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Improved arctic ocean mass variability inferred from time-variable gravity with constraints and dual leakage correction / Dapeng Mu in Marine geodesy, Vol 43 n° 3 (May 2020)  

Public [article]  inMarine geodesy > Vol 43 n° 3 (May 2020) . - pp 269 - 284 Titre : Improved arctic ocean mass variability inferred from time-variable gravity with constraints and dual leakage correction Type de document : Article/Communication Auteurs : Dapeng Mu, Auteur ; Tianhe Xu, Auteur ; Guochang Xu, Auteur Année de publication : 2020 Article en page(s) : pp 269 - 284 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Arctique, océan [Termes IGN] données GRACE [Termes IGN] harmonique sphérique [Termes IGN] marée océanique Résumé : (Auteur) The ocean mass variability inferred from Gravity Recovery and Climate Experiment (GRACE) satellites mission is challenged by the stripes and the leakage across land-ocean boundary. The recently released GRACE mascons solutions are advanced by applying constraints that remove efficiently the stripes and dual leakage correction that restores the coastal ocean mass variability. Here we quantitatively evaluate the improvement in the Arctic Ocean mass variability by GRACE mascons. To do so, we compare the combination of GRACE solutions (including the mascons solutions and traditional spherical harmonic coefficients (SHCs) solutions) and the steric estimates against the altimeter observations. Our results suggest that mascons solutions produce stronger correlations compared to SHCs solutions, especially along the coastal zone, indicating the importance of the dual leakage correction. Stronger correlation is produced by the mascons over a small basin in the interior of the Arctic Ocean, suggesting that mascons solutions deliver better ocean mass variability than the SHCs solutions. Since the comparisons are carried out over two sub-basins, we conclude that mascons are able to provide better regional ocean mass variability that may have implications for regional sea level budget, in particular over the coastal zone. Numéro de notice : A2020-185 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/01490419.2020.1711832 Date de publication en ligne : 17/01/2020 En ligne : https://doi.org/10.1080/01490419.2020.1711832 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94975 [article]

Revisit the calibration errors on experimental slant total electron content (TEC) determined with GPS / Wenfeng Nie in GPS solutions, vol 22 n° 3 (July 2018)  

Public [article]  inGPS solutions > vol 22 n° 3 (July 2018) Titre : Revisit the calibration errors on experimental slant total electron content (TEC) determined with GPS Type de document : Article/Communication Auteurs : Wenfeng Nie, Auteur ; Tianhe Xu, Auteur ; Adria Rovira-Garcia, Auteur ; José Miguel Juan Zornoza, Auteur ; Jaume Sanz, Auteur ; Guillermo Gonzalez-Casado, Auteur ; Chen Wu, Auteur ; Guochang Xu, Auteur Année de publication : 2018 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] code GPS [Termes IGN] coordonnées GPS [Termes IGN] erreur systématique [Termes IGN] étalonnage des données [Termes IGN] station permanente [Termes IGN] teneur totale en électrons Mots-clés libres : differential code bias Résumé : (Auteur) The calibration errors on experimental slant total electron content (TEC) determined with global positioning system (GPS) observations is revisited. Instead of the analysis of the calibration errors on the carrier phase leveled to code ionospheric observable, we focus on the accuracy analysis of the undifferenced ambiguity-fixed carrier phase ionospheric observable determined from a global distribution of permanent receivers. The results achieved are: (1) using data from an entire month within the last solar cycle maximum, the undifferenced ambiguity-fixed carrier phase ionospheric observable is found to be over one order of magnitude more accurate than the carrier phase leveled to code ionospheric observable and the raw code ionospheric observable. The observation error of the undifferenced ambiguity-fixed carrier phase ionospheric observable ranges from 0.05 to 0.11 total electron content unit (TECU) while that of the carrier phase leveled to code and the raw code ionospheric observable is from 0.65 to 1.65 and 3.14 to 7.48 TECU, respectively. (2) The time-varying receiver differential code bias (DCB), which presents clear day boundary discontinuity and intra-day variability pattern, contributes the most part of the observation error. This contribution is assessed by the short-term stability of the between-receiver DCB, which ranges from 0.06 to 0.17 TECU in a single day. (3) The remaining part of the observation errors presents a sidereal time cycle pattern, indicating the effects of the multipath. Further, the magnitude of the remaining part implies that the code multipath effects are much reduced. (4) The intra-day variation of the between-receiver DCB of the collocated stations suggests that estimating DCBs as a daily constant can have a mis-modeling error of at least several tenths of 1 TECU. Numéro de notice : A2018-372 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-018-0753-7 Date de publication en ligne : 26/06/2018 En ligne : https://doi.org/10.1007/s10291-018-0753-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90766 [article]

GNSS navigation and positioning for the GEOHALO experiment in Italy / Kaifei He in GPS solutions, vol 20 n° 2 (April 2016)  

Public [article]  inGPS solutions > vol 20 n° 2 (April 2016) . - pp 215 - 224 Titre : GNSS navigation and positioning for the GEOHALO experiment in Italy Type de document : Article/Communication Auteurs : Kaifei He, Auteur ; Guochang Xu, Auteur ; Tianhe Xu, Auteur ; Frank Flechtner, Auteur Année de publication : 2016 Article en page(s) : pp 215 - 224 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] gravimétrie aérienne [Termes IGN] Italie [Termes IGN] positionnement cinématique [Termes IGN] positionnement par GNSS Résumé : (Auteur) GEOHALO is a joint experiment of several German institutes for atmospheric research and earth observation where exploring airborne gravimetry over Italy using the High Altitude and LOng Range (HALO) aircraft data is one of the major goals. The kinematic positioning of the aircraft, on which all remote sensing instruments are located, by Global Navigation Satellite System (GNSS) is affected by the characteristics of long-distance, long-time duration, and high-platform dynamics which are a key factor for the success of the GEOHALO project. We outline the strategy and method of GNSS data processing which takes into account multiple GNSS systems (GPS and GLONASS), multiple static reference stations including stations from the International GNSS Service (IGS) and the EUropean REFerence network (EUREF), multiple GNSS-receiving equipments mounted on the kinematic platform, geometric relations between multiple antennas, and assumptions of similar characteristic of atmospheric effects within a small area above the aircraft. From this precondition, various data processing methods for kinematic positioning have been developed, applied and compared. It is shown that the proposed method based on multiple reference stations and multiple kinematic stations with a common atmospheric delay parameter can effectively improve the reliability and accuracy of GNSS kinematic positioning. Numéro de notice : A2016-612 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-0430-4 En ligne : http://dx.doi.org/10.1007/s10291-014-0430-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81811 [article]

Spatiotemporal filtering of regional GNSS network’s position time series with missing data using principle component analysis / Yunzhong Shen in Journal of geodesy, vol 88 n° 1 (January 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 1 (January 2014) . - pp 1 - 12 Titre : Spatiotemporal filtering of regional GNSS network’s position time series with missing data using principle component analysis Type de document : Article/Communication Auteurs : Yunzhong Shen, Auteur ; Weiwei Li, Auteur ; Guochang Xu, Auteur ; Bofeng Li, Auteur Année de publication : 2014 Article en page(s) : pp 1 - 12 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse en composantes principales [Termes IGN] déformation de la croute terrestre [Termes IGN] filtrage spatiotemporel [Termes IGN] positionnement par GNSS [Termes IGN] série temporelle [Termes IGN] vecteur propre Résumé : (Auteur) The existing spatiotemporal analysis methods suppose that the involved time series are complete and have the same data interval. However missing data inevitably occur in the position time series of Global Navigation Satellite Systems networks for many reasons. In this paper, we develop a modified principal component analysis to extract the Common Mode Error (CME) from the incomplete position time series. The principle of the proposed method is that a time series can be reproduced from its principle components. The method is equivalent to the method of Dong et al. (J Geophys Res 111:3405–3421, 2006) in case of no missing data in the time series and to the extended ‘stacking’ approach under the assumption of a uniformly spatial response. The new method is first applied to extract the CME from the position time series of the Crustal Movement Observation Network of China (CMONOC) over the period of 1999–2009 where the missing data occur in all stations with the different gaps. The results show that the CMEs are significant in CMONOC. The size of the first principle components for the North, East and Up coordinates are as large as 40, 41 and 37 % of total principle components and their spatial responses are not uniform. The minimum amplitudes of the first eigenvectors are only 41, 15 and 29 % for the North, East and Up coordinate components, respectively. The extracted CMEs of our method are close to the data filling method, and the Root Mean Squared error (RMS) values computed from the differences of maximum CMEs between two methods are only 0.31, 0.52 and 1.55 mm for North, East and Up coordinates, respectively. The RMS of the position time series is greatly reduced after filtering out the CMEs. The accuracies of the reconstructed missing data using the two methods are also comparable. To further comprehensively test the efficiency of our method, the repeated experiments are then carried out by randomly deleting different percentages of data at some stations. The results show that the CMEs can be extracted with high accuracy at the non missing-data epochs. And at the missing-data epochs, the accuracy of extracted CMEs has a strong dependence on the number of stations with missing data. Numéro de notice : A2014-100 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0663-y Date de publication en ligne : 18/10/2013 En ligne : https://doi.org/10.1007/s00190-013-0663-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=33005 [article]

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Sciences of geodesy, vol 2. Innovations and future developments / Guochang Xu (2013)

Public Titre de série : Sciences of geodesy, vol 2 Titre : Innovations and future developments Type de document : Guide/Manuel Auteurs : Guochang Xu, Éditeur scientifique Editeur : Berlin, Heidelberg, Vienne, New York, ... : Springer Année de publication : 2013 Format : 16 x 24 cm ISBN/ISSN/EAN : 978-3-642-27999-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie [Termes IGN] champ de pesanteur terrestre [Termes IGN] compensation de coordonnées [Termes IGN] fonction de Green [Termes IGN] géodésie spatiale [Termes IGN] Global Positioning System [Termes IGN] interférométrie à très grande base [Termes IGN] International Terrestrial Reference Frame [Termes IGN] International Terrestrial Reference System [Termes IGN] marégraphie [Termes IGN] photogrammétrie [Termes IGN] relativité générale [Termes IGN] réseau géodésique terrestre [Termes IGN] surcharge océanique [Termes IGN] système de référence mondial [Termes IGN] télémétrie laser sur satellite Note de contenu : 1 COMPUTATION OF GREEN'S FUNCTIONS FOR OCEAN TIDE LOADING 1 Introduction 2 Equations of Motions and Rheology 3 Spheroidal and Toroidal Motions 4 Fluid Core 5 Resonance Effects 6 Boundary Conditions 7 Simple Earth Models and Love Numbers 8 Degree-1 Response and Translational Invariance 9 Numerical Methods 10 Rheology: Viscosity and Anelasticity 11 Green's Functions 12 Final Remarks 2 GENERAL RELATIVITY AND SPACE GEODESY 1 Background 2 Satellite Laser Ranging 3 Global Positioning System 4 Very Long Baseline Interferometry 5 Concluding Remarks 3 GLOBAL TERRESTRIAL REFERENCE SYSTEMS AND THEIR REALIZATIONS 1 Introduction 2 Basic Concepts and Fundamentals 3 International Terrestrial Reference System 4 International Terrestrial Reference Frame 5 The Latest Realization, the ITRF2008 6 Discussion and Challenges for the Future 4 PHOTOGRAMMETRY 1 Introduction 2 Image Acquisition 3 Image Georeferencing 4 Image Processing 5 REGIONAL GRAVITY FIELD MODELING: THEORY AND PRACTICAL RESULTS 1 Introduction 2 Fundamentals of Physical Geodesy 3 Gravity Field Modeling 4 Practical Results 6 REGULARIZATION AND ADJUSTMENT 6-Part I: Regularized Solution to Ill-Posed Problems 1 Introduction. 2 Unstable Analysis of Least Squares Solution to Ill-Posed Observation Equation 3 Regularized Solution to Ill-Posed Observation Equations 4 Determination of the Regularization Parameter 5 Numerical Cases 6 Summary 6-Part II: Adjustment 7 Introduction 8 Least Squares Adjustment 9 Sequential Least Squares Adjustment 10 Conditional Least Squares Adjustment 11 Block-Wise Least Squares Adjustment 12 Equivalently Eliminated Observation Equation System 13 A Priori Constrained Least Squares Adjustment 14 Summary 7 VERY LONG BASELINE INTERFEROMETRY FOR GEODESY AND ASTROMETRY 1 Introduction 2 Theoretical Delays 3 Least-Squares Adjustment in VLBI 4 Results from Geodetic VLBI and the IVS 5 The Next Generation VLBI System, VLBI2010 6 Concluding Remarks Numéro de notice : 20959B Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Manuel de cours Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62778

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• Sciences of geodesy, vol 1. Advanced and future directions / Guochang Xu (2010)

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Sciences of geodesy, vol 1. Advanced and future directions / Guochang Xu (2010)

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GPS : Theory, algorithms and applications / Guochang Xu (2003)

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Kinematic GPS software, KGsoft / Guochang Xu (1999)

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