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Impact of seasonal station motions on VLBI UT1 intensives results / Zinovy Malkin in Journal of geodesy, vol 87 n° 6 (June 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 6 (June 2013) . - pp 505 - 514 Titre : Impact of seasonal station motions on VLBI UT1 intensives results Type de document : Article/Communication Auteurs : Zinovy Malkin, Auteur Année de publication : 2013 Article en page(s) : pp 505 - 514 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] déformation de la croute terrestre [Termes IGN] erreur systématique [Termes IGN] European VLBI network [Termes IGN] interférométrie à très grande base [Termes IGN] orientation de la Terre [Termes IGN] positionnement par ITGB [Termes IGN] station VLBI [Termes IGN] variation saisonnière Résumé : (Auteur) UT1 estimates obtained from the very long baseline interferometry (VLBI) Intensives data depend on the station displacement model used during processing. In particular, because of seasonal variations, the instantaneous station position during the specific intensive session differs from the position predicted by the linear model generally used. This can cause systematic errors in UT1 Intensives results. In this paper, we first investigated the seasonal signal in the station displacements for the 5 VLBI antennas participating in UT1 Intensives observing programs, along with the 8 collocated GPS stations. It was found that a significant annual term is present in the time series for most stations, and its amplitude can reach 8 mm in the height component, and 2 mm in horizontal components. However, the annual signals found in the displacements of the collocated VLBI and GPS stations at some sites differ substantially in amplitude and phase. The semiannual harmonics are relatively small and unstable, and for most stations no prevailing signal was found in the corresponding frequency band. Then two UT1 Intensives series were computed with and without including the seasonal term found in the previous step in the station movement model. Comparison of these series has shown that neglecting the seasonal station position variations can cause a systematic error in UT1 estimates, which can exceed 1us, depending on the observing program. Numéro de notice : A2013-338 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0624-5 Date de publication en ligne : 24/02/2013 En ligne : https://doi.org/10.1007/s00190-013-0624-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32476 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013061	SL	Revue	Centre de documentation	Revues en salle	Disponible

Ambiguity resolution for triple-frequency geometry-free and ionosphere-free combination tested with real data / K. Wang in Journal of geodesy, vol 87 n° 6 (June 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 6 (June 2013) . - pp 539 - 553 Titre : Ambiguity resolution for triple-frequency geometry-free and ionosphere-free combination tested with real data Type de document : Article/Communication Auteurs : K. Wang, Auteur ; Markus Rothacher, Auteur Année de publication : 2013 Article en page(s) : pp 539 - 553 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] combinaison linéaire [Termes IGN] filtrage du bruit [Termes IGN] mesurage de la fréquence [Termes IGN] phase GNSS [Termes IGN] résolution d'ambiguïté [Termes IGN] signal BeiDou [Termes IGN] signal Galileo [Termes IGN] signal GNSS Résumé : (Auteur) The recent GPS Block IIF satellites SVN62 and SVN63 and the Galileo satellites GIOVE-A, GIOVE-B, PFM and FM2 already send signals on more than two frequencies, and more GNSS satellites will provide tracking data on at least three frequencies in the near future. In this paper, a simplified general method for ambiguity resolution minimizing the noise level for the triple-frequency geometry-free (GF) and ionosphere-free (IF) linear combinations is presented, where differently scaled code noise on the three frequencies was introduced. For the third of three required linear combinations, the most demanding one in triple-frequency ambiguity resolution, we developed a general method using the ambiguity-corrected phase observations without any constraints to search for the optimal GF and IF linear combination. We analytically demonstrate that the noise level of this third linear combination only depends on the three frequencies. The investigation concerning this frequency-dependent noise factor was performed for GPS, Galileo and Compass frequency triplets. We verified the theoretical derivations with real triple-frequency GPS and Galileo data from the Multi-GNSS Experiment (M–GEX) of the International GNSS Service (IGS). The data of about 30 M–GEX stations around the world over 11 days from 29 April 2012 to 9 May 2012 were used for the test. For the third linear combinaton using Galileo E1, E5b and E5a, which is expected to have the worst performance among all the GNSS frequency triplets in our investigation, the formal errors of the estimated ambiguities are in most cases below 0.2 cycles after 400 observation epochs. If more GPS satellites sending signals on three frequencies or more stations tracking Galileo E6 signal are available in the future, an improvement by a factor of two to three can be expected. Numéro de notice : A2013-339 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0630-7 Date de publication en ligne : 09/04/2013 En ligne : https://doi.org/10.1007/s00190-013-0630-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32477 [article]

Exemplaires(1)

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266-2013061	SL	Revue	Centre de documentation	Revues en salle	Disponible

Combination of modeled short-term angular momentum function forecasts from atmosphere, ocean, and hydrology with 90-day EOP predictions / Robert Dill in Journal of geodesy, vol 87 n° 6 (June 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 6 (June 2013) . - pp 567 - 577 Titre : Combination of modeled short-term angular momentum function forecasts from atmosphere, ocean, and hydrology with 90-day EOP predictions Type de document : Article/Communication Auteurs : Robert Dill, Auteur ; H. Dobslaw, Auteur ; M. Thomas, Auteur Année de publication : 2013 Article en page(s) : pp 567 - 577 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] moment cinétique atmosphérique [Termes IGN] moment cinétique océanique [Termes IGN] orientation de la Terre [Termes IGN] prévision Résumé : (Auteur) Angular momentum forecasts for up to 10 days into the future, modeled from predicted states of the atmosphere, ocean and continental hydrosphere, are combined with the operational IERS EOP prediction bulletin A to reduce the prediction error in the very first day and to improve the subsequent 90-day prediction by exploitation of the revised initial state and trend information. EAM functions derived from ECMWF short-range forecasts and corresponding LSDM and OMCT simulations can account for high-frequency mass variations within the geophysical fluids for up to 7 days into the future primarily limited by the accuracy of the forecasted atmospheric wind fields. Including these wide-band stochastic signals into the first days of the 90-day statistical IERS predictions reduces the mean absolute prediction error even for predictions beyond day 10, especially for polar motion, where the presently used prediction approach does not include geophysical fluids data directly. In a hindcast experiment using 1 year of daily predictions from May 2011 till July 2012, the mean prediction error in polar motion, compared to bulletin A, is reduced by 32, 12, and 3 % for prediction days 10, 30, and 90, respectively. In average, the prediction error for medium-range forecasts (30–90 days) is reduced by 1.3–1.7 mas. Even for UT1-UTC, where AAM forecasts are already included in IERS bulletin A, we obtain slight improvements of up to 5 % (up to 0.5 ms) after day 10 due to the additional consideration of oceanic angular momentum forecasts. The improved 90-day predictions can be generated operationally on a daily basis directly after the publication of the related IERS bulletin A product finals2000A daily. Numéro de notice : A2013-340 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0631-6 Date de publication en ligne : 17/03/2013 En ligne : https://doi.org/10.1007/s00190-013-0631-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32478 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013061	SL	Revue	Centre de documentation	Revues en salle	Disponible

Assessment of correct fixing rate for precise point positioning ambiguity resolution on a global scale / Xiaohong Zhang in Journal of geodesy, vol 87 n° 6 (June 2013)  

Public [article]  inJournal of geodesy > vol 87 n° 6 (June 2013) . - pp 579 - 589 Titre : Assessment of correct fixing rate for precise point positioning ambiguity resolution on a global scale Type de document : Article/Communication Auteurs : Xiaohong Zhang, Auteur ; Pan Li, Auteur Année de publication : 2013 Article en page(s) : pp 579 - 589 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] dégradation du signal [Termes IGN] données GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] propagation ionosphérique [Termes IGN] résolution d'ambiguïté [Termes IGN] simple différence [Termes IGN] variance de phase Résumé : (Auteur) Ambiguity resolution (AR) for a single receiver has been a popular topic in Global Positioning System (GPS) recently. Ambiguity-resolution methods for precise point positioning (PPP) have been well documented in recent years, demonstrating that it can improve the accuracy of PPP. However, users are often concerned about the reliability of ambiguity-fixed PPP solution in practical applications. If ambiguities are fixed to wrong integers, large errors would be introduced into position estimates. In this paper, we aim to assess the correct fixing rate (CFR), i.e., number of ambiguities correctly fixing to the total number of ambiguities correctly and incorrectly fixing, for PPP user ambiguity resolution on a global scale. A practical procedure is presented to evaluate the CFR of PPP user ambiguity resolution. GPS data of the first 3 days in each month of 2010 from about 390 IGS stations are used for experiments. Firstly, we use GPS data collected from about 320 IGS stations to estimate global single-differenced (SD) wide-lane and narrow-lane satellite uncalibrated phase delays (UPDs). The quality of UPDs is evaluated. We found that wide-lane UPD estimates have a rather small standard deviation (Std) between 0.003 and 0.004 cycles while most of Std of narrow-lane estimates are from 0.01 to 0.02 cycles. Secondly, many experiments have been conducted to investigate the CFR of integer ambiguity resolution we can achieve under different conditions, including reference station density, observation session length and the ionospheric activity. The results show that the CFR of PPP can exceed 98.0 % with only 1 h of observations for most user stations. No obvious correlation between the CFR and the reference station density is found. Therefore, nearly homogeneous CFR can be achieved in PPP AR for global users. At user end, higher CFR could be achieved with longer observations. The average CFR for 30-min, 1-h, 2-h and 4-h observation is 92.3, 98.2, 99.5 and 99.7 %, respectively. In order to get acceptable CFR, 1 h is a recommended minimum observation time. Furthermore, the CFR of PPP can be affected by diurnal variation and geomagnetic latitude variation in the ionosphere. During one day at the hours when rapid ionospheric variations occur or in low geomagnetic latitude regions where equatorial electron density irregularities are produced relatively frequently, a significant degradation of the CFR is demonstrated. Numéro de notice : A2013-341 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-013-0632-5 Date de publication en ligne : 23/03/2013 En ligne : https://doi.org/10.1007/s00190-013-0632-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32479 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2013061	SL	Revue	Centre de documentation	Revues en salle	Disponible