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Generating GPS decoupled clock products for precise point positioning with ambiguity resolution / Shuai Liu in Journal of geodesy, vol 96 n° 1 (January 2022)  

Public [article]  inJournal of geodesy > vol 96 n° 1 (January 2022) . - n° 6 Titre : Generating GPS decoupled clock products for precise point positioning with ambiguity resolution Type de document : Article/Communication Auteurs : Shuai Liu, Auteur ; Yunbin Yan, Auteur Année de publication : 2022 Article en page(s) : n° 6 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur de phase [Termes IGN] horloge du récepteur [Termes IGN] modèle stochastique [Termes IGN] onde porteuse [Termes IGN] positionnement cinématique [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté Résumé : (auteur) Carrier-phase integer ambiguity resolution (AR) is the key to improving the positioning accuracy of precise point positioning (PPP). However, in theory, the integer property of ambiguities in PPP are destroyed due to the absorption of phase biases. In this study, we analyzed a set of clock products consisting of a code clock, phase clock and wide-lane (WL) bias based on the decoupled clock (DCK) model, to facilitate PPP AR. The determination of the datum of the receiver clock as well as ambiguity were analyzed in detail to arrive at ways to eliminate rank deficiency. To fix ambiguity at the server end, we propose an approach by rounding directly with “fixing solution” (FS) and “partial ambiguity hold” (PAH) strategies, to increase the fixing rate and avoid the biased solution resulting from ambiguity datum loss. With respect to the International GNSS Service (IGS) legacy clocks, the mean standard deviations (STDs) of the phase clock and code clock were about 0.02 and 1.05 ns respectively, while the WL bias was about 0.12 cycles. Additionally, the convergence speed and stability of the decoupled phase clock are significantly improved compared with the conventional PPP model. Experiments on PPP positioning performance were conducted using 1 week of GPS data from more than 100 stations, considering the IGS weekly solutions as a benchmark. The ambiguity-fixed PPP with decoupled clocks had almost the same accuracy as the integer-recovered clock model, but the average accuracy improvements compared with the conventional PPP model in the east, north, and up components were 59.2, 32.4, and 20.3%, respectively, in the static mode, and approximately 38.0, 26.2, and 19.2% in the kinematic mode. These results demonstrate that users can achieve ambiguity-fixed solutions and obtain high-precision positioning coordinates with our decoupled clock products. Numéro de notice : A2022-093 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-021-01593-7 En ligne : https://doi.org/10.1007/s00190-021-01593-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99517 [article]

A framework for interactive visual analysis of heterogeneous marine data in an integrated problem solving environment / Shuai Liu in Computers & geosciences, vol 104 (July 2017)  

Public [article]  inComputers & geosciences > vol 104 (July 2017) Titre : A framework for interactive visual analysis of heterogeneous marine data in an integrated problem solving environment Type de document : Article/Communication Auteurs : Shuai Liu, Auteur ; Ge Chen, Auteur ; Shifeng Yao, Auteur ; Fenglin Tian, Auteur ; Wei Liu, Auteur Année de publication : 2017 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] base de données marines [Termes IGN] carte interactive [Termes IGN] données spatiotemporelles [Termes IGN] environnement géographique virtuel [Termes IGN] monde virtuel [Termes IGN] océanographie spatiale [Termes IGN] positionnement par Argos [Termes IGN] visualisation de données [Vedettes matières IGN] Géovisualisation Résumé : (auteur) This paper presents a novel integrated marine visualization framework which focuses on processing, analyzing the multi-dimension spatiotemporal marine data in one workflow. Effective marine data visualization is needed in terms of extracting useful patterns, recognizing changes, and understanding physical processes in oceanography researches. However, the multi-source, multi-format, multi-dimension characteristics of marine data pose a challenge for interactive and feasible (timely) marine data analysis and visualization in one workflow. And, global multi-resolution virtual terrain environment is also needed to give oceanographers and the public a real geographic background reference and to help them to identify the geographical variation of ocean phenomena. This paper introduces a data integration and processing method to efficiently visualize and analyze the heterogeneous marine data. Based on the data we processed, several GPU-based visualization methods are explored to interactively demonstrate marine data. GPU-tessellated global terrain rendering using ETOPO1 data is realized and the video memory usage is controlled to ensure high efficiency. A modified ray-casting algorithm for the uneven multi-section Argo volume data is also presented and the transfer function is designed to analyze the 3D structure of ocean phenomena. Based on the framework we designed, an integrated visualization system is realized. The effectiveness and efficiency of the framework is demonstrated. This system is expected to make a significant contribution to the demonstration and understanding of marine physical process in a virtual global environment. Numéro de notice : A2017-128 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.cageo.2017.03.021 En ligne : http://doi.org/10.1016/j.cageo.2017.03.021 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84543 [article]

Tight integration of ambiguity-fixed PPP and INS: model description and initial results / Shuai Liu in GPS solutions, vol 20 n° 1 (January 2016)  

Public [article]  inGPS solutions > vol 20 n° 1 (January 2016) . - pp 39 - 49 Titre : Tight integration of ambiguity-fixed PPP and INS: model description and initial results Type de document : Article/Communication Auteurs : Shuai Liu, Auteur ; Fuping Sun, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 39 - 49 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] ambiguïté entière [Termes IGN] centrale inertielle [Termes IGN] couplage GNSS-INS [Termes IGN] positionnement ponctuel précis [Termes IGN] précision centimétrique [Vedettes matières IGN] Traitement de données GNSS Résumé : (Auteur) The traditional PPP/INS system is still not used as widely as the DGNSS/INS system in precise applications, although no local reference stations are required. The main reason that prevents its use is that the traditional PPP/INS system is based on the float ambiguity solution, which leads to long convergence period and unstable positioning accuracy. We propose a tightly coupled ambiguity-fixed PPP/INS integration. First, the derivation of the observation model of the ambiguity-fixed PPP at the single-difference level using integer phase clock products from Center National d’Etudes Spatiales is presented in detail. Then the inertial navigation system model is presented. With these two models, the tightly coupled model of the PPP/INS integration is established. Finally, two carborne tests are used to evaluate the performance of the tight integration of ambiguity-fixed PPP and INS. Experimental results indicate that the proposed ambiguity-fixed PPP/INS integration is able to reach stable centimeter-level positioning after the first-fixed solution and its overall performance is comparable to that of the DGNSS/INS integration, and rapid re-convergence and re-fixing are achievable after a short period of GNSS outage for the PPP/INS integration. Numéro de notice : A2016-602 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0464-2 En ligne : http://dx.doi.org/10.1007/s10291-015-0464-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81788 [article]