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Determination of precise Galileo orbits using combined GNSS and SLR observations / Grzegorz Bury in GPS solutions, vol 25 n° 1 (January 2021)  

Public [article]  inGPS solutions > vol 25 n° 1 (January 2021) . - n° 11 Titre : Determination of precise Galileo orbits using combined GNSS and SLR observations Type de document : Article/Communication Auteurs : Grzegorz Bury, Auteur ; Krzysztof Sosnica, Auteur ; Radoslaw Zajdel, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 11 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes descripteurs IGN] données GNSS [Termes descripteurs IGN] données TLS (télémétrie) [Termes descripteurs IGN] Galileo [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] orbite précise [Termes descripteurs IGN] orbitographie [Termes descripteurs IGN] pondération Résumé : (auteur) Galileo satellites are equipped with laser retroreflector arrays for satellite laser ranging (SLR). In this study, we develop a methodology for the GNSS-SLR combination at the normal equation level with three different weighting strategies and evaluate the impact of laser observations on the determined Galileo orbits. We provide the optimum weighting scheme for precise orbit determination employing the co-location onboard Galileo. The combined GNSS-SLR solution diminishes the semimajor axis formal error by up to 62%, as well as reduces the dependency between values of formal errors and the elevation of the Sun above the orbital plane—the β angle. In the combined solution, the standard deviation of the SLR residuals decreases from 36.1 to 29.6 mm for Galileo-IOV satellites and |β|> 60°, when compared to GNSS-only solutions. Moreover, the bias of the Length-of-Day parameter is 20% lower for the combined solution when compared to the microwave one. As a result, the combination of GNSS and SLR observations provides promising results for future co-locations onboard the Galileo satellites for the orbit determination, realization of the terrestrial reference frames, and deriving geodetic parameters. Numéro de notice : A2021-008 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-01045-3 date de publication en ligne : 31/10/2020 En ligne : https://doi.org/10.1007/s10291-020-01045-3 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96298 [article]

CORS usage for GPS survey in the greater accra region: Advantages, limitation, and suggested remedies / Sebastian Botsyo in Journal of Geovisualization and Spatial Analysis, vol 4 n° 2 (December 2020)  

Public [article]  inJournal of Geovisualization and Spatial Analysis > vol 4 n° 2 (December 2020) . - n° 20 Titre : CORS usage for GPS survey in the greater accra region: Advantages, limitation, and suggested remedies Type de document : Article/Communication Auteurs : Sebastian Botsyo, Auteur ; Bernard Borketey Bortei, Auteur ; John Ayer, Auteur Année de publication : 2020 Article en page(s) : n° 20 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes descripteurs IGN] balise [Termes descripteurs IGN] géopositionnement [Termes descripteurs IGN] Ghana [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] positionnement statique [Termes descripteurs IGN] station de référence [Termes descripteurs IGN] station permanente [Termes descripteurs IGN] système de référence local Résumé : (auteur) The use of Continuously Operating Reference Stations (CORS) enables surveyors to differentially correct static Global Positioning System (GPS) measurements. CORS are designed to support the broad spectrum of post-processed, relative GPS techniques, and applications. Enhancing geospatial positioning applications of CORS data involves the critical role in defining the nation’s geodetic reference system. With the establishment of a coordinated system of CORS, an Online Positioning User Service can become available for processing in single positioning mode to provide corresponding accurate and homogeneous positional coordinates. The Survey and Mapping Division (SMD), Lands Commission of Ghana, has established four CORS in the Greater Accra, and Ashanti, Western and Brong-Ahafo Regions, respectively, to provide a basic CORS network in accordance with the International Terrestrial Reference Frame (ITRF). However, most surveyors continue to reference their works in these regions to ground survey beacons that have been coordinated and adjusted by variable survey methods. This obviously makes homogeneity of data unpredictable. This study explored the extent of usage of existing CORS network established by SMD with particular focus on the CORS in the Greater Accra Region for GPS surveys and to determine its usefulness in ensuring homogeneity in GPS data collection. The professional participatory (interviews) technique was coupled with differential GPS field observations with the CORS as reference in one case and ground control stations as reference in the other in making relatively conclusive analysis. Test results showed that GPS field survey of an approximate range of 23 km away from the Accra CORS yielded an average positional change in Northings and Eastings of − 0.790 m, − 0.176 m and − 0.681 m, − 0.098 m for single and dual frequency, respectively, in different localities within the study area. Beyond a range of 25 km from the Accra CORS, the average positional change in Northings and Eastings are − 0.536 m, − 0.007 m and − 1.370 m, 0.334 m for single and dual frequency respectively. Of 128 geomatic professionals interviewed, 39% are aware of the availability of COR stations in Greater Accra, 61% are unaware, and 28% are aware and users of the Accra CORS whereas 11% are aware but non-users of the Accra COR station. Of all users sampled, 17.5% are regular and frequent users of the Accra COR station and 10.5% are occasional or seldom users. The results show that the Accra CORS is vital to ensuring a uniform homogenous GPS data. However, very few people are using it due to low public awareness of the usefulness of the CORS among professional surveyors and other users and a cumbersome, bureaucratic nature in CORS data acquisition for post-processing and RTK GPS surveys. Numéro de notice : A2020-723 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s41651-020-00061-8 date de publication en ligne : 11/09/2020 En ligne : https://doi.org/10.1007/s41651-020-00061-8 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96324 [article]

Reference system origin and scale realization within the future GNSS constellation “Kepler” / Susanne Glaser in Journal of geodesy, vol 94 n° 12 (December 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 12 (December 2020) . - n° 117 Titre : Reference system origin and scale realization within the future GNSS constellation “Kepler” Type de document : Article/Communication Auteurs : Susanne Glaser, Auteur ; Grzegorz Michalak, Auteur ; Benjamin Männel, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : n° 117 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] centre de phase [Termes descripteurs IGN] constellation Galileo [Termes descripteurs IGN] constellation GNSS [Termes descripteurs IGN] décorrélation [Termes descripteurs IGN] géocentre [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] Kepler, Johannes [Termes descripteurs IGN] orbite basse [Termes descripteurs IGN] orbite terrestre [Termes descripteurs IGN] orbitographie Résumé : (auteur) Currently, Global Navigation Satellite Systems (GNSS) do not contribute to the realization of origin and scale of combined global terrestrial reference frame (TRF) solutions due to present system design limitations. The future Galileo-like medium Earth orbit (MEO) constellation, called “Kepler”, proposed by the German Aerospace Center DLR, is characterized by a low Earth orbit (LEO) segment and the innovative key features of optical inter-satellite links (ISL) delivering highly precise range measurements and of optical frequency references enabling a perfect time synchronization within the complete constellation. In this study, the potential improvements of the Kepler constellation on the TRF origin and scale are assessed by simulations. The fully developed Kepler system allows significant improvements of the geocenter estimates (realized TRF origin in long-term). In particular, we find improvements by factors of 43 for the Z and of 8 for the X and Y component w. r. t. a contemporary MEO-only constellation. Furthermore, the Kepler constellation increases the reliability due to a complete de-correlation of the geocenter coordinates and the orbit parameters related to the solar radiation pressure modeling (SRP). However, biases in SRP modeling cause biased geocenter estimates and the ISL of Kepler can only partly compensate this effect. The realized scale enabling all Kepler features improves by 34% w. r. t. MEO-only. The dependency of the estimated satellite antenna phase center offsets (PCOs) upon the underlying TRF impedes a scale realization by GNSS. In order to realize the network scale with 1 mm accuracy, the PCOs have to be known within 2 cm for the MEO and 4 mm for the LEO satellites. Independently, the scale can be realized by estimating the MEO PCOs and by simultaneously fixing the LEO PCOs. This requires very accurate LEO PCOs; the simulations suggest them to be smaller than 1 mm in order to keep scale changes below 1 mm. Numéro de notice : A2020-736 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01441-0 date de publication en ligne : 19/11/2020 En ligne : https://doi.org/1https://doi.org/10.1007/s00190-020-01441-0 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96352 [article]

GNSS scale determination using calibrated receiver and Galileo satellite antenna patterns / Arturo Villiger in Journal of geodesy, vol 94 n° 9 (September 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 9 (September 2020) . - n° 93 Titre : GNSS scale determination using calibrated receiver and Galileo satellite antenna patterns Type de document : Article/Communication Auteurs : Arturo Villiger, Auteur ; Rolf Dach, Auteur ; Stefan Schaer, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : n° 93 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes descripteurs IGN] antenne Galileo [Termes descripteurs IGN] centre de phase [Termes descripteurs IGN] chambre anéchoïque [Termes descripteurs IGN] étalonnage d'instrument [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] métadonnées [Termes descripteurs IGN] positionnement par ITGB [Termes descripteurs IGN] positionnement par télémétrie laser sur satellite [Termes descripteurs IGN] réseau géodésique terrestre [Termes descripteurs IGN] robot Résumé : (auteur) The reference frame of a global terrestrial network is defined by the origin, the orientation and the scale. The origin of the ITRF2014 is defined by the ILRS long-term solution, the orientation by no-net rotation conditions w.r.t. the previous reference frame (ITRF2008), and the scale by the mean values from global VLBI and SLR solution series (Altamimi et al. in J Geophys Res Solid Earth 121:6109–6131, 2016). With the release of the Galileo satellite antenna phase center offsets (PCO) w.r.t. the satellites center of mass (GSA in Galileo IOV and FOC satellite metadata, 2019) and the availability of new ground antenna calibrations for GNSS receivers, based on anechoic chamber measurements or on robot calibrations, GNSS global network solutions qualify to contribute to the scale determination of terrestrial networks, as well. Our analysis is based on global multi-GNSS solutions of the years 2017 and 2018 and may be seen as “proof of concept” for the contribution of GNSS data to the scale determination of the terrestrial reference frame. In a first step, the currently used Galileo PCO estimations (Steigenberger et al. in J Geod 90:773–785, 2016) are compared to the released PCO values, which show discrepancies on the decimeter-level. Eventually, the published Galileo PCOs are used in an experimental solution as known values. GNSS-specific PCOs are estimated, as well, for GPS and GLONASS, together with the “standard” parameters set up in global GNSS solutions. From the estimated network coordinates, a time series of daily scale parameters of the terrestrial network is extracted, which shows an offset of the order of 1 ppb (parts per billion, corresponding to a height difference of 6.4 mm on the Earth’s surface) w.r.t. to the ITRF2014 network and an annual variation with an amplitude of about 0.3 ppb. Numéro de notice : A2020-539 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01417-0 date de publication en ligne : 05/09/2020 En ligne : https://doi.org/10.1007/s00190-020-01417-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95739 [article]

Past and present ITRF solutions from geophysical perspectives / Laurent Métivier in Advances in space research, vol 65 n° 12 (15 June 2020)  

Public [article]  inAdvances in space research > vol 65 n° 12 (15 June 2020) . - pp 2711 - 2722 Titre : Past and present ITRF solutions from geophysical perspectives Type de document : Article/Communication Auteurs : Laurent Métivier , Auteur ; Zuheir Altamimi , Auteur ; Hélène Rouby , Auteur Année de publication : 2020 Projets : TOSCA / Article en page(s) : pp 2711 - 2722 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes descripteurs IGN] ajustement glacio-isostatique [Termes descripteurs IGN] champ de vitesse [Termes descripteurs IGN] fonte des glaces [Termes descripteurs IGN] International Terrestrial Reference Frame [Termes descripteurs IGN] positionnement par GNSS [Termes descripteurs IGN] vitesse Résumé : (auteur) Questions about the accuracy of the origin of the different versions of International Terrestrial Reference Frame (ITRF), have been regularly raised. In particular the origin drift between ITRF2000 and ITRF2005 (and subsequent ITRF solutions) is well-known to be problematic. Here, we look forward a sort of geophysical evaluation of ITRF solutions. We investigate GNSS vertical velocities provided by the last four ITRF solutions (ITRF2000 to ITRF2014; Altamimi et al., 2005, 2007, 2011, 2016) that we compare with different Global Isostatic Adjustment (GIA) model predictions. We find that each new ITRF solution appears to be more and more consistent with all GIA predictions, except ITRF2014 whose consistency with the GIA models depends on the date of observation. Indeed, GNSS observations and GIA predictions appear consistent at global scale at a level of ~4 mm/yr using ITRF2000 data, ~2.5–3 mm/yr using ITRF2005 data, and ~2 mm/yr using ITRF2008 data (global weighted root mean squares). For ITRF2014, the consistency between GNSS observations and GIA predictions is extremely high in 2000 (~1.5 mm/yr) but seems then to decrease with time (~2 mm/yr in 2013). This discrepancy is due to the recent ice melting effect that is not accounted for in GIA models, but clearly evidenced by ITRF2014 vertical velocities during the last years of observations, in particular in Greenland. Numéro de notice : A2020-364 Affiliation des auteurs : UMR IPGP-Géod (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2020.03.031 date de publication en ligne : 06/04/2020 En ligne : https://doi.org/10.1016/j.asr.2020.03.031 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96828 [article]

Comparative analysis of different atmospheric surface pressure models and their impacts on daily ITRF2014 GNSS residual time series / Zhao Li in Journal of geodesy, vol 94 n°4 (April 2020)  

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Description and evaluation of DTRF2014, JTRF2014 and ITRF2014 / Zuheir Altamimi (2020)  

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Description and evaluation of DTRF2014, JTRF2014 and ITRF2014, ch. 3. ITRS Center evaluation of DTRF2014 and JTRF2014 with respect to ITRF2014 / Zuheir Altamimi (2020)  

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Position, navigation, and timing technologies in the 21st century: Integrated satellite navigation, sensor systems, and civil applications, ch. 27. Global geodesy and reference frames / Chris Rizos (2020)  

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Impact of network constraining on the terrestrial reference frame realization based on SLR observations to LAGEOS / Radoslaw Zajdel in Journal of geodesy, vol 93 n°11 (November 2019)  

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Systematic errors in SLR data and their impact on the ILRS products / Vincenza Luceri in Journal of geodesy, vol 93 n°11 (November 2019)  

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Regional integration of long-term national dense GNSS network solutions / A. Kenyeres in GPS solutions, vol 23 n° 4 (October 2019)  

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Utilisation d’infrastructures géodésiques mondiales pour la réalisation nationale / Raphaël Legouge in XYZ, n° 158 (mars 2019)

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Combined orbits and clocks from IGS second reprocessing / Jake Griffiths in Journal of geodesy, vol 93 n° 2 (February 2019)  

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Influence of subdaily model for polar motion on the estimated GPS satellite orbits / Natalia Panafidina in Journal of geodesy, vol 93 n° 2 (February 2019)  

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