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Ionosphere probing with simultaneous GNSS radio occultations / Viet-Cuong Pham in GPS solutions, vol 21 n° 1 (January 2017)  

Public [article]  inGPS solutions > vol 21 n° 1 (January 2017) . - pp 101 - 109 Titre : Ionosphere probing with simultaneous GNSS radio occultations Type de document : Article/Communication Auteurs : Viet-Cuong Pham, Auteur ; Jyh-Ching Juang, Auteur Année de publication : 2017 Article en page(s) : pp 101 - 109 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] données GNSS [Termes IGN] gradient ionosphèrique [Termes IGN] inversion [Termes IGN] occultation du signal [Termes IGN] orbite basse [Termes IGN] régularisation de Tychonoff [Termes IGN] teneur totale en électrons Résumé : (Auteur) Radio occultation (RO) is a powerful technique for providing vertical profiles of refractivity, temperature, pressure, and water vapor of the neutral atmosphere and electron density of the ionosphere. The Abel inversion method which is based on the spherical symmetry assumption has been widely utilized to retrieve electron density profiles (EDPs) from RO measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit satellites. It is well known that the Abel inversion is subject to errors in the presence of ionospheric horizontal gradients. With the arrival of new navigation systems, the opportunities of establishing simultaneous GNSS RO events are increasing. We develop an improved Abel inversion technique that accounts for pairs of simultaneous RO events to relax the spherical symmetry assumption. Through the use of Tikhonov regularization, the problem is formulated so that numerical conditioning is improved and a priori information such as expected electron density, asymmetric factor, and vertical total electron content can be incorporated. Appropriate weighting can be determined to reflect the availability and quality of information. By balancing the reference data and measurements, the method thus paves a way for ionospheric probing in challenging geomagnetic conditions as both the EDP at the intersection and the horizontal gradients are retrieved. Simulation and experimental results are provided to show the effectiveness of the proposed method. The robustness and sensitivity of the proposed method are also assessed. Numéro de notice : A2017-014 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0501-1 Date de publication en ligne : 02/01/2016 En ligne : http://dx.doi./org/10.1007/s10291-015-0501-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83936 [article]

Laser ranging plus GNSS / Jyh-Ching Juang in GPS world, vol 27 n° 5 (May 2016)

Public [article]  inGPS world > vol 27 n° 5 (May 2016) . - pp 24 - 29 Titre : Laser ranging plus GNSS Type de document : Article/Communication Auteurs : Jyh-Ching Juang, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 24 - 29 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] appariement de points [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] indicateur de qualité [Termes IGN] semis de points Résumé : (éditeur) Context-dependent scan matching for aided navigation, finding the rotation and translation that best align two consecutive scans, provides laser-ranging data that can be blended into a GNSS navigation system. A quality index based on analysis of intra-frame point clouds assesses the scan context, accounting for variations in feature richness, to yield a robust aided navigation solution. Numéro de notice : A2016-226 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80695 [article]