References of "Warnant, René"
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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 ▲]

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See detailEnhancement of Total Electron Content monitoring using triple frequency GNSS data
Spits, Justine; Warnant, René ULg

Conference (2011, August 31)

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See detailMagnetic Valley : a knowledge transfer project
Humbled, François; Rasson, Jean; Spassov, Simo et al

in Data Science Journal (2011), 10

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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 ▲]

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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),

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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

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See detailRMI-Dourbes ionosonde database - Status 2010
Stankov, Stanimir; Stegen, Koen; Jodogne, Jean-Claude et al

Report (2011)

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See detailLocal Operational Geomagnetic Index K Calculation (K-LOGIC) from digital ground-based magnetic measurements
Stankov, Stanimir; Stegen, Koen; Warnant, René ULg

Report (2011)

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See detailIonosphere modelling for Galileo single frequency users: illustration of the combination of the NeQuick model and GNSS data ingestion
Bidaine, Benoît ULg; Warnant, René ULg

in Advances in Space Research (2011), 47(2), 312-322

The ionospheric effect remains one of the main factors limiting the accuracy of Global Navigation Satellite Systems (GNSS) including Galileo. For single frequency users, this contribution to the error ... [more ▼]

The ionospheric effect remains one of the main factors limiting the accuracy of Global Navigation Satellite Systems (GNSS) including Galileo. For single frequency users, this contribution to the error budget will be mitigated by an algorithm based on the NeQuick global ionospheric model. This quick-run empirical model provides flexible solutions for combining ionospheric information obtained from various sources, from GNSS to ionosondes and topside sounders. Hence it constitutes an interesting simulation tool not only serving Galileo needs for mitigation of the ionospheric effect but also widening the use of new data. In this study, we perform slant TEC data ingestion - the optimisation procedure underlying the Galileo single frequency ionospheric correction algorithm - into NeQuick for a dozen locations around the world where both an ionosonde and a GPS receiver are installed. These co-located instruments allow us to compare measured and modelled vertical TEC showing for example global statistics or dependence towards latitude. We analyse measurements for the year 2002 (high solar activity level) giving an insight into the situation we could observe when Galileo reaches its Full Operation Capability, during the next solar maximum. At last we compare Galileo and GPS ionospheric corrections. For Galileo, we end up with an underestimation of 11% and 4% depending on the version of NeQuick embedded in the algorithm, as well as a 22% standard deviation. This means respectively twice, five and 1.5 times better than GPS. [less ▲]

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See detailK-type geomagnetic index nowcast with data quality control
Stankov, Stanimir; Stegen, Koen; Warnant, René ULg

in Annals of Geophysics = Annali di Geofisica (2011), 54(3), 285-295

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See detailTotal Electron Content Monitoring using triple frequency GNSS: results with Giove-A/-B data
Spits, Justine; Warnant, René ULg

in Advances in Space Research (2011), 47

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See detailSystèmes de positionnement par satellites
Warnant, René ULg

Learning material (2011)

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See detailThéorie des erreurs
Warnant, René ULg

Learning material (2011)

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See detailA GPS/GNSS dense network used to monitor ionospheric positioning error
Wautelet, Gilles ULg; Lejeune, Sandrine; Warnant, René ULg

Poster (2010, December)

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See detailThe RMI Space Weather and Navigation Systems (SWANS) project
Warnant, René ULg; Lejeune, Sandrine; Wautelet, Gilles ULg et al

Conference (2010, July)

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See detailUnderstanding the occurrence of mid-latitude ionospheric irregularities by using GPS, ionosonde and geomagnetic measurements
Wautelet, Gilles ULg; Lejeune, Sandrine; Stankov, Stan et al

Conference (2010, June 11)

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See detailTEC reconstruction using dual frequency modernized GPS (L1/L5) and GALILEO (E1/E5A) measurements
Warnant, René ULg; Lonchay, Matthieu ULg; Spits, Justine et al

Conference (2010, June)

GPS dual frequency L1/L2 measurements have been used for many years to reconstruct the ionosphere Total Electron Content and to detect small-scale irregular structures in the ionospheric plasma. TEC is ... [more ▼]

GPS dual frequency L1/L2 measurements have been used for many years to reconstruct the ionosphere Total Electron Content and to detect small-scale irregular structures in the ionospheric plasma. TEC is usually computed by forming the geometry-free combination of L1/L2 phase measurements. Most of the existing techniques use the geometry-free combination of code measurements to solve the non-integer geometry-free ambiguity. This methodology requires the computation of satellite and receiver hardware biases. In addition, the quality of the ambiguity resolution process strongly depends on code multipath. New signals from Galileo and from modernized GPS offer new opportunities for TEC reconstruction. First attempts to compute TEC using triple frequency measurements from modernized GPS (L1/L2/L5) and from Galileo (E1, E5a, E5b) give very promising results but, at the present time, only a few triple frequency GPS/Galileo receivers are available. The University of Liege has purchased two Septentrio PolaRx3G receivers which allow tracking GPS L1/L5 and Galileo E1/E5a signals. These receivers have been installed at the Geophysical Observatory of Dourbes (50.1°N, 4.6° E) and are continuously tracking all GPS and Galileo satellites in view (including GPS SVN49/PRN01, Giove A and Giove B) since November 2009. The paper analyzes the added value of L1/L5 and E1/E5a geometry free combinations and of the new GPS and Galileo signals for TEC reconstruction. It discusses the influence of multipath and of SVN49/PRN1, Giove A and Giove B hardware biases. [less ▲]

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See detailA statistical study of the TEC storm-time response at European middle latitudes for use in ionospheric nowcast and forecast
Stankov, Stanimir; Stegen, Koen; Warnant, René ULg

in Doherty, P.; Hernandez-Pajares, M.; Juan, J.-M. (Eds.) et al The International Beacon Satellite Symposium 2010 (2010, June)

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