References of "Bidaine, Benoît"
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See detailGalileo Single Frequency Ionospheric Correction: Performances in Terms of Position
Bidaine, Benoît ULg; Lonchay, Matthieu ULg; Warnant, René ULg

in GPS Solutions (2013), 17(1), 63-73

For GPS single frequency users, the ionospheric contribution to the error budget is estimated by the well-known Klobuchar algorithm. For Galileo, it will be mitigated by a global algorithm based on the ... [more ▼]

For GPS single frequency users, the ionospheric contribution to the error budget is estimated by the well-known Klobuchar algorithm. For Galileo, it will be mitigated by a global algorithm based on the NeQuick model. This algorithm relies on the adaptation of the model to slant Total Electron Content (sTEC) measurements. Although the performance specifications of these algorithms are expressed in terms of delay and TEC, the users might be more interested in their impact on positioning. Therefore, we assessed the ability of the algorithms to improve the positioning accuracy using globally distributed permanent stations for the year 2002 marked by a high level of solar activity. We present uncorrected and corrected performances, interpret these and identify potential causes for Galileo correction discrepancies. We show vertical errors dropping by 56–64 % due to the analyzed ionospheric corrections, but horizontal errors decreasing by 27 % at most. By means of a fictitious symmetric satellite distribution, we highlight the role of TEC gradients in residual errors. We describe mechanisms permitted by the Galileo correction, which combine sTEC adaptation and topside mismodeling, and limit the horizontal accuracy. Hence, we support further investigation of potential alternative ionospheric corrections. We also provide an interesting insight into the ionospheric effects possibly experienced during the next solar maximum coinciding with Galileo Initial Operation Capability. [less ▲]

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See detailIonosphere Modelling for Galileo Single Frequency Users
Bidaine, Benoit ULg

Doctoral thesis (2012)

Nowadays the ionosphere constitutes one of the most often modelled natural media. Indeed each GPS receiver among nearly two million units sold daily throughout the world runs a model to mitigate the ... [more ▼]

Nowadays the ionosphere constitutes one of the most often modelled natural media. Indeed each GPS receiver among nearly two million units sold daily throughout the world runs a model to mitigate the ionospheric effect affecting the signal propagation from the satellites. This propagation is delayed by the free electrons in the atmosphere so that the navigation signals appear to travel distances larger than actual ones by 7 m on average. Hence this delayed propagation deteriorates the positioning accuracy deemed on a 10−m level for mass-market applications mainly involving single frequency users. Tomorrow the European navigation system Galileo will offer a new mitigation strategy to single frequency users. This strategy will rely on the NeQuick ionospheric model and associated broadcast information. To be properly implemented, it must be extensively described to future Galileo users. These users will also wonder about its effectiveness in accounting for the ionospheric delay. The PhD research covered by the present thesis has built on Belgian expertise in ionosphere monitoring to investigate the NeQuick model and its use for Galileo. It began with the collection and handling of ionosphere measurements including GPS data. It analysed various situations at different places in the world encompassing a whole year (2002). This PhD thesis provides the ins and outs of the Galileo Single Frequency Ionospheric Correction Algorithm. It gathers an algorithm description, a performance evaluation and a variant investigation. In the shape of a paper collection, it discloses many figures as visual entry-points into the juxtaposed text and includes many references allowing to dig into the details. The algorithm performances are usefully characterised both in terms of delay mitigation and positioning accuracy. On the one hand, the residual ionospheric delay reaches 31% for the chosen sites and year. On the other hand, the positioning accuracy amounts to 6 m horizontally and 9.3 m vertically. The performance evaluation allowed to emphasise several aspects of the Galileo ionospheric correction. This correction depends largely on the modelling of the topside, the upper part of the ionosphere, which hosts more complex physical processes. It owes its good performances to data ingestion, the model adaptation technique to actual measurements underlying the Galileo algorithm. It does not necessarily provide highly correlated correction levels in terms of delay on the one hand and positioning on the other. It enables the definition of alternative regional procedures following a compatible design but coping with its weaknesses. The present thesis paves the way for future work related to ionosphere modelling for Galileo single frequency users. It supplies comparative information for the algorithm assessment in the framework of successive phases of Galileo deployment. It establishes a conceptual basis for an Assisted Ionospheric Correction Algorithm (A-ICA) disseminating more flexible ionospheric information thanks to the integration of Global Navigation Satellite Systems and telecommunications. [less ▲]

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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 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 detailDetermining the Geographical Origin of a Serial Offender Considering the Temporal Uncertainty of the Recorded Crime Data
Trotta, Marie ULg; Bidaine, Benoît ULg; Donnay, Jean-Paul ULg

in GEOProcessing 2011 : The Third International Conference on Advanced Geographic Information Systems, Applications, and Services (2011, February)

Since the days the investigating officers used ”pin maps” to locate and to think about crime events, crime mapping has become widespread thanks to spatial analysis mainly supplied by GIS-like software. In ... [more ▼]

Since the days the investigating officers used ”pin maps” to locate and to think about crime events, crime mapping has become widespread thanks to spatial analysis mainly supplied by GIS-like software. In particular these methods suit well to geographic profiling devoted to crime series characterised by a single offender and hence limited space and time variability. Although spatial techniques are now regularly performed to delineate an offender’s area of residence, the temporal dimension is underemployed due to the wider uncertainty of time records. This paper proposes a methodology based on a least-squares adjustment in order to cope with this temporal issue for determining the most probable offender’s residence. Moreover, a chi-square test is described to check the significance of the solutions suggested by the method. The process is carried out on the real road network which has been discretised (rasterised) for computing convenience. Three simulations show the validity of the reasoning. Finally the main time and speed assumptions introduced in the model are discussed paving the way for further research. [less ▲]

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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 detailExercices de théorie des erreurs
Bidaine, Benoît ULg

Learning material (2011)

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See detailLa clé est aux intersections...
Bidaine, Benoît ULg

Learning material (2011)

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See detailM-Ingestion: Simultaneous Ingestion of Ionosonde and GNSS Data into the NeQuick Model
Bidaine, Benoît ULg; Nava, Bruno; Stankov, Stanimir et al

in Doherty, P.; Hernández-Pajares, M.; Juan, J.-M. (Eds.) et al The International Beacon Satellite Symposium BSS2010 (2010, June)

The steady increase in volume and quality of ionospheric measurements allows for potential improvements in the existing ionospheric models. In particular ionosonde and Global Navigation Satellite Systems ... [more ▼]

The steady increase in volume and quality of ionospheric measurements allows for potential improvements in the existing ionospheric models. In particular ionosonde and Global Navigation Satellite Systems (GNSS) data provide complementary information for original developments regarding the NeQuick model, a quick-run empirical model of the electron density supplying flexible solutions for various applications. Indeed NeQuick is often used to investigate radiowave propagation issues: among others it has been implemented within the Galileo Single Frequency Ionospheric Correction Algorithm. The model is particularly suited to be used within an optimization procedure called ingestion. In this framework, an "effective ionization level" Az plays the role of solar activity input in order to fit a specific dataset eg of slant Total Electron Content (TEC). However larger discrepancies can then obviously be observed towards other parameters eg the F2-layer critical frequency foF2. This draws the interest for a multiple ingestion - or m-ingestion - scheme implying an adaptation towards several datasets by defining several effective parameters. In our study, we perform m-ingestion of ionosonde and GNSS data providing us with slant TEC. In fact it allows us to constrain the electron density profile slab thickness. For the purpose, a high solar activity period (year 2002) was analysed based on collocated digisonde and EUREF GNSS observations at a mid-latitude site, Dourbes (50.1◦N, 4.6◦E). In this way, we can gather some clues on expected ionospheric effects on Galileo applications during the next solar activity maximum. [less ▲]

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See detailComparison of GPS-derived vTEC over Cyprus with NeQuick Model
Haralambous, Haris; Bidaine, Benoît ULg

in Doherty, P.; Hernández-Pajares, M.; Juan, J.-M. (Eds.) et al The International Beacon Satellite Symposium BSS2010 (2010, June)

This paper presents a comparison of ionospheric vertical total electron content (vTEC) values evaluated from Nicosia (35.1 N, 33.4 E) ground-based GPS station in Cyprus and the corresponding predictions ... [more ▼]

This paper presents a comparison of ionospheric vertical total electron content (vTEC) values evaluated from Nicosia (35.1 N, 33.4 E) ground-based GPS station in Cyprus and the corresponding predictions with the latest version of the NeQuick model during periods of low (2008), and high (2001) solar activity for different seasons. According to the study the NeQuick predictions generally underestimate vTEC values during high solar activity periods and overestimate vTEC values during low solar activity periods. [less ▲]

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See detailAssessment of the NeQuick model at mid-latitudes using GNSS TEC and ionosonde data
Bidaine, Benoît ULg; Warnant, René

in Advances in Space Research (2010), 45(9), 1122-1128

The modelling of the Total Electron Content (TEC) plays an important role in global navigation satellite systems (GNSS) accuracy, especially for single-frequency receivers, the most common ones ... [more ▼]

The modelling of the Total Electron Content (TEC) plays an important role in global navigation satellite systems (GNSS) accuracy, especially for single-frequency receivers, the most common ones constituting the mass market. For the latter and in the framework of Galileo, the NeQuick model has been chosen for correcting the ionospheric error contribution and will be integrated into a global algorithm providing the users with daily updated information. In order to reach the ionosphere error correction level objective, the model itself as well as its use for Galileo are investigated. In our comparison process, we take advantage of various ionosphere data from several European stations (Dourbes in Belgium, El Arenosillo and Roquetes in Spain) where ionosonde and GPS TEC data are available for different solar activity levels. These data allow us to study NeQuick representation of the ionosphere at mid-latitudes. Constraining the model with ionosonde measurements, we investigate the difference between GPS-derived vertical TEC and corresponding values from NeQuick for a high solar activity level (year 2002). With this approach, we reach residual errors of less than 20% in standard deviation. We especially highlight the improvements from the latest (second) version of NeQuick and show the critical importance of the topside formulation. [less ▲]

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See detailModélisation de l’ionosphère pour les utilisateurs Galileo simple fréquence
Bidaine, Benoît ULg

Scientific conference (2010, January 21)

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See detailExercices d'astronomie de position
Bidaine, Benoît ULg

Learning material (2010)

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See detailSIDC Telescience
Warnant, René ULg; Bidaine, Benoît ULg; Brenot, Hugues et al

Report (2010)

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See detailModéliser l’ionosphère pour les utilisateurs Galileo simple fréquence
Bidaine, Benoît ULg

Learning material (2009)

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See detailIonosphere Modelling Based on the NeQuick Model and GNSS Data Ingestion
Bidaine, Benoît ULg; Warnant, René ULg

in Second International Colloquium - Scientific and Fundamental Aspects of the Galileo Programme (2009, October)

As for other GNSS, the ionospheric effect remains one of the main factors limiting Galileo accuracy. For single frequency users, this contribution to the error budget will be mitigated by a global ... [more ▼]

As for other GNSS, the ionospheric effect remains one of the main factors limiting Galileo accuracy. For single frequency users, this contribution to the error budget will be mitigated by a global algorithm based on the NeQuick model. This quick-run empirical model provides flexible solutions for combining ionospheric information obtained from various systems, from GNSS to ionosondes and topside sounders thanks to which NeQuick has been designed. 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 available thanks to the future European system. NeQuick provides the electron density as a function of location, time and solar activity. Thanks to numerical integration, the total content in free electrons of the ionosphere (Total Electron Content, TEC) can be deduced as well as the ionospheric propagation delay depending linearly on TEC on satellite-to-receiver path. The model is particularly suited to be used within an optimization procedure called ingestion. In this framework, an “effective ionization level” Az plays the role of the solar activity input in order to fit a specific dataset. For Galileo single frequency operation, daily Az values will be computed from slant TEC measurements performed within the ground segment. In this study, we perform slant TEC ingestion for a dozen of locations around the world where both an ionosonde and a GPS receiver are installed. These collocated instruments allow us to compare measured and modelled vertical TEC in different ways showing for example global statistics or dependence towards latitude. We analyze such results for the year 2002 (high solar activity level) giving an interesting insight in the situation we could observe when Galileo reach its Full Operation Capability, during the next solar maximum. [less ▲]

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See detailModélisation de l’ionosphère pour les utilisateurs Galileo simple fréquence
Bidaine, Benoît ULg

Conference (2009, May 11)

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See detailGalileo : une boussole spatiale européenne réglée par des ingénieurs belges
Bidaine, Benoît ULg

in Journal des Ingénieurs (Le) (2009), (121), 9-11

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See detailMeasuring Total Electron Content with GNSS: Investigation of Two Different Techniques
Bidaine, Benoît ULg; Warnant, René ULg

in The Institution of Engineering and Technology 11th International Conference on Ionospheric Radio Systems and Techniques (IRST 2009) (2009, April)

The ionosphere widely affects Global Navigation Satellite Systems (GNSS) applications, inducing among others a delay in GNSS measurements. This delay is closely linked to the Total Electron Content (TEC ... [more ▼]

The ionosphere widely affects Global Navigation Satellite Systems (GNSS) applications, inducing among others a delay in GNSS measurements. This delay is closely linked to the Total Electron Content (TEC) of the ionosphere, a major parameter which can hence be monitored using GNSS. To this extent, phase measurements are taken as a basis for their lower noise level. Levelling strategies have then to be defined for the phase measurements are obtained with an initial unknown number of cycles called ambiguity. The most common technique, referred to as carrier-to-code levelling, consists in using the differences between code and phase measurements and their average on a continuous set of epochs. This option, chosen at the Royal Meteorological Institute (RMI) of Belgium to compute TEC for Belgian GPS stations, requires code hardware delays estimation. Another has been proposed which takes benefit from Global Ionospheric Maps (GIMs) to compute a reference TEC used for ambiguity resolution. In order to understand the consequences of using one method or the other, we compare slant TEC data obtained from both techniques for a mid-latitude station (Brussels) during a high solar activity period (2002). We observed large differences (6.8 TECu on average) showing features apparently related to ionospheric and geomagnetic activity. We attribute these observations to a combination of effects originating in code delays estimation, multipath and noise as well as GIMs errors. We try to differentiate between these effects by focusing on several days and satellites. We concentrate for example on days presenting large TEC differences and geomagnetic disturbances simultaneously (or not) or on satellites displaying recurrent patterns on consecutive days. Finally we highlight the impact of the choice of GIMs involved in sTEC calibration. To this extent, we analyse vertical TEC statistics showing a general underestimation from RMI data. The highest bias (5.8 TECu) is obtained for the UPC GIMs used in the second levelling technique. [less ▲]

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See detailModéliser l’ionosphère pour les utilisateurs Galileo simple fréquence
Bidaine, Benoît ULg

Learning material (2009)

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