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4.810,45 m pour le toit de l'Europe / Michel Ravelet in Géomètre, n° 2064 (novembre 2009)
[article]
Titre : 4.810,45 m pour le toit de l'Europe Type de document : Article/Communication Auteurs : Michel Ravelet, Auteur Année de publication : 2009 Article en page(s) : pp 6 - 7 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Nivellement
[Termes IGN] antenne GPS
[Termes IGN] calotte glaciaire
[Termes IGN] Mont-Blanc, massif du
[Termes IGN] nivellement par GPS
[Termes IGN] précision centimétrique
[Termes IGN] TeriaRésumé : (Auteur) Pour la cinquième fois consécutive, les géomètres-experts ont mesuré l'altitude du sommet des Alpes. Le mont Blanc reste fidèle à lui-même. Copyright Géomètre Numéro de notice : A2009-412 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30043
in Géomètre > n° 2064 (novembre 2009) . - pp 6 - 7[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 063-09101 RAB Revue Centre de documentation En réserve L003 Disponible Polar Radar for Ice Sheet Measurements (PRISM) / S. Gogineni in Remote sensing of environment, vol 111 n° 2-3 (30 November 2007)
[article]
Titre : Polar Radar for Ice Sheet Measurements (PRISM) Type de document : Article/Communication Auteurs : S. Gogineni, Auteur ; D. Braaten, Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 204 - 211 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] Antarctique
[Termes IGN] calotte glaciaire
[Termes IGN] épaisseur de la glace
[Termes IGN] glaciologie
[Termes IGN] Groenland
[Termes IGN] image radar
[Termes IGN] morphologie glaciaire
[Termes IGN] onde décimétriqueRésumé : (Auteur) We provide an overview of a project to develop and demonstrate radars for imaging the ice-bed interface, mapping shallow and deep internal layers, and measuring ice thickness. We developed an ultra-wideband very high-frequency (VHF) radar (120 to 300 MHz) for simultaneously measuring ice thickness, mapping internal layers at depth, and imaging the ice-bed interface, and an ultra high-frequency (UHF) ultra-wideband radar (500 to 2000 MHz) for fine-resolution mapping of near-surface internal layers. We used these radars to collect data at Summit Camp, Greenland, during July 2005, and the West Antarctic Ice Sheet (WAIS) deep drill core site during January 2006. These results provide us with an unprecedented view of basal characteristics and internal layers. We also developed an outreach program, a communications system, and rovers to facilitate geophysical measurements in the future. Copyright Elsevier Numéro de notice : A2007-487 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2007.01.022 En ligne : https://doi.org/10.1016/j.rse.2007.01.022 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28850
in Remote sensing of environment > vol 111 n° 2-3 (30 November 2007) . - pp 204 - 211[article]Dual-frequency altimeter signal from Envisat on the Amery ice-shelf / Pascal Lacroix in Remote sensing of environment, vol 109 n° 3 (15 August 2007)
[article]
Titre : Dual-frequency altimeter signal from Envisat on the Amery ice-shelf Type de document : Article/Communication Auteurs : Pascal Lacroix, Auteur ; Benoit Legrésy, Auteur ; et al., Auteur ; et al., Auteur Année de publication : 2007 Article en page(s) : pp 285 - 294 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal
[Termes IGN] altimétrie par radar
[Termes IGN] Antarctique
[Termes IGN] bande S
[Termes IGN] calotte glaciaire
[Termes IGN] crevasse
[Termes IGN] écho radar
[Termes IGN] épaisseur de la glace
[Termes IGN] image Envisat-AATSR
[Termes IGN] réflectance de surface
[Termes IGN] réflexion spéculaire
[Termes IGN] traitement du signal
[Termes IGN] variation saisonnièreRésumé : (Auteur) In Antarctica, radar altimeter measurements are sensitive to dielectric and penetration properties of the sensed medium (snow) such that the spacecraft's altitude can be biased. Since 2002, relatively low frequency radar measurements over the Amery Ice Shelf, east Antarctica, have been acquired using the Envisat dual frequency altimeter at S (3.2 GHz) and Ku (13.6 GHz) bands, which penetrate a few meters into the firn. The altimeter signal is however modified in summer by the presence of snowfilled crevasses. Indeed, the specularity of the snow surfaces in summer makes the altimetric signal sensitive mostly to nadir echoes, that increases the ratio between the crevasse signal and the surrounding ice-shelf signal at nadir. Crevasses are distinguished by differences in backscattering behavior compared with the surrounding ice-shelf signal. Crevasses are characterized by a strong backscatter coefficient at Ku band and anomalies in the S band altitude estimation. These two characteristics make snowfilled crevasses detectable by the dual frequency altimeter of Envisat. We first retrieve the geometric properties of the crevasses using a hyperbolic shape function, created by strong crevasse backscatter in the Ku waveform measurements. From this retrieved crevasse signal and further waveform analysis, we assess the properties of the snow surface and its sub-surface. The crevasse, due to its small size compared to the altimeter footprint, is found to be an excellent target to study snow properties of the ice-shelf. The anomalies in the S band altitude measurements over crevasses can then be explained by the presence of a double echo in the S band waveforms. This echo is attributed to a reflection at the base of the snowbridge, where we see evidence of sub-surface echos in the individual altimeter waveforms. Based on this observation, a methodology is developed to estimate the thickness of the snowbridge. We calculate the penetration depths in the summer snow surface of the Amery at Ku band, that is found to be around 6 m. Copyright Elsevier Numéro de notice : A2007-312 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.rse.2007.01. En ligne : https://doi.org/10.1016/j.rse.2007.01.007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28675
in Remote sensing of environment > vol 109 n° 3 (15 August 2007) . - pp 285 - 294[article]Satellite evidence of the melting Greenland's ice cap: Ice losses now far surpass ice gains / J. Triglav in Geoinformatics, vol 10 n° 4 (01/06/2007)
[article]
Titre : Satellite evidence of the melting Greenland's ice cap: Ice losses now far surpass ice gains Type de document : Article/Communication Auteurs : J. Triglav, Auteur Année de publication : 2007 Article en page(s) : pp 6 - 8 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] calotte glaciaire
[Termes IGN] eau de fonte
[Termes IGN] GRACE
[Termes IGN] Groenland
[Termes IGN] image DMSP-SSM/IRésumé : (Editeur) For the first time, NASA scientists have analyzed data from direct, detailed satellite measurements to show that ice losses now far surpass ice gains in the shrinking Greenland ice sheet. Will this trend continue? Today, thanks to modern satellite technology, the quickest and easiest way for scientists to survey the polar regions on a daily basis is from the unique vantage point of space. We compiled texts and images from various sources - mostly NASA - to bring you a short overview of this 'hot' subject. Numéro de notice : A2007-226 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28589
in Geoinformatics > vol 10 n° 4 (01/06/2007) . - pp 6 - 8[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 262-07041 SL Revue Centre de documentation Revues en salle Disponible Simultane Schätzung von Topographie und Dynamik polarer Gletscher aus multi-temporalen SAR Interferogrammen / F.J. Meyer (2004)
Titre : Simultane Schätzung von Topographie und Dynamik polarer Gletscher aus multi-temporalen SAR Interferogrammen Titre original : [Simultaneous estimation of topography and motion of polar glaciers and ice sheets from multi-temporal SAR interferograms] Type de document : Thèse/HDR Auteurs : F.J. Meyer, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2004 Collection : DGK - C Sous-collection : Dissertationen num. 579 Importance : 113 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5018-1 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] Arctique
[Termes IGN] calotte glaciaire
[Termes IGN] glacier
[Termes IGN] image multitemporelle
[Termes IGN] image radar moirée
[Termes IGN] interferométrie différentielle
[Termes IGN] interféromètrie par radar à antenne synthétique
[Termes IGN] position directeRésumé : (Auteur) This thesis presents a new technique to simultaneously estimate topography and motion of polar glaciers and ice sheets from multi-temporal SAR interferograms. In this approach the unknown parameters, i.e. topography and surface displacement, are estimated from a redundant number of observations. The resulting redundancy is systematically used to attach realistic accuracy and robustness measures to all estimated unknowns and to reveal possible gross errors in the observations or errors in the model. Additionally, the redundancy facilitates replacing very restrictive model components by more flexible models with a higher amount of free parameters. This leads to a better description of the real behavior of the object.
The approach combines several SAR interferograms into a least-squares adjustment based on the Gauss-Markov model. In order to connect the multi-temporal data sets, a spatio-temporal model is proposed that describes the properties of the surface and its temporal evolution. The parameterization of the model can be adapted considering the properties of the object under investigation. Tests with simulated data show that, with this technique, both topography and motion of polar ice caps can be estimated with an accuracy of a few meters or a few centimeters per day, depending on the configuration of the adjustment. The quality of the estimated parameters depends on the accuracy of the phase observations, the observation geometry, and the number of involved data sets. Analyses of the robustness of the approach additionally indicate a high robustness of the estimated unknowns with respect to gross errors in the observations. The influence of the atmospheric path delay on the unknowns is analyzed and quantified for various observation geometries and different atmospheric conditions. It is shown that errors in the assumed deformation model significantly falsify the estimated parameters. Thus, the configuration of the spatio-temporal model must be chosen carefully. In addition to the estimation of surface topography and motion, the method and its inherent analysis tools allow to determine the observation geometry that is necessary to reach a pre-defined accuracy level in advance. Therefore, the method is a very useful tool for project planing. By means of a case study aimed at the observation of a huge ice dome in the Russian arctic the feasibility of the approach in real-life situations is demonstrated.Numéro de notice : 13257 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54941 Exemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 13257-01 35.45 Livre Centre de documentation Télédétection Disponible 13257-02 35.45 Livre Centre de documentation Télédétection Disponible Topographie des calottes glaciaires par altimétrie satellite / F. Remy in XYZ, n° 83 (juin - août 2000)PermalinkMetric relations in INSAR topographic modelling / G. Brandstätter (31/05/1999)PermalinkClimatic impact of glacial cycle polar motion: Coupled oscillations of ice sheet mass and rotation pole position / Bruce G. Bills in Journal of geophysical research : Solid Earth, vol 104 n° 1 (01/01/1999)PermalinkAnwendungen der satellitengestützten Radarinterferometrie zur Bestimmung von Topographie und Geschwindig-keitsfeldern / X. Wu (1998)PermalinkGravity and GPS survey on the summit of the Greenland ice sheet 1991-1992 / S. Ekholm (1993)PermalinkUsing Landsat MSS data for measuring ice sheet retreat / P. Knight in International Journal of Remote Sensing IJRS, vol 8 n° 7 (July 1987)PermalinkProceedings of the sixth symposium on Antarctic geosciences, 1985 / Y. Yoshida (1986)PermalinkTraité de glaciologie, 2. Tome 2, Glaciers, variations du climat, sols gelés / Louis Lliboutry (1965)Permalink