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Tidal analysis experiments with sun-synchronous satellite altimeter data / R.D. Ray in Journal of geodesy, vol 81 n° 4 (April 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 4 (April 2007) . - pp 247 - 257 Titre : Tidal analysis experiments with sun-synchronous satellite altimeter data Type de document : Article/Communication Auteurs : R.D. Ray, Auteur Année de publication : 2007 Article en page(s) : pp 247 - 257 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] altimétrie satellitaire par radar [Termes IGN] données altimétriques [Termes IGN] image Envisat [Termes IGN] image ERS [Termes IGN] Indien (océan) [Termes IGN] marée océanique [Termes IGN] océanographie spatiale [Termes IGN] orbite héliosynchrone [Vedettes matières IGN] Altimétrie Résumé : (Auteur) The ERS-1, ERS-2 and Envisat series of satellite altimeters provide the only extensive datasets that could conceivably be usedto constrain ocean tide models in high latitudes. Their sun-synchronous sampling, however, severely limits theobservations of solar tides, especially the principal semidiurnal S2 constituent. The Munk–Cartwright response method is anatural choice when attempting to analyze sun-synchronous data. The present study examines various ways a response analysis might be implemented to extract tides from ERS data. Admittances expressed as simple linear or constant functions of frequency cansometimes improve estimates over standard parameterizations, especially if done in conjunction with a reasonably accurate priorsolution. Some form of regularization, such as ridge regression, is also shown to improve the estimates. The approach provesbeneficial in a test for the southern Indian Ocean tides. It offers some promise for regions otherwise void of usefulobservations. Copyright Springer Numéro de notice : A2007-185 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0105-1 En ligne : https://doi.org/10.1007/s00190-006-0105-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28548 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07041	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07042	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Higher order ionospheric effects in precise GNSS positioning / M. Mainul Hoque in Journal of geodesy, vol 81 n° 4 (April 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 4 (April 2007) . - pp 259 - 268 Titre : Higher order ionospheric effects in precise GNSS positioning Type de document : Article/Communication Auteurs : M. Mainul Hoque, Auteur ; N. Jakowski, Auteur Année de publication : 2007 Article en page(s) : pp 259 - 268 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] correction ionosphérique [Termes IGN] phase GPS [Termes IGN] positionnement par GNSS [Termes IGN] réfraction atmosphérique [Termes IGN] résidu [Termes IGN] teneur totale en électrons Résumé : (Auteur) With the increasing number of precise navigation and positioning applications using Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS), higher order ionospheric effects and their correction become more and more important. Whereas the first-order error can be completely eliminated by a linear combination of dual- frequency measurements, the second- and third-order residual effects remain uncorrected in this approach. To quantify the second-order residual effect, a simple formula has been derived for GNSS users in Germany. Our proposed correction algorithm reduces the second-order effects to a residual error of fractions of 1 mm up to 2 mm at a vertical total electron content level of 1018 electrons/m (100 TECU), depending on satellite azimuth and elevation angles. The correction formula can be implemented in real-time applications as it does not require the knowledge of the geomagnetic field or the electron density distribution in the ionosphere along the signal path. It is expected that the correction will enable more accurate positioning using the line-of-sight carrier-phase measurements. Copyright Springer Numéro de notice : A2007-186 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0106-0 En ligne : https://doi.org/10.1007/s00190-006-0106-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28549 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07041	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07042	RAB	Revue	Centre de documentation	En réserve L003	Disponible

Airborne LaCoste & Romberg gravimetry: a space domain approach / M. Abbasi in Journal of geodesy, vol 81 n° 4 (April 2007)  

Public [article]  inJournal of geodesy > vol 81 n° 4 (April 2007) . - pp 269 - 283 Titre : Airborne LaCoste & Romberg gravimetry: a space domain approach Type de document : Article/Communication Auteurs : M. Abbasi, Auteur ; Jean-Pierre Barriot, Auteur ; Jérome Verdun , Auteur Année de publication : 2007 Article en page(s) : pp 269 - 283 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] équation différentielle [Termes IGN] équation intégrale [Termes IGN] filtre passe-bas [Termes IGN] gravimétrie aérienne [Termes IGN] levé gravimétrique [Termes IGN] matrice de covariance [Termes IGN] méthode des moindres carrés [Termes IGN] modèle de géopotentiel Résumé : (Auteur) This paper introduces a new approach to reduce the airborne gravity data acquired by a LaCoste & Romberg (L&R) air/sea gravimeter, or other similar gravimeters. The acceleration exerted on the gravimeter is the sum of gravity and the vertical and Eötvös accelerations of the aircraft. The L&R gravimeter outputs are: (1) the beam position, (2) the spring tension and (3) the cross coupling. Vertical and Eötvös accelerations are computed from GPS-derived aircraft positions. However, the vertical perturbing acceleration sensed by the gravimeter is not the same as the one sensed by the aircraft (via GPS). A determination of the aircraft-to-sensor transfer function is necessary. The second-order differential equation of the motion of the gravimeter’s beam mixes all the input and output parameters of the gravimeter. Conventionally, low-pass filtering in the frequency domain is used to extract the gravity signal, the filter being applied to each flight-line individually. By transforming the differential equation into an integral equation and by introducing related covariance matrices, we develop a new filtering method based on a least-squares approach that is able to take into account, in one stage, the data corresponding to all flight-lines. The a posteriori covariance matrix of the estimated gravity signal is an internal criterion of the precision of the method. As an example, we estimate the gravity values along the flight-lines from an airborne gravity survey over the Alps and introduce an a priori covariance matrix of the gravity disturbances from a global geopotential model. This matrix is used to regularize the ill-posed Fredholm integral equation introduced in this paper. Copyright Springer Numéro de notice : A2007-187 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-006-0107-z En ligne : https://doi.org/10.1007/s00190-006-0107-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28550 [article]

Exemplaires(2)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-07041	RAB	Revue	Centre de documentation	En réserve L003	Disponible
266-07042	RAB	Revue	Centre de documentation	En réserve L003	Disponible