute of Information and Communications Technology (NICT), Japan (2) Ajou University, Republic of Korea

2. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 2/24 Content 1.Motivation 2.KARAT 3.Mapping Functions 4.Position Error Simulation 5.PPP Analysis Results 6.Summary and Outlook

3. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 3/24 Motivation VLBI GNSS Atmosphere Analysis DATA Result

4. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 4/24 Motivation (cont’d)  Estimation of Atmospheric Path Delay by Ray Tracing Technique through Numerical Weather Models Mitigation of Atmospheric Path Delay ErrorMitigation of Atmospheric Path Delay Error  GNSS, VLBI, In-SAR, …etc. Understanding of Position Error Behavior due to Atmospheric Path DelayUnderstanding of Position Error Behavior due to Atmospheric Path Delay

5. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 5/24 KARAT KAshima RAy-tracing Tool through Numerical Weather Models Kashima We are here

6. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 6/24 Numerical Weather Model Numerical Weather Model

7. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 7/24 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 – P v )Pressure (P), temperature (T), rel. humidity (which allows to calculate partial pressure of water vapour – P v ) Refractivity N can be used to compute troposphere delayRefractivity N can be used to compute troposphere delay  Mesoscale Analysis Data (MANAL data) Raster width 10km (≈ 0.1 deg)Raster width 10km (≈ 0.1 deg) 21 pressure levels up to 10hPa 21 pressure levels up to 10hPa Time resolution: 3 hrsTime resolution: 3 hrs

8. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 8/24 Covered region of JMA MANAL data Boundaries =[107˚,157˚]  = [19˚,49 ˚ ] Countries covered: - Japan (100%) - Korea (100%) - Taiwan (100%) - China (partly)

9. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 9/24 Estimated Zenith Total Delay using KARAT 1 st -31 st of July, 2006 Epoch: 1hr

10. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 10/24 Mapping Functions e

11. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 11/24 a, b, and c are determined by NWM NMFNiell[1996] lat, doy, hgt [none] IMF Niell et al.[2001] NWMNCEP GMF Boehm et al.[2006] lat, lon, doy, hgt (indirect use of NWM) ECMWF VMF Boehm and Schuh[2004] NWMECMWF Typical Mapping Functions

12. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 12/24 Comparison of Mapping Functions (Example) Accuracy: VMF < GMF << NMF (Boehm and Schuh[2004]) Kashima

13. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 13/24 Position Error Simulation using KARAT  Position Error Behavior  Evaluation of Mapping Functions

14. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 14/24 NWM misfit residual misfit residual misfit residual misfit residual Estimated ZWD gradient vector position error Position Error Simulation using KARAT water vapor water vapor water vapor water vapor KARAT slant delay Slant delay calculated by MF

15. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 15/24 Simulated Position Error due to the Neglection of Atmospheric Asymmetry IR Images by GMS

16. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 16/24 Simulated Position Error: Comparison at Uchinoura GMF onlyGMF with gradient 2007

17. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 17/24 PPP Analysis  Period: July 1 st – August 31 st, 2007  Whole GEONET Stations (~1350 stations)  GPSTools Ver.0.6.3 (Takasu and Kasai, 2005)  Comparison of Atmospheric Delay Corrections 1.KARAT reduced RINEX 2.GMF with horizontal gradient 3.GMF w/o horizontal gradient

18. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 18/24 Meteorological Condition (JMA,2007) Total Precipitation during 2 nd – 17 th of July, 2007 Typhoon #4 (MAN-YI) (JMA,2007) Heavy Rain Fall

19. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 19/24 North-South Repeatability during 2 Months GMF with gradient < KARAT < GMF only

20. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 20/24 East-West Repeatability during 2 Months GMF with gradient < KARAT < GMF only

21. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 21/24 Station Height Repeatability during 2 Months GMF with gradient ≤ KARAT < GMF only

22. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 22/24 Concluding Remarks  Position error simulation is available. large position errors during heavy rain fall eventslarge 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 onlyGMF with gradient ≤ KARAT < GMF only

23. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 23/24 Outlook  High Spatial and Temporal Resolution Numerical weather prediction data with more fine meshNumerical weather prediction data with more fine mesh  Ex. JMA 5km MANAL Improvement of time interpolation between two NWM epochsImprovement of time interpolation between two NWM epochs  ex. To use numerical weather model such as MM5 is one possibility

24. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 24/24 Thank you for your attention

25. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 25/24

26. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 26/24 Result

27. GNSS2008@Odaiba,Tokyo Nov. 11-14, 2008 27/24 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 points3D - intersection points with the slices with the slices Delay inside the segmentsDelay inside the segments Bending angle due toBending angle due to refractivity gradients  Output of total delay, bending angle and ground refractivity