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GNSS ionosphere research activities at FCT/UNESP

GNSS ionosphere research activities at FCT/UNESP João Francisgo Galera Monico , Paulo De Oliveira Camargo FCT/UNESP - Presidente Prudente , SP. Outline. Introduction Developments on GNSS/Ionosphere Brazilian Ionospheric Model Mod_ION Mod_ION_FK /IG Rinex_HO GNSS demands in Brazil

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GNSS ionosphere research activities at FCT/UNESP

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  1. GNSS ionosphere research activities at FCT/UNESP JoãoFrancisgoGaleraMonico, Paulo De Oliveira Camargo FCT/UNESP - PresidentePrudente, SP.

  2. Outline • Introduction • Developments on GNSS/Ionosphere • Brazilian Ionospheric Model • Mod_ION • Mod_ION_FK/IG • Rinex_HO • GNSS demands in Brazil • CIGALA & CALIBRA Projects • Final Comments

  3. Ionosphere and GNSS • Ionospheric effects (delayandfrequencydispersion & phase scintillation and amplitude fading) are one of the main barriers to achieve high accuracy GNSS positioning and navigation. • It affects the quality of positioning and navigation: PPP, relative carrier phase based positioning, DGNSS, GBAS and SBAS, mainly for users of one frequency receiver. • Measurements made on two different frequencies allow the correction of the first order ionospheric delay by means of the widely used ionospheric-free linear combination (2nd order still has to be corrected).

  4. Ionosphere and GNSS • Effects as ionospheric scintillations, may cause problems such as: • signal power fading, • phase cycle slips, • receiver loss of lock, etc., • Such effects degrade the position quality provided by the satellite navigation systems (GNSS). This problem is still to be solved !

  5. Developments on GNSS/Ionosphere at FCT/UNESP

  6. A Ion-model based on GNSS data has been under development since 1997; • Mod_Ion (in-house iono model) initially generated coefficients for L1 users (Camargo et al., 2000) • Mod_Ion expanded to generate Ionex files and Ionospheric maps from Brazilian GNSS data • Real time: Mod_Ion_FK to generate the biases and a IG with respective GIVE are provided (Aguiar 2010).

  7. MOD_Ion - Fundamental (GPS & GLONASS)

  8. Mod_Ion with inequality equation Problem: at some situations, even with calibrated equipments, negative values of TEC may be obtained. One solution: to apply inequality equation as follows:

  9. GNSS Ionospheric Products TEC Maps

  10. Mod_ION_FK/IG (Aguiar, 2010) Kalman Filter ALDAR dss, drr Ionosphere Model: Polynomial Function IonosphereMonitoring Coeficients: dssanddrr BNC VTEC, ROT, IPP Real time ionospheremaps GMT IG & GIVE

  11. Mod_ION_FK/IG Kalman Filter ALDAR dss, drr Ionosphere Model: Polynomial Function IonosphereMonitoring Coeficients: dssanddrr BNC VTEC, ROT, IPP Real time ionospheremaps GMT IG & GIVE

  12. GridMapsand GIVE/ Brazil • November 22, 2009; • Real time processing; • 29 NTRIP stations. L1 Ionospheric Delay (m) GIVE

  13. IONEX Files

  14. 2nd and 3rd order Ionosphere corrections • In-house software was developed (RINEX_HO) • GPS Solutions, Online First: 21 April 2011, DOI: 10.1007/s10291-011-0220-1, "RINEX_HO: second- and third-order ionospheric corrections for RINEX observation files"  by H. A. Marques, J. F. G. Monico and M. Aquino

  15. 2nd and 3rd order Ionosphere corrections • The earth’s magnetic field • Dipolar Approximation • International Geomagnetic Reference Field (IGRF) model (IGRF11 model) • Corrected Geomagnetic Model from PIM (Parameterized Ionospheric Model) • TEC • From raw pseudoranges, from pseudoranges smoothed by phase, or from Global Ionosphere Maps (GIM).

  16. 2nd order Ionosphere correctionsDipolar – IGRF and Differences

  17. Ionosphere irregularities Index (Fp ) RECIFE/PE – RECF (28/10/2003)

  18. IonosphereirregularitiesIndex (Fp ) Estação RECIFE/PE – RECF (21/11/2007)

  19. GNSS demands in Brazil Off shore applications Air Navigation Positioning in general Precision agriculture Rural Cadastre (50 cm or better – 1 sigma) ….

  20. PA in Brazil is demanding 24 hours RTK service

  21. Concerning Air Navigation, Brazilian authorities decided to invest in GBAS instead of SBAS. A system from HoneywellAerospace is under certification at Rio de Janeiro Airport (Galeão). (Cosendeypresentationon Nov 09).

  22. Challenges for such GNSS applications • Ionospheric Scintillation!

  23. CIGALA Project “Concept for Ionospheric scintillation mitiGAtion for professional GNSS in Latin America” Goal: Understand the cause and implication of IS disturbances at low latitudes, model their effects and develop mitigations through: • Research of the underlying causes of IS and the development of state-of-the-art models capable of predicting signal propagation and tracking perturbations • Field measurement via the deployment in close collaboration with local academic and industrial partners of multi-frequency multi-constellation Ionospheric Scintillation Monitoring (ISM) network • Design and implementation of novel IS mitigation techniquesin state-of-the-art GNSS receivers • Field testing the mitigation techniques, leveraging the same partnership as during the measurement campaign.

  24. CIGALA partners

  25. CIGALA IS Monitoring Network in Brazil Continuous recording of : • Amplitude scintillation index S4 : standard deviation of received power normalized by its mean value • Phase scintillation index σΦ: standard deviation of de-trended carrier phase, with Phi60 its 60” version • TEC (Total Electron Content) • Lock time • Code – Carrier Divergence • Spectral parameters of phase Power Spectral Density: • Spectral slope p • Spectral strength T • Raw high-rate I&Q correlation values (50Hz)

  26. IS Monitoring Network in Brazil • 8 ISM stations • Latitudinal and longitudinal distribution over Brazil • Two stations at São José dos Campos (crest of EIA) and Pres. Prudente • Data stored locally and sent to repository at UNESP, Pres. Prudente • Data mirrored at INGV, Rome • Ended on Feb 2012, but the network is still collecting data. ISMR Query Tool was developed

  27. CALIBRA PROJECT • A follow up of the CIGALA Project • Countering GNSS high Accuracy applications Limitations due to Ionospheric disturbances in BRAzil • Focus on high accuracy GNSS positioning techniques • Better than 10cm

  28. Stationsequipped GNSS receiversPolaRxS-PRO, Five newstationswillbeinstalled for the CALIBRA Project. CIGALA/CALIBRA Network

  29. Final comments GNSS/Ionosphere developments at FCT/UNESP were presented; Brazil is a very challenge place for GNSS applications, mainly due to the Ionosphere behavior in the equatorial region; Several applications have suffered of the effects of such problem (IS); In the PA and aviation there is a need for more developments and tests; CIGALA/CALIBRA is collecting data that may provide more data for scientific and operational purposes.

  30. More information? http://gege.fct.unesp.br

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