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See detailPrecise positioning in multi-GNSS mode
Deprez, Cécile ULiege

Scientific conference (2018, November 22)

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See detailGalileo: positioning evolution
Deprez, Cécile ULiege

Conference (2018, October 25)

Summary of the evolution of Galileo over the last years. The evolution of the number of satellites, of the geometry and of the positioning are addressed successively from 2014 to 2018. W e concluded that ... [more ▼]

Summary of the evolution of Galileo over the last years. The evolution of the number of satellites, of the geometry and of the positioning are addressed successively from 2014 to 2018. W e concluded that GPS + Galileo combination improves quality of GPS-only and Galileo-only positioningbased on SPP, DGPS and RTK results. [less ▲]

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See detailGPS + Galileo Single-Frequency Relative Positioning with low-cost receivers
Deprez, Cécile ULiege; Warnant, René ULiege

Conference (2018, September 28)

During the past decade, Galileo (Europe) and BeiDou (China) satellite systems have been expanded, bringing their total number of in-orbit satellites to 26 and 35, respectively. In combination with GPS ... [more ▼]

During the past decade, Galileo (Europe) and BeiDou (China) satellite systems have been expanded, bringing their total number of in-orbit satellites to 26 and 35, respectively. In combination with GPS (USA), the redundancy of observations has increased, improving the precision, availability and robustness of satellite positioning worldwide. Low-cost single-frequency receivers could largely benefit from these combinations of GNSS, as for instance in the case of safety-of-life applications, for which system failure may be critical. In this contribution, we aimed at testing the possibility of improving the positioning performances of single-frequency low-cost receivers by using a tight combination of Galileo E1 + GPS L1 frequency. We evaluated positioning precisions of u-blox EVK M8T receivers, which cost a few hundred USDs, in multi-GNSS relative positioning based on code and phase double differences. We compared the results obtained with these low-cost receivers with those of geodetic receivers, which cost thousands of USDs. To create a valid stochastic model for u-blox combinations, we designed a very short baseline experiment (5.6 meters) on the roof of the Physics building of the University of Liège (Belgium) in which two low-cost u-blox receivers were connected to two choke-ring Trimble TRM 59800 SCIS antennas. The use of these geodetic antennas instead of the low-cost u-blox patch antennas provides better multipath mitigation performances as well as more precise signal tracking. We had the antenna positions fixed at a few millimetre level precision so that no error coming from an a priori position estimation could influence our results. On this basis, we computed u-blox GPS L1 and Galileo E1 code and phase observation precisions by the means of double differences. First results showed code observation precisions ranging from 30 to 40 centimetres for both GPS L1 and Galileo E1 signals and phase observation precisions of 1 millimetre. The use of a unique-pivot satellite for both constellations in GPS L1 + Galileo E1 double differences introduces differential receiver hardware delays between GPS and Galileo, also called inter-system biases (ISBs). They need to be estimated as new unknowns in an ISBs-float model. The code ISBs are estimated as an additional unknown in a least square adjustment together with the position unknowns (X, Y, Z). The method is different when it comes to carrier phase ISBs, the entire part of the ISBs being estimated all together with the integer ambiguity thanks to the LAMBDA method, so that only the fractional part (between -0.5 and 0.5 cycles) remains to be estimated as an additional error. We first evaluated these ISBs over short baselines where low-cost u-blox receivers were connected to choke-ring Trimble antennas. In this experiment, both ISBs between u-blox receivers as well as the ISBs between u-blox and geodetic receivers were studied. The University of Liège owns 2 Septentrio PolaRx4 and 2 Trimble NetR9, which were used in this contribution. We performed an analysis of ISBs stability over time and studied the possibility of removing these errors as a constant biases in ISBs-fixed model. We computed different values of ISBs for each different u-blox unit used in the experiment we conducted on the roof of the building. Trimble - u-blox code ISBs showed ISBs varying between 1.9 and 2.3 meters while Septentrio - u-blox code ISBS were ranging between 0.4 and 0.8 meters. Between u-blox code ISBs were also computed, showing results varying from 34 to 43 centimetres. We quantified the positioning accuracy improvement brought by multi-GNSS single-frequency models using ISBs-fixed and ISBs-float solutions to models ignoring ISBs. Eventually, we enlarged the baselines from a few meters to 13 kilometres. We concluded that ISBs estimated over very short baselines could be used to characterize ISBs encountered on larger baselines. This is a first analysis of GPS L1 + Galileo E1 ISBs between low-cost receivers and between low-cost and geodetic receivers. The contribution presents reference values of observation precision and positioning accuracy over distances ranging from 5 meters to 13 kilometres. We used a software of our own, developed under MATLAB, to provide these results on 1 second data. Observations under 10° of elevation were not considered in the analysis as well as positioning solutions with bad geometry (PDOP greater than 6). We computed broadcast orbits thanks to IGS MGEX products. [less ▲]

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See detailGPS, Galileo et BeiDou :Évolution du positionnement par satellites
Deprez, Cécile ULiege

Conference (2018, June 21)

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See detailGPS + Galileo Single-Frequency Relative Positioning with low-cost receivers
Deprez, Cécile ULiege; Warnant, René ULiege

in Proceedings of ION GNSS+ 2018 (2018)

During the past decade, Galileo (Europe) and BeiDou (China) satellite systems have been expanded, bringing their total number of in-orbit satellites to 26 and 35, respectively. In combination with GPS ... [more ▼]

During the past decade, Galileo (Europe) and BeiDou (China) satellite systems have been expanded, bringing their total number of in-orbit satellites to 26 and 35, respectively. In combination with GPS (USA), the redundancy of observations has increased, improving the precision, availability and robustness of satellite positioning worldwide. Low-cost single-frequency receivers could largely benefit from these combinations of GNSS, as for instance in the case of safety-of-life applications, for which system failure may be critical. In this contribution, we aimed at testing the possibility of improving the positioning performances of single-frequency low-cost receivers by using a tight combination of Galileo E1 + GPS L1 frequency. We evaluated positioning precisions of u-blox EVK M8T receivers, which cost a few hundred USDs, in multi-GNSS relative positioning based on code and phase double differences. We compared the results obtained with these low-cost receivers with those of geodetic receivers, which cost thousands of USDs. To create a valid stochastic model for u-blox combinations, we designed a very short baseline experiment (5.6 meters) on the roof of the Physics building of the University of Liège (Belgium) in which two low-cost u-blox receivers were connected to two choke-ring Trimble TRM 59800 SCIS antennas. The use of these geodetic antennas instead of the low-cost u-blox patch antennas provides better multipath mitigation performances as well as more precise signal tracking. We had the antenna positions fixed at a few millimetre level precision so that no error coming from an a priori position estimation could influence our results. On this basis, we computed u-blox GPS L1 and Galileo E1 code and phase observation precisions by the means of double differences. First results showed code observation precisions ranging from 30 to 40 centimetres for both GPS L1 and Galileo E1 signals and phase observation precisions of 1 millimetre. The use of a unique-pivot satellite for both constellations in GPS L1 + Galileo E1 double differences introduces differential receiver hardware delays between GPS and Galileo, also called inter-system biases (ISBs). They need to be estimated as new unknowns in an ISBs-float model. The code ISBs are estimated as an additional unknown in a least square adjustment together with the position unknowns (X, Y, Z). The method is different when it comes to carrier phase ISBs, the entire part of the ISBs being estimated all together with the integer ambiguity thanks to the LAMBDA method, so that only the fractional part (between -0.5 and 0.5 cycles) remains to be estimated as an additional error. We first evaluated these ISBs over short baselines where low-cost u-blox receivers were connected to choke-ring Trimble antennas. In this experiment, both ISBs between u-blox receivers as well as the ISBs between u-blox and geodetic receivers were studied. The University of Liège owns 2 Septentrio PolaRx4 and 2 Trimble NetR9, which were used in this contribution. We performed an analysis of ISBs stability over time and studied the possibility of removing these errors as a constant biases in ISBs-fixed model. We computed different values of ISBs for each different u-blox unit used in the experiment we conducted on the roof of the building. Trimble - u-blox code ISBs showed ISBs varying between 1.9 and 2.3 meters while Septentrio - u-blox code ISBS were ranging between 0.4 and 0.8 meters. Between u-blox code ISBs were also computed, showing results varying from 34 to 43 centimetres. We quantified the positioning accuracy improvement brought by multi-GNSS single-frequency models using ISBs-fixed and ISBs-float solutions to models ignoring ISBs. Eventually, we enlarged the baselines from a few meters to 13 kilometres. We concluded that ISBs estimated over very short baselines could be used to characterize ISBs encountered on larger baselines. This is a first analysis of GPS L1 + Galileo E1 ISBs between low-cost receivers and between low-cost and geodetic receivers. The contribution presents reference values of observation precision and positioning accuracy over distances ranging from 5 meters to 13 kilometres. We used a software of our own, developed under MATLAB, to provide these results on 1 second data. Observations under 10° of elevation were not considered in the analysis as well as positioning solutions with bad geometry (PDOP greater than 6). We computed broadcast orbits thanks to IGS MGEX products. [less ▲]

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See detailPrecise Positioning with Smartphones running Android 7 or later
Warnant, René ULiege; Deprez, Cécile ULiege; Warnant, Quentin

Conference (2017, November 17)

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See detailPrecise Positioning in multi-GNSS mode
Deprez, Cécile ULiege; Warnant, René ULiege

Conference (2017, November 17)

Detailed reference viewed: 35 (3 ULiège)
See detailPositioning in multi-GNSS mode
Deprez, Cécile ULiege; Warnant, René ULiege

Conference (2017, March 16)

Satellite positioning is facing new challenges with the appearance of mass-market receivers and smartphones. Mainly, the reliability of the car navigation systems, the accuracy of positioning in ... [more ▼]

Satellite positioning is facing new challenges with the appearance of mass-market receivers and smartphones. Mainly, the reliability of the car navigation systems, the accuracy of positioning in smartphone—based applications and the availability of positions in urban canyon or deep forests suffer from the hardware limitations of these low-cost receivers. Would the multi-GNSS positioning be the solution to handle those challenges? Indeed, the number of satellites available has dramatically increased, given the expansion of two new global satellite constellations (Galileo (EU) and BeiDou (C)), and might meet these positioning challenges, at least to some extent. [less ▲]

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See detailMulti-GNSS relative positioning with Galileo, BeiDou and GPS
Deprez, Cécile ULiege; Warnant, René ULiege

in Proceedings of NAVITEC 2016 (2016, December 16)

For several years, the number of Global Navigation Satellite Systems (GNSS) has been increasing, opening new perspectives in the field of precise positioning. Particularly, the European system, Galileo ... [more ▼]

For several years, the number of Global Navigation Satellite Systems (GNSS) has been increasing, opening new perspectives in the field of precise positioning. Particularly, the European system, Galileo, is experiencing a prompt expansion with the launch, in 2015 and 2016, of 8 satellites belonging to the new Full Operational Capability (FOC) generation. Broadcasting new signals, with new modulations, the first studies addressing this system reveal promising level of precisions on both code and carrier phase observables. Yet, Galileo is far from being the only GNSS undergoing a noteworthy revolution. Alternatively, the Chinese program BeiDou, still in a developing phase, as well as the American GPS, currently undergoing a modernization of its signals, also knew major progress these last two years. Indeed, 7 new satellites have reached the initial BeiDou constellation, bringing to 20 the number of active satellites. Among them, 5 spacecraft inaugurated the Phase III generation, broadcasting the new B1, B2 and B3 signals. Regarding GPS, the block IIF, made of L5 signal broadcasting satellites, kept expanding but at a less steep rate than BeiDou or Galileo. In this study, we first estimated the individual precisions of each signals broadcast by the aforementioned GNSS. For this purpose, we created two short baselines of approximatively 5 meters between similar type receivers. We combined their measurements to form double differences, leaving in the position equations only multipath and receiver noise. The great expectations regarding Galileo’s quality turned into affirmations as long as we studied this system. As a matter of a fact, the code pseudoranges values of the 4 signals of Galileo we have considered (E1, E5a, E5b, E5a+b) presented outstanding precisions (from 5 to 17 centimetres on code pseudoranges with an elevation mask of 10 degrees) when compared to GPS (from 12 to 20 centimetres on codes pseudoranges) and BeiDou (from 26 to 40 centimetres for codes and for phases) in identical conditions. Even though the precision of Galileo observables is noticeable, the influence of the poor geometry of the satellite constellation degrades in a significant way the resulting precision of the position estimated, no matter the recent increase in the number of satellites. Indeed, in this incomplete constellation, the addition of new satellites results in longer visibility period but not in larger number of satellites observed at a single epoch. Combining Galileo with GPS or BeiDou is a way to solve this issue, as the three systems have been designed to be compatible. Therefore, multi-GNSS relative positioning based on overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. The overlapping frequencies of these GNSS are the L1 and L5 frequencies of GPS with the E1 and E5a signals of Galileo, respectively. As far as BeiDou is concerned, the B2 signal of emitted by the Phase II BeiDou satellites corresponds to the E5b frequency of Galileo. Regarding the new Phase III satellites, the B2 frequencies will correspond to the Galileo E5a+b signal and B1 of BeiDou will be compatible with E1 of Galileo and GPS. The combined use of these overlapping frequencies in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependent error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. We conducted this study on the L1/E1, L5/E5a, B1(phase II)/E5b overlapping frequencies. Our receivers were not able to receive the phase III signals of BeiDou satellites. An analysis of the long-term stability of ISBs (GPS- Galileo and Galileo - BeiDou) was conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values was also investigated. Our study is based on the 6 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS, 1 Septentrio PolaRx5 and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi- GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS, Galileo and BeiDou standalone solutions. [less ▲]

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See detailThe added value of new GNSS for ionosphere monitoring
Warnant, René ULiege; Deprez, Cécile ULiege

in Proceedings of Navitec 2016 (2016, December)

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See detailRelative positioning with Galileo E5 AltBOC code measurements
Deprez, Cécile ULiege; Warnant, René ULiege

Conference (2016, October 11)

For over a decade, Europe has started to develop its own Global Navigation Satellite System (GNSS). Initiated in 1999, the Galileo project finally materialized a few years ago, recently experiencing a ... [more ▼]

For over a decade, Europe has started to develop its own Global Navigation Satellite System (GNSS). Initiated in 1999, the Galileo project finally materialized a few years ago, recently experiencing a prompt expansion with the launch, in 2015 and 2016, of 8 satellites belonging to the Full Operational Capability (FOC) generation. Broadcasting new signals, with new modulations, the first studies addressing this system reveal promising level of precisions on both code and carrier phase observables. Still in test phase but already available for measurements, this recent system can be used to estimate positions. Among the new signals developed by the Galileo program, the Galileo E5 AltBOC, also known as Galileo E5a+b or Galileo E5, reveals great characteristics. Thanks to its particular AltBOC modulation, it allows more precise code and phase observations besides being less affected by multipath. These innovative performances should lead to more precise position estimations than with any other signal presently in use. In this master thesis, we compared the positions estimated with GPS and Galileo on their different frequencies (L1, L2, L5 for GPS and E1, E5a, E5b and E5 AltBOC for Galileo). We combined the observations made by the receivers belonging to the University of Liège (2 Trimble NetR9 receivers, 1 Septentrio PolaRxS receiver and one Septentrio PolaRx4 receiver) in double differences (DD) combinations using various configurations (zero baseline (ZB), short baseline (SB) and medium baseline (MB)). It turns out that Galileo E5 AltBOC outperforms all other signal in terms of observation precision (estimated in a DD SB configuration in order to remove atmospheric and clock error sources affecting the signal). Regarding the precision obtained on the computed positions, we could reach a few decimetres with Galileo E5 code pseudoranges on baselines up to 25 kilometres. [less ▲]

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See detailGPS, Galileo and BeiDou inter-system biases estimation in relative positioning with code and phase pseudoranges
Deprez, Cécile ULiege; Warnant, René ULiege

Conference (2016, September 07)

The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the Chinese BeiDou satellite system and the ... [more ▼]

The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the Chinese BeiDou satellite system and the European Galileo program have experienced major progress in 2015 and 2016 with the launch of 7 and 8 satellites respectively. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo, B2 from BeiDou and E5b from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependent error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs (GPS- Galileo and Galileo - BeiDou) is conducted onvariouspairsof receiversover large timespans. Thepossibleinfluenceof temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 6 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS, 1 Septentrio PolaRx5 and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS, Galileo and BeiDou standalone solutions. [less ▲]

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See detailThe added value of new GNSS to monitor the ionosphere
Warnant, René ULiege; Deprez, Cécile ULiege; Van de Vyvere, Laura

Conference (2016, September)

Detailed reference viewed: 22 (3 ULiège)
See detailMonitoring the ionosphere using new GNSS
Warnant, René ULiege; Deprez, Cécile ULiege; Wautelet, Gilles ULiege et al

Conference (2016, June 27)

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See detailInter-system biases estimation in multi-GNSS relative positioning with GPS and Galileo
Deprez, Cécile ULiege; Warnant, René ULiege

Conference (2016, April 18)

The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the European Galileo program has ... [more ▼]

The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the European Galileo program has experienced major progress in 2015 with the launch of 6 satellites belonging to the new Full Operational Capability (FOC) generation. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on GPS and Galileo overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. Once these biases estimated and removed from the model, a solution involving a unique pivot satellite for the two considered constellations can be obtained. Such an approach implies that the addition of even one single Galileo satellite to the GPS-only model will strengthen it. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satelliteand receiver-dependant error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs is conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 5 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS and Galileo standalone solutions. [less ▲]

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See detailRelative positioning with Galileo E5 AltBOC code measurements
Deprez, Cécile ULiege

Conference (2016, March 03)

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de ... [more ▼]

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de la technologie, les horloges atomiques embarquées à bord de ses satellites ainsi que les signaux transmis par ces derniers sont extrêmement prometteurs dans beaucoup de domaines. Bien que toujours en phase de test à l’heure actuelle, ce système a déjà conduit à de premières mesures, notamment en matière de positionnement. Parmi ces nouvelles technologies, un signal en particulier semble très prometteur : Galileo E5, aussi appelé Galileo E5a+b ou encore Galileo E5 AltBOC. Ce signal permet d’effectuer des mesures de code et de phase plus précises. Il est également moins sensible au multi-trajet. Grâce à ses caractéristiques innovantes, Galileo E5 devrait permettre d’estimer des positions avec une précision supérieure à tous les autres signaux utilisés aujourd’hui. Une étude comparative des positions estimées avec les systèmes GPS (américain) et Galileo (européen) sur leurs différentes fréquences émises (GPS L1, GPS L2, GPS L5 pour GPS et Galileo E1, Galileo E5a, Galileo E5b et Galileo E5 AltBOC pour Galileo) a été menée dans ce mémoire. Pour ce faire, une combinaison d’observations appelée double différence (DD) est utilisée sous différentes configurations (ligne de base nulle (ZB), courte (SB) et moyenne (MB)) de récepteurs GNSS. Les récepteurs utilisés appartiennent à l’Université de Liège (2 récepteurs Trimble NetR9, 1 récepteur Septentrio XS et un récepteur Septentrio X4). Il ressort de cette étude que Galileo E5 AltBOC présente les observations les plus précises (en ZB, toutes sources d’erreurs éliminées). L’analyse démontre également qu’une précision de l’ordre de quelques décimètres sur la position à déterminer peut être atteinte avec les codes transmis par le signal Galileo E5, et ce jusqu’à 25 kilomètres de distance. [less ▲]

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See detailRelative positioning with Galileo E5 AltBOC code measurements
Deprez, Cécile ULiege

Master's dissertation (2015)

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de ... [more ▼]

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de la technologie, les horloges atomiques embarquées à bord de ses satellites ainsi que les signaux transmis par ces derniers sont extrêmement prometteurs dans beaucoup de domaines. Bien que toujours en phase de test à l’heure actuelle, ce système a déjà conduit à de premières mesures, notamment en matière de positionnement. Parmi ces nouvelles technologies, un signal en particulier semble très prometteur : Galileo E5, aussi appelé Galileo E5a+b ou encore Galileo E5 AltBOC. Ce signal permet d’effectuer des mesures de code et de phase plus précises. Il est également moins sensible au multi-trajet. Grâce à ses caractéristiques innovantes, Galileo E5 devrait permettre d’estimer des positions avec une précision supérieure à tous les autres signaux utilisés aujourd’hui. Une étude comparative des positions estimées avec les systèmes GPS (américain) et Galileo (européen) sur leurs différentes fréquences émises (GPS L1, GPS L2, GPS L5 pour GPS et Galileo E1, Galileo E5a, Galileo E5b et Galileo E5 AltBOC pour Galileo) a été menée dans ce mémoire. Pour ce faire, une combinaison d’observations appelée double différence (DD) est utilisée sous différentes configurations (ligne de base nulle (ZB), courte (SB) et moyenne (MB)) de récepteurs GNSS. Les récepteurs utilisés appartiennent à l’Université de Liège (2 récepteurs Trimble NetR9, 1 récepteur Septentrio XS et un récepteur Septentrio X4). Il ressort de cette étude que Galileo E5 AltBOC présente les observations les plus précises (en ZB, toutes sources d’erreurs éliminées). L’analyse démontre également qu’une précision de l’ordre de quelques décimètres sur la position à déterminer peut être atteinte avec les codes transmis par le signal Galileo E5, et ce jusqu’à 25 kilomètres de distance. [less ▲]

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Peer Reviewed
See detailImpact de l’anisotropie du milieu dans les études de profilage géographique
Trotta, Marie ULiege; Deprez, Cécile ULiege; Donnay, Jean-Paul ULiege

in Revue Internationale de Géomatique (2015), 25(4), 561-579

This article aims at assessing the bias introduced by the use of the Euclidean distance in the context of geographic profiling analyzes. It proceeds by a comparison of road and Euclidean distances of ... [more ▼]

This article aims at assessing the bias introduced by the use of the Euclidean distance in the context of geographic profiling analyzes. It proceeds by a comparison of road and Euclidean distances of about 1 000 pairs of origin-destination (crime sites – criminal’s anchor point) from the database of the Belgian Federal Police. Comparisons are differentiated by the density of road network (rural and urban areas) and the statistical parameters of the resulting distributions are exploited in the application of the most common geographic profiling model called the distance decay model. [less ▲]

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