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Auteur Hui Liu |
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Fast ambiguity resolution for long-range reference station networks with ionospheric model constraint method / Ming Zhang in GPS solutions, vol 21 n° 2 (April 2017)
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Titre : Fast ambiguity resolution for long-range reference station networks with ionospheric model constraint method Type de document : Article/Communication Auteurs : Ming Zhang, Auteur ; Hui Liu, Auteur ; Zhengdong Bai, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 617 – 626 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] antenne GNSS
[Termes IGN] erreur
[Termes IGN] modèle ionosphérique
[Termes IGN] résolution d'ambiguïté
[Termes IGN] retard ionosphèrique
[Termes IGN] station de référenceRésumé : (auteur) Ambiguity resolution (AR) speed is one of the most important performance indicators of a network RTK (real-time kinematics) system. Given the low correlation between the error sources of two stations, the effect of the atmospheric delay of double-difference observations cannot be ignored, thus making it difficult to fix the ambiguities. Ionospheric delay is one of the largest error sources affecting AR. This error source is reduced by the ionospheric-free combination with traditional methods. The AR speed of these methods is slow; generally, tens of minutes and even more are required for initialization. This study proposes an ionospheric model constraint (IMC) method to improve the AR speed. External information is not required apart from observations. The double-difference ionospheric delay is described with a regional double-difference ionospheric model, the coefficients of which are estimated as parameters together with ambiguities and tropospheric delays. Experimental results show that the initialization speed significantly improves by 72.5 % and that the AR speed for the newly risen satellites increases by 84.3 % with the proposed IMC method. Furthermore, the percentage of correctly fixed integer ambiguities after initialization increases to some extent. Numéro de notice : A2017-215 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0551-z En ligne : http://dx.doi.org/10.1007/s10291-016-0551-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85087
in GPS solutions > vol 21 n° 2 (April 2017) . - pp 617 – 626[article]A new method to improve the performance of multi-GNSS pseudorange positioning in signal-degraded environment / Hui Liu in Advances in space research, vol 58 n° 4 (August 2016)
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Titre : A new method to improve the performance of multi-GNSS pseudorange positioning in signal-degraded environment Type de document : Article/Communication Auteurs : Hui Liu, Auteur ; Longwei Xu, Auteur ; Bao Shu, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 577 - 586 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] interopérabilité
[Termes IGN] mesurage de pseudo-distance
[Termes IGN] système de positionnement par satellites
[Termes IGN] visibilitéRésumé : (auteur) There are two existing multi-GNSS positioning methods, (1) separate receiver clock parameter is set for each constellation, (2) estimating intersystem biases (ISBs) in advance to obtain position solutions with only four unknowns. The former is the regular method and its unknowns include three receiver-coordinate parameters and several receiver clock parameters (depend on the number of participant constellations), so that it may disable when few satellites belonging to different GNSS are in view. The latter is one workable way to obtain position solution with only four visible satellites. In addition to the disabled regular method, the positioning results by the ISB-corrected method are often unsatisfactory for navigation users in signal-degraded environment. Both the deviation of ISB-solutions and the remaining measurement errors of the need corrected observations are factors to degrade location precision. Apart from these, fewer visible satellites usually cause a low robustness of the positioning model, which cause the negative influence of various errors is amplified. Based on the variation of various measurement errors, we propose a new ISSB-corrected method with observations corrected by corresponding satellite-dependent parameters. The new parameter contains the difference of time scales, hardware delays and uncorrected measurement errors between the corresponding satellite and reference, in other words, it can synthetically consider measurement errors and the ISB. By the ISSB-corrected method, we not only achieve positioning solutions with four satellites, but also significantly reduce the accuracy loss. Many experiments are conducted to present the superiority of the ISSB-corrected method. In open-area, the accuracies of regular and ISB-corrected methods are nearly equal. Apart from a similar accuracy in horizontal, the accuracy is improved by approximate 10% in up direction with respect to the two existing methods. Given the high redundancy of model in open-area, the new method may not improve the accuracy remarkably. However, it can make great contributions in signal-degraded environments. In order to compare the performance of ISB- and ISSB-corrected methods in environment with limited visible satellites, we simulate several scenarios (different satellites participant or various receivers) with only four participant satellites in the positioning solution. By the ISSB-corrected method, the 3D RMS of positioning results with four satellites is about 15 m, while it is usually worse than 25 m for the ISB-corrected method. In an urban vehicular test, the horizontal positioning error of the ISSB-corrected method is less than 20 m; and the ISB-corrected method may reach up to 70 m. Numéro de notice : A2016-592 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2016.05.016 En ligne : http://dx.doi.org/10.1016/j.asr.2016.05.016 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81748
in Advances in space research > vol 58 n° 4 (August 2016) . - pp 577 - 586[article]