1. VTEC prediction using a recursive artificial neural networks approach in Brazil: initial results Engineer School - University of São Paulo Wagner Carrupt Machado Edvaldo Simões da Fonseca Junior MImOSA workshop – february 26th 2013 – INPE - São José dos Campos - Brazil

2. 2 Presentation outline IBGE interest, infrastructure and needs; Artificial Neural Networks approach; Experiments and Results: Solar activity and geomagnetic field status; Data processing and results; Conclusion and future work.

3. IBGE and Ionosphere (X,Y,Z) GNSS positioning.

4. Ionospheric delay First-order delay - More than 99% - Proportional to TEC pseudorange carrier-phase

5. Since 1996; Actually 88 stations; Needs densification. RBMC

6. Real time GNSS data stream on internet (NTRIP – Networked Transport of RTCM via Internet Protocol); Since 2009; Actually 28 stations. RBMC-IP

7. On-line PPP service Double or single frequency data processing; Global Ionospheric Maps (IONEX) applied to single frequency solutions;

8. IGS Global Ionospheric Maps Combination of four different solutions: CODE (Center for Orbit Determination in Europe); ESOC (European Space Operations Centre ESA); UPC (Polytechnical University of Catalonia); JPL (Jet Propulsion Laboratory).

9. 9 IBGE collaborations Providing GNSS data free of charge to ionosphere monitoring projects: Unesp - Presidente Prudente (Brazil); INPE/EMBRACE (Brazil); La Plata University (Argentina); IGS – currently 9 stations (international).

10. ANN approach Architecture: Multilayer Perceptrons; 1 hidden layer with 16 neurons. samples taken from 3 previous days IGS GIM, resulting in 39 grids with 276 points (10,764 samples) Recursive training: Updated daily. Output: 72 hours ahead of regional ionospheric Maps (IONEX).

11. Experiments 30 ANNs trained; Comparison between VTEC GIM and VTEC ANN in four cases: IGS GIM high: March 21 to April 04 2001 (Day 80 to 94) low: June 16 to june 30 2009 (Day 167 to 181) 1) high solar activity; 2) day of the geomagnetic storm; 3) 3 days after the day of the geomagnetic storm; 4) low solar activity.

12. Solar activity status High solar activity: from 139.8 sfu to 273.5 sfu Low solar activity: from 66.5 sfu to 68.5 sfu Solar Flux 10.7 cm (NOAA - Pentiction station)

13. Geomagnetic field status Dst index (Kyoto) High solar activity: Day 90 => -400nT. Low solar activity: less than -50 nT.

14. Differences Increases as approaching to daily VTEC maximum; High solar activity < 15 TECU: –86% - geomagnetic storm; –88% - not disturbed days. Low solar activity: < 5 TECU: –99%.

15. Relative differences (  ) from 0% to 20% during most of the time in both periods; Day 90 (case 2) between 2 h and 5 h (Local Time) VTEC GIM were pushed down due to the geomagnetic storm;

16. Conclusion 70% to 85% of VTEC GIM was correctly mapped by the ANN; Vertical ionospheric delay from 0.24 m to 1.79 m can be expected in L1 observables; Insufficient for high precision applications (ambiguity resolution); The proposed approach: auto-adaptive to seasonal and longer period variations; real-time GNSS positioning;

17. Future work Mod_Ion regional ionospheric maps with spacial resolution of 2° x 4° and 1 hour frequency; Extend the model coverage to South America; Use data from the actual solar cycle maximum; Include solar activity and geomagnetic indices in the model.

18. Acknowledgments