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The US Gravimetric Geoid of 2009 (USGG2009): model development and evaluation / Y. Wang in Journal of geodesy, vol 86 n° 3 (March 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 3 (March 2012) . - pp 165 - 180 Titre : The US Gravimetric Geoid of 2009 (USGG2009): model development and evaluation Type de document : Article/Communication Auteurs : Y. Wang, Auteur ; J. Saleh, Auteur ; D. Roman, Auteur Année de publication : 2012 Article en page(s) : pp 165 - 180 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] Etats-Unis [Termes IGN] géoïde gravimétrique [Termes IGN] géoïde local [Termes IGN] hauteur ellipsoïdale [Termes IGN] United States Gravimetric Geoid 2009 Résumé : (Auteur) A new gravimetric geoid model, USGG2009 (see Abbreviations), has been developed for the United States and its territories including the Conterminous US (CONUS), Alaska, Hawaii, Guam, the Commonwealth of the Northern Mariana Islands, American Samoa, Puerto Rico and the US Virgin Islands. USGG2009 is based on a 1' x 1' gravity grid derived from the NGS surface gravity data and the DNSC08 altimetry-derived anomalies, the SRTM-DTED1 3" DEM for its topographic reductions, and the global geopotential model EGM08 as a reference model. USGG2009 geoid heights are compared with control values determined at 18,398 Bench Marks over CONUS, where both the ellipsoidal height above NAD 83 and the Helmert orthometric height above NAVD 88 are known. Correcting for the ellipsoidal datum difference, this permits a comparison of the geoid heights to independent data. The standard deviation of the differences is 6.3 cm in contrast to 8.4 cm for its immediate predecessor— USGG2003. To minimize the effect of long-wavelength errors that are known to exist in NAVD88, these comparisons were made on a state-by-state basis. The standard deviations of the differences range from 3–5 cm in eastern states to about 6–9 cm in the more mountainous western states. If the GPS/Bench Marks-derived geoid heights are corrected by removing a GRACE-derived estimate of the long-wavelength NAVD88 errors before the comparison, the standard deviation of their differences from USGG2009 drops to 4.3 cm nationally and 2–4 cm in eastern states and 4–8 in states with a maximum error of 26.4 cm in California and minimum of -32.1 cm in Washington. USGG2009 is also compared with geoid heights derived from 40 tide-gauges and a physical dynamic ocean topography model in the Gulf of Mexico; the mean of the differences is 3.3 cm and their standard deviation is 5.0 cm. When USGG2009-derived deflections of the vertical are compared with 3,415 observed surface astro-geodetic deflections, the standard deviation of the differences in the N–S and E–W components are 0.87" and 0.94", respectively. Numéro de notice : A2012-149 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0506-7 Date de publication en ligne : 17/09/2011 En ligne : https://doi.org/10.1007/s00190-011-0506-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31596 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2012031	RAB	Revue	Centre de documentation	En réserve L003	Disponible

GPS snow depth meter with geometry-free linear combinations of carrier phases / M. Ozeki in Journal of geodesy, vol 86 n° 3 (March 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 3 (March 2012) . - pp 209 - 217 Titre : GPS snow depth meter with geometry-free linear combinations of carrier phases Type de document : Article/Communication Auteurs : M. Ozeki, Auteur ; K. Heki, Auteur Année de publication : 2012 Article en page(s) : pp 209 - 217 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] antenne GPS [Termes IGN] combinaison linéaire [Termes IGN] Hokkaido (Japon) [Termes IGN] neige [Termes IGN] phase GPS [Termes IGN] rapport signal sur bruit [Termes IGN] traitement de données GNSS [Termes IGN] trajet multiple Résumé : (Auteur) Multipath in global positioning system (GPS) is the interference of the microwave signals directly from satellites and those reflected before reaching the antenna, typically by the ground. Because reflected signals cause positioning errors, GPS antennas are designed to reduce such interference. Recent studies show that multipath could be utilized to infer the properties of the ground around the antenna. Here, we report one such application, i.e. a fixed GPS station used as a snow depth meter. Because the satellite moves in the sky, the excess path length of reflected waves changes at rates dependent on the antenna height. This causes quasi-periodic variations of the amplitude and phase of the received signals. Accumulation of snow reduces effective antenna heights, and we can see it by analyzing multipath signatures. Signal-to-noise ratios (SNR) are often used to analyze multipath, but they are not always available in raw GPS data files. Here, we demonstrate that the geometry-free linear combination (L4), normally used to study the ionosphere, can also be used to analyze multipath signatures. We obtained snow depth time series at a GPS station in Hokkaido, Japan, from January to April in 2009 using L4 and SNR. Then, we compared their precisions. We also discuss mechanisms responsible for the possible underestimation of the snow depth by GPS. Finally, we investigate the possibility of inferring physical conditions of the snow surface using amplitudes of multipath signatures. Numéro de notice : A2012-150 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0511-x Date de publication en ligne : 14/09/2011 En ligne : https://doi.org/10.1007/s00190-011-0511-x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31597 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2012031	RAB	Revue	Centre de documentation	En réserve L003	Disponible