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Impact of GPS differential code bias in dual- and triple-frequency positioning and satellite clock estimation / Haojun Li in GPS solutions, vol 21 n° 3 (July 2017)  

Public [article]  inGPS solutions > vol 21 n° 3 (July 2017) . - pp 897 – 903 Titre : Impact of GPS differential code bias in dual- and triple-frequency positioning and satellite clock estimation Type de document : Article/Communication Auteurs : Haojun Li, Auteur ; Bofeng Li, Auteur ; Lizhi Lou, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 897 – 903 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] code GPS [Termes IGN] erreur corrélée au temps [Termes IGN] erreur systématique [Termes IGN] géodésie spatiale [Termes IGN] GPS en mode différentiel [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur bifréquence [Termes IGN] récepteur trifréquence [Termes IGN] retard ionosphèrique Résumé : (auteur) The features and differences of various GPS differential code bias (DCB)s are discussed. The application of these biases in dual- and triple-frequency satellite clock estimation is introduced based on this discussion. A method for estimating the satellite clock error from triple-frequency uncombined observations is presented to meet the need of the triple-frequency uncombined precise point positioning (PPP). In order to evaluate the estimated satellite clock error, the performance of these biases in dual- and triple-frequency positioning is studied. Analysis of the inter-frequency clock bias (IFCB), which is a result of constant and time-varying frequency-dependent hardware delays, in ionospheric-free code-based (P1/P5) single point positioning indicates that its influence on the up direction is more pronounced than on the north and east directions. When the IFCB is corrected, the mean improvements are about 29, 35 and 52% for north, east and up directions, respectively. Considering the contribution of code observations to PPP convergence time, the performance of DCB(P1–P2), DCB(P1–P5) and IFCB in GPS triple-frequency PPP convergence is investigated. The results indicate that the DCB correction can accelerate PPP convergence by means of improving the accuracy of the code observation. The performance of these biases in positioning further verifies the correctness of the estimated dual- and triple-frequency satellite clock error. Numéro de notice : A2017-441 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0578-1 En ligne : https://doi.org/10.1007/s10291-016-0578-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86358 [article]

Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation / Junbo Shi in Journal of geodesy, vol 89 n° 8 (August 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 8 (August 2015) . - pp 747-756 Titre : Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation Type de document : Article/Communication Auteurs : Junbo Shi, Auteur ; Chaoqian Xu, Auteur ; Yihe Li, Auteur ; Yang Gao, Auteur Année de publication : 2015 Article en page(s) : pp 747-756 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] erreur corrélée au temps [Termes IGN] horloge atomique [Termes IGN] orbite précise [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] retard troposphérique zénithal [Termes IGN] temps réel [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Global Positioning System (GPS) has become a cost-effective tool to determine troposphere zenith total delay (ZTD) with accuracy comparable to other atmospheric sensors such as the radiosonde, the water vapor radiometer, the radio occultation and so on. However, the high accuracy of GPS troposphere ZTD estimates relies on the precise satellite orbit and clock products available with various latencies. Although the International GNSS Service (IGS) can provide predicted orbit and clock products for real-time applications, the predicted clock accuracy of 3 ns cannot always guarantee the high accuracy of troposphere ZTD estimates. Such limitations could be overcome by the use of the newly launched IGS real-time service which provides ∼5 cm orbit and 0.2–1.0 ns (an equivalent range error of 6–30 cm) clock products in real time. Considering the relatively larger magnitude of the clock error than that of the orbit error, this paper investigates the effect of real-time satellite clock errors on the GPS precise point positioning (PPP)-based troposphere ZTD estimation. Meanwhile, how the real-time satellite clock errors impact the GPS PPP-based troposphere ZTD estimation has also been studied to obtain the most precise ZTD solutions. First, two types of real-time satellite clock products are assessed with respect to the IGS final clock product in terms of accuracy and precision. Second, the real-time GPS PPP-based troposphere ZTD estimation is conducted using data from 34 selected IGS stations over three independent weeks in April, July and October, 2013. Numerical results demonstrate that the precision, rather than the accuracy, of the real-time satellite clock products impacts the real-time PPP-based ZTD solutions more significantly. In other words, the real-time satellite clock product with better precision leads to more precise real-time PPP-based troposphere ZTD solutions. Therefore, it is suggested that users should select and apply real-time satellite products with better clock precision to obtain more consistent real-time PPP-based ZTD solutions. Numéro de notice : A2015-374 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0811-7 Date de publication en ligne : 04/04/2015 En ligne : https://doi.org/10.1007/s00190-015-0811-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76852 [article]

Satellite SAR geocoding with refined RPC model / L. Zhang in ISPRS Journal of photogrammetry and remote sensing, vol 69 (April 2012)  

Public [article]  inISPRS Journal of photogrammetry and remote sensing > vol 69 (April 2012) . - pp 37 - 49 Titre : Satellite SAR geocoding with refined RPC model Type de document : Article/Communication Auteurs : L. Zhang, Auteur ; Timo Balz, Auteur ; M. Liao, Auteur Année de publication : 2012 Article en page(s) : pp 37 - 49 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] appariement d'images [Termes IGN] erreur corrélée au temps [Termes IGN] géoréférencement indirect [Termes IGN] image radar moirée [Termes IGN] modèle numérique de surface [Termes IGN] modèle par fonctions rationnelles [Termes IGN] propagation du signal Résumé : (Auteur) Recent studies have proved that the Rational Polynomial Camera (RPC) model is able to act as a reliable replacement of the rigorous Range-Doppler (RD) model for the geometric processing of satellite SAR datasets. But its capability in absolute geolocation of SAR images has not been evaluated quantitatively. Therefore, in this article the problems of error analysis and refinement of SAR RPC model are primarily investigated to improve the absolute accuracy of SAR geolocation. Range propagation delay and azimuth timing error are identified as two major error sources for SAR geolocation. An approach based on SAR image simulation and real-to-simulated image matching is developed to estimate and correct these two errors. Afterwards a refined RPC model can be built from the error-corrected RD model and then used in satellite SAR geocoding. Three experiments with different settings are designed and conducted to comprehensively evaluate the accuracies of SAR geolocation with both ordinary and refined RPC models. All the experimental results demonstrate that with RPC model refinement the absolute location accuracies of geocoded SAR images can be improved significantly, particularly in Easting direction. In another experiment the computation efficiencies of SAR geocoding with both RD and RPC models are compared quantitatively. The results show that by using the RPC model such efficiency can be remarkably improved by at least 16 times. In addition the problem of DEM data selection for SAR image simulation in RPC model refinement is studied by a comparative experiment. The results reveal that the best choice should be using the proper DEM datasets of spatial resolution comparable to that of the SAR images. Numéro de notice : A2012-193 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2012.02.004 En ligne : https://doi.org/10.1016/j.isprsjprs.2012.02.004 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31640 [article]

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081-2012031	SL	Revue	Centre de documentation	Revues en salle	Disponible

Consideration of time-correlated errors in a Kalman filter applicable to GNSS / M.G. Potovello in Journal of geodesy, vol 83 n° 1 (January 2009)  

Public [article]  inJournal of geodesy > vol 83 n° 1 (January 2009) . - pp 51 - 56 Titre : Consideration of time-correlated errors in a Kalman filter applicable to GNSS Type de document : Article/Communication Auteurs : M.G. Potovello, Auteur ; Kyle O'Keefe, Auteur ; Gérard Lachapelle, Auteur ; M.E. Cannon, Auteur Année de publication : 2009 Article en page(s) : pp 51 - 56 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] bruit blanc [Termes IGN] covariance [Termes IGN] erreur corrélée au temps [Termes IGN] filtre de Kalman [Termes IGN] GPS en mode cinématique [Termes IGN] GPS en mode différentiel [Termes IGN] positionnement par GNSS [Termes IGN] traitement différé [Termes IGN] traitement du signal Résumé : (Auteur) An algorithm for considering time-correlated errors in a Kalman filter is presented. The algorithm differs from previous implementations in that it does not suffer from numerical problems; does not contain inherent time latency or require reinterpretation of Kalman filter parameters, and gives full consideration to additive white noise that is often still present but ignored in previous implementations. Simulation results indicate that the application of the new algorithm yields more realistic and therefore useful state and covariance information than the standard implementation. Results from a field test of the algorithm applied to the problem of kinematic differential GPS demonstrate that the algorithm provides slightly pessimistic covariance estimates whereas the standard Kalman filter provides optimistic covariance estimates. Copyright Springer Numéro de notice : A2009-181 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-008-0231-z En ligne : https://doi.org/10.1007/s00190-008-0231-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29811 [article]

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266-09012	RAB	Revue	Centre de documentation	En réserve L003	Disponible