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Determination of the free core nutation period from tidal gravity observations of the GGP superconducting gravimeter network / B. Ducarme in Journal of geodesy, vol 81 n° 3 (March 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 3 (March 2007) . - pp 179 - 187 Titre : Determination of the free core nutation period from tidal gravity observations of the GGP superconducting gravimeter network Type de document : Article/Communication Auteurs : B. Ducarme, Auteur ; H.P. Sun, Auteur ; J.Q. Xu, Auteur Année de publication : 2007 Article en page(s) : pp 179 - 187 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] gravimètre supraconducteur [Termes IGN] levé gravimétrique [Termes IGN] marée océanique [Termes IGN] pesanteur terrestre [Termes IGN] réseau gravimétrique [Termes IGN] surcharge océanique Résumé : (Auteur) This study is based on 25 long time-series of tidal gravity observations recorded with superconducting gravimeters at 20 stations belonging to the Global Geodynamic Project (GGP). We investigate the diurnal waves around the liquid core resonance, i.e., K 1, ?1 and ?1, to determine the free core nutation (FCN) period, and compare these experimental results with models of the Earth response to the tidal forces. For this purpose, it is necessary to compute corrected amplitude factors and phase differences by subtracting the ocean tide loading (OTL) effect. To determine this loading effect for each wave, it was thus necessary to interpolate the contribution of the smaller oceanic constituents from the four well determined diurnal waves, i.e., Q 1, O 1, P 1, K 1. It was done for 11 different ocean tide models: SCW80, CSR3.0, CSR4.0, FES95.2, FES99, FES02, TPXO2, ORI96, AG95, NAO99 and GOT00. The numerical results show that no model is decisively better than the others and that a mean tidal loading vector gives the most stable solution for a study of the liquid core resonance. We compared solutions based on the mean of the 11 ocean models to subsets of six models used in a previous study and five more recent ones. The calibration errors put a limit on the accuracy of our global results at the level of 1 0.1%, although the tidal factors of O 1 and K 1 are determined with an internal precision of close to 0.05%. The results for O 1 more closely fit the DDW99 non-hydrostatic anelastic model than the elastic one. However, the observed tidal factors of K 1 and ?1 correspond to a shift of the observed resonance with respect to this model. The MAT01 model better fits this resonance shape. From our tidal gravity data set, we computed the FCN eigenperiod. Our best estimation is 429.7 sidereal days (SD), with a 95% confidence interval of (427.3, 432.1). Copyright Springer Numéro de notice : A2007-182 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0098-9 En ligne : https://doi.org/10.1007/s00190-006-0098-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28545 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07031	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07032	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Contribution of ionospheric irregularities to the error of dual-frequency GNSS positioning / B.C. Kim in Journal of geodesy, vol 81 n° 3 (March 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 3 (March 2007) . - pp 189 - 199 Titre : Contribution of ionospheric irregularities to the error of dual-frequency GNSS positioning Type de document : Article/Communication Auteurs : B.C. Kim, Auteur ; M.V. Tinin, Auteur Année de publication : 2007 Article en page(s) : pp 189 - 199 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction ionosphérique [Termes IGN] positionnement par GPS [Termes IGN] propagation ionosphérique [Termes IGN] récepteur bifréquence [Termes IGN] résidu Résumé : (Auteur) This paper investigates the third-order residual range error in the dual-frequency correction of ionospheric effects on satellite navigation. We solve the two-point trajectory problem using the perturbation method to derive second-approximation formulas for the phase path of the wave propagating through an inhomogeneous ionosphere. It is shown that these formulas are consistent with the results derived from applying perturbation theory directly to the eikonal equation. The resulting expression for the phase path is used in calculating the residual range error of dual-frequency global positioning system (GPS) observations, in view of second- and third-order terms. The third-order correction includes not only the quadratic correction of the refractive index but also the correction for ray bending in an inhomogeneous ionosphere. Our calculations took into consideration that the ionosphere has regular large-scale irregularities, as well as smaller-scale random irregularities. Numerical examples show that geomagnetic field effects, which constitute a second-order correction, typically exceed the effects of the quadratic correction and the regular ionospheric inhomogeneity. The contribution from random irregularities can compare with or exceed that made by the second-order correction. Therefore, random ionospheric irregularities can make a significant (sometimes dominant) contribution to the residual range error. Copyright Springer Numéro de notice : A2007-183 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0099-8 En ligne : https://doi.org/10.1007/s00190-006-0099-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28546 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07031	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07032	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Assessment of long-range kinematic GPS positioning errors by comparison with airborne laser altimetry and satellite altimetry / X. Zhang in Journal of geodesy, vol 81 n° 3 (March 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 3 (March 2007) . - pp 201 - 211 Titre : Assessment of long-range kinematic GPS positioning errors by comparison with airborne laser altimetry and satellite altimetry Type de document : Article/Communication Auteurs : X. Zhang, Auteur ; René Forsberg, Auteur Année de publication : 2007 Article en page(s) : pp 201 - 211 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] altimétrie satellitaire par radar [Termes IGN] analyse comparative [Termes IGN] Atlantique Nord [Termes IGN] glace de mer [Termes IGN] GPS en mode cinématique [Termes IGN] Groenland [Termes IGN] positionnement ponctuel précis [Termes IGN] précision décimétrique [Termes IGN] télémétrie laser aéroporté Résumé : (Auteur) Long-range airborne laser altimetry and laser scanning (LIDAR) or airborne gravity surveys in, for example, polar or oceanic areas require airborne kinematic GPS baselines of many hundreds of kilometers in length. In such instances, with the complications of ionospheric biases, it can be a real challenge for traditional differential kinematic GPS software to obtain reasonable solutions. In this paper, we will describe attempts to validate an implementation of the precise point positioning (PPP) technique on an aircraft without the use of a local GPS reference station. We will compare PPP solutions with other conventional GPS solutions, as well as with independent data by comparison of airborne laser data with “ground truth” heights. The comparisons involve two flights: A July 5, 2003, airborne laser flight line across the North Atlantic from Iceland to Scotland, and a May 24, 2004, flight in an area of the Arctic Ocean north of Greenland, near-coincident in time and space with the ICESat satellite laser altimeter. Both of these flights were more than 800 km long. Comparisons between different GPS methods and four different software packages do not suggest a clear preference for any one, with the heights generally showing decimeter-level agreement. For the comparison with the independent ICESat- and LIDAR-derived “ground truth” of ocean or sea-ice heights, the statistics of comparison show a typical fit of around 10 cm RMS in the North Atlantic, and 30 cm in the sea-ice region north of Greenland. Part of the latter 30 cm error is likely due to errors in the airborne LIDAR measurement and calibration, as well as errors in the “ground truth” ocean surfaces due to drifting sea-ice. Nevertheless, the potential of the PPP method for generating 10 cm level kinematic height positioning over long baselines is illustrated. Numéro de notice : A2007-184 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0100-6 En ligne : https://doi.org/10.1007/s00190-006-0100-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28547 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07031	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07032	RAB	Revue	Centre de documentation	En réserve L003	Disponible