HR: 14:15h
AN: A53C-02 INVITED     [Abstracts]
TI: Accurate real-time ionospheric corrections as the key to extend the centimeter-error-level GNSS navigation at continental scale (WARTK)
AU: * Hernandez-Pajares, M
EM: manuel@ma4.upc.edu
AF: Res. group Astron. & Geomatics, Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1-3, Barcelona, E08034, Spain
AU: Juan, J
EM: miguel@fa.upc.edu
AF: Res. group Astron. & Geomatics, Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1-3, Barcelona, E08034, Spain
AU: Sanz, J
EM: jaume@ma4.upc.edu
AF: Res. group Astron. & Geomatics, Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1-3, Barcelona, E08034, Spain
AU: Aragon-Angel, A
EM: angela@ma4.upc.edu
AF: Res. group Astron. & Geomatics, Technical Univ. Catalonia (gAGE/UPC), Mod. C3 Campus Nord UPC Jordi Girona 1-3, Barcelona, E08034, Spain
AB: The main focus of this presentation is to show the recent improvements in real-time GNSS ionospheric determination extending the service area of the so called "Wide Area Real Time Kinematic" technique (WARTK), which allow centimeter-error-level navigation up to hundreds of kilometers far from the nearest GNSS reference site.[-4mm] The real-time GNSS navigation with centimeters of error has been feasible since the nineties thanks to the so- called "Real-Time Kinematic" technique (RTK), by exactly solving the integer values of the double-differenced carrier phase ambiguities. This was possible thanks to dual-frequency carrier phase data acquired simultaneously with data from a close (less than 10-20 km) reference GNSS site, under the assumption of common atmospheric effects on the satellite signal. This technique has been improved by different authors with the consideration of a network of reference sites. However the differential ionospheric refraction has remained as the main limiting factor in the extension of the applicability distance regarding to the reference site.[-4mm] In this context the authors have been developing the Wide Area RTK technique (WARTK) in different works and projects since 1998, overworking the mentioned limitations. In this way the RTK applicability with the existing sparse (Wide Area) networks of reference GPS stations, separated hundreds of kilometers, is feasible. And such networks are presently deployed in the context of other projects, such as SBAS support, over Europe and North America (EGNOS and WAAS respectively) among other regions.[-4mm] In particular WARTK is based on computing very accurate differential ionospheric corrections from a Wide Area network of permanent GNSS receivers, and providing them in real-time to the users. The key points addressed by the technique are an accurate real-time ionospheric modeling -combined with the corresponding geodetic model- by means of:[-4mm] a) A tomographic voxel model of the ionosphere, estimated from the GNSS data only, and which reduces the errors associated to non-tomographic approaches, taking care of electron density vertical distribution.[-4mm] b) A simple GNSS model for the "Medium Scale Traveling Ionospheric Disturbances", being this one of the main ionospheric perturbations affecting the carrier phase ambiguity fixing, and hence the capability of accurate navigation.[-4mm] The corresponding models and performances will be illustrated with several experiments involving actual data. And finally the existing and new WARTK applications will be briefly mentioned, in the context of different projects. References: Hernandez-Pajares, M.; Juan, J. M.; Sanz, J.; Colombo, O. L., Improving the real-time ionospheric determination from GPS sites at very long distances over the equator, Journal of Geophysical Research (Space Physics), Volume 107, Issue A10, pp. SIA 10-1, CiteID 1296, DOI 10.1029/2001JA009203, 10/2002. Hernandez-Pajares, M.; Juan, J. M.; Sanz, J., Medium-scale traveling ionospheric disturbances affecting GPS measurements: Spatial and temporal analysis, Journal of Geophysical Research, Volume 111, Issue A7, CiteID A07S11, DOI 10.1029/2005JA011474, 06/2006.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 2435 Ionospheric disturbances
DE: 2447 Modeling and forecasting
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly