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Galileo orbit determination using combined GNSS and SLR observations / Stefan Hackel in GPS solutions, vol 19 n° 1 (January 2015)  

Public [article]  inGPS solutions > vol 19 n° 1 (January 2015) . - pp 15 - 25 Titre : Galileo orbit determination using combined GNSS and SLR observations Type de document : Article/Communication Auteurs : Stefan Hackel, Auteur ; Peter Steigenberger, Auteur ; Urs Hugentobler, Auteur Année de publication : 2015 Article en page(s) : pp 15 - 25 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] données TLS (télémétrie) [Termes IGN] erreur systématique [Termes IGN] GIOVE (satellite) [Termes IGN] indicateur de qualité [Termes IGN] modèle linéaire [Termes IGN] orbite [Termes IGN] orbitographie [Termes IGN] positionnement par GNSS [Termes IGN] qualité des données Résumé : (auteur) The first two Galileo In-Orbit Validation satellites were launched in October 2011 and started continuous signal transmission on all frequencies in early 2012. Both satellites are equipped with two different types of clocks, namely rubidium clocks and hydrogen masers. Based on two test periods, the quality of the Galileo orbit determination based on Global Navigation Satellite System (GNSS) and Satellite Laser Ranging (SLR) observations is assessed. The estimated satellite clock parameters are used as quality indicator for the orbits: A bump at orbital periods in the Allan deviation indicates systematic errors in the GNSS-only orbit determination. These errors almost vanish if SLR observations are considered in addition. As the internal consistency is degraded by the combination, the offset of the SLR reflector is shifted by +5 cm, resulting in an improved orbit consistency as well as accuracy. Another approach to reduce the systematic errors of the GNSS-only orbit determination employs constraints for the clock estimates with respect to a linear model. In general, one decimeter orbit accuracy could be achieved. Numéro de notice : A2015-202 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-013-0361-5 Date de publication en ligne : 09/01/2014 En ligne : https://doi.org/10.1007/s10291-013-0361-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76015 [article]

Real-time high-precision earthquake monitoring using single-frequency GPS receivers / Min Li in GPS solutions, vol 19 n° 1 (January 2015)  

Public [article]  inGPS solutions > vol 19 n° 1 (January 2015) . - pp 27 - 35 Titre : Real-time high-precision earthquake monitoring using single-frequency GPS receivers Type de document : Article/Communication Auteurs : Min Li, Auteur ; Wenwen Li, Auteur ; Rongxin Fang, Auteur ; Chuang Shi, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 27 - 35 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] récepteur monofréquence [Termes IGN] séisme [Termes IGN] Setchouan (Chine) [Termes IGN] surveillance géologique [Termes IGN] vitesse Résumé : (auteur) We present a new method for high-precision real-time earthquake monitoring that focuses on station velocity using single-frequency GPS receivers. By means of GPS absolute velocity determination (AVD), real-time station velocity of millimeter per second precision can be obtained epoch by epoch using the GPS broadcast ephemeris. While the monitoring stations are considered stationary during aseismic time, the coseismic displacement can be instantaneously recorded by the velocity changes. The 1-Hz GPS data at selected stations during the M w 8.0 Wenchuan earthquake, the M w 9.0 Tohoku-Oki earthquake and the M w 6.6 Lushan earthquake are processed with the AVD approach. The results indicate that the phase and amplitude of AVD-derived velocity time series induced by the earthquakes coincide with those derived from post-mission kinematic PPP approach. Even when coseismic displacements at some stations are occasionally not visible in the position time series, the velocity series can still clearly manifest the earthquake displacement signal. With the AVD approach, the precision and reliability of the real-time monitoring can be improved significantly. It is also indicated the velocity series can be used for fast post-earthquake assessment such as rapid determination of earthquake magnitude, locating epicenter, determining seismic wave propagation velocity and other earthquake studies. Numéro de notice : A2015-203 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-013-0362-4 Date de publication en ligne : 09/01/2014 En ligne : https://doi.org/10.1007/s10291-013-0362-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76016 [article]

The carrier-multipath observable: a new carrier-phase multipath mitigation technique / Ramin Moradi in GPS solutions, vol 19 n° 1 (January 2015)  

Public [article]  inGPS solutions > vol 19 n° 1 (January 2015) . - pp 73 - 82 Titre : The carrier-multipath observable: a new carrier-phase multipath mitigation technique Type de document : Article/Communication Auteurs : Ramin Moradi, Auteur ; Wolfgang Schuster, Auteur ; Shaojun Feng, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 73 - 82 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction du trajet multiple [Termes IGN] trajet multiple Résumé : (auteur) Modeling and mitigating carrier-phase multipath errors continue to be a significant challenge for high-accuracy positioning using global navigation satellite systems. The multipath error is dependent on the operational environment and therefore cannot be mitigated by differencing techniques. The effect of multipath is accentuated when observables based on linear combinations of measurements from two or more frequencies are formulated. We develop a new carrier-phase multipath error observable that isolates the inter-frequency carrier-phase multipath error for linear combinations of observables, such as wide-lane (WL). Real-time kinematic positioning results from varying baseline lengths show that a significant reduction in between 14 and 47 % in the time to initial ambiguity resolution are achieved by correcting the WL observable using the new carrier-phase multipath error observable. Numéro de notice : A2015-204 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-0366-8 Date de publication en ligne : 22/01/2014 En ligne : https://doi.org/10.1007/s10291-014-0366-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76017 [article]

Generating statistically robust multipath stacking maps using congruent cells / Thomas Fuhrmann in GPS solutions, vol 19 n° 1 (January 2015)  

Public [article]  inGPS solutions > vol 19 n° 1 (January 2015) . - pp 83 - 92 Titre : Generating statistically robust multipath stacking maps using congruent cells Type de document : Article/Communication Auteurs : Thomas Fuhrmann, Auteur ; Xiaoguang Luo, Auteur ; Andreas Knöpfler, Auteur ; Michael Mayer, Auteur Année de publication : 2015 Article en page(s) : pp 83 - 92 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] congruence [Termes IGN] correction du trajet multiple [Termes IGN] résidu [Termes IGN] superposition [Termes IGN] trajet multiple [Termes IGN] valeur aberrante Résumé : (auteur) Multipath effects caused by reflections in the near-field and far-field of a GNSS antenna represent a major error source in static and kinematic GNSS positioning applications. Since these effects are strongly site-specific, a generally valid and practicable analytical multipath model is still lacking. In contrast, using GNSS carrier phase observation residuals, the multipath stacking (MPS) methods are able to take site-specific conditions into account. We propose an advanced approach to performing residual-based MPS in the space domain. Being superior to most conventional attempts in which stacking cells have a fixed azimuthal resolution, our suggested method makes use of congruent cells and rigorous statistical assessments in terms of outlier detection and significance evaluation of the stacked values. The advanced stacking approach is applied to representative phase residuals from static precise point positioning. The results show that the use of congruent cells allows for MPS at high elevation angles and with a fine spatial resolution. Applying the resulting MPS maps at the residual level, both near-field and far-field effects at high and low elevation angles, respectively, can be significantly mitigated. In comparison with the conventional approach, the advanced one enables a larger reduction of about 20 % in the SD of residuals. Numéro de notice : A2015-205 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1007/s10291-014-0367-7 Date de publication en ligne : 23/02/2014 En ligne : https://doi.org/10.1007/s10291-014-0367-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76018 [article]

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]