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GPS/BDS short-term ISB modelling and prediction / Nan Jiang in GPS solutions, vol 21 n° 1 (January 2017)
[article]
Titre : GPS/BDS short-term ISB modelling and prediction Type de document : Article/Communication Auteurs : Nan Jiang, Auteur ; Yan Xu, Auteur ; Tianhe Xu, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 163 - 175 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] analyse comparative
[Termes IGN] données BeiDou
[Termes IGN] données GNSS
[Termes IGN] erreur systématique
[Termes IGN] erreur systématique inter-systèmes
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle d'erreur
[Termes IGN] orbitographie
[Termes IGN] positionnement par BeiDou
[Termes IGN] positionnement par GNSS
[Termes IGN] positionnement ponctuel précisRésumé : (Auteur) The Chinese BeiDou Navigation Satellite System (BDS) has completed its first milestone by providing coverage of the Asia–Pacific area navigation service since December 27, 2012. With the combination of BDS, the GNSS precise point positioning (PPP) can improve its positioning accuracy, availability and reliability. However, in order to achieve the best positioning solutions, the inter-system bias (ISB) between GPS and BDS must be resolved as precisely as possible. In this study, a 1-week period (GPS week 1810) of GPS/BDS observations for 18 distributed stations from the International GNSS Service Multi-GNSS Experiment are processed. Primarily, the ISB is estimated by an extended Kalman filter as a piece-wise parameter every 30 min. Then we generate a smoothed ISB series (ISB_s) with a sliding window median filter to reject the outliers from the original estimated ISB series (ISB_o). After analysing the characteristics of the ISB_s, a short-term station-dependent ISB model based on a 1-week period is proposed in this study. This model consists of a quadratic polynomial in time and two or three periodic functions with diurnal and semi-diurnal periods. Frequency spectrum analysis is used to determine the periods of the periodic functions, and the coefficients of the quadratic function and the periodic functions are estimated by least squares. For model verification, we compare the ISB derived from the model (ISB_m) with ISB_s (assumed the true values). The comparisons indicate an almost normal distribution. It is found that the proposed model is consistent with the true values: the root-mean-square (RMS) values being about 0.7 ns, and some stations are even better. This means that the short-term ISB model proposed has a high fitting accuracy. Hence, it can be used for ISB prediction. Comparing the prediction ISB series (ISB_p) with ISB_s in the following week (GPS week 1811), we can draw the conclusion that the accuracy of the prediction declines with an increase in the time period. The 1-day period precision can achieve 0.57–1.21 ns, while the accuracy of the 2-day prediction decreases to 0.77–1.72 ns. Hence, we recommend a predicting duration of 1 day. The proposed model will be beneficial for subsequent GPS/BDS PPP or precise orbit determination (POD) since the ISB derived from this model can be considered as a priori constraint in the PPP/POD solutions. With this a priori constraint, the convergence time can be shortened by 19.6, 16.1 and 2.4 % in N, E and U components, respectively. The accuracy of result in the E component is remarkably improved by 11.9 %. Numéro de notice : A2017-015 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0513-x Date de publication en ligne : 09/01/2016 En ligne : https://doi.org/10.1007/s10291-015-0513-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83946
in GPS solutions > vol 21 n° 1 (January 2017) . - pp 163 - 175[article]Ionosphere probing with simultaneous GNSS radio occultations / Viet-Cuong Pham in GPS solutions, vol 21 n° 1 (January 2017)
[article]
Titre : Ionosphere probing with simultaneous GNSS radio occultations Type de document : Article/Communication Auteurs : Viet-Cuong Pham, Auteur ; Jyh-Ching Juang, Auteur Année de publication : 2017 Article en page(s) : pp 101 - 109 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] données GNSS
[Termes IGN] gradient ionosphèrique
[Termes IGN] inversion
[Termes IGN] occultation du signal
[Termes IGN] orbite basse
[Termes IGN] régularisation de Tychonoff
[Termes IGN] teneur totale en électronsRésumé : (Auteur) Radio occultation (RO) is a powerful technique for providing vertical profiles of refractivity, temperature, pressure, and water vapor of the neutral atmosphere and electron density of the ionosphere. The Abel inversion method which is based on the spherical symmetry assumption has been widely utilized to retrieve electron density profiles (EDPs) from RO measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit satellites. It is well known that the Abel inversion is subject to errors in the presence of ionospheric horizontal gradients. With the arrival of new navigation systems, the opportunities of establishing simultaneous GNSS RO events are increasing. We develop an improved Abel inversion technique that accounts for pairs of simultaneous RO events to relax the spherical symmetry assumption. Through the use of Tikhonov regularization, the problem is formulated so that numerical conditioning is improved and a priori information such as expected electron density, asymmetric factor, and vertical total electron content can be incorporated. Appropriate weighting can be determined to reflect the availability and quality of information. By balancing the reference data and measurements, the method thus paves a way for ionospheric probing in challenging geomagnetic conditions as both the EDP at the intersection and the horizontal gradients are retrieved. Simulation and experimental results are provided to show the effectiveness of the proposed method. The robustness and sensitivity of the proposed method are also assessed. Numéro de notice : A2017-014 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0501-1 Date de publication en ligne : 02/01/2016 En ligne : http://dx.doi./org/10.1007/s10291-015-0501-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83936
in GPS solutions > vol 21 n° 1 (January 2017) . - pp 101 - 109[article]Local tie survey at McDonald / Mathilde Kremp (2017)
Titre : Local tie survey at McDonald Type de document : Mémoire Auteurs : Mathilde Kremp, Auteur Editeur : Champs-sur-Marne : Ecole nationale des sciences géographiques ENSG Année de publication : 2017 Importance : 98 p. Format : 21 x 30 cm Note générale : Bibliographie
Rapport de projet pluridisciplinaire, cycle Ingénieur 2e annéeLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] Comp3D
[Termes IGN] données GPS
[Termes IGN] estimation de précision
[Termes IGN] lever topométrique
[Termes IGN] point de liaison (géodésie)
[Termes IGN] précision des mesures
[Termes IGN] précision millimétrique
[Termes IGN] rattachement métrologiqueIndex. décimale : PROJET Mémoires : Rapports de projet - stage des ingénieurs de 2e année Résumé : (Auteur) L’International Terrestrial Reference Frame (ITRF) est le système de référence global utilise dans de nombreuses applications dans les sciences de la Terre, et notamment dans les systèmes de navigation. L’ITRF est calculé en utilisant les techniques de géodésie spatiale comme le GPS, DORIS, SLR et VLBI. L’observatoire de McDonald (Fort Davis, Texas – USA), géré par l’Université du Texas (Austin), dispose d’une station GNSS permanente et d’un télescope a télémétrie laser sur satellite. Ainsi, l’observatoire de McDonald participe depuis de nombreuses années au calcul de la solution ITRF. Dans les années a venir, la NASA va installer un VLBI sur le site afin de multiplier les types de mesures et d’obtenir une solution plus précise. Cependant, une distance de 800 mètres et une dénivelée d’environ 100 mètres séparent les deux sites instrumentaux. L’Université du Texas a reçu des fonds de la NASA pour déterminer les positions relatives avec une précision de l’ordre du mm entre les différentes stations géodésiques de l’ensemble du site. L’objectif du stage est de travailler sur l’établissement d’un réseau de rattachement, reposant sur des techniques de topométrie et de mesures GNSS. Un travail de recherche est tout d’abord effectue afin de proposer des simulations du réseau et de ses possibles défauts et améliorations, tout en respectant les contraintes matérielles du site, des contraintes instrumentales et des contraintes de précision. Cette étude fait l’objet de la rédaction d’un rapport qui comporte également les rapports des différentes campagnes menées sur le terrain pendant le stage et l’analyse des données disponibles pour estimer une précision sur le résultat du rattachement. Note de contenu : INTRODUCTION
1. SIMULATIONS OF THE NETWORK
1.1 Presentation of the softwares
1.2 Simulations on comp3d
2. CAMPAIGNS AT THE MCDONALD OBSERVATORY
2.1 Presentation of the instruments
2.2 Construction of the target monuments
2.3 Measurements
3. DATA ANALYSIS
3.1 Processing gnss data
3.2 Processing ts30 data
CONCLUSIONNuméro de notice : 22841 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Mémoire de projet pluridisciplinaire Organisme de stage : Center for Space Research CSR (University of Texas) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89074 Exemplaires(1)
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Local tie survey at McDonald_AnnexesAdobe Acrobat PDF Spatial–temporal variations of water vapor content over Ethiopia: a study using GPS observations and the ECMWF model / Kibrom Ebuy Abraha in GPS solutions, vol 21 n° 1 (January 2017)
[article]
Titre : Spatial–temporal variations of water vapor content over Ethiopia: a study using GPS observations and the ECMWF model Type de document : Article/Communication Auteurs : Kibrom Ebuy Abraha, Auteur ; Elias Lewi, Auteur ; Frédéric Masson, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 89 - 99 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] analyse spatio-temporelle
[Termes IGN] données GPS
[Termes IGN] Ethiopie
[Termes IGN] humidité de l'air
[Termes IGN] modèle météorologique
[Termes IGN] sécheresse
[Termes IGN] station GPS
[Termes IGN] teneur en vapeur d'eau
[Termes IGN] teneur intégrée en vapeur d'eau
[Termes IGN] variation saisonnièreRésumé : (Auteur) We characterize the spatial–temporal variability of integrated water vapor (IWV) in Ethiopia from a network of global positioning system (GPS) stations and the European Center for Medium range Weather Forecasting (ECMWF) model. The IWV computed from the ECMWF model is integrated from the height of the GPS stations on 60 pressure levels to take both the actual earth surface and the model orography discrepancies into account. First, we compare the IWV estimated from GPS and from the model. The bias varies from site to site, and the correlation coefficients between the two datasets exceed 0.85 at different time scales. The results of this study show that the general ECMWF IWV trend is underestimation over highlands and overestimation over lowlands for wet periods, and overestimation over highlands and underestimation over lowlands for dry periods with very few exceptional stations. Second, we observe the spatial variation of the IWV. High values are obtained in those stations that are located in the north-eastern (Afar depression) sites and the south-western part of the country. This distribution is related to the spatial variability of the climate in Ethiopia. Finally, we study the seasonal cycle and inter-annual variability of IWV for all stations over Ethiopia. The main result is the strong inter-annual variability observed for the dry seasons. Numéro de notice : A2017-013 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-015-0508-7 En ligne : http://dx.doi.org/10.1007/s10291-015-0508-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83935
in GPS solutions > vol 21 n° 1 (January 2017) . - pp 89 - 99[article]Study of trends and variability of atmospheric water vapour with climate models and observations from global GNSS network / Ana-Claudia Bernardes Parracho (2017)
Titre : Study of trends and variability of atmospheric water vapour with climate models and observations from global GNSS network Type de document : Thèse/HDR Auteurs : Ana-Claudia Bernardes Parracho , Auteur ; Sophie Bastin, Directeur de thèse ; Olivier Bock , Directeur de thèse Editeur : Paris : Université de Paris 6 Pierre et Marie Curie Année de publication : 2017 Importance : 147 p. Format : 21 x 30 cm Note générale : bibliographie
Thèse de Doctorat de Sciences de l’EnvironnementLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] analyse diachronique
[Termes IGN] données GPS
[Termes IGN] données météorologiques
[Termes IGN] humidité de l'air
[Termes IGN] modèle atmosphérique
[Termes IGN] précipitation
[Termes IGN] série temporelle
[Termes IGN] teneur intégrée en vapeur d'eau
[Termes IGN] variabilitéIndex. décimale : THESE Thèses et HDR Résumé : (auteur) Water vapour is a key component of the Earth’s climate system, and its distribution and variability are sources of uncertainty in climate models. The use of long-term integrated water vapour (IWV) observations and reanalyses can help in their assessment. This work pioneered the use of reprocessed GPS IWV data for 1995-2010, converted from estimates of Zenith Total Delay. The conversion was assessed, with the goal of producing a high quality long-term IWV data set. Due to uncertainties in the GPS observations and homogeneity concerns, a global comparison with ERA-Interim reanalysis data was made. Although a general good agreement in means, variability and trends was found, issues in both data sets were highlighted. In GPS, gaps and inhomogeneities in the time series were evidenced, as well as representativeness differences in coastal areas and regions of complex topography. In ERA-Interim, too strong trends in certain regions were found. ERA-Interim was also compared with other reanalyses (MERRA-2, ERA-20C, 20CR), and differences were found in the IWV trends over Africa, Australia, and Antarctica. Finally, GPS and ERA-Interim IWV were used to assess four configurations of the LMDZ atmospheric general circulation model with two different physics and with or without nudging towards ERA-Interim wind fields. Impact of the model physics on the IWV mean was found, with the new physics being moister at tropical latitudes. Overall, the model free runs in both physics have difficulty reproducing the trends and variability observed in ERA-Interim and GPS. This is improved with the nudging, which confirms the importance of large-scale dynamics on IWV trends and variability. Note de contenu : 1- Introduction
2- Elaboration of a reference long-term IWV dataset from ground-based GNSS measurements
3- Observation of IWV trends and variability from GPS data and reanalyses
4- Assessment of simulations from global climate models using GPS data and atmospheric reanalyses
5- Conclusions and perspectivesNuméro de notice : 25862 Affiliation des auteurs : LASTIG LAREG (2012-mi2018) Thématique : POSITIONNEMENT Nature : Thèse française Note de thèse : Thèse de Doctorat : Sciences de l’Environnement : Paris : 2017 Organisme de stage : LAREG (IGN) & LATMOS nature-HAL : Thèse DOI : sans En ligne : https://tel.hal.science/tel-01881083 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95505 Is the Jason-2 DORIS oscillator also affected by the South Atlantic Anomaly? / Pascal Willis in Advances in space research, vol 58 n° 12 (15 December 2016)PermalinkModeling and assessment of triple-frequency BDS precise point positioning / Fei Guo in Journal of geodesy, vol 90 n° 11 (November 2016)PermalinkRelevé topographique des environnements urbains [article originellement paru dans le numéro mai/juin 2016 de la revue italienne GEOMedia] / Luigi Colombo in Géomatique expert, n° 113 (novembre - décembre 2016)PermalinkReview of the state of the art and future prospects of the ground-based GNSS meteorology in Europe / Guergana Guerova in Atmospheric measurement techniques, vol 9 n° 11 (November 2016)PermalinkSingle-frequency, dual-GNSS versus dual-frequency, single-GNSS: a low-cost and high-grade receivers GPS-BDS RTK analysis / Robert Odolinski in Journal of geodesy, vol 90 n° 11 (November 2016)PermalinkA statistical characterization of the Galileo-to-GPS inter-system bias / Ciro Gioia in Journal of geodesy, vol 90 n° 11 (November 2016)PermalinkA new ZTD model based on permanent ground-based GNSS-ZTD data / M. Ding in Survey review, vol 48 n° 351 (October 2016)PermalinkOutlier detection by using fault detection and isolation techniques in geodetic networks / U.M. Durdag in Survey review, vol 48 n° 351 (October 2016)PermalinkA novel methodology for identifying environmental exposures using GPS data / Andreea Cetateanu in International journal of geographical information science IJGIS, vol 30 n° 9-10 (September - October 2016)PermalinkTaking correlations in GPS least squares adjustments into account with a diagonal covariance matrix / Gaël Kermarrec in Journal of geodesy, vol 90 n° 9 (September 2016)Permalink