Claudinei Rodrigues de Aguiar Federal University of Technology - Parana 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 LISN Workshop 2011

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); LISN Workshop 2011 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; LISN Workshop 2011 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) LISN Workshop 2011

Real time ionospheric modeling and monitoring Two- dimensional Analytical Models Analytical functions Grid Three- dimensional Fourier series Spherical harmonics Taylor series Analytical functions Empirical functions LISN Workshop 2011

Bidimensional Analytical Models Analytical functions Grid Tridimensional Fourier series Spherical harmonics Taylor series Analytical functions Empirical functions LISN Workshop 2011 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 LISN Workshop 2011

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 LISN Workshop 2011

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 LISN Workshop 2011

Calculation of ionospheric delay for each IPP: GIVE LISN Workshop 2011 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 LISN Workshop 2011

GNSS SP Network: Currently, eleven GNSS active stations providing data in real time Real time ionospheric modeling and monitoring LISN Workshop 2011

RBMC-IP (Brazilian Network for Continuous Monitoring of GNSS), maintained by IBGE (Brazilian Institute of Geography and Statistics ); Real time ionospheric modeling and monitoring LISN Workshop 2011

RBMC-IP Real time ionospheric modeling and monitoring LISN Workshop 2011

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 LISN Workshop 2011

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 LISN Workshop 2011

Kalman Filter Post-processingReal Time GNSS Positioning Ionosphere GNSS Navigation Ionosphere Monitoring Data via FTP RBMC GNSS SP Network Data via NTRIP RBMC-IP GNSS SP Network LISN Workshop 2011 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 LISN Workshop 2011

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 ; LISN Workshop 2011 Data Processing in Real Time

BNC ALDAR Kalman Filter Ionosphere Model: Fourier Series a 1,..., a 19, ds s and dr r Ionosphere Monitoring ds s, dr r VTEC, ROT, IPP Real time ionosphere maps GMT Graphic visualization maps Data Processing in Real Time LISN Workshop 2011 ALDAR make possible process the data supplied by the reference stations in real time

BNC ALDAR Kalman Filter Ionosphere Model: Fourier Series a 1,..., a 19, ds s and dr r Ionosphere Monitoring ds s, dr r VTEC, ROT, IPP Real time ionosphere maps GMT Graphic visualization maps LISN Workshop 2011 Data Processing in Real Time

Grid Maps - Brazil GIVEL1 Ionospheric Delay November 22, 2009; Real time processing; 29 NTRIP stations. LISN Workshop 2011

Grid Maps – South America GIVEL1 Ionospheric Dealy May 11, 2006; Processing for Central and South America stations, simulating real time; 52 stations. LISN Workshop 2011

Surface Maps - Brazil GIVE L1 Ionospheric Delay VTEC and ROT Map generated near real time from Grid. ROT Map VTEC Map LISN Workshop 2011

Surface Maps – South America GIVE L1 Ionospheric Delay VTEC and ROT Map generated simulating real time. ROT Map VTEC Map LISN Workshop 2011

Output File LISN Workshop 2011

Output File GIVE map Grid Map LISN Workshop 2011

Analyze of the quality of ionospheric grid:  I GI versus I REFERENCE  I GI - I REFERENCE < ε GIVE Grid Quality LISN Workshop 2011

I GI versus I REFERENCE Grid Quality LISN Workshop 2011

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 LISN Workshop 2011

Temporal availability varies from 10% (2.4 h) to 90%(21.6 h) ; Average of 70% (16.8 h monitored / unmonitored 7.2 h); LISN Workshop 2011 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. LISN Workshop 2011

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 reach es 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). LISN Workshop 2011 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; LISN Workshop 2011 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 LISN Workshop 2011 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. LISN Workshop 2011

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. LISN Workshop 2011

Thank you for your attention! LISN Workshop 2011