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Auteur Giovanna Venuti |
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The impact of relative and absolute GNSS positioning strategies on estimated coordinates and ZWD in the framework of meteorological applications / Alessandro Fermi in Applied geomatics, vol 11 n° 1 (March 2019)
[article]
Titre : The impact of relative and absolute GNSS positioning strategies on estimated coordinates and ZWD in the framework of meteorological applications Type de document : Article/Communication Auteurs : Alessandro Fermi, Auteur ; Eugenio Realini, Auteur ; Giovanna Venuti, Auteur Année de publication : 2019 Article en page(s) : pp 25 - 38 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] coordonnées GNSS
[Termes IGN] données météorologiques
[Termes IGN] positionnement absolu
[Termes IGN] positionnement différentiel
[Termes IGN] retard troposphérique
[Termes IGN] retard troposphérique zénithal
[Termes IGN] teneur en vapeur d'eauRésumé : (Auteur) Since many years, the GNSS has been regarded by the meteorological community as one of the systems for atmospheric water vapour remote sensing. Time series of wet delays, estimated as by-products of accurate positioning, have been assimilated into numerical weather prediction models. However, a dedicated use the system for water vapour monitoring is still under investigation. Ad hoc dense networks have been designed and implemented to collect data at a high spatial resolution, baseline lengths lower than 10 km, with the aim of describing the high spatial and temporal variability of tropospheric water vapour. Within this framework, the paper reports a study on how the positioning strategy affects the estimated coordinates and tropospheric parameters. The study was conducted on the data collected by an experimental network of geodetic receivers, used as single or dual frequency ones. More specifically, investigations were made on the use of L1-only or iono-free combinations in differential positioning of receivers 100 to 10 km apart, finding that L1-only data provide more accurate results. Therefore, comparisons between local coordinates and ZWD obtained from relative and absolute positioning were performed to provide the statistics of the differences; the agreement between the results for short baselines is always better than 1 cm standard deviation. In order to assess the differences in the results that can be obtained from the two strategies when applied to the same observation set, a further comparison was carried out in terms of baseline components and ZWD increments. It results that, even for dense networks, the differential approach produces accurate results without losing information compared to the absolute one. Numéro de notice : A2019-159 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s12518-018-0234-2 Date de publication en ligne : 19/07/2018 En ligne : https://doi.org/10.1007/s12518-018-0234-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92520
in Applied geomatics > vol 11 n° 1 (March 2019) . - pp 25 - 38[article]The height datum problem and the role of satellite gravity models / A. Gatti in Journal of geodesy, vol 87 n° 1 (January 2013)
[article]
Titre : The height datum problem and the role of satellite gravity models Type de document : Article/Communication Auteurs : A. Gatti, Auteur ; M. Reguzzoni, Auteur ; Giovanna Venuti, Auteur Année de publication : 2013 Article en page(s) : pp 15 - 22 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] altitude normale
[Termes IGN] anomalie de pesanteur
[Termes IGN] données GOCE
[Termes IGN] données GRACE
[Termes IGN] Earth Gravity Model 2008
[Termes IGN] erreur en altitude
[Termes IGN] erreur systématique
[Termes IGN] géoïde altimétrique
[Termes IGN] hauteur ellipsoïdale
[Termes IGN] modèle de géopotentiel
[Termes IGN] niveau moyen des mers
[Termes IGN] réseau de nivellement
[Termes IGN] système de référence altimétriqueRésumé : (Auteur) Regional height systems do not refer to a common equipotential surface, such as the geoid. They are usually referred to the mean sea level at a reference tide gauge. As mean sea level varies (by +1 to 2 m) from place to place and from continent to continent each tide gauge has an unknown bias with respect to a common reference surface, whose determination is what the height datum problem is concerned with. This paper deals with this problem, in connection to the availability of satellite gravity missions data. Since biased heights enter into the computation of terrestrial gravity anomalies, which in turn are used for geoid determination, the biases enter as secondary or indirect effect also in such a geoid model. In contrast to terrestrial gravity anomalies, gravity and geoid models derived from satellite gravity missions, and in particular GRACE and GOCE, do not suffer from those inconsistencies. Those models can be regarded as unbiased. After a review of the mathematical formulation of the problem, the paper examines two alternative approaches to its solution. The first one compares the gravity potential coefficients in the range of degrees from 100 to 200 of an unbiased gravity field from GOCE with those of the combined model EGM2008, that in this range is affected by the height biases. This first proposal yields a solution too inaccurate to be useful. The second approach compares height anomalies derived from GNSS ellipsoidal heights and biased normal heights, with anomalies derived from an anomalous potential which combines a satellite-only model up to degree 200 and a high-resolution global model above 200. The point is to show that in this last combination the indirect effects of the height biases are negligible. To this aim, an error budget analysis is performed. The biases of the high frequency part are proved to be irrelevant, so that an accuracy of 5 cm per individual GNSS station is found. This seems to be a promising practical method to solve the problem. Numéro de notice : A2013-070 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0574-3 Date de publication en ligne : 03/07/2012 En ligne : https://doi.org/10.1007/s00190-012-0574-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32208
in Journal of geodesy > vol 87 n° 1 (January 2013) . - pp 15 - 22[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 266-2013011 SL Revue Centre de documentation Revues en salle Disponible On the explicit determination of stability constants for linearized geodetic boundary value problems / Fernando Sanso in Journal of geodesy, vol 82 n° 12 (December 2008)
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Titre : On the explicit determination of stability constants for linearized geodetic boundary value problems Type de document : Article/Communication Auteurs : Fernando Sanso, Auteur ; Giovanna Venuti, Auteur Année de publication : 2008 Article en page(s) : pp 909 - 916 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] problème des valeurs limitesRésumé : (Auteur) The theory of GBVPs provide the basis to the approximate methods used to compute global gravity models. A standard approximation procedure is least squares, which implicitly assumes that data, e.g. gravity disturbance and gravity anomaly, are given functions in L 2(S). We know that solutions in these cases exist, but uniqueness (and coerciveness which implies stability of the numerical solutions) is the real problem. Conditions of uniqueness for the linearized fixed boundary and Molodensky problems are studied in detail. They depend on the geometry of the boundary; however, the case of linearized fixed boundary BVP puts practically no constraint on the surface S, while the linearized Molodensky BVP requires the previous knowledge of very low harmonics, for instance up to degree 25, if we want the telluroid to be free to have inclinations up to 60°. Copyright Springer Numéro de notice : A2008-473 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-008-0221-1 En ligne : https://doi.org/10.1007/s00190-008-0221-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29542
in Journal of geodesy > vol 82 n° 12 (December 2008) . - pp 909 - 916[article]Exemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 266-08111 RAB Revue Centre de documentation En réserve L003 Disponible 266-08112 RAB Revue Centre de documentation En réserve L003 Disponible The Bayesian detection of discontinuities in a polynomial regression and its application to the cycle-slip problem / M.C. DE Lacy in Journal of geodesy, vol 82 n° 9 (September 2008)
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Titre : The Bayesian detection of discontinuities in a polynomial regression and its application to the cycle-slip problem Type de document : Article/Communication Auteurs : M.C. DE Lacy, Auteur ; M. Reguzzoni, Auteur ; Fernando Sanso, Auteur ; Giovanna Venuti, Auteur Année de publication : 2008 Article en page(s) : pp 527 - 542 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] Bernese
[Termes IGN] correction du signal
[Termes IGN] phase GNSS
[Termes IGN] Ploynôme
[Termes IGN] quantité discrète
[Termes IGN] régression
[Termes IGN] réseau bayesien
[Termes IGN] traitement de données GNSSRésumé : (Auteur) This paper deals with the problem of detecting and correcting cycle-slips in Global Navigation Satellite System (GNSS) phase data by exploiting the Bayesian theory. The method is here applied to undifferenced observations, because repairing cycle-slips already at this stage could be a useful pre-processing tool, especially for a network of permanent GNSS stations. If a dual frequency receiver is available, the cycle-slips can be easily detected by combining two phase observations or phase and range observations from a single satellite to a single receiver. These combinations, expressed in a distance unit form, are completely free from the geometry and depend only on the ionospheric effect, on the electronic biases and on the initial integer ambiguities; since these terms are expected to be smooth in time, at least in a short period, a cycle-slip in one or both the two carriers can be modelled as a discontinuity in a polynomial regression. The proposed method consists in applying the Bayesian theory to compute the marginal posterior distribution of the discontinuity epoch and to detect it as a maximum a posteriori (MAP) in a very accurate way. Concerning the cycle-slip correction, a couple of simultaneous integer slips in the two carriers is chosen by maximazing the conditional posterior distribution of the discontinuity amplitude given the detected epoch. Numerical experiments on simulated and real data show that the discontinuities with an amplitude 2 or 3 times larger than the noise standard deviation are successfully identified. This means that the Bayesian approach is able to detect and correct cycle-slips using undifferenced GNSS observations even if the slip occurs by one cycle. A comparison with the scientific software BERNESE 5.0 confirms the good performance of the proposed method, especially when data sampled at high frequency (e.g. every 1 s or every 5 s) are available. Copyright Springer Numéro de notice : A2008-349 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-007-0203-8 En ligne : https://doi.org/10.1007/s00190-007-0203-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29342
in Journal of geodesy > vol 82 n° 9 (September 2008) . - pp 527 - 542[article]Exemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 266-08081 RAB Revue Centre de documentation En réserve L003 Disponible 266-08082 RAB Revue Centre de documentation En réserve L003 Disponible Bayesian classification by data augmentation / B. Regguzoni in International Journal of Remote Sensing IJRS, vol 24 n° 20 (October 2003)
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Titre : Bayesian classification by data augmentation Type de document : Article/Communication Auteurs : B. Regguzoni, Auteur ; Fernando Sanso, Auteur ; Giovanna Venuti, Auteur ; P.A. Brivio, Auteur Année de publication : 2003 Article en page(s) : pp 3961 - 3981 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image
[Termes IGN] axiome de Bayes
[Termes IGN] classification automatique d'objets
[Termes IGN] classification bayesienne
[Termes IGN] classification par maximum de vraisemblanceRésumé : (Auteur) A typical remote sensing data clustering is the maximum likelihood supervised procedure. It consists of the estimation of a suitable mixture of distributions, based on training samples only, and in the subsequent pixelbypixel classification, performed by maximizing the likelihood ratio. In this way all the information on the parameters of the distributions, contained in the unsurveyed samples, is lost. In the paper it is proposed to apply a suitable Bayesian method, known as a data augmentation algorithm, to fully exploit the information contained in the data. The method is presented in detail and applied to an elementary simulated example proving its capability of achieving almost the theoretical limit for the classification error. Comparisons with current classification methods as well as an application to a real dataset are reported. Numéro de notice : A2003-286 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/0143116031000103817 En ligne : https://doi.org/10.1080/0143116031000103817 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=22581
in International Journal of Remote Sensing IJRS > vol 24 n° 20 (October 2003) . - pp 3961 - 3981[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 080-03201 RAB Revue Centre de documentation En réserve L003 Exclu du prêt