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Galileo and QZSS precise orbit and clock determination using new satellite metadata / Xingxing Li in Journal of geodesy, vol 93 n° 8 (August 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 8 (August 2019) . - pp 1123 - 1136 Titre : Galileo and QZSS precise orbit and clock determination using new satellite metadata Type de document : Article/Communication Auteurs : Xingxing Li, Auteur ; Yongqiang Yuan, Auteur ; Jiande Huang, Auteur ; et al., Auteur Année de publication : 2019 Article en page(s) : pp 1123 - 1136 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] centre de phase [Termes IGN] constellation Galileo [Termes IGN] données satellitaires [Termes IGN] GIOVE (satellite) [Termes IGN] horloge du satellite [Termes IGN] lacet [Termes IGN] métadonnées [Termes IGN] modèle d'orbite [Termes IGN] orbite précise [Termes IGN] orbitographie [Termes IGN] Quasi-Zenith Satellite System [Termes IGN] rayonnement solaire [Termes IGN] variance d'Allan Résumé : (auteur) During 2016–2018, satellite metadata/information including antenna parameters, attitude laws and physical characteristics such as mass, dimensions and optical properties were released for Galileo and QZSS (except for the QZS-1 optical coefficients). These metadata are critical for improving the accuracy of precise orbit and clock determination. In this contribution, we evaluate the benefits of these new metadata to orbit and clock in three aspects: the phase center offsets and variations (PCO and PCV), the yaw-attitude model and solar radiation pressure (SRP) model. The updating of Galileo PCO and PCV corrections, from the values estimated by Deutsches Zentrum für Luft- und Raumfahrt and Deutsches GeoForschungsZentrum to the chamber calibrations disclosed by new metadata, has only a slight influence on Galileo orbits, with overlap differences within only 1 mm. By modeling the yaw attitude of Galileo satellites and QZS-2 spacecraft (SVN J002) according to new published attitude laws, the residuals of ionosphere-free carrier-phase combinations can be obviously decreased in yaw maneuver seasons. With the new attitude models, the 3D overlap RMS in eclipse seasons can be decreased from 12.3 cm, 14.7 cm, 16.8 cm and 34.7 cm to 11.7 cm, 13.4 cm, 15.8 cm and 32.9 cm for Galileo In-Orbit Validation (IOV), Full Operational Capability (FOC), FOC in elliptical orbits (FOCe) and QZS-2 satellites, respectively. By applying the a priori box-wing SRP model with new satellite dimensions and optical coefficients, the 3D overlap RMS are 5.3 cm, 6.2 cm, 5.3 cm and 16.6 cm for Galileo IOV, FOCe, FOC and QZS-2 satellites, with improvements of 11.0%, 14.7%, 14.0% and 13.8% when compared with the updated Extended CODE Orbit Model (ECOM2). The satellite laser ranging (SLR) validation reveals that the a priori box-wing model has smaller mean biases of − 0.4 cm, − 0.4 cm and 0.6 cm for Galileo FOCe, FOC and QZS-2 satellites, while a slightly larger mean bias of − 1.0 cm is observed for Galileo IOV satellites. Moreover, the SLR residual dependencies of Galileo IOV and FOC satellites on the elongation angle almost vanish when the a priori box-wing SRP model is applied. As for satellite clocks, a visible bump appears in the Modified Allan deviation at integration time of 20,000 s for Galileo Passive Hydrogen Maser with ECOM2, while it almost vanishes when the a priori box-wing SRP model and new metadata are applied. The standard deviations of clock overlap can also be significantly reduced by using new metadata. Numéro de notice : A2019-383 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-019-01230-4 Date de publication en ligne : 02/02/2019 En ligne : https://doi.org/10.1007/s00190-019-01230-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93462 [article]

Estimating the yaw-attitude of an BDS IGSO and MEO satellites / Xiaolei Dai in Journal of geodesy, vol 89 n° 10 (october 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 10 (october 2015) . - pp 1005-1018 Titre : Estimating the yaw-attitude of an BDS IGSO and MEO satellites Type de document : Article/Communication Auteurs : Xiaolei Dai, Auteur ; Maorong Ge, Auteur ; Yidong Lou, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 1005-1018 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] constellation BeiDou [Termes IGN] instabilité du vecteur (télédétection) [Termes IGN] lacet [Termes IGN] orbitographie [Termes IGN] orientation du capteur [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement ponctuel précis Résumé : (auteur) Precise knowledge and consistent modeling of the yaw-attitude of GNSS satellites are essential for high-precision data processing and applications. As the exact attitude control mechanism for the satellites of the BeiDou Satellite Navigation System (BDS) is not yet released, the reverse kinematic precise point positioning (PPP) method was applied in our study. However, we confirm that the recent precise orbit determination (POD) processing for GPS satellites could not provide suitable products for estimating BDS attitude using the reverse PPP because of the special attitude control switching between the nominal and the orbit-normal mode. In our study, we propose a modified processing schema for studying the attitude behavior of the BDS satellites. In this approach, the observations of the satellites during and after attitude switch are excluded in the POD processing, so that the estimates, which are needed in the reverse PPP, are not contaminated by the inaccurate initial attitude mode. The modified process is validated by experimental data sets and the attitude yaw-angles of the BDS IGSO and MEO satellites are estimated with an accuracy of better than 9∘. Furthermore, the results confirm that the switch is executed when the Sun elevation is about 4∘ and the actual orientation is very close to its target one. Based on the estimated yaw-angles, a preliminary attitude switch model was established and reintroduced into the POD, yielding to a substantial improvement in the orbit overlap RMS. Numéro de notice : A2015-880 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0829-x En ligne : https://doi.org/10.1007/s00190-015-0829-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79412 [article]

Algorithms for vision-based path following along previously taught paths / Deon George Sabatta (2015)  

Public Titre : Algorithms for vision-based path following along previously taught paths Type de document : Thèse/HDR Auteurs : Deon George Sabatta, Auteur Editeur : Zurich : Eidgenossische Technische Hochschule ETH - Ecole Polytechnique Fédérale de Zurich EPFZ Année de publication : 2015 Collection : Dissertationen ETH num. 22391 Format : 21 x 30 cm Note générale : bibliographie A thesis submitted to attain the degree of doctor of sciences of ETH Zurich Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géomatique [Termes IGN] base de données d'images [Termes IGN] calcul d'itinéraire [Termes IGN] chemin le plus court, algorithme du [Termes IGN] lacet [Termes IGN] milieu urbain [Termes IGN] navigation autonome [Termes IGN] optimisation (mathématiques) [Termes IGN] vision par ordinateur Résumé : (auteur) This thesis focusses on the task of navigating an autonomous vehicle along a previously driven path using feedback obtained from a camera system. The desired path is stored in the form of a “visual memory”, essentially a collection of images, captured when the vehicle was first driven along the path. Algorithms of this form find applications in many semi-autonomous inspection/exploration tasks, where the vehicle is initially navigated by an operator, using the visual data for other purposes. On completion of the task, the operator has provided the autonomous vehicle with all the information it needs to find its way back to the starting location, and potentially repeat the entire trip. By using reference images recorded along the initial path, the system is afforded a form of global localisation using only local sensing, by providing relative information to specific key-points within the environment. The work presented in this thesis uses, as a base, two well established path following controllers, and extends these control algorithms into the visual domain, by deriving the required parameters of each of the controllers from information gathered in the images. One of the key focus points of this work is the use of only the bearing (yaw) information from the images. By only working with feature bearing information we essentially reduce the number of parameters by half (by ignoring elevation) without sacrificing performance on 2D-manifolds. The first controller extends the well-known shortest distance to path control algorithm, by deriving a scaled distance to path and relative orientation from the visual memory. Using the scaled distance to path, we incorporate the unknown scale that typically plagues vision-based systems, into the controller to remove the velocity dependence of the control law. This algorithm was implemented and tested in an indoor environment with a motion capture system. The second controller extends a model predictive control (MPC) based algorithm, derived during the 2007 DARPA Grand Challenge and initially reliant on GPS information, to make use of image data, thereby alleviating the need for GPS position information. To achieve this, a novel image-based cost function is proposed that can relate the relative distances between several images. This cost function guides the choice of control trajectories to minimise the computed cost from the reference path. The performance of the proposed cost function is examined in detail, including the effects of the number of features, average distance to feature, feature observation noise and the number of outliers. To use this cost function, the control algorithm also needs an indication of how future actions will affect the cost, and to this end feature extrapolation becomes necessary. With limited visual information, and short baselines, this process is often not very successful, and various techniques are presented to improve the performance. These include the weighting of features based on their error prediction, and the reduction of the prediction horizon required by the controller. This control algorithm was demonstrated in both urban and extra-urban settings over paths on the order of 400m where the performance is shown to be comparable to that of differential GPS. Finally, it is also shown how the algorithm can be simply adapted to incorporate collision avoidance behaviour during the path replay in the event that the environment has changed between recording and playback. Numéro de notice : 17201 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/IMAGERIE Nature : Thèse étrangère Note de thèse : Doctoral thesis : Sciences : ETH Zurich : 2015 En ligne : http://dx.doi.org/10.3929/ethz-a-010419338 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81177

Reducing the draconitic errors in GNSS geodetic products / C.J. Rodriguez-Solano in Journal of geodesy, vol 88 n° 6 (June 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 6 (June 2014) . - pp 559 - 574 Titre : Reducing the draconitic errors in GNSS geodetic products Type de document : Article/Communication Auteurs : C.J. Rodriguez-Solano, Auteur ; Urs Hugentobler, Auteur ; et al., Auteur Année de publication : 2014 Article en page(s) : pp 559 - 574 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] éclipse (astronomie) [Termes IGN] harmonique sphérique [Termes IGN] lacet [Termes IGN] positionnement par GNSS [Termes IGN] rayonnement solaire Résumé : (Auteur) Systematic errors at harmonics of the GPS draconitic year have been found in diverse GPS-derived geodetic products like the geocenter Z -component, station coordinates, Y -pole rate and orbits (i.e. orbit overlaps). The GPS draconitic year is the repeat period of the GPS constellation w.r.t. the Sun which is about 351 days. Different error sources have been proposed which could generate these spurious signals at the draconitic harmonics. In this study, we focus on one of these error sources, namely the radiation pressure orbit modeling deficiencies. For this purpose, three GPS+GLONASS solutions of 8 years (2004–2011) were computed which differ only in the solar radiation pressure (SRP) and satellite attitude models. The models employed in the solutions are: (1) the CODE (5-parameter) radiation pressure model widely used within the International GNSS Service community, (2) the adjustable box-wing model for SRP impacting GPS (and GLONASS) satellites, and (3) the adjustable box-wing model upgraded to use non-nominal yaw attitude, specially for satellites in eclipse seasons. When comparing the first solution with the third one we achieved the following in the GNSS geodetic products. Orbits: the draconitic errors in the orbit overlaps are reduced for the GPS satellites in all the harmonics on average 46, 38 and 57 % for the radial, along-track and cross-track components, while for GLONASS satellites they are mainly reduced in the cross-track component by 39 %. Geocenter Z -component: all the odd draconitic harmonics found when the CODE model is used show a very important reduction (almost disappearing with a 92 % average reduction) with the new radiation pressure models. Earth orientation parameters: the draconitic errors are reduced for the X -pole rate and especially for the Y -pole rate by 24 and 50 % respectively. Station coordinates: all the draconitic harmonics (except the 2nd harmonic in the North component) are reduced in the North, East and Height components, with average reductions of 41, 39 and 35 % respectively. This shows, that part of the draconitic errors currently found in GNSS geodetic products are definitely induced by the CODE radiation pressure orbit modeling deficiencies Numéro de notice : A2014-287 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0704-1 Date de publication en ligne : 07/03/2014 En ligne : https://doi.org/10.1007/s00190-014-0704-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33190 [article]

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Séparation des décalages induits par l'attitude et le relief entre images d'un couple stéréoscopique / Sylvie Roques (2001)  

Public Titre : Séparation des décalages induits par l'attitude et le relief entre images d'un couple stéréoscopique Type de document : Article/Communication Auteurs : Sylvie Roques, Auteur ; Fabien Brachère, Auteur ; Bernard Rouge, Auteur ; Michel Pausader , Auteur Editeur : Saint-Martin-d'Hères : Groupe de Recherche et d'Etude du Traitement du Signal et des Images GRETSI Année de publication : 2001 Conférence : GRETSI 2001, 18e colloque sur le traitement du signal et des images 10/09/2001 13/09/2001 Toulouse France OA proceedings Importance : pp 765 - 768 Note générale : bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] couple stéréoscopique [Termes IGN] instabilité du vecteur (télédétection) [Termes IGN] lacet [Termes IGN] modèle géométrique de prise de vue [Termes IGN] roulis [Termes IGN] tangage Résumé : (auteur) L'objet de cet article est d'identifier les microvibrations subies par un satellite à partir d'un couple d'images stéréoscopiques dans lesquelles se combinent les effets du relief d'un paysage et ceux des vibrations de la plate-forme. Les résultats que nous présentons, qui utilisent quelques concepts de géométrie des surfaces, permettent de reconstituer les variations d'attitude (roulis, tangage et lacet) de manière quantitative. Des comparaisons avec les méthodes traditionnelles sont également présentées. Numéro de notice : C2001-055 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Communication DOI : sans En ligne : http://hdl.handle.net/2042/13408 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86512