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Galileo status: orbits, clocks, and positioning / Peter Steigenberger in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 319 – 331 Titre : Galileo status: orbits, clocks, and positioning Type de document : Article/Communication Auteurs : Peter Steigenberger, Auteur ; Oliver Montenbruck, Auteur Année de publication : 2017 Article en page(s) : pp 319 – 331 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] constellation Galileo [Termes IGN] données Galileo [Termes IGN] Galileo [Termes IGN] positionnement ponctuel précis Résumé : (auteur) The European Global Navigation Satellite System Galileo is close to declaration of initial services. The current constellation comprises a total of 12 active satellites, four of them belonging to the first generation of In-Orbit Validation satellites, while the other eight are Full Operational Capability (FOC) satellites. Although the first pair of FOC satellites suffered from a launch anomaly resulting in an elliptical orbit, these satellites can be used for scientific applications without relevant limitations. The quality of broadcast orbits and clocks has significantly improved since the beginning of routine transmissions and has reached a signal-in-space range error of 30 cm. Precise orbit products generated by the scientific community achieve an accuracy of about 5 cm if appropriate models for the solar radiation pressure are applied. The latter is also important for an assessment of the clock stability as orbit errors are mapped to the apparent clock. Dual-frequency single point positioning with broadcast orbits and clocks of nine Galileo satellites that have so far been declared healthy already enables an accuracy at a few meters. Galileo-only precise point positioning approaches a precision of 2 cm in static mode using daily solutions. Numéro de notice : A2017-211 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0566-5 En ligne : http://dx.doi.org/10.1007/s10291-016-0566-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85051 [article]

Ionospheric tomography based on GNSS observations of the CMONOC: performance in the topside ionosphere / Zhe Yang in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 363 – 375 Titre : Ionospheric tomography based on GNSS observations of the CMONOC: performance in the topside ionosphere Type de document : Article/Communication Auteurs : Zhe Yang, Auteur ; Shuli Song, Auteur ; Wenhai Jiao, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 363 – 375 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] Chine [Termes IGN] données localisées 3D [Termes IGN] ionosphère [Termes IGN] propagation ionosphérique [Termes IGN] station GNSS [Termes IGN] tomographie par GPS [Termes IGN] voxel Résumé : (auteur) This study carries out a quantitative analysis of the performance of ionospheric tomography in the topside ionosphere, utilizing data of October 2011 collected from 260 Global Navigation Satellite System (GNSS) stations in the Crustal Movement Observation Network of China. This tomographic reconstruction with a resolution of 2° in latitude, 2° in longitude and 20 km in altitude has more than 70 % of voxels traversed by GPS raypaths and is able to provide reliable bottom parts of ionospheric profiles. Compared with the observations measured by the Defense Meteorological Satellite Program (DMSP) satellites (F16, F17 and F18) at an altitude of 830–880 km, the results show that there is an overestimation in the reconstructed plasma density at the DMSP altitude, and the reconstruction is better during daytime than nighttime. In addition, the reconstruction at nighttime also indicates a solar activity and latitudinal dependence. In summary, with respect to DMSP measurements, the daytime bias is on average from −0.32 × 105/cm3 to −0.28 × 105/cm3, while the nighttime bias is between −0.37 × 105/cm3 and −0.24 × 105/cm3, and the standard deviation at daytime and at nighttime is, respectively, 0.082 × 105/cm3 to 0.244 × 105/cm3 and 0.086 × 105/cm3 to 0.428 × 105/cm3. This study suggests that vertical ionospheric profiles from other sources, such as ionosondes or GNSS occultation satellites, should be incorporated into ground-based GNSS topside tomographic studies. Numéro de notice : A2017-212 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0526-0 En ligne : http://dx.doi.org/10.1007/s10291-016-0526-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85054 [article]

GPS real-time precise point positioning for aerial triangulation / Junbo Shi in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 405 – 414 Titre : GPS real-time precise point positioning for aerial triangulation Type de document : Article/Communication Auteurs : Junbo Shi, Auteur ; Xiuxiao Yuan, Auteur ; Yang Cai, Auteur ; Gaojing Wang, Auteur Année de publication : 2017 Article en page(s) : pp 405 – 414 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] aérotriangulation [Termes IGN] antenne [Termes IGN] coordonnées GNSS [Termes IGN] point de vérification [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis Résumé : (auteur) We extend the application of real-time kinematic PPP to aerial triangulation using GPS to determine coordinates of the antenna installed on the airplane, using real-time satellite products from IGS and the CNES Analysis Center. In order to verify the performance of real-time kinematic PPP for aerial triangulation, three tests with varying aerial and ground conditions are assessed. Numerical results show that real-time kinematic PPP using IGS real-time products of 5-cm orbit accuracy and 0.1- to 0.3-ns clock precision can provide comparable accuracy for aerial photogrammetric mapping at the scale of 1:1000 as does post-mission kinematic PPP using IGS final products. Millimeter-to-centimeter-level differences and centimeter-to-2-decimeter differences are identified for horizontal and vertical coordinates of ground check points, respectively, in the three tests. The comparison between real-time IGS and CNES products for GPS positioning and aerial triangulation unveils that real-time products with a better clock precision can result in better performance of GPS real-time kinematic PPP as applied to aerial triangulation. Numéro de notice : A2017-248 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0532-2 En ligne : http://dx.doi.org/10.1007/s10291-016-0532-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85055 [article]

GPS, Galileo, QZSS and IRNSS differential ISBs: estimation and application / Dennis Odijk in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 439 – 450 Titre : GPS, Galileo, QZSS and IRNSS differential ISBs: estimation and application Type de document : Article/Communication Auteurs : Dennis Odijk, Auteur ; Nandakumaran Nadarajah, Auteur ; Safoora Zaminpardaz, Auteur ; Peter J.G. Teunissen, Auteur Année de publication : 2017 Article en page(s) : pp 439 – 450 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] base géodésique [Termes IGN] constellation GNSS [Termes IGN] données GNSS [Termes IGN] erreur systématique inter-systèmes [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement différentiel [Termes IGN] positionnement par GNSS [Termes IGN] résolution d'ambiguïté Résumé : (auteur) Knowledge of inter-system biases (ISBs) is essential to combine observations of multiple global and regional navigation satellite systems (GNSS/RNSS) in an optimal way. Earlier studies based on GPS, Galileo, BDS and QZSS have demonstrated that the performance of multi-GNSS real-time kinematic positioning is improved when the differential ISBs (DISBs) corresponding to signals of different constellations but transmitted at identical frequencies can be calibrated, such that only one common pivot satellite is sufficient for inter-system ambiguity resolution at that particular frequency. Recently, many new GNSS satellites have been launched. At the beginning of 2016, there were 12 Galileo IOV/FOC satellites and 12 GPS Block IIF satellites in orbit, while the Indian Regional Navigation Satellite System (IRNSS) had five satellites launched of which four are operational. More launches are scheduled for the coming years. As a continuation of the earlier studies, we analyze the magnitude and stability of the DISBs corresponding to these new satellites. For IRNSS this article presents for the first time DISBs with respect to the L5/E5a signals of GPS, Galileo and QZSS for a mixed-receiver baseline. It is furthermore demonstrated that single-frequency (L5/E5a) ambiguity resolution is tremendously improved when the multi-GNSS observations are all differenced with respect to a common pivot satellite, compared to classical differencing for which a pivot satellite is selected for each constellation. Numéro de notice : A2017-214 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0536-y En ligne : http://dx.doi.org/10.1007/s10291-016-0536-y Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85084 [article]

An examination of the Galileo NeQuick model: comparison with GPS and JASON TEC / Ningbo Wang in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 605 – 615 Titre : An examination of the Galileo NeQuick model: comparison with GPS and JASON TEC Type de document : Article/Communication Auteurs : Ningbo Wang, Auteur ; Yunbin Yuan, Auteur ; Zishen Li, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 605 – 615 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] modèle ionosphérique [Termes IGN] retard ionosphèrique [Termes IGN] teneur totale en électrons [Termes IGN] test de performance Résumé : (auteur) We evaluate the performance of Galileo broadcast NeQuick model by comparing it with GPS broadcast Klobuchar and the original NeQuick2 models. The broadcast coefficients of Galileo NeQuick model are computed from 23 globally distributed tracking stations of the International GNSS Service (IGS), by ingesting the Global Positioning System (GPS)-derived ionospheric total electron content (TEC) into the original NeQuick2 model. The accuracy of the three ionospheric models is evaluated over both the continental and oceanic regions for the year 2013. In continental regions, ionospheric TEC derived from 34 IGS stations is used as references for comparison. In oceanic regions, where the IGS stations are sparse, high-quality vertical TEC sources provided by JASON-1&2 altimeters are used as references. The evaluation results show that in continental regions, GPS broadcast Klobuchar and the original and broadcast NeQuick can mitigate the ionospheric delay by 56.8, 63.3 and 72.4 %, respectively. In oceanic regions, the three models can correct for 51.1, 61.2 and 68.6 % of the ionospheric delay. Galileo broadcast NeQuick model outperforms Klobuchar by 15.6 and 17.5 % over the continental and oceanic regions, respectively, for the test period. The broadcast NeQuick model can provide accurate ionospheric error corrections when Galileo begins full operational capability. Numéro de notice : A2017-213 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0553-x En ligne : http://dx.doi.org/10.1007/s10291-016-0553-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85085 [article]

Fast ambiguity resolution for long-range reference station networks with ionospheric model constraint method / Ming Zhang in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 617 – 626 Titre : Fast ambiguity resolution for long-range reference station networks with ionospheric model constraint method Type de document : Article/Communication Auteurs : Ming Zhang, Auteur ; Hui Liu, Auteur ; Zhengdong Bai, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 617 – 626 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] antenne GNSS [Termes IGN] erreur [Termes IGN] modèle ionosphérique [Termes IGN] résolution d'ambiguïté [Termes IGN] retard ionosphèrique [Termes IGN] station de référence Résumé : (auteur) Ambiguity resolution (AR) speed is one of the most important performance indicators of a network RTK (real-time kinematics) system. Given the low correlation between the error sources of two stations, the effect of the atmospheric delay of double-difference observations cannot be ignored, thus making it difficult to fix the ambiguities. Ionospheric delay is one of the largest error sources affecting AR. This error source is reduced by the ionospheric-free combination with traditional methods. The AR speed of these methods is slow; generally, tens of minutes and even more are required for initialization. This study proposes an ionospheric model constraint (IMC) method to improve the AR speed. External information is not required apart from observations. The double-difference ionospheric delay is described with a regional double-difference ionospheric model, the coefficients of which are estimated as parameters together with ambiguities and tropospheric delays. Experimental results show that the initialization speed significantly improves by 72.5 % and that the AR speed for the newly risen satellites increases by 84.3 % with the proposed IMC method. Furthermore, the percentage of correctly fixed integer ambiguities after initialization increases to some extent. Numéro de notice : A2017-215 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0551-z En ligne : http://dx.doi.org/10.1007/s10291-016-0551-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85087 [article]

Global ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS / Peng Chen in GPS solutions, vol 21 n° 2 (April 2017)  

Public [article]  inGPS solutions > vol 21 n° 2 (April 2017) . - pp 639 – 650 Titre : Global ionosphere maps based on GNSS, satellite altimetry, radio occultation and DORIS Type de document : Article/Communication Auteurs : Peng Chen, Auteur ; Yi Bin Yao, Auteur ; Wanqiang Yao, Auteur Année de publication : 2017 Article en page(s) : pp 639 – 650 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] coordonnées GNSS [Termes IGN] données altimétriques [Termes IGN] données DORIS [Termes IGN] ionosphère [Termes IGN] modèle ionosphérique [Termes IGN] occultation du signal [Termes IGN] radiooccultation [Termes IGN] teneur verticale totale en électrons Résumé : (auteur) Global ionosphere maps (GIMs) provided by the global navigation satellite systems (GNSS) data are essential in ionospheric research as the source of the global vertical total electron content (VTEC). However, conventional GIMs experience lower accuracy and reliability from uneven distribution of GNSS tracking stations, especially in ocean areas with few tracking stations. The orbits of ocean altimetry satellite cover vast ocean areas and can directly provide VTEC at nadir with two different wavelengths of radio waves. Radio occultation observations and the beacons of Doppler orbitography and radio positioning integrated by satellite (DORIS) are evenly distributed globally. Satellite altimetry, radio occultation and DORIS can compensate GNSS data in ocean areas, allowing a more accurate and reliable GIMs to be formed with the integration of these observations. This study builds GIMs with temporal intervals of 2 h by the integration of GNSS, satellite altimetry, radio occultation and DORIS data. We investigate the integration method for multi-source data and used the data in May 2013 to validate the effectiveness of integration. Result shows that VTEC changes by −11.0 to −7.0 TECU after the integration of satellite altimetry, radio occultation and DORIS data. The maximum root mean square decreases by 5.5 TECU, and the accuracy of GIMs in ocean areas improves significantly. Numéro de notice : A2017-216 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-016-0554-9 En ligne : http://dx.doi.org/10.1007/s10291-016-0554-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85089 [article]