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Monitoring precipitable water vapor in real-time using global navigation satellite systems / Seung-Woo Lee in Journal of geodesy, vol 87 n° 10-12 (October - December 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 10-12 (October - December 2013) . - pp 923 - 934 Titre : Monitoring precipitable water vapor in real-time using global navigation satellite systems Type de document : Article/Communication Auteurs : Seung-Woo Lee, Auteur ; Jan Kouba, Auteur ; Bob Schutz, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 923 - 934 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse diachronique [Termes IGN] données GNSS [Termes IGN] précipitation [Termes IGN] surveillance météorologique [Termes IGN] temps de propagation [Termes IGN] temps réel [Termes IGN] vapeur d'eau Résumé : (Auteur) This paper addresses real-time monitoring of the precipitable water vapor (PWV) from GNSS measurements and presents some results obtained from 6-month long GNSS PWV experiments using international and domestic GNSS networks. In the real-time GNSS PWV monitoring system a server/client structure is employed to facilitate formation of PWV networks and single-differenced GNSS measurements are utilized to mitigate errors in GNSS satellites’ orbits and clocks. An issue relating to baseline length between the server and clients is discussed in detail and as a result the PWV monitor is configured to perform in two modes depending on the baseline length. The server estimates sequentially the zenith wet delay of the individual stations, which is then converted into the PWV of the stations. We evaluate system performance by comparing the real-time PWV solution with reference solutions including meteorological measurements obtained with radiosondes and deferred-time precision GNSS PWV solutions. Results showed that the standard deviation of difference between the real-time PWV and the reference solutions ranged from 2.1 to 3.4 mm in PWV for a 6-month long comparison, which was improved to 1.4 to 2.9 mm by reducing comparison period to 20 days in winter. Numéro de notice : A2013-667 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0655-y Date de publication en ligne : 11/08/2013 En ligne : https://doi.org/10.1007/s00190-013-0655-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32803 [article]

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A reference station-based GNSS computing mode to support unified precise point positioning and real-time kinematic services / Yanming Feng in Journal of geodesy, vol 87 n° 10-12 (October - December 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 10-12 (October - December 2013) . - pp 945 - 960 Titre : A reference station-based GNSS computing mode to support unified precise point positioning and real-time kinematic services Type de document : Article/Communication Auteurs : Yanming Feng, Auteur ; Shengfeng Gu, Auteur ; et al., Auteur Année de publication : 2013 Article en page(s) : pp 945 - 960 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement par GNSS [Termes IGN] positionnement ponctuel précis [Termes IGN] station de référence [Termes IGN] traitement de données GNSS Résumé : (Auteur) Currently, the GNSS computing modes are of two classes: network-based data processing and user receiver-based processing. A GNSS reference receiver station essentially contributes raw measurement data in either the RINEX file format or as real-time data streams in the RTCM format. Very little computation is carried out by the reference station. The existing network-based processing modes, regardless of whether they are executed in real-time or post-processed modes, are centralised or sequential. This paper describes a distributed GNSS computing framework that incorporates three GNSS modes: reference station-based, user receiver-based and network-based data processing. Raw data streams from each GNSS reference receiver station are processed in a distributed manner, i.e., either at the station itself or at a hosting data server/processor, to generate station-based solutions, or reference receiver-specific parameters. These may include precise receiver clock, zenith tropospheric delay, differential code biases, ambiguity parameters, ionospheric delays, as well as line-of-sight information such as azimuth and elevation angles. Covariance information for estimated parameters may also be optionally provided. In such a mode the nearby precise point positioning (PPP) or real-time kinematic (RTK) users can directly use the corrections from all or some of the stations for real-time precise positioning via a data server. At the user receiver, PPP and RTK techniques are unified under the same observation models, and the distinction is how the user receiver software deals with corrections from the reference station solutions and the ambiguity estimation in the observation equations. Numerical tests demonstrate good convergence behaviour for differential code bias and ambiguity estimates derived individually with single reference stations. With station-based solutions from three reference stations within distances of 22–103 km the user receiver positioning results, with various schemes, show an accuracy improvement of the proposed station-augmented PPP and ambiguity-fixed PPP solutions with respect to the standard float PPP solutions without station augmentation and ambiguity resolutions. Overall, the proposed reference station-based GNSS computing mode can support PPP and RTK positioning services as a simpler alternative to the existing network-based RTK or regionally augmented PPP systems. Numéro de notice : A2013-668 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0659-7 Date de publication en ligne : 26/09/2013 En ligne : https://doi.org/10.1007/s00190-013-0659-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32804 [article]

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Towards a 1 mGal accuracy and 1 min resolution altimetry gravity field / Lifeng Bao in Journal of geodesy, vol 87 n° 10-12 (October - December 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 10-12 (October - December 2013) . - pp 961 - 969 Titre : Towards a 1 mGal accuracy and 1 min resolution altimetry gravity field Type de document : Article/Communication Auteurs : Lifeng Bao, Auteur ; Houze Xu, Auteur ; Zhicai Li, Auteur Année de publication : 2013 Article en page(s) : pp 961 - 969 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] altimétrie satellitaire par radar [Termes IGN] champ de pesanteur terrestre [Termes IGN] géodésie marine [Termes IGN] gradient [Termes IGN] océanographie spatiale [Termes IGN] surface de la mer Résumé : (Auteur) Over the past three decades, radar altimetry has made a significant contribution to marine gravity field modeling. To improve the accuracy and resolution, we propose a new twin-satellite altimetry. Such a system has several advantages. Among others, it provides (i) twice the number of samples per time epoch, and (ii) information about the cross-track surface gradient with high accuracy because most of the environmental and tidal errors will be common to the simultaneous measurements and therefore cancel out when computing the cross-track gradient computation. We describe a rigorous procedure for the deduction of the sea surface gradient at each altimeter observation point (i.e., not only at the crossovers), from the twin-satellite altimetry system. The precision of the gradient will be slightly affected by orbit errors, instrument drift, and inaccuracies in the geophysical corrections to be applied. We also demonstrate that a 1 mGal accuracy and 1 min resolution marine altimetry gravity field can be obtained if certain conditions are met. To achieve the expected goal, we recommend an orbital configuration, phasing two satellites in 4-s time delay such that the Earth rotation creates a natural baseline between the two satellites, and a 18 kHz SAR altimeter. Numéro de notice : A2013-669 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0660-1 Date de publication en ligne : 25/09/2013 En ligne : https://doi.org/10.1007/s00190-013-0660-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32805 [article]

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Troposphere delays from space geodetic techniques, water vapor radiometers, and numerical weather models over a series of continuous VLBI campaigns / Kamil Teke in Journal of geodesy, vol 87 n° 10-12 (October - December 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 10-12 (October - December 2013) . - pp 981 - 1001 Titre : Troposphere delays from space geodetic techniques, water vapor radiometers, and numerical weather models over a series of continuous VLBI campaigns Type de document : Article/Communication Auteurs : Kamil Teke, Auteur ; Tobias Nilsson, Auteur ; Johannes Böhm , Auteur ; Thomas Hobiger, Auteur ; et al., Auteur ; Pascal Willis , Auteur Année de publication : 2013 Article en page(s) : pp 981 - 1001 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] campagne VLBI [Termes IGN] données DORIS [Termes IGN] données GNSS [Termes IGN] données ITGB [Termes IGN] gradient de troposphère [Termes IGN] interférométrie à très grande base [Termes IGN] modèle météorologique [Termes IGN] propagation troposphérique [Termes IGN] retard troposphérique Résumé : (Auteur) Continuous, very long baseline interferometry (VLBI) campaigns over 2 weeks have been carried out repeatedly, i.e., CONT02 in October 2002, CONT05 in September 2005, CONT08 in August 2008, and CONT11 in September 2011, to demonstrate the highest accuracy the current VLBI was capable at that time. In this study, we have compared zenith total delays (ZTD) and troposphere gradients as consistently estimated from the observations of VLBI, Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) at VLBI sites participating in the CONT campaigns. We analyzed the CONT campaigns using the state-of-the-art software following common processing strategies as closely as possible. In parallel, ZTD and gradients were derived from numerical weather models, i.e., from the global European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields, the High Resolution Limited Area Model (European sites), the Japan Meteorological Agency-Operational Meso-Analysis Field (MANAL, over Japan), and the Cloud Resolving Storm Simulator (Tsukuba, Japan). Finally, zenith wet delays were estimated from the observations of water vapor radiometers (WVR) at sites where the WVR observables are available during the CONT sessions. The best ZTD agreement, interpreted as the smallest standard deviation, was found between GNSS and VLBI techniques to be about 5–6 mm at most of the co-located sites and CONT campaigns. We did not detect any significant improvement in the ZTD agreement between various techniques over time, except for DORIS and MANAL. On the other hand, the agreement and thus the accuracy of the troposphere parameters mainly depend on the amount of humidity in the atmosphere. Numéro de notice : A2013-670 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0662-z Date de publication en ligne : 10/10/2013 En ligne : https://doi.org/10.1007/s00190-013-0662-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32806 [article]

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