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Hydrological deformation induced by the West African Monsoon : Comparison of GPS, GRACE and loading models / Samuel Nahmani in Journal of geophysical research : Solid Earth, Vol 117 n° B5 (May 2012)
[article]
Titre : Hydrological deformation induced by the West African Monsoon : Comparison of GPS, GRACE and loading models Type de document : Article/Communication Auteurs : Samuel Nahmani , Auteur ; Olivier Bock , Auteur ; Marie-Noëlle Bouin , Auteur ; Alvaro Santamaria Gomez, Auteur ; Jean-Paul Boy, Auteur ; Xavier Collilieux , Auteur ; Laurent Métivier , Auteur ; Isabelle Panet , Auteur ; Pierre Genthon, Auteur ; Caroline de Linage, Auteur ; Guy Wöppelmann , Auteur Année de publication : 2012 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Afrique occidentale
[Termes IGN] coordonnées GPS
[Termes IGN] déformation de la croute terrestre
[Termes IGN] données GRACE
[Termes IGN] données météorologiques
[Termes IGN] effet de charge
[Termes IGN] Gao
[Termes IGN] mousson
[Termes IGN] Niamey (Niger)
[Termes IGN] oscillation
[Termes IGN] Ouagadougou
[Termes IGN] station permanente
[Termes IGN] Tombouctou
[Termes IGN] variation saisonnièreRésumé : (Auteur) Three‐dimensional ground deformation measured with permanent GPS stations in West Africa was used for investigating the hydrological loading deformation associated with Monsoon precipitation. The GPS data were processed within a global network for the 2003–2008 period. Weekly station positions were retrieved with a repeatability (including unmodeled loading effects) of 1–2 mm in the horizontal components and between 2.5 and 6 mm in the vertical component. The annual signal in the vertical component for sites located between 9.6°N and 16.7°N is in the range 10–15 mm. It is consistent at the 3 mm‐level with the annual regional‐scale loading deformations estimated from GRACE satellite products and modeled with a combination of hydrological, atmospheric, and nontidal oceanic models. An additional 6 month transient signal was detected in the vertical component of GPS estimates at most of the West African sites. It takes the form of an oscillation occurring between September and March, and reaching a maximum amplitude of 12–16 mm at Ouagadougou (12.5°N). The analysis of in situ hydro‐geological data revealed a strong coincidence between this transient signal and peak river discharge at three sites located along the Niger River (Timbuktu, Gao, and Niamey). At Ouagadougou, a similar coincidence was found with the seasonal variations of the water table depth. We propose a mechanism to account for this signal that involves a sequence of swelling/shrinking of clays combined with local loading effects associated with flooding of the Niger River. Numéro de notice : A2012-753 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2011JB009102 Date de publication en ligne : 12/05/2012 En ligne : https://doi.org/10.1029/2011JB009102 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91470
in Journal of geophysical research : Solid Earth > Vol 117 n° B5 (May 2012)[article]Robust hyperspectral vision-based classification for multi-season weed mapping / Y. Zhang in ISPRS Journal of photogrammetry and remote sensing, vol 69 (April 2012)
[article]
Titre : Robust hyperspectral vision-based classification for multi-season weed mapping Type de document : Article/Communication Auteurs : Y. Zhang, Auteur ; D. Slaughter, Auteur ; E. Staab, Auteur Année de publication : 2012 Article en page(s) : pp 65 - 73 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique
[Termes IGN] apprentissage automatique
[Termes IGN] Californie (Etats-Unis)
[Termes IGN] classification bayesienne
[Termes IGN] cultures
[Termes IGN] herbe
[Termes IGN] identification de plantes
[Termes IGN] image hyperspectrale
[Termes IGN] photogrammétrie métrologique
[Termes IGN] réflectance végétale
[Termes IGN] système expert
[Termes IGN] variation saisonnièreRésumé : (Auteur) This study investigated the robustness of hyperspectral image-based plant recognition to seasonal variability in a natural farming environment in the context of automated in-row weed control. A machine vision system was developed and equipped with a CCD camera integrated with a line-imaging spectrograph for close-range weed sensing and mapping. Three canonical Bayesian classifiers were developed using canopy reflectance (400–795 nm) collected over three seasons for tomato and weeds. The performance of the three season-specific classifiers was tested by changing environmental conditions, resulting in an increase in total error rate of up to 36%. Global calibration across the complete span of the three seasons produced overall classification accuracies of 85.0%, 90.0% and 92.7%, respectively, for 2005, 2006 and 2008. To improve the stability of global classifier over multiple seasons, a multiclassifier system was constructed with three canonical Bayesian classifiers optimized for the three seasons individually. This system was tested on a data set simulating an upcoming season with field conditions similar to that in 2005. The system increased the total discrimination accuracy to 95.8% for the tested season under simulation. This method provided an innovative direction for achieving robust plant recognition over multiple seasons by integrating expert knowledge from historical data that most closely matched the new field environment. Numéro de notice : A2012-194 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2012.02.006 En ligne : https://doi.org/10.1016/j.isprsjprs.2012.02.006 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31641
in ISPRS Journal of photogrammetry and remote sensing > vol 69 (April 2012) . - pp 65 - 73[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 081-2012031 SL Revue Centre de documentation Revues en salle Disponible Study of seasonal-scale atmospheric water cycle with ground-based GPS receivers, radiosondes and NWP models over Morocco / Achraf Koulali in Atmospheric Research, vol 104 - 105 (February 2012)
[article]
Titre : Study of seasonal-scale atmospheric water cycle with ground-based GPS receivers, radiosondes and NWP models over Morocco Type de document : Article/Communication Auteurs : Achraf Koulali, Auteur ; Driss Ouazar, Auteur ; Olivier Bock , Auteur ; Abdelali Fadil, Auteur Année de publication : 2012 Article en page(s) : pp 273 - 291 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] Canaries
[Termes IGN] circulation atmosphérique
[Termes IGN] données GPS
[Termes IGN] données météorologiques
[Termes IGN] Maroc
[Termes IGN] précipitation
[Termes IGN] radiosondage
[Termes IGN] récepteur GPS
[Termes IGN] retard troposphérique zénithal
[Termes IGN] teneur en vapeur d'eau
[Termes IGN] variation saisonnièreRésumé : (Auteur) This study investigates the seasonal variation of precipitable water vapor, moisture transport and precipitation over Morocco and the Canary Islands using data from ground-based GPS receivers, radiosondes, GPCP and NCEP reanalysis II. In a first part, the datasets are inter-compared. Humidity biases are evidenced in both radiosonde observations (dry) and NCEP reanalysis (dry and wet) compared to GPS. Moisture transport and precipitation from the reanalysis and observations show a good agreement. Precipitable water shows a maximum in late summer whereas precipitation is peaking in winter and spring over Morocco. Moisture transport occurs preferentially in two layers, below and above 850 hPa. The monthly mean precipitable water variation over Morocco is controlled by the upper layer zonal and meridional moisture flux. Precipitation is rather controlled by the lower layer moisture flux and the upper layer meridional flux. The GPS tropospheric gradients show also a consistent seasonal evolution, which is explained by gradients both in the thickness of the troposphere and in the precipitable water vapor. Tropospheric gradients are correlated with moisture fluxes, mostly in the upper layer, and may therefore provide valuable information for meteorology and climatology. Numéro de notice : A2012-737 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.atmosres.2011.11.002 Date de publication en ligne : 13/11/2011 En ligne : https://doi.org/10.1016/j.atmosres.2011.11.002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91460
in Atmospheric Research > vol 104 - 105 (February 2012) . - pp 273 - 291[article]Accuracy assessment of the GPS-TEC calibration constants by means of a simulation technique / Jacques Conte in Journal of geodesy, vol 85 n° 10 (October 2011)
[article]
Titre : Accuracy assessment of the GPS-TEC calibration constants by means of a simulation technique Type de document : Article/Communication Auteurs : Jacques Conte, Auteur ; F. Azpilicueta, Auteur ; C. Brunini, Auteur Année de publication : 2011 Article en page(s) : pp 707 - 714 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] analyse diachronique
[Termes IGN] GPS en mode différentiel
[Termes IGN] ionosphère
[Termes IGN] propagation ionosphérique
[Termes IGN] rayonnement solaire
[Termes IGN] teneur totale en électrons
[Termes IGN] variation saisonnièreRésumé : (Auteur) During the last 2 decades, Global Positioning System (GPS) measurements have become a very important data-source for ionospheric studies. However, it is not a direct and easy task to obtain accurate ionospheric information from these measurements because it is necessary to perform a careful estimation of the calibration constants affecting the GPS observations, the so-called differential code biases (DCBs). In this paper, the most common approximations used in several GPS calibration methods, e.g. the La Plata Ionospheric Model (LPIM), are applied to a set of specially computed synthetic slant Total Electron Content datasets to assess the accuracy of the DCB estimation in a global scale scenario. These synthetic datasets were generated using a modified version of the NeQuick model, and have two important features: they show a realistic temporal and spatial behavior and all a-priori DCBs are set to zero by construction. Then, after the application of the calibration method the deviations from zero of the estimated DCBs are direct indicators of the accuracy of the method. To evaluate the effect of the solar activity radiation level the analysis was performed for years 2001 (high solar activity) and 2006 (low solar activity). To take into account seasonal changes of the ionosphere behavior, the analysis was repeated for three consecutive days close to each equinox and solstice of every year. Then, a data package comprising 24 days from approximately 200 IGS permanent stations was processed. In order to avoid unwanted geomagnetic storms effects, the selected days correspond to periods of quiet geomagnetic conditions. The most important results of this work are: i) the estimated DCBs can be affected by errors around +8 TECu for high solar activity and +3 TECu for low solar activity; and ii) DCB errors present a systematic behavior depending on the modip coordinate, that is more evident for the positive modip region. Numéro de notice : A2011-435 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0477-8 Date de publication en ligne : 15/05/2011 En ligne : https://doi.org/10.1007/s00190-011-0477-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31213
in Journal of geodesy > vol 85 n° 10 (October 2011) . - pp 707 - 714[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 266-2011101 RAB Revue Centre de documentation En réserve L003 Disponible Simulation study of the influence of the ionospheric layer height in the thin layer ionospheric model / C. Brunini in Journal of geodesy, vol 85 n° 9 (September 2011)
[article]
Titre : Simulation study of the influence of the ionospheric layer height in the thin layer ionospheric model Type de document : Article/Communication Auteurs : C. Brunini, Auteur ; E. Camilion, Auteur ; F. Azpilicueta, Auteur Année de publication : 2011 Article en page(s) : pp 637 - 645 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] altitude
[Termes IGN] données GNSS
[Termes IGN] erreur systématique
[Termes IGN] modèle ionosphérique
[Termes IGN] propagation ionosphérique
[Termes IGN] simulation
[Termes IGN] teneur totale en électrons
[Termes IGN] variation saisonnièreRésumé : (Auteur) This work aims to contribute to the understanding of the influence of the ionospheric layer height (ILH) on the thin layer ionospheric model (TLIM) used to retrieve ionospheric information from the GNSS observations. Particular attention is paid to the errors caused on the estimation of the vertical total electron content (vTEC) and the GNSS satellites and receivers inter-frequency biases (IFB), by the use of an inappropriate ILH. The work relies upon numerical simulations performed with an empirical model of the Earth’s ionosphere: the model is used to create realistic but controlled ionospheric scenarios and the errors are evaluated after recovering those scenarios with the TLIM. The error assessment is performed in the Central and the northern part of the South American continents, a region where large errors are expected due to the combined actions of the Appleton Anomaly of the ionosphere and the South-Atlantic anomaly of the geomagnetic field. According to this study, there does not exist a unique ILH that cancels the vTEC error for the whole region under consideration. The ILH that cancels the regional mean vTEC error varies with the solar activity and season. The latitude-dependent conversion error propagates to the parameters of the model used to represent the latitudinal variation on the vTEC on the ionospheric layer, and to the IFB, when these values are simultaneously estimated from the observed sTEC. Besides, the ILH that cancels the regional mean vTEC error is different from the one that cancels the IFB error and the difference between both ILH varies with the solar activity and season. Numéro de notice : A2011-377 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0470-2 Date de publication en ligne : 19/04/2011 En ligne : https://doi.org/10.1007/s00190-011-0470-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31156
in Journal of geodesy > vol 85 n° 9 (September 2011) . - pp 637 - 645[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 266-2011091 RAB Revue Centre de documentation En réserve L003 Disponible Monitoring elevation variations in leaf phenology of deciduous broadleaf forests from SPOT/VEGETATION time-series / Dominique Guyon in Remote sensing of environment, vol 115 n° 2 ([15/02/2011])PermalinkEvaluation of the impact of atmospheric pressure loading modeling on GNSS data analysis / Rolf Dach in Journal of geodesy, vol 85 n° 2 (February 2011)PermalinkThe large‐scale water cycle of the West African monsoon / Olivier Bock in Atmospheric Science Letters, vol 12 n° 1 (January - March 2011)PermalinkWest African Monsoon water cycle: 1. A hybrid water budget data set / Rémi Meynadier in Journal of geophysical research : Atmospheres, vol 115 n° D19 (2010)PermalinkGlobal gravity field determination using the GPS measurements made onboard the low Earth orbiting satellite CHAMP / Lars Prange (2010)PermalinkInvestigating tropospheric effects and seasonal position variations in GPS and DORIS time-series from the Nepal Himalaya / Mireille Flouzat in Geophysical journal international, vol 178 n° 3 (September 2009)PermalinkLandsat sub-pixel analysis in mapping impact of climatic variability on prairie pothole changes / B. Zhang in Transactions in GIS, vol 13 n° 2 (April 2009)PermalinkWest African Monsoon observed with ground-based GPS receivers during African Monsoon Multidisciplinary Analysis (AMMA) / Olivier Bock in Journal of geophysical research : Atmospheres, vol 113 n° D21 (16 November 2008)PermalinkTen years of fluxes and stand growth in a young beech forest at Hesse, North-eastern France / André Granier in Annals of Forest Science, Vol 65 n° 7 (October - November 2008)PermalinkUse of a Kalman filter for the retrieval of surface BRDF coefficients with a time-evolving model based on the ECOCLIMAP land cover classification / O. Samain in Remote sensing of environment, vol 112 n° 4 (15/04/2008)Permalink