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Computation of GPS P1–P2 differential code biases with JASON-2 / Gilles Wautelet in GPS solutions, vol 21 n° 4 (October 2017)  

Public [article]  inGPS solutions > vol 21 n° 4 (October 2017) . - pp 1619 - 1631 Titre : Computation of GPS P1–P2 differential code biases with JASON-2 Type de document : Article/Communication Auteurs : Gilles Wautelet, Auteur ; Sylvain Loyer, Auteur ; Flavien Mercier, Auteur ; Félix Perosanz, Auteur Année de publication : 2017 Article en page(s) : pp 1619 - 1631 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] code GPS [Termes IGN] corrélation [Termes IGN] données Jason [Termes IGN] erreur systématique [Termes IGN] GPS en mode différentiel [Termes IGN] orbitographie [Termes IGN] plasmasphère [Termes IGN] teneur verticale totale en électrons Résumé : (Auteur) GPS Differential Code Biases (DCBs) computation is usually based on ground networks of permanent stations. The drawback of the classical methods is the need for the ionospheric delay so that any error in this quantity will map into the solution. Nowadays, many low-orbiting satellites are equipped with GPS receivers which are initially used for precise orbitography. Considering spacecrafts at an altitude above the ionosphere, the ionized contribution comes from the plasmasphere, which is less variable in time and space. Based on GPS data collected onboard JASON-2 spacecraft, we present a methodology which computes in the same adjustment the satellite and receiver DCBs in addition to the plasmaspheric vertical total electron content (VTEC) above the satellite, the average satellite bias being set to zero. Results show that GPS satellite DCB solutions are very close to those of the IGS analysis centers using ground measurements. However, the receiver DCB and VTEC are closely correlated, and their value remains sensitive to the choice of the plasmaspheric parametrization. Numéro de notice : A2017-617 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-017-0638-1 Date de publication en ligne : 19/05/2017 En ligne : https://doi.org/10.1007/s10291-017-0638-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86927 [article]

Evaluating the performance of using PPK-GPS technique in producing topographic contour map / Ahmed El Shouny in Marine geodesy, vol 40 n° 4 (July 2017)  

Public [article]  inMarine geodesy > vol 40 n° 4 (July 2017) . - pp 224 - 238 Titre : Evaluating the performance of using PPK-GPS technique in producing topographic contour map Type de document : Article/Communication Auteurs : Ahmed El Shouny, Auteur ; Nagy Yakoub, Auteur ; Magdy Hosny, Auteur Année de publication : 2017 Article en page(s) : pp 224 - 238 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] altitude orthométrique [Termes IGN] analyse comparative [Termes IGN] carte topographique [Termes IGN] courbe de niveau [Termes IGN] données GPS [Termes IGN] Egypte [Termes IGN] GPS en mode différentiel [Termes IGN] Nil (delta du) [Termes IGN] niveau à bulle [Termes IGN] post-traitement [Vedettes matières IGN] Altimétrie Résumé : (Auteur) The Global Positioning System (GPS) is considered as one of the most powerful tools that are used in geodetic works. It is increasingly considered as an alternative tool for conventional surveying techniques. The goal of this research paper is to produce a methodology for generating topographic contour maps using the post-processed kinematic differential GPS technique (PPK-GPS). The performance of this technique is assessed by comparing it with the traditional spirit-leveling technique taking into consideration the accuracy, time, and cost. The study area is located along the Mediterranean coast in the Rosetta area of the middle Delta in Egypt with a total area of about 39 km2. The field work includes 14 control points and about 50,000 PPK observations. In addition, 20 check cross sections that extend along the coastal line from Rosetta to El Burullus cities were observed using both spirit-leveling and GPS-PPK techniques. The results of the comparison indicate that the PPK-GPS technique can be used instead of spirit leveling in producing a topographic contour map with an accuracy of about 20 cm in orthometric height. We find that the PPK-GPS technique reduces the estimated time of leveling works in our study area by about 70%. Numéro de notice : A2017-667 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2017.1321594 En ligne : https://doi.org/10.1080/01490419.2017.1321594 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=87142 [article]

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]

Advanced modeling and algorithms for high-precision GNSS analysis / Kan Wang (2016)  

Public Titre : Advanced modeling and algorithms for high-precision GNSS analysis Type de document : Thèse/HDR Auteurs : Kan Wang, Auteur Editeur : Zurich : Eidgenossische Technische Hochschule ETH - Ecole Polytechnique Fédérale de Zurich EPFZ Année de publication : 2016 Collection : Dissertationen ETH num. 23188 Note générale : bibliographie thesis submitted to attain the degree of doctor of sciences of ETH Zurich Langues : Anglais (eng) Descripteur : [Termes IGN] ambiguïté entière [Termes IGN] antenne GPS [Termes IGN] centre de phase [Termes IGN] données BeiDou [Termes IGN] données Galileo [Termes IGN] données GPS [Termes IGN] double différence [Termes IGN] erreur systématique [Termes IGN] GPS en mode différentiel [Termes IGN] horloge [Termes IGN] phase GNSS [Termes IGN] positionnement cinématique [Termes IGN] récepteur GNSS [Termes IGN] récepteur trifréquence [Termes IGN] résolution d'ambiguïté [Termes IGN] retard ionosphèrique [Termes IGN] Suisse [Termes IGN] trajet multiple [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) In the recent ten years, the Global Navigation Satellite System (GNSS) processing has experienced a fast development in many areas including the increasing number of frequencies, the higher quality of positioning instruments, e.g. the receiver clocks and the satellite clocks, and more integrated modeling and calculation strategies. This thesis includes investigations of different modeling and parameterization methods in modern GNSS positioning with the focus on three important positioning error sources: the receiver clock errors, the phase ambiguities and the ionospheric delays. The thesis shows that making use of the high-quality receiver clocks and applying appropriate receiver clock modeling can help to improve the kinematic height estimates, which are highly correlated with the receiver clock parameters. An efficient pre-elimination and back-substitution strategy of epoch parameters with relative clock constraints between subsequent and near-subsequent epochs has been developed to enable processing of, e.g., high-rate data. A detailed analysis of the relationship between the clock quality and the improvement of kinematic heights has been performed. Studies were also conducted to decorrelate the receiver clock parameters, the kinematic heights and the troposphere parameters. Experiments with real data have shown that appropriate deterministic and stochastic clock models can also be helpful to increase the resolution of the estimated Zenith Path Delay (ZPD) parameters without obvious degradation of the stability of the kinematic heights. The second aspect of the thesis focuses on the resolution of triple-frequency phase ambiguities with different linear combinations. A complete analytical investigation of Geometry-Free (GF) and Ionosphere-Free (IF) triple-frequency phase ambiguity resolution with minimized noise level has been performed for different frequency triplets. The analysis was done separately for the best two linear combinations and the third one. Experiments have shown that the fractional parts and the formal errors of the combined ambiguities of the best two linear combinations are relatively small for Galileo E1, E5b and E5a and GPS L1, L2 and L5 triplets, while the third linear combination remains a challenge. Further analysis with the geostationary satellites of the Beidou Navigation Satellite System (BDS) elaborated in the framework of this thesis has also confirmed that the combined ambiguities from the best two GF and IF linear combinations can be fixed by rounding, while the estimated ambiguities on L1 have relatively large deviations from the values obtained from the traditional dual-frequency double-difference ambiguity resolution. Apart from the triple-frequency ambiguity resolution on the double-difference level, the so-called track-to-track ambiguities between different tracks of the same receiver and the same satellite have also been investigated for the best two triple-frequency linear combinations using GPS L1, L2 and L5 as well as Galileo E1, E5b and E5a observations. The outcome demonstrates that elevation-dependent influences on the observations like Phase Center Variations (PCVs), Phase Center Offsets (PCOs) and multipath are important for the fixing of the track-to-track ambiguities. The combined track-to-track ambiguities using the best two linear combinations are also effective in detecting problems in the observation data. The third aspect of the thesis includes the investigation of the differential ionospheric delays and gradients in the region of Switzerland from 1999 to 2013. In differential Global Positioning System (GPS) positioning, the ionospheric delays for short baselines are in most cases small enough to be ignored, except under extreme conditions, e.g., during ionospheric stormy days, and for applications with high integrity requirements, e.g., during approach and landing of aircrafts. This thesis introduces an algorithm using double-difference phase measurements with resolved phase ambiguities and global ionosphere maps provided by the Center for Orbit Determination in Europe (CODE) to extract the single-difference ionospheric delays, and enabling an automatic and robust processing of the data over 15 years. The results show that the daily maximum slant ionospheric gradients calculated from the differential slant ionopheric delays and the baseline lengths from 1999 to 2013 are below the slant ionosphere gradient boundary of the Conterminous United States (CONUS) ionospheric anomaly threat model. Numéro de notice : 17250 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : dissertation : sciences : ETH Zurich : 2016 En ligne : http://dx.doi.org/10.3929/ethz-a-010610972 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81986

Assessing and mitigating the effects of the ionospheric variability on DGPS / Duojie Weng in GPS solutions, vol 19 n° 1 (January 2015)  

Public [article]  inGPS solutions > vol 19 n° 1 (January 2015) . - pp 107 - 116 Titre : Assessing and mitigating the effects of the ionospheric variability on DGPS Type de document : Article/Communication Auteurs : Duojie Weng, Auteur ; Shengyue Ji, Auteur ; Wu Chen, Auteur ; Zhihua Li, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 107 - 116 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] GPS en mode différentiel [Termes IGN] gradient ionosphèrique [Termes IGN] ionosphère [Termes IGN] modèle ionosphérique [Termes IGN] retard ionosphèrique [Termes IGN] traitement de données GNSS Résumé : (auteur) The differential GPS (DGPS) performance can be affected by the ionospheric variability, especially in low-latitude areas. We evaluated the behavior of the ionospheric variability in low-latitude areas in the 11-year cycle of the solar activity. During periods of solar maximum, the percentage of the daily maximum gradient that exceeds 50 mm/km has reached 73 % in 2001. Assuming that the baseline length is 20 km, the gradient larger than 50 mm/km can lead to more than 1.0-m ranging error, which is significant if we want to achieve meter-level accuracy with DGPS. An ionospheric gradient model built from a number of reference stations is proposed for estimating the differential ionospheric delays. The effectiveness of the model is demonstrated under both the quiet and active ionospheric conditions in low-latitude areas. For a short baseline length of 16.9 km in Hong Kong, the horizontal positioning accuracy can be improved by 41 and 61 % during active solar years and geomagnetic storms, respectively. The improvements show that the model is capable of reducing the spatial decorrelation caused by the ionospheric variability, and the model can be used in DGPS especially over the regions, such as low-latitude areas, where the large ionospheric variability happens frequently. Numéro de notice : A2015-201 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-0372-x Date de publication en ligne : 13/04/2014 En ligne : https://doi.org/10.1007/s10291-014-0372-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76019 [article]

Combining terrestrial stereophotogrammetry, DGPS and GIS-based 3D voxel modelling in the volumetric recording of archaeological features / H. Orengo in ISPRS Journal of photogrammetry and remote sensing, vol 76 (February 2013)  

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Introduction to a portable stereo mapping system for unmanned vehicles / Julien Li-Chee-Ming in Geomatica, vol 66 n° 4 (December 2012)  

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Mitigation of atmospheric perturbations and solid Earth movements in a TerraSAR-X time-series / D. Small in Journal of geodesy, vol 86 n° 4 (April 2012)  

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Accuracy assessment of the GPS-TEC calibration constants by means of a simulation technique / Jacques Conte in Journal of geodesy, vol 85 n° 10 (October 2011)  

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Strapdown INS/DGPS airborne gravimetry tests in the Gulf of Mexico / X. Li in Journal of geodesy, vol 85 n° 9 (September 2011)  

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Positional accuracy analysis of satellite imagery by circular statistics / A. Cuartero in Photogrammetric Engineering & Remote Sensing, PERS, vol 76 n° 11 (November 2010)  

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New results in airborne vector gravimetry using strapdown INS/DGPS / M. Senobari in Journal of geodesy, vol 84 n° 5 (May 2010)  

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Real-time registration of airborne laser with sub-decimeter accuracy / Jan Skaloud in ISPRS Journal of photogrammetry and remote sensing, vol 65 n° 2 (March - April 2010)  

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Sea surface topography and marine geoid by airborne laser altimetry and shipborne ultrasound altimetry / Philippe Limpach (2010)  

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The application of GPS precise point positioning technology in aerial triangulation / Xiuxiao Yuan in ISPRS Journal of photogrammetry and remote sensing, vol 64 n° 6 (November - December 2009)  

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