gnss ionosphere research activities at fct/unesp
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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 - PowerPoint PPT PresentationTRANSCRIPT
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GNSS ionosphere research activities at FCT/UNESP
João Francisgo Galera Monico, Paulo De Oliveira Camargo
FCT/UNESP - Presidente Prudente, SP.
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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
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Ionosphere and GNSS• Ionospheric effects (delay and frequency dispersion & 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).
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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 !
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Developments on GNSS/Ionosphere at FCT/UNESP
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• 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).
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n 4 m 4s s s s s s
1 2 j j 1 n*2 3 j j 1i 1 i 1j 2i 1 j 2i 10
VTEC a a B {a cos(i h ) a sin(i h )} a h {a cos(i B ) a sin(i B )}
2 2 2i 2i 1i 2iF f /(f f )
n 4s s s s s s s2 1 r r 1 2 j j 1 n*2 3
i 1j 2i 1
m 4s s s s
j j 1 P2 P1 r P2 P1 P21i 1j 2i 10
F(P P ) SF (a a B {a cos(i h ) a sin(i h )} a h
{a cos(i B ) a sin(i B )} F(R R ) F(S S ) F .
TEC s s TEC s s TECi 2r 1r i p2 p1 p2 p1 r i P21s
r
VTECF (P P ) + F [(S -S ) + (R -R ) ] + Fcos(z )
MOD_Ion - Fundamental (GPS & GLONASS)
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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:n 4
s s s1 2 j j 1
i 1j 2i 1
m 4s s s
n*2 3 j j 1 i 1j 2i 10
VTEC a a B {a cos(i h ) a sin(i h )}
a h {a cos(i B ) a sin(i B )} 0
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GNSS Ionospheric Products
• TEC Maps
-75 -70 -65 -60 -55 -50 -45 -40 -35 -30
Longitude G eográfica (graus) + E stações G PS da RB M C
M apa do VTEC - 06/10/2001 - 01:00 U T
-35
-30
-25
-20
-15
-10
-5
0
5
Latit
ude
Geo
gráf
ica
(gra
us)
VTE
C (x
10E
+16
el/m
2)
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
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BNC
ALDAR
Kalman Filter
Ionosphere Model:Polynomial
Function
Coeficients: dss and drr
Ionosphere Monitoring
dss, drr
VTEC, ROT, IPP
Real time ionosphere maps
GMT
IG & GIVE
Mod_ION_FK/IG (Aguiar, 2010)
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BNC
Mod_ION_FK/IG
ALDAR
Kalman Filter
Ionosphere Model:Polynomial
Function
Coeficients: dss and drr
Ionosphere Monitoring
dss, drr
VTEC, ROT, IPP
Real time ionosphere maps
GMT
IG & GIVE
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Grid Maps and GIVE/ Brazil
GIVEL1 Ionospheric Delay (m)
• November 22, 2009;• Real time processing;• 29 NTRIP stations.
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IONEX Files
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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
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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).
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2nd order Ionosphere correctionsDipolar – IGRF and Differences
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RECIFE/PE – RECF (28/10/2003)
Ionosphere irregularities Index (Fp )
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Estação RECIFE/PE – RECF (21/11/2007)
Ionosphere irregularities Index (Fp )
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GNSS demands in Brazil
Off shore applicationsAir Navigation
Positioning in generalPrecision agriculture
Rural Cadastre (50 cm or better – 1 sigma)
….
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PA in Brazil is demanding 24 hours RTK service
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Concerning Air Navigation, Brazilian authorities decided to invest in GBAS
instead of SBAS.
A system from Honeywell Aerospace is under certification at Rio de Janeiro
Airport (Galeão). (Cosendey presentation on Nov 09).
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Challenges for such GNSS applications
Ionospheric Scintillation!
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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 techniques in state-of-the-art GNSS receivers
– Field testing the mitigation techniques, leveraging the same partnership as during the measurement campaign.
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CIGALA partners
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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)
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• 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.
IS Monitoring Network in Brazil
ISMR Query Tool was developed
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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
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CIGALA/CALIBRA Network• Stations
equipped GNSS receivers PolaRxS-PRO,
• Five new stations will be installed for the CALIBRA Project.
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• 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.
Final comments
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More information?http://gege.fct.unesp.br