Claudinei Rodrigues de AguiarFederal University of Technology - Parana

rodrigues.aguiar@gmail.com

Paulo de Oliveira Camargo São Paulo State University - UNESP

Real Time Ionosphere Maps from GNSS Active

Networks

Outline

• Introduction• Real time ionospheric modeling and

monitoring• Data Processing in Real Time• Experiments• Summary

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• GNSS has definitely been an important tool for observation of the atmosphere parameters, especially those from the ionosphere.

• Mod_Ion (Camargo, 1999) (1995 a 1999): for post processing applications was developed at FCT/UNESP;

• Kalman Filter was further implemented (Camargo, 2001);

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Introduction

• Mod_Ion_FK (Aguiar, 2005) - (2003 a 2005): Mod_Ion+Kalman Filter – changes in the functional model, and quality control was implemented in the Kalman filter algorithm;

• GNSS SP Network (2006): availability of real time data;

• GI e GIVE: current;

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Introduction

Introduction

• This work is part of a research project for atmospheric studies based on real time reference stations equipped with dual frequency GNSS receivers:

– GNSS SP (GNSS Active Network of São Paulo State)– RBMC (Brazilian Network for Continuous

Monitoring)

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Real time ionospheric modeling and monitoring

Two-dimensional

Analytical Models

Analytical functions Grid

Three-dimensional

Fourier seriesSpherical harmonics

Taylor series

Analytical functions

Empirical functions

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Bidimensional

Analytical Models

Analytical functions Grid

Tridimensional

Fourier seriesSpherical harmonics

Taylor series

Analytical functions

Empirical functions

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Real time ionospheric modeling and monitoring

• An ionospheric model has been developed for applications in real time;

• An algorithm based on a Kalman filter has been developed for ionosphere modeling at low latitudes and for the estimation of ionospheric parameters: absolute vertical TEC (VTEC);

• In this work we have utilized the two dimensional Fourier series for modeling the vertical ionospheric delay. However, other modeling functions are being implemented;

Real time ionospheric modeling and monitoring

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• The ionospheric delay values have been estimated from the geometry free linear combination of GPS dual frequency code-phase pseudorange smoothed by carrier phase observables (PS):

.1

drc

1ds

cI)'z(sf1

)PS(PS PsPv

1sr

sr12

647,1)f/f( 22L1L

Real time ionospheric modeling and monitoring

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• The ionospheric delay values have been estimated from the geometry free linear combination of GPS dual frequency code-phase pseudorange smoothed by carrier phase observables (PS):

Real time ionospheric modeling and monitoring

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.1

drc

1ds

c])B sin(i a)B cos(ia[

ha])h sin(i a)h cos(ia[Baa

)'z(sf1

)PS(PS PsP

4m

102ij1i

s1j

sj

s32*n

4n

12ij1i

s1j

sj

s21

sr

sr12

• Calculation of ionospheric delay for each IPP:

1)drsc(d

1)PS(PSI P

sP

sr12s

r 1

e3,01)el(sf

240/el2

2IFB

2PS2

i

GIVE

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Real time ionospheric modeling and monitoring

• The real time modeling of the ionosphere is performed using data collected by active GNSS reference stations in Brazil;

• GNSS SP Network (GNSS Active Network of São Paulo State), leaded by FCT/UNESP and financed by FAPESP (São Paulo Research Foundation);

Real time ionospheric modeling and monitoring

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• GNSS SP Network: Currently, eleven GNSS active stations providing data in real time

Real time ionospheric modeling and monitoring

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• RBMC-IP (Brazilian Network for Continuous Monitoring of GNSS), maintained by IBGE (Brazilian Institute of Geography and Statistics );

Real time ionospheric modeling and monitoring

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• RBMC-IP

Real time ionospheric modeling and monitoring

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• These networks provide their data via the Internet using Internet Protocol (NTRIP);

• The availability of GNSS data via the NTRIP protocol brings new perspectives in research related to modeling and/or monitoring of the ionosphere in real time;

Real time ionospheric modeling and monitoring

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• NTRIP was projected to disseminate differential data correction or other types of GNSS data to users, moving or still, by the Internet.

Real time ionospheric modeling and monitoring

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Kalman Filter

Post-processing Real Time

GNSS PositioningIonosphere

GNSS Navigation Ionosphere Monitoring

Data via FTPRBMC

GNSS SP Network

Data via NTRIPRBMC-IP

GNSS SP Network

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Data Processing in Real Time

Data Processing in Real Time

•In Brazil some reference estations are providing real time data (RBMC-IP and GNSS SP Network);•These stations are equipped with dual frequency GNSS receivers that use NTRIP transport protocol;

•The station receivers are directly connected to the Internet, and the collected data are sent to a central computer that manages and storages the data

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BNC•Using a Ntrip Client program we can download these data into a computer (convert ed to RINEX);

•We developed a package of algorithms for reading RINEX files in real time and the processing these data ;

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Data Processing in Real Time

BNC

ALDAR

Kalman Filter

Ionosphere Model:

Fourier Series

a1, ..., a19, dss and drr

Ionosphere Monitoring

dss, drr

VTEC, ROT, IPP

Real time ionosphere maps

GMT

Graphic visualization maps

Data Processing in Real Time

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ALDAR make possible process the data supplied by the reference stations in real time

BNC

ALDAR

Kalman Filter

Ionosphere Model:

Fourier Series

a1, ..., a19, dss and drr

Ionosphere Monitoring

dss, drr

VTEC, ROT, IPP

Real time ionosphere maps

GMT

Graphic visualization maps

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Data Processing in Real Time

Grid Maps - Brazil

GIVEL1 Ionospheric Delay

• November 22, 2009;• Real time processing;• 29 NTRIP stations.

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Grid Maps – South America

GIVEL1 Ionospheric Dealy

• May 11, 2006;• Processing for Central and South America stations, simulating real time;• 52 stations.

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Surface Maps - Brazil

GIVEL1 Ionospheric Delay

VTEC and ROT Map generated near real time from Grid.

ROT MapVTEC Map

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Surface Maps – South America

GIVEL1 Ionospheric Delay

VTEC and ROT Map generated simulating real time.

ROT Map

VTEC Map

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Output File

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Output File GIVE map Grid Map

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• Analyze of the quality of ionospheric grid: IGI versus IREFERENCE

IGI- IREFERENCE < εGIVE

Grid Quality

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IGI versus IREFERENCE

Grid Quality

IUEPP IDGrd_r2.5 Limite de erro

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• The results show a limitation of the use of GI for the period of high solar activity, due to low number of the reference stations wich, consequently, results in a low number of IPP available to the generation of GI;

• When the GI degraded the results we observed that: GIVE was’nt available; GIVE was available but did’nt have a minimum

of 3 IGPs;

Impact of the density of reference stations

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Dez/2001 Out/2003

• Temporal availability varies from 10% (2.4 h) to 90%(21.6 h);

• Average of 70% (16.8 h monitored / unmonitored 7.2 h);

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Impact of the density of reference stations

Impact Analysis of the distribution of reference stations in GI

• It was developed the algortihm GS (Grid Simulator);

• GS is responsible for analyzing the distribution of reference stations.

• It is a software package that have their own libraries and also uses the GMT  and ImageMagick libraries.

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• 29 stations (GNSS SP, RBMC-IP)• 24 hours of data;• 5º: coverage of 95% (22.8 h) in

most of Brazil, the region under the influence SP GNSS coverage reaches 98% (23.5 h).

• 2,5º: 25% (6 hours) in the worst case, and 97% (23,3 h) in the best situation.

• 1º: the cell with better coverage (67% - 16 h); in other cell the coverage varies from 3% (0.7 h) to 50% (12 h).

5° x 5°

2,5° x 2,5°

1° x 1°

5° x 5°

2,5° x 2,5°

1° x 1°

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Impact Analysis of the distribution of reference stations in GI

• Considering the current configuration of the available networks in Brazil, the best results are obtained when using grids with spatial resolution greater than 2.5 °.

• In the modeling of the ionosphere in real time, the best results are to be expected in the southeast, because of the influence of GNSS SP network;

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Impact Analysis of the distribution of reference stations in GI

• Analysis of the average distance: Resolution 5ºx5º spacing of approx. 600 km Resolution 2,5ºx2,5º spacing of approx. 250 km Resolution 1ºx1º spacing of approx. 100 km

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Impact Analysis of the distribution of reference stations in GI

Summary• The development of real time ionospheric model is

under progress.

• Some problems of dynamic programming have to be solved.

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Summary• The next step is to provide, near real time, the

ionospheric model coefficients and an ionospheric grid to users.

• Tests carried out in point positioning show that the corrections provided by the GI should be used only when the GIVE is available;

• The software developed also use libraries of the GMT (Generic Map Tools) and Image Magick, both open source.

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Thank you for your attention!

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