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Benefits of combining GPS and GLONASS for measuring ocean tide loading displacement / Majid Abbaszadeh in Journal of geodesy, vol 94 n° 7 (July 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 7 (July 2020) . - n° 63 Titre : Benefits of combining GPS and GLONASS for measuring ocean tide loading displacement Type de document : Article/Communication Auteurs : Majid Abbaszadeh, Auteur ; Peter J. Clarke, Auteur Année de publication : 2020 Article en page(s) : n° 63 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] constellation GLONASS [Termes IGN] données GLONASS [Termes IGN] données GPS [Termes IGN] données marégraphiques [Termes IGN] marée océanique [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement ponctuel précis [Termes IGN] surcharge océanique [Termes IGN] trajet multiple Résumé : (auteur) GPS has been used to estimate ocean tide loading (OTL) height displacement amplitudes to accuracies of within 0.5 mm at the M2 frequency, but such estimation has been problematic at luni-solar K2 and K1 frequencies because they coincide with the GPS orbital period and revisit period, leading to repeating multipath and satellite orbit errors. We therefore investigate the potential of using the GLONASS constellation (with orbital period 11.26 h and true site revisit period of 8 sidereal days distinct from K2 and K1) for OTL displacement estimation, analysing 3–7 years of GPS and GLONASS data from 49 globally distributed stations. Using the PANDA software in kinematic precise point positioning mode with float ambiguities, we demonstrate that GLONASS can estimate OTL height displacement at the M2, N2, O1 and Q1 lunar frequencies with similar accuracy to GPS: 95th percentile agreements of 0.6–1.3 mm between estimated and FES2014b ocean tide model displacements. At the K2 and K1 luni-solar frequencies, 95th percentile agreements between GPS estimates and model values of 3.9–4.4 mm improved to 2.0–2.8 mm using GLONASS-only solutions. A combined GPS+GLONASS float solution improves accuracy of the lunar OTL constituents and P1 (but not significantly for K1 or K2) compared with a single-constellation solution and results in hourly-to-weekly spectral noise very similar to a GPS ambiguity-fixed solution, but without needing uncalibrated phase delay information. GLONASS estimates are more accurate at higher compared with lower latitudes because of improved satellite visibility, although this can be countered by using a lower elevation cut-off angle. Numéro de notice : A2020-535 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01393-5 Date de publication en ligne : 08/07/2020 En ligne : https://doi.org/10.1007/s00190-020-01393-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95727 [article]

Secular changes in Earth’s shape and surface mass loading derived from combinations of reprocessed global GPS networks / david Booker in Journal of geodesy, vol 88 n° 9 (September 2014)  

Public [article]  inJournal of geodesy > vol 88 n° 9 (September 2014) . - pp 839 - 855 Titre : Secular changes in Earth’s shape and surface mass loading derived from combinations of reprocessed global GPS networks Type de document : Article/Communication Auteurs : david Booker, Auteur ; Peter J. Clarke, Auteur ; David Lavallée, Auteur Année de publication : 2014 Article en page(s) : pp 839 - 855 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] croute terrestre [Termes IGN] détection de changement [Termes IGN] masse d'eau [Termes IGN] masse de la Terre [Termes IGN] traitement de données GNSS Résumé : (Auteur) The changing distribution of surface mass (oceans, atmospheric pressure, continental water storage, groundwater, lakes, snow and ice) causes detectable changes in the shape of the solid Earth, on time scales ranging from hours to millennia. Transient changes in the Earth’s shape can, regardless of cause, be readily separated from steady secular variation in surface mass loading, but other secular changes due to plate tectonics and glacial isostatic adjustment (GIA) cannot. We estimate secular station velocities from almost 11 years of high quality combined GPS position solutions (GPS weeks 1,000–1,570) submitted as part of the first international global navigation satellite system service reprocessing campaign. Individual station velocities are estimated as a linear fit, paying careful attention to outliers and offsets. We remove a suite of a priori GIA models, each with an associated set of plate tectonic Euler vectors estimated by us; the latter are shown to be insensitive to the a priori GIA model. From the coordinate time series residuals after removing the GIA models and corresponding plate tectonic velocities, we use mass-conserving continental basis functions to estimate surface mass loading including the secular term. The different GIA models lead to significant differences in the estimates of loading in selected regions. Although our loading estimates are broadly comparable with independent estimates from other satellite missions, their range highlights the need for better, more robust GIA models that incorporate 3D Earth structure and accurately represent 3D surface displacements. Numéro de notice : A2014-455 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0725-9 Date de publication en ligne : 06/05/2014 En ligne : https://doi.org/10.1007/s00190-014-0725-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=74027 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2014091	SL	Revue	Centre de documentation	Revues en salle	Disponible

A comparison of GPS, VLBI and model estimates of ocean tide loading displacements / I.D. Thomas in Journal of geodesy, vol 81 n° 5 (May 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 5 (May 2007) . - pp 359 - 368 Titre : A comparison of GPS, VLBI and model estimates of ocean tide loading displacements Type de document : Article/Communication Auteurs : I.D. Thomas, Auteur ; Matt A. King, Auteur ; Peter J. Clarke, Auteur Année de publication : 2007 Article en page(s) : pp 359 - 368 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] analyse comparative [Termes IGN] interférométrie à très grande base [Termes IGN] positionnement par GPS [Termes IGN] positionnement par ITGB [Termes IGN] surcharge océanique Résumé : (Auteur) In recent years, ocean tide loading displacements (OTLD) have been measured using the Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI). This study assesses the accuracy of GPS measurements of OTLD by comparison with VLBI measurements and estimates derived from numerical ocean tide models. A daily precise point positioning (PPP) analysis was carried out on ?11 years of GPS data for each of 25 sites that have previous OTLD estimates based on data from co-located VLBI sites. Ambiguities were fixed to integer values where possible. The resulting daily estimates of OTLD, at eight principal diurnal and semi-diurnal tidal frequencies, were combined to give GPS measurements of OTLD at each site. The 3D GPS and VLBI measurements of OTLD were compared with estimates computed (by convolution with Green’s functions) from five modern ocean tide models (CSR4.0, FES2004, GOT00.2, NAO99b and TPXO6.2). The GPS/model agreement is shown to be similar to the VLBI/model agreement. In the important radial direction, the GPS/model misfit is shown to be smaller than the VLBI/model misfit for seven of the eight tidal constituents; the exception being the K2 constituent. Fixing of GPS carrier-phase ambiguities to integer values resulted in a marginal improvement to the GPS/model agreement. Statistically, it is shown there is no significance to the difference between the fit of the GPS and VLBI measurements of OTLD to modelled values. Equally, differences in fit of either the complete set of GPS or VLBI estimates to the five sets of model-derived values cannot be identified with statistical significance. It is thus concluded that, overall, we cannot distinguish between GPS and VLBI measurements of OTLD, and that at the global scale, present ocean tide models are accurate to within the current measurement noise of these techniques. Copyright Springer Numéro de notice : A2007-125 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0118-9 En ligne : https://doi.org/10.1007/s00190-006-0118-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28488 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07051	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07052	RAB	Revue	Centre de documentation	En réserve L003	Disponible

GPS sidereal filtering: coordinate- and carrier-phase-level strategies / A.E. Ragheb in Journal of geodesy, vol 81 n° 5 (May 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 5 (May 2007) . - pp 325 - 335 Titre : GPS sidereal filtering: coordinate- and carrier-phase-level strategies Type de document : Article/Communication Auteurs : A.E. Ragheb, Auteur ; Peter J. Clarke, Auteur ; S.J. Edwards, Auteur Année de publication : 2007 Article en page(s) : pp 325 - 335 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] autocorrélation [Termes IGN] données GPS [Termes IGN] filtrage du signal [Termes IGN] phase GPS [Termes IGN] positionnement par GPS [Termes IGN] traitement de données GNSS [Termes IGN] trajet multiple Résumé : (Auteur) Multipath error is considered one of the major errors affecting GPS observations. One can benefit from the repetition of satellite geometry approximately every sidereal day, and apply filtering to help minimize this error. For GPS data at 1 s interval processed using a double-difference strategy, using the day-to-day coordinate or carrier-phase residual autocorrelation determined with a 10-h window leads to the steadiest estimates of the error-repeat lag, although a window as short as 2 h can produce an acceptable value with > 97% of the optimal lag’s correlation. We conclude that although the lag may vary with time, such variation is marginal and there is little advantage in using a satellite-specific or other time-varying lag in double-difference processing. We filter the GPS data either by stacking a number of days of processed coordinate residuals using the optimum “sidereal” lag (23 h 55 m 54 s), and removing these stacked residuals from the day in question (coordinate space), or by a similar method using double-difference carrier-phase residuals (observational space). Either method results in more consistent and homogeneous set of coordinates throughout the dataset compared with unfiltered processing. Coordinate stacking reduces geometry-related repeating errors (mainly multipath) better than carrier-phase residual stacking, although the latter takes less processing time to achieve final filtered coordinates. Thus, the optimal stacking method will depend on whether coordinate precision or computational time is the over-riding criterion. Copyright Springer Numéro de notice : A2007-122 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0113-1 En ligne : https://doi.org/10.1007/s00190-006-0113-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28485 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07051	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07052	RAB	Revue	Centre de documentation	En réserve L003	Disponible