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Survie des semis de ligneux pionniers dans les lits fluviaux : approche in et ex situ des facteurs de contrôle abiotiques et biologiques des espèces Populus nigra et Salix alba / Coraline Lise Wintenberger in Géomorphologie, vol 23 ([01/10/2017])
[article]
Titre : Survie des semis de ligneux pionniers dans les lits fluviaux : approche in et ex situ des facteurs de contrôle abiotiques et biologiques des espèces Populus nigra et Salix alba Type de document : Article/Communication Auteurs : Coraline Lise Wintenberger, Auteur ; Stéphane Rodrigues, Auteur ; Philippe Jugé, Auteur ; Marc Villar, Auteur Année de publication : 2017 Note générale : bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Végétation
[Termes IGN] crue
[Termes IGN] érosion hydrique
[Termes IGN] Loire (bassin)
[Termes IGN] Populus nigra
[Termes IGN] Salix albaRésumé : (auteur) La survie des semis de ligneux pionniers aux contraintes exercées lors des épisodes de crue subséquents à leur recrutement dépend des contraintes hydro-sédimentaires exercées mais également de leur capacité à résister à ces contraintes. L’objectif de cette étude est de comprendre à fine résolution spatio-temporelle les conditions de survie des semis des espèces Populus nigra et Salix alba aux crues survenant après leur recrutement. Une double approche in et ex situ a été conduite permettant (i) de caractériser les contraintes exercées sur les semis au cours des épisodes de crue et (ii) d’analyser leur capacité de résistance aux contraintes. L’approche in situ s’est focalisée sur une barre sédimentaire de centre de chenal localisée en Loire moyenne. Des mesures de topographie, bathymétrie, courantométrie et granulométrie ont permis de caractériser l’intensité, l’évolution temporelle et la répartition spatiale des forces de traînée impliquées dans l’arrachage des semis, des processus d’érosion-dépôt respectivement responsables de l’excavation et de l’enfouissement des semis. Les résultats montrent que la dynamique hydro-sédimentaire spécifique de la barre sédimentaire colonisée a une influence sur la répartition de la survie des semis. L’approche ex situ a permis de caractériser la diversité de croissance du système racinaire et de la partie aérienne des semis en fonction du substrat ainsi que les forces nécessaires à l’arrachage des semis et leur résistance à l’enfouissement. La confrontation des mesures réalisées ex situ avec les contraintes exercées in situ permettent d’affiner la compréhension de la répartition de la survie des semis sur la barre forcée. Numéro de notice : A2017-523 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.4000/geomorphologie.11789 En ligne : http://geomorphologie.revues.org/11789 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86541
in Géomorphologie > vol 23 [01/10/2017][article]Assessing the performance of multi-GNSS precise point positioning in Asia-Pacific region / X. Zhao in Survey review, vol 49 n° 354 (September 2017)
[article]
Titre : Assessing the performance of multi-GNSS precise point positioning in Asia-Pacific region Type de document : Article/Communication Auteurs : X. Zhao, Auteur ; S. Wang, Auteur ; C. Liu, Auteur ; J. Ou, Auteur ; X. Yu, Auteur Année de publication : 2017 Article en page(s) : pp 186 - 196 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] Asie (géographie politique)
[Termes IGN] données BeiDou
[Termes IGN] données GLONASS
[Termes IGN] données GPS
[Termes IGN] filtre de Kalman
[Termes IGN] modèle stochastique
[Termes IGN] Pacifique (océan)
[Termes IGN] positionnement ponctuel précis
[Termes IGN] test de performanceRésumé : (Auteur) Multi-Global Navigation Satellite System (GNSS) integration can effectively improve the satellite geometry strength, and certain effect on the precise point positioning (PPP) accuracy and convergence speed. Taking the system difference into account, this paper deduces the unified GNSS observation model, which is extended to the multi-GNSS PPP functional model. Meanwhile, the stochastic model used in Kalman filter parameter estimation is presented in the paper. Furthermore, to evaluate the performance of the multi-GNSS PPP in Asia-Pacific region, observed data from the International GNSS Service reference stations are analysed using the self-developed software. In detail, the results from Global Positioning System (GPS)-, GLObal NAvigation Satellite System (GLONASS)- and BeiDou Navigation Satellite System (BDS)-only PPP, double combined PPP and GPS/GLONASS/BDS combined PPP under the different observation duration and cut-off elevation angles are analysed. Results demonstrate: (1) compared with the single system PPP, the convergence speed of the multi-GNSS PPP is improved while the accuracy is not significantly improved after processing the 24-h data set; (2) when the observation duration is short, such as 0.5 h, the mean convergence percentage of the BDS combined with GPS and GLONASS PPP increases by an average of 49.6% compared with the single individual systems except for BDS, respectively, under the cut-off angle of 5° and (3) when PPP positioning with high cut-off elevation angles, and at the point of centimetre-level positioning, the GPS/GLONASS/BDS combined PPP has a better performance on the convergence percentage and convergence speed. For example, the percentages of the position biases within 0–5 cm for GPS/GLONASS/BDS are increased by 7.2 and 4.5% in North and East direction compared with GPS/GLONASS under the cut-off angle of 35°, more than any other. And the mean convergence time is only 14.5 min. Numéro de notice : A2017-544 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/00396265.2016.1151576 En ligne : https://doi.org/10.1080/00396265.2016.1151576 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86599
in Survey review > vol 49 n° 354 (September 2017) . - pp 186 - 196[article]Extension of satellite altimetry Jason-2 sea level anomalies towards the Red Sea coast using polynomial harmonic techniques / A. M. Taqi in Marine geodesy, vol 40 n° 5 (September 2017)
[article]
Titre : Extension of satellite altimetry Jason-2 sea level anomalies towards the Red Sea coast using polynomial harmonic techniques Type de document : Article/Communication Auteurs : A. M. Taqi, Auteur ; A. M. Al-Subhi, Auteur ; M. A. Alsaafani, Auteur Année de publication : 2017 Article en page(s) : pp 315 - 328 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] altimétrie satellitaire par radar
[Termes IGN] AVISO
[Termes IGN] données altimétriques
[Termes IGN] données Jason
[Termes IGN] équation polynomiale
[Termes IGN] fonction harmonique
[Termes IGN] littoral
[Termes IGN] niveau de la mer
[Termes IGN] Rouge, mer
[Termes IGN] série de Fourier
[Vedettes matières IGN] AltimétrieRésumé : (Auteur) Satellite altimetry data are facing big challenges near the coasts. These challenges arise due to the fundamental difficulties of correction and land contamination in the foot print, which result in rejection of these data near the coast. Several studies have been carried out to extend these data towards the coast. Over the Red Sea, altimetry data consist of gaps, which extend to about 30–50 km from the coast. Two methods are used for processing and extending Jason-2 satellite altimetry sea level anomalies (SLAs) towards the Red Sea coast; Fourier Series Model (FSM), and the polynomial sum of sine model (SSM). FSM model technique uses Fourier series and statistical analysis reflects strong relationship with both the observation and AVISO data, with strong and positive correlation. The second prediction technique, SSM model, depends on the polynomial sum of sine, and does not reflect any relationship with the observations and AVISO data close to the coast and the correlation coefficient (CC) is weak and negative. The FSM model output results in SLA data significantly better and more accurate than the SSM model output. Numéro de notice : A2017-668 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2017.1333549 En ligne : https://doi.org/10.1080/01490419.2017.1333549 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=87143
in Marine geodesy > vol 40 n° 5 (September 2017) . - pp 315 - 328[article]Forest canopy height estimation using satellite laser altimetry : a case study in the Western Ghats, India / S.M. Ghosh in Applied geomatics, vol 9 n° 3 (September 2017)
[article]
Titre : Forest canopy height estimation using satellite laser altimetry : a case study in the Western Ghats, India Type de document : Article/Communication Auteurs : S.M. Ghosh, Auteur ; M. Dev Behera, Auteur Année de publication : 2017 Article en page(s) : pp 159 - 166 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] altimétrie satellitaire par laser
[Termes IGN] données altimétriques
[Termes IGN] données ICEsat
[Termes IGN] données laser
[Termes IGN] données localisées 3D
[Termes IGN] forêt tropicale
[Termes IGN] Ghats occidentaux
[Termes IGN] hauteur des arbres
[Termes IGN] Inde
[Termes IGN] modèle numérique de surface de la canopée
[Termes IGN] penteRésumé : (Auteur) Canopy height is a crucial metric required to quantify the aboveground plant biomass accurately. The study explores the data derived using Light Detection and Ranging (LiDAR) technology from GeoScience Laser Altimeter System (GLAS) aboard Ice, Cloud, and Land Elevation satellite (ICESat) to derive canopy height estimate equations in the tropical forests of the Western Ghats, India. The interpretation of LiDAR waveforms for the purpose of estimating canopy heights is not straightforward, especially over sloping terrain where vegetation and ground are found at comparable heights. Canopy height models are developed using GLAS waveform extent and terrain index, derived from ASTER digital elevation, to counter the effect of topographic relief effects in canopy height estimates over steep terrain. The model was applied to calculate tree heights for whole of the Western Ghats. Results showed that the model can estimate tree heights within the specified height range with an accuracy of more than 90% while using percent overestimation/underestimation method of validation. This shows the effectiveness of the model, especially over steep slopes, also revealing that the models were able to successfully account for the pulse broadening effect. The study highlights the development of a LiDAR-based canopy height model for tropical forest and its ability to yield better canopy height estimates especially over steep slopes. Numéro de notice : A2017-597 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.1007/s12518-017-0190-2 En ligne : https://doi.org/10.1007/s12518-017-0190-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86815
in Applied geomatics > vol 9 n° 3 (September 2017) . - pp 159 - 166[article]Improving the prediction of African savanna vegetation variables using time series of MODIS products / Miriam Tsalyuk in ISPRS Journal of photogrammetry and remote sensing, vol 131 (September 2017)
[article]
Titre : Improving the prediction of African savanna vegetation variables using time series of MODIS products Type de document : Article/Communication Auteurs : Miriam Tsalyuk, Auteur ; Maggi Kelly, Auteur ; Wayne M. Getz, Auteur Année de publication : 2017 Article en page(s) : pp 77 - 91 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation
[Termes IGN] Afrique (géographie physique)
[Termes IGN] biomasse forestière
[Termes IGN] dégradation de la flore
[Termes IGN] Enhanced vegetation index
[Termes IGN] image Terra-MODIS
[Termes IGN] Leaf Area Index
[Termes IGN] Namibie
[Termes IGN] Normalized Difference Vegetation Index
[Termes IGN] prédiction
[Termes IGN] savane
[Termes IGN] variationRésumé : (Auteur) African savanna vegetation is subject to extensive degradation as a result of rapid climate and land use change. To better understand these changes detailed assessment of vegetation structure is needed across an extensive spatial scale and at a fine temporal resolution. Applying remote sensing techniques to savanna vegetation is challenging due to sparse cover, high background soil signal, and difficulty to differentiate between spectral signals of bare soil and dry vegetation. In this paper, we attempt to resolve these challenges by analyzing time series of four MODIS Vegetation Products (VPs): Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Leaf Area Index (LAI), and Fraction of Photosynthetically Active Radiation (FPAR) for Etosha National Park, a semiarid savanna in north-central Namibia. We create models to predict the density, cover, and biomass of the main savanna vegetation forms: grass, shrubs, and trees. To calibrate remote sensing data we developed an extensive and relatively rapid field methodology and measured herbaceous and woody vegetation during both the dry and wet seasons. We compared the efficacy of the four MODIS-derived VPs in predicting vegetation field measured variables. We then compared the optimal time span of VP time series to predict ground-measured vegetation. We found that Multiyear Partial Least Square Regression (PLSR) models were superior to single year or single date models. Our results show that NDVI-based PLSR models yield robust prediction of tree density (R2 = 0.79, relative Root Mean Square Error, rRMSE = 1.9%) and tree cover (R2 = 0.78, rRMSE = 0.3%). EVI provided the best model for shrub density (R2 = 0.82) and shrub cover (R2 = 0.83), but was only marginally superior over models based on other VPs. FPAR was the best predictor of vegetation biomass of trees (R2 = 0.76), shrubs (R2 = 0.83), and grass (R2 = 0.91). Finally, we addressed an enduring challenge in the remote sensing of semiarid vegetation by examining the transferability of predictive models through space and time. Our results show that models created in the wetter part of Etosha could accurately predict trees’ and shrubs’ variables in the drier part of the reserve and vice versa. Moreover, our results demonstrate that models created for vegetation variables in the dry season of 2011 could be successfully applied to predict vegetation in the wet season of 2012. We conclude that extensive field data combined with multiyear time series of MODIS vegetation products can produce robust predictive models for multiple vegetation forms in the African savanna. These methods advance the monitoring of savanna vegetation dynamics and contribute to improved management and conservation of these valuable ecosystems. Numéro de notice : A2017-537 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.isprsjprs.2017.07.012 En ligne : https://doi.org/10.1016/j.isprsjprs.2017.07.012 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86575
in ISPRS Journal of photogrammetry and remote sensing > vol 131 (September 2017) . - pp 77 - 91[article]Réservation
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