References of "Warnant, René"
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See detailGALOCAD User interface
Warnant, René ULg; Wautelet, Gilles ULg

Report (2008)

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See detailEffects of small-scale atmospheric activity on precise positioning
Wautelet, Gilles ULg; Lejeune, Sandrine; Stankov, Stanimir et al

Report (2008)

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See detailLes GNSS et l’ionosphère
Warnant, René ULg; Lejeune, Sandrine; Wautelet, Gilles ULg

Conference given outside the academic context (2008)

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See detailGalileo Local Component for the detection of atmospheric threats
Warnant, René ULg; Bavier, Michaël; Brenot, Hugues et al

in Goodman, John (Ed.) Proceedings of the 12th International Ionospheric Effects Symposium (IES2008) (2008, May)

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See detailIonospheric slab thickness: analysis and monitoring applications
Stankov, Stanimir; Warnant, René ULg

in Proceedings of the 12th International Ionospheric Effects Symposium (IES2008) (2008, May)

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Peer Reviewed
See detailA novel method for the quantitative assessment of the ionosphere effect on high accuracy GNSS applications which require ambiguity resolution
Lejeune, Sandrine; Warnant, René ULg

in Journal of Atmospheric & Solar-Terrestrial Physics (2008), 70

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Peer Reviewed
See detailTotal Electron Content monitoring using triple frequency GNSS data: a three-step approach
Spits, Justine; Warnant, René ULg

in Journal of Atmospheric & Solar-Terrestrial Physics (2008), 70

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See detailCharacterization of the tropospheric small-scale activity
Brenot, Hugues; Warnant, René ULg

Report (2008)

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See detailConstitution of a data set for atmospheric studies
Warnant, René ULg

Report (2008)

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See detailProject Office - Final report
Warnant, René ULg

Report (2008)

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See detailProject Office - Third synthetic report
Warnant, René ULg

Report (2008)

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See detailIonospheric Products and Services from the Regional Warning Centers of the International Space Environment Service (ISES) for GNSS Users
Kunches, J.; Terkildsen, M.; Stanislawska, I. et al

Conference (2008)

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See detailTotal Electron Content monitoring using triple frequency GNSS data: a three-step approach
Spits, Sandrine; Warnant, René ULg

Conference (2008)

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See detailTotal Electron Content monitoring using triple frequency GNSS data: a three-step approach
Spits, Justine; Warnant, René ULg

Conference (2008)

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See detailDetection of small-scale structures in the neutral atmosphere using double differences of GNSS measurements
Brenot, Hugues; Lejeune, Sandrine; Warnant, René ULg

Conference (2008)

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See detailIonosphere Modelling for GALILEO Single Frequency Users
Bidaine, Benoît ULg; Warnant, René ULg

Poster (2007, October 17)

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See detailReal time TEC monitoring using triple frequency GNSS data : a three step approach
Spits, Justine; Warnant, René ULg

in Proceedings of the First International Colloquium - Scientific and Fundamental Aspects of the Galileo Programme (2007, October)

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See detailAssessment of the NeQuick Model at Mid-latitudes using GPS TEC and Ionosonde Data
Bidaine, Benoît ULg; Warnant, René ULg

in First Colloquium Scientific and Fundamental Aspects of the Galileo Programme (2007, October)

The ionosphere plays a crucial role in Global Navigation Satellite Systems (GNSS) accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding ... [more ▼]

The ionosphere plays a crucial role in Global Navigation Satellite Systems (GNSS) accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding 100 $m$. At first approximation, ionospheric effects depend mainly on the total content in free electrons of the ionosphere ("total electron content", TEC). The modelling of the latter parameter reveals thus itself critical in particular for single frequency receivers, the most common ones constituting the mass market. In the framework of GALILEO, the NeQuick model has been chosen to this extent and will be integrated into a global algorithm providing the users with daily updated information. In order to reach the specified correction level, the model itself and its latest evolutions as well as its use for GALILEO are investigated. As a first step in a thorough analysis, we take benefit of ionosonde and GPS TEC data from the Dourbes Geophysical Observatory (Belgium) to study the mid-latitudes. Constraining the model with ionosonde measurements, we first investigate the difference between GPS-derived vertical TEC (vTEC) for Dourbes station and corresponding values from NeQuick for the latest years for solar maximum in 2002 and minimum in 2006. With this approach, we reach residual errors of about 20% RMS for 2002 and 30% for 2006. Through a focusing process, we identify then gradually best and worst months and days for which we observe the evolution between two versions of NeQuick. We highlight among others improvements from the latest modification in the topside formulation which appears clearly in the electron density profiles examined at the end of the assessment. [less ▲]

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See detailAssessment of the NeQuick Model at Mid-latitudes using GPS TEC and Ionosonde Data
Bidaine, Benoît ULg; Warnant, René ULg

Conference (2007, July 11)

The ionosphere plays a crucial role in GNSS accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding 100m. At first approximation, the ... [more ▼]

The ionosphere plays a crucial role in GNSS accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding 100m. At first approximation, the ionospheric effect depends on the frequency of the incident signal and on the total content in free electrons of the ionosphere (“total electron content”, TEC) which is the integral of the electron density on the path between the satellite and the receiver. The modelling of this parameter reveals then itself to be critical in particular for single-frequency receivers, the most common ones constituting the mass market, but also for multiple-frequency devices which will comprise a fallback mode in single frequency within the framework of critical applications such as civil aviation where the level of precision must be guaranteed in all circumstances. The NeQuick model, which has been chosen for correcting the ionospheric error contribution in GALILEO single frequency users, calculates the electron density at a given point of the ionosphere according to the time conditions and the solar activity. This electron density can be integrated along the path from the receiver to the considered satellite to provide the TEC. The NeQuick model depends on a parameter Az (“effective ionization level”) which will be daily updated by the GALILEO ground stations to give the solar activity information to the model. In order to reach the ionosphere error correction level objective (70% or 20 TECu whichever is larger), the model itself as well as its use for GALILEO are investigated. Different situations have to be considered: different latitude regions (space conditions), different hours, seasons and years (time conditions) and specific phenomena appearance (magnetic storms, Travelling Ionospheric Disturbances – TIDs). In addition the results can be compared to different data sets among which GPS slant or vertical TEC measurements, Global Ionospheric Maps, ionosonde profiles, topside soundings but also other ionosphere models results such as IRI. As a first step in a thorough comparison process, we take benefit of various ionosphere data from the Dourbes Observatory (Belgium) where ionosonde and GPS TEC data are available on a period of more than one solar cycle, to study the mid-latitudes. We first investigate the difference between GPS-derived vTEC for Dourbes station and vTEC values from NeQuick for the latest years (between solar maximum in 2000 and minimum in 2006) in order to observe the temporal dependencies towards Universal Time, season and solar activity. The paper analyses the different situations when NeQuick fails to represent TEC in an adequate way to provide an efficient correction for navigation. Ionosonde measurements will help in the interpretation of these situations. [less ▲]

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