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A fast and accurate algorithm for high-frequency trans-ionospheric path length determination / Dudy D Wijaya in Journal of geodesy, vol 89 n° 12 (december 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 12 (december 2015) . - pp 1183 - 1196 Titre : A fast and accurate algorithm for high-frequency trans-ionospheric path length determination Type de document : Article/Communication Auteurs : Dudy D Wijaya, Auteur Année de publication : 2015 Article en page(s) : pp 1183 - 1196 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] longueur d'onde [Termes IGN] réfraction atmosphérique [Termes IGN] troposphère Résumé : (auteur) This paper presents a fast and accurate algorithm for high-frequency trans-ionospheric path length determination. The algorithm is merely based on the solution of the Eikonal equation that is solved using the conformal theory of refraction. The main advantages of the algorithm are summarized as follows. First, the algorithm can determine the optical path length without iteratively adjusting both elevation and azimuth angles and, hence, the computational time can be reduced. Second, for the same elevation and azimuth angles, the algorithm can simultaneously determine the phase and group of both ordinary and extra-ordinary optical path lengths for different frequencies. Results from numerical simulations show that the computational time required by the proposed algorithm to accurately determine 8 different optical path lengths is almost 17 times faster than that required by a 3D ionospheric ray-tracing algorithm. It is found that the computational time to determine multiple optical path lengths is the same with that for determining a single optical path length. It is also found that the proposed algorithm is capable of determining the optical path lengths with millimeter level of accuracies, if the magnitude of the squared ratio of the plasma frequency to the transmitted frequency is less than 1.33×10−3, and hence the proposed algorithm is applicable for geodetic applications. Numéro de notice : A2015-886 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0841-1 En ligne : https://doi.org/10.1007/s00190-015-0841-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79433 [article]

Error analysis of a new planar electrostatic gravity gradiometer for airborne surveys / Karim Douch in Journal of geodesy, vol 89 n° 12 (december 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 12 (december 2015) . - pp 1217 - 1231 Titre : Error analysis of a new planar electrostatic gravity gradiometer for airborne surveys Type de document : Article/Communication Auteurs : Karim Douch , Auteur ; Isabelle Panet , Auteur ; Gwendoline Pajot-Métivier , Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 1217 - 1231 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] accélération de la pesanteur [Termes IGN] accéléromètre [Termes IGN] champ de pesanteur terrestre [Termes IGN] erreur systématique [Termes IGN] gradiométrie [Termes IGN] gravimètre [Termes IGN] gravimétrie aérienne [Termes IGN] gyroscope [Termes IGN] lever aérien Résumé : (auteur) Moving-base gravity gradiometry has proven to be a convenient method to determine the Earth’s gravity field. The ESA mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) has enabled to map the Earth gravity field and its gradients with a resolution of 80 km, leading to significant advances in physical oceanography and solid Earth physics. At smaller scales, airborne gravity gradiometry has been increasingly used during the past decade in mineral and hydrocarbon exploration. In both cases the sensitivity of gradiometers to the short wavelengths of the gravity field is of crucial interest. Here, we quantify and characterize the error on the gravity gradients estimated from measurements performed with a new instrument concept, called GREMLIT, for typical airborne conditions. GREMLIT is an ultra-sensitive planar gravitational gradiometer which consists in a planar acceleration gradiometer together with 3 gyroscopes. To conduct this error analysis, a simulation of a realistic airborne survey with GREMLIT is carried out. We first simulate realistic GREMLIT synthetic data, taking into account the acceleration gradiometer and gyroscope noises and biases and the variation of orientation of the measurement reference frame. Then, we estimate the gravity gradients from these data. Special attention is paid to the processing of the gyroscopes measurements whose accuracy is not commensurate with the ultra-sensitive gradiometer. We propose a method to calibrate the gyroscopes biases with a precision of the order 10−8 rad/s. In order to transform the tensor from the measurement frame to the local geodetic frame, we estimate the error induced when replacing the non-measured elements of the gravity gradient tensor by an a priori model. With the appropriate smoothing, we show that it is possible to achieve a precision better than 2E for an along-track spatial resolution of 2 km. Numéro de notice : A2015-887 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0847-8 Date de publication en ligne : 07/08/2015 En ligne : https://doi.org/10.1007/s00190-015-0847-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79435 [article]

Revisiting the pole tide for and from satellite altimetry / Shailen Desai in Journal of geodesy, vol 89 n° 12 (december 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 12 (december 2015) . - pp 1233 - 1243 Titre : Revisiting the pole tide for and from satellite altimetry Type de document : Article/Communication Auteurs : Shailen Desai, Auteur ; John Wahr, Auteur Année de publication : 2015 Article en page(s) : pp 1233 - 1243 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] altimètre [Termes IGN] altimétrie satellitaire par radar [Termes IGN] analyse diachronique [Termes IGN] géocentre [Termes IGN] marée terrestre [Termes IGN] masse d'eau [Termes IGN] masse de la Terre [Termes IGN] mouvement du pôle [Termes IGN] surcharge océanique Résumé : (auteur) Satellite altimeter sea surface height observations include the geocentric displacements caused by the pole tide, namely the response of the solid Earth and oceans to polar motion. Most users of these data remove these effects using a model that was developed more than 20 years ago. We describe two improvements to the pole tide model for satellite altimeter measurements. Firstly, we recommend an approach that improves the model for the response of the oceans by including the effects of self-gravitation, loading, and mass conservation. Our recommended approach also specifically includes the previously ignored displacement of the solid Earth due to the load of the ocean response, and includes the effects of geocenter motion. Altogether, this improvement amplifies the modeled geocentric pole tide by 15 %, or up to 2 mm of sea surface height displacement. We validate this improvement using two decades of satellite altimeter measurements. Secondly, we recommend that the altimetry pole tide model exclude geocentric sea surface displacements resulting from the long-term drift in polar motion. The response to this particular component of polar motion requires a more rigorous approach than is used by conventional models. We show that erroneously including the response to this component of polar motion in the pole tide model impacts interpretation of regional sea level rise by ±0.25 mm/year. Numéro de notice : A2015-888 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0848-7 Date de publication en ligne : 27/08/2020 En ligne : https://doi.org/10.1007/s00190-015-0848-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79436 [article]