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GPS inter-frequency clock bias estimation for both uncombined and ionospheric-free combined triple-frequency precise point positioning / Lin Pan in Journal of geodesy, vol 93 n° 4 (April 2019)  

Public [article]  inJournal of geodesy > vol 93 n° 4 (April 2019) . - pp 473 - 487 Titre : GPS inter-frequency clock bias estimation for both uncombined and ionospheric-free combined triple-frequency precise point positioning Type de document : Article/Communication Auteurs : Lin Pan, Auteur ; Xiaohong Zhang, Auteur ; Fei Guo, Auteur ; Jingnan Liu, Auteur Année de publication : 2019 Article en page(s) : pp 473 - 487 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] erreur systématique interfréquence d'horloge [Termes IGN] mesurage de phase [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur trifréquence Résumé : (Auteur) The time-varying biases within carrier phase observations will be integrated with satellite clock offset parameters in the precise clock estimation. The inconsistency among signal-dependent phase biases within a satellite results in the inadequacy of the current L1/L2 ionospheric-free (IF) satellite clock products for the GPS precise point positioning (PPP) involving L5 signal. The inter-frequency clock bias (IFCB) estimation approaches for triple-frequency PPP based on either uncombined (UC) observations or IF combined observations within a single arbitrary combination are proposed in this study. The key feature of the IFCB estimation approaches is that we only need to obtain a set of phase-specific IFCB (PIFCB) estimates between the L1/L5 and L1/L2 IF satellite clocks, and then, we can directly convert the obtained L1/L5 IF PIFCBs into L5 UC PIFCBs and L1/L2/L5 IF PIFCBs by multiplying individual constants. The mathematical conversion formula is rigorously derived. The UC and IF triple-frequency PPP models are developed. Datasets from 171 stations with a globally even distribution on seven consecutive days were adopted for analysis. After 24-h observation, the UC and IF triple-frequency PPP without PIFCB corrections can achieve an accuracy of 8, 6 and 13 mm, and 8, 5 and 13 mm in east, north and up coordinate components, respectively, while the corresponding positioning accuracy of the cases with PIFCB consideration can be improved by 38, 33 and 31%, and 50, 40 and 23% to 5, 4 and 9 mm, and 4, 3 and 10 mm in the three components, respectively. The corresponding improvement in convergence time is 17, 1 and 22% in the three components in UC model, respectively. Moreover, the phase observation residuals on L5 frequency in UC triple-frequency PPP and of L1/L2/L5 IF combination in IF triple-frequency PPP are reduced by about 4 mm after applying PIFCB corrections. The performance improvement in UC triple-frequency PPP over UC dual-frequency PPP is 7, 4 and 2% in terms of convergence time in the three components, respectively. The daily solutions of UC triple-frequency PPP have a comparable positioning accuracy to the UC dual-frequency PPP. Numéro de notice : A2019-155 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1176-5 Date de publication en ligne : 17/07/2018 En ligne : https://doi.org/10.1007/s00190-018-1176-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92494 [article]

BeiDou phase bias estimation and its application in precise point positioning with triple-frequency observable / Shengfeng Gu in Journal of geodesy, vol 89 n° 10 (october 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 10 (october 2015) . - pp 979 - 992 Titre : BeiDou phase bias estimation and its application in precise point positioning with triple-frequency observable Type de document : Article/Communication Auteurs : Shengfeng Gu, Auteur ; Yidong Lou, Auteur ; Chuang Shi, Auteur ; Jingnan Liu, Auteur Année de publication : 2015 Article en page(s) : pp 979 - 992 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] BeiDou [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) At present, the BeiDou system (BDS) enables the practical application of triple-frequency observable in the Asia-Pacific region, of many possible benefits from the additional signal; this study focuses on exploiting the contribution of zero difference (ZD) ambiguity resolution (AR) to the precise point positioning (PPP). A general modeling strategy for multi-frequency PPP AR is presented, in which, the least squares ambiguity decorrelation adjustment (LAMBDA) method is employed in ambiguity fixing based on the full variance-covariance ambiguity matrix generated from the raw data processing model. Because of the reliable fixing of BDS L1 ambiguity faces more difficulty, the LAMBDA method with partial ambiguity fixing is proposed to enable the independent and instantaneous resolution of extra wide-lane (EWL) and wide-lane (WL). This mechanism of sequential ambiguity fixing is demonstrated for resolving ZD satellite phase bias and performing triple-frequency PPP AR with two reference station networks with a typical baseline of up to 400 and 800 km, respectively. Tests show that about 90% of the EWL and WL phase bias of BDS has a consistency of better than 0.1 cycle, and this value decreases to Numéro de notice : A2015-879 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0827-z Date de publication en ligne : 23/06/2015 En ligne : https://doi.org/10.1007/s00190-015-0827-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79411 [article]

Instantaneous ambiguity resolution for URTK and its seamless transition with PPP-AR / Xuan Zou in GPS solutions, vol 19 n° 4 (october 2015)  

Public [article]  inGPS solutions > vol 19 n° 4 (october 2015) . - pp 559 - 567 Titre : Instantaneous ambiguity resolution for URTK and its seamless transition with PPP-AR Type de document : Article/Communication Auteurs : Xuan Zou, Auteur ; Weiming Tang, Auteur ; Chuang Shi, Auteur ; Jingnan Liu, Auteur Année de publication : 2015 Article en page(s) : pp 559 - 567 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] résolution d'ambiguïté [Termes IGN] système d'extension [Termes IGN] véhicule automobile Résumé : (auteur) We extend the current Undifferenced network RTK (URTK) approaches by additionally using P1/CA augmentation information from reference stations. P1/CA augmentation information can shorten the convergence time and help to fix the ionosphere-free combination ambiguities in several epochs. Instantaneous and centimeter-level positioning solutions can be achieved for rovers within the coverage of regional reference network. Also, we develop an approach for seamless transition between URTK and precise point positioning with ambiguity resolution (PPP-AR) and present a new scheme to provide URTK service. Therefore, a service for a large number of rovers can be easily realized in real-time data communication for ambiguity fixing. In addition, the period when augmentation information from a particular reference station is not available can be bridged with the help of PPP-AR. Rovers can experience more operational time with fewer interruptions, which are difficult tasks for current URTK and Network Real-Time Kinematic services. More importantly, with this new scheme, URTK and PPP-AR services can be integrated into a unique PPP-AR system. The obtained convergence time only depends on whether or not the rover is receiving the regional augmentation information. Numéro de notice : A2015-465 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-0411-7 Date de publication en ligne : 14/10/2014 En ligne : https://doi.org/10.1007/s10291-014-0411-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=77152 [article]

Ionospheric effects in uncalibrated phase delay estimation and ambiguity-fixed PPP based on raw observable model / Shengfeng Gu in Journal of geodesy, vol 89 n° 5 (May 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 5 (May 2015) . - pp 447 - 457 Titre : Ionospheric effects in uncalibrated phase delay estimation and ambiguity-fixed PPP based on raw observable model Type de document : Article/Communication Auteurs : Shengfeng Gu, Auteur ; Chuang Shi, Auteur ; Yidong Lou, Auteur ; Jingnan Liu, Auteur Année de publication : 2015 Article en page(s) : pp 447 - 457 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction ionosphérique [Termes IGN] modèle ionosphérique [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] propagation ionosphérique [Termes IGN] résolution d'ambiguïté [Termes IGN] retard ionosphèrique [Termes IGN] signal GNSS [Termes IGN] teneur totale en électrons Résumé : (auteur) Zero-difference (ZD) ambiguity resolution (AR) reveals the potential to further improve the performance of precise point positioning (PPP). Traditionally, PPP AR is achieved by Melbourne–Wübbena and ionosphere-free combinations in which the ionosphere effect are removed. To exploit the ionosphere characteristics, PPP AR with L1 and L2 raw observable has also been developed recently. In this study, we apply this new approach in uncalibrated phase delay (UPD) generation and ZD AR and compare it with the traditional model. The raw observable processing strategy treats each ionosphere delay as an unknown parameter. In this manner, both a priori ionosphere correction model and its spatio-temporal correlation can be employed as constraints to improve the ambiguity resolution. However, theoretical analysis indicates that for the wide-lane (WL) UPD retrieved from L1/L2 ambiguities to benefit from this raw observable approach, high precision ionosphere correction of better than 0.7 total electron content unit (TECU) is essential. This conclusion is then confirmed with over 1 year data collected at about 360 stations. Firstly, both global and regional ionosphere model were generated and evaluated, the results of which demonstrated that, for large-scale ionosphere modeling, only an accuracy of 3.9 TECU can be achieved on average for the vertical delays, and this accuracy can be improved to about 0.64 TECU when dense network is involved. Based on these ionosphere products, WL/narrow-lane (NL) UPDs are then extracted with the raw observable model. The NL ambiguity reveals a better stability and consistency compared to traditional approach. Nonetheless, the WL ambiguity can be hardly improved even constrained with the high spatio-temporal resolution ionospheric corrections. By applying both these approaches in PPP-RTK, it is interesting to find that the traditional model is more efficient in AR as evidenced by the shorter time to first fix, while the three-dimensional positioning accuracy of the RAW model outperforms the combination model by about 7.9%. This reveals that, with the current ionosphere models, there is actually no optimal strategy for the dual-frequency ZD ambiguity resolution, and the combination approach and raw approach each has merits and demerits. Numéro de notice : A2015-345 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0789-1 Date de publication en ligne : 15/02/2015 En ligne : https://doi.org/10.1007/s00190-015-0789-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76717 [article]