References of "Warnant, René"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailMonitoring, tracking and forecasting ionospheric perturbations using GNSS techniques
Jakowski, Norbert; Béniguel, Yannick; De Franceschi, Giorgiana et al

in Journal of Space Weather and Space Climate (2012), 2(A22),

The paper reviews the current state of GNSS-based detection, monitoring and forecasting of ionospheric perturbations in Europe in relation to the COST action ES0803 ‘‘Developing Space Weather Products and ... [more ▼]

The paper reviews the current state of GNSS-based detection, monitoring and forecasting of ionospheric perturbations in Europe in relation to the COST action ES0803 ‘‘Developing Space Weather Products and Services in Europe’’. Space weather research and related ionospheric studies require broad international collaboration in sharing databases, developing analysis software and models and providing services. Reviewed is the European GNSS data basis including ionospheric services providing derived data products such as the Total Electron Content (TEC) and radio scintillation indices. Fundamental ionospheric perturbation phenomena covering quite different scales in time and space are discussed in the light of recent achievements in GNSS-based ionospheric monitoring. Thus, large-scale perturbation processes characterized by moving ionization fronts, wave-like travelling ionospheric disturbances and finally small-scale irregularities causing radio scintillations are considered. Whereas ground and space-based GNSS monitoring techniques are well developed, forecasting of ionospheric perturbations needs much more work to become attractive for users who might be interested in condensed information on the perturbation degree of the ionosphere by robust indices. Finally, we have briefly presented a few samples illustrating the space weather impact on GNSS applications thus encouraging the scientific community to enhance space weather research in upcoming years. [less ▲]

Detailed reference viewed: 108 (5 ULg)
Full Text
Peer Reviewed
See detailLocal climatological modeling of ionospheric irregularities detected by GPS in mid-latitude region
Wautelet, Gilles ULg; Warnant, René ULg

in Journal of Atmospheric & Solar-Terrestrial Physics (2012), 89

Detailed reference viewed: 52 (5 ULg)
Full Text
See detailMonitoring the ionospheric activity using GNSS. From dual frequency GPS to multi-constellation multi-frequency GNSS
Warnant, René ULg; Bidaine, Benoît; Lonchay, Matthieu ULg et al

Scientific conference (2012, June 20)

Detailed reference viewed: 57 (2 ULg)
Full Text
See detailPrecise Point Positioning: Performances under Ionospheric Scintillations
Lonchay, Matthieu ULg; Aquino, Marcio; Hancock, Craig et al

Scientific conference (2012, June 14)

The Precise Point Positioning (PPP) has become a powerful satellite positioning technique which nearly equals performances provided by advanced relative positioning techniques. Exploiting the growing ... [more ▼]

The Precise Point Positioning (PPP) has become a powerful satellite positioning technique which nearly equals performances provided by advanced relative positioning techniques. Exploiting the growing availability and quality of IGS products (satellite orbit and clock products), the PPP technique can now provide a centimetre level solution in static mode and a decimetre level in kinematic mode. However, the PPP technique still presents some weaknesses. In order to reach a high precision level, it requires a significant convergence period which can typically reach 30 minutes under normal conditions. Moreover, the PPP seems to be especially sensitive to ionospheric scintillations effects which involve signal amplitude and phase variations of GNSS signals. These weaknesses still limit the use of the PPP technique in the frame of some specific and demanding applications (agricultural industry, airborne mapping, etc.). The goal of our research project is to develop new data processing strategies attempting both to make the PPP technique more reliable under ionospheric scintillations and to optimize the PPP convergence time. The project is composed of several workpackages aiming to improve the mentioned current PPP weaknesses with specific strategies. One of the workpackages is devoted to the impact of satellite geometry on PPP performances. Ionospheric scintillations are susceptible to reduce the number of tracked satellites which degrades the quality of satellite geometry. Based on an analytical development, we first attempt to figure out what types of satellite geometry can be harmful. Then, we discuss about the improvement of the satellite geometry quality involved by the combined use of GPS and Galileo and its benefits in the frame of the PPP. Another workpackage is related to the weighting scheme. Based on an iterative least-square adjustment, the PPP algorithm requires the definition of a stochastic model composed of an observation covariance matrix. Usually, this matrix is chosen as diagonal with zero covariances assuming that correlations between observations can be neglected. In particular, our project aims to study the validity of this stochastic model for the PPP in order to determine whether tuning the weighting scheme of the stochastic model can improve the PPP performances. By exploiting spatial analysis techniques, we try to characterize the spatial auto-correlation between GNSS observations, considering the signal-to-noise ratio as the main observable. From the results of these experiments, we will discuss about the spatial correlation between GNSS observations both under normal conditions and ionospheric scintillations. [less ▲]

Detailed reference viewed: 101 (11 ULg)
See detailThe added value of triple frequency GNSS for TEC reconstruction
Warnant, René ULg; Spits, Justine

Conference (2012, May)

Detailed reference viewed: 43 (3 ULg)
Full Text
See detailHumidity 3D field comparisons between GNSS tomography, IASI satellite observations and ALARO model
Brenot, Hugues; Champollion, Cedric; Deckmyn, Alex et al

in Geophysical Research Abstracts (2012, April), 14

Detailed reference viewed: 94 (2 ULg)
Full Text
Peer Reviewed
See detailIonospheric effects on relative positioning within GPS dense network
Lejeune, Sandrine; Wautelet, Gilles ULg; Warnant, René ULg

in GPS Solutions (2012), 16(1), 105-116

Detailed reference viewed: 124 (15 ULg)
Full Text
Peer Reviewed
See detailEvaluation of the automatic ionogram scaling for use in real-time ionospheric density profile specification: Dourbes DGS-256/ARTIST-4 performance.
Stankov, Stanimir; Jodogne, Jean-Claude; Kutiev, Ivan et al

in Annals of Geophysics = Annali di Geofisica (2012), 55(2), 283-291

Detailed reference viewed: 53 (2 ULg)
Full Text
See detailIntroduction aux GNSS
Warnant, René ULg

Learning material (2012)

Detailed reference viewed: 68 (4 ULg)
Full Text
See detailBelgian Report of activity in the frame of the International Association of Geodesy
Bruyninx, Carine; Dehant, Véronique ULg; Defraigne, Pascale et al

Report (2012)

Detailed reference viewed: 29 (1 ULg)
See detailGéodésie spatiale
Warnant, René ULg

Learning material (2011)

Detailed reference viewed: 104 (6 ULg)
Full Text
See detailAn Efficient Dual and Triple Frequency Preprocessing Method for GALILEO and GPS Signals
Lonchay, Matthieu ULg; Bidaine, Benoît ULg; Warnant, René ULg

in 3rd International Colloquium – Scientific and Fundamentals Aspects of the GALILEO Programme (2011, September 02)

Data preprocessing is a mandatory stage for most of GNSS applications. In the frame of space weather and precise point positioning applications, the Geomatics Unit of the University of Liège has purchased ... [more ▼]

Data preprocessing is a mandatory stage for most of GNSS applications. In the frame of space weather and precise point positioning applications, the Geomatics Unit of the University of Liège has purchased two Septentrio PolaRx3eG receivers which allow tracking GPS L1/L5 and Galileo E1/E5a signals. In order to fully exploit these new data, we developed a preprocessing method extending existing techniques. Our preprocessing method consists of three consecutive steps. The first step is devoted to the compensation of receiver clock slips affecting code pseudorange and carrier-phase measurements. The second step covers cycle slips detection and the third step assesses data quality in terms of noise essentially affecting code pseudorange measurements. This preprocessing method was initially developed for GPS L1/L5 and Galileo E1/E5a dual frequency data but finally enhanced to also preprocess triple frequency data from first operational Galileo satellites as soon as data are available. The developed method already showed promising results. [less ▲]

Detailed reference viewed: 301 (38 ULg)
Full Text
See detailEnhancement of Total Electron Content monitoring using triple frequency GNSS data
Spits, Justine; Warnant, René ULg

Conference (2011, August 31)

Detailed reference viewed: 41 (3 ULg)
Full Text
Peer Reviewed
See detailMagnetic Valley : a knowledge transfer project
Humbled, François; Rasson, Jean; Spassov, Simo et al

in Data Science Journal (2011), 10

Detailed reference viewed: 31 (4 ULg)
Full Text
See detailGalileo Single Frequency Ionospheric Correction: Performances in Terms of Position
Bidaine, Benoît ULg; Warnant, René ULg

in Goodman, John M. (Ed.) 2011 Ionospheric Effects Symposium Proceedings (2011, May)

The ionospheric effect remains one of the main factors limiting GNSS accuracy. For GPS single frequency users, this contribution to the error budget is estimated thanks to the well-known Klobuchar ... [more ▼]

The ionospheric effect remains one of the main factors limiting GNSS accuracy. For GPS single frequency users, this contribution to the error budget is estimated thanks to the well-known Klobuchar algorithm. For Galileo, it will be mitigated by a global algorithm based on the NeQuick model. This algorithm relies on an optimisation procedure called ingestion. In this framework, an "effective ionisation level" Az plays the role of the solar activity information provided to the model in order to fit a specific dataset. For Galileo single frequency operation, daily Az values will be computed from slant Total Electron Content (sTEC) measurements performed within the ground segment and three coefficients will be broadcast to the users within the navigation message allowing them to run the model. The performance specifications of these algorithms are respectively expressed in terms of delay and TEC but the users might find more interest in their impact on positioning. Hence we propose to investigate their performances in terms of positioning accuracy. To this extent we compare positions of permanent stations calculated with and without the ionospheric correction to the actual ones which are known at the sub-centimetre level. Our simulation uses sTEC generated from Global Ionospheric Maps to provide the effective ionization level coefficients and GPS single frequency code measurements to compute positions. We present results for Brussels station in Belgium (mid-latitudes) and for 2002 (high solar activity level). It gives an interesting insight in the situation we could observe when Galileo reaches its Initial Operation Capability, during the next solar maximum. This study constitutes a first step in the development of a real-time service in the framework of the SWANS project of the University of Liège and the Royal Meteorological Institute of Belgium. As two Galileo receivers have been bought in this context, this service will be available for the In-Orbit Validation phase of Galileo. [less ▲]

Detailed reference viewed: 241 (19 ULg)
Full Text
See detailOn the impact of ionospheric variability and disturbances on GNSS-based positioning applications
Stankov, Stanimir; Wautelet, Gilles ULg; Lejeune, Sandrine et al

in Geophysical Research Abstracts (2011, April), 13(ABS. No EGU2011-12067),

Detailed reference viewed: 36 (5 ULg)
Full Text
Peer Reviewed
See detailLocal ionospheric electron density profile reconstruction in real time from simultaneous ground-based GNSS and ionosonde measurements
Stankov, Stanimir; Stegen, Koen; Muhtarov, Plamen et al

in Advances in Space Research (2011), 47(7), 1172-1180

Detailed reference viewed: 44 (6 ULg)
Full Text
See detailRMI-Dourbes ionosonde database - Status 2010
Stankov, Stanimir; Stegen, Koen; Jodogne, Jean-Claude et al

Report (2011)

Detailed reference viewed: 45 (2 ULg)