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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]Exemplaires(3)
Code-barres Cote Support Localisation Section Disponibilité 081-2017091 RAB Revue Centre de documentation En réserve L003 Disponible 081-2017093 DEP-EXM Revue LASTIG Dépôt en unité Exclu du prêt 081-2017092 DEP-EAF Revue Nancy Dépôt en unité Exclu du prêt Evaluating the performance of using PPK-GPS technique in producing topographic contour map / Ahmed El Shouny in Marine geodesy, vol 40 n° 4 (July 2017)
[article]
Titre : Evaluating the performance of using PPK-GPS technique in producing topographic contour map Type de document : Article/Communication Auteurs : Ahmed El Shouny, Auteur ; Nagy Yakoub, Auteur ; Magdy Hosny, Auteur Année de publication : 2017 Article en page(s) : pp 224 - 238 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] altitude orthométrique
[Termes IGN] analyse comparative
[Termes IGN] carte topographique
[Termes IGN] courbe de niveau
[Termes IGN] données GPS
[Termes IGN] Egypte
[Termes IGN] GPS en mode différentiel
[Termes IGN] Nil (delta du)
[Termes IGN] niveau à bulle
[Termes IGN] post-traitement
[Vedettes matières IGN] AltimétrieRésumé : (Auteur) The Global Positioning System (GPS) is considered as one of the most powerful tools that are used in geodetic works. It is increasingly considered as an alternative tool for conventional surveying techniques. The goal of this research paper is to produce a methodology for generating topographic contour maps using the post-processed kinematic differential GPS technique (PPK-GPS). The performance of this technique is assessed by comparing it with the traditional spirit-leveling technique taking into consideration the accuracy, time, and cost. The study area is located along the Mediterranean coast in the Rosetta area of the middle Delta in Egypt with a total area of about 39 km2. The field work includes 14 control points and about 50,000 PPK observations. In addition, 20 check cross sections that extend along the coastal line from Rosetta to El Burullus cities were observed using both spirit-leveling and GPS-PPK techniques. The results of the comparison indicate that the PPK-GPS technique can be used instead of spirit leveling in producing a topographic contour map with an accuracy of about 20 cm in orthometric height. We find that the PPK-GPS technique reduces the estimated time of leveling works in our study area by about 70%. Numéro de notice : A2017-667 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1080/01490419.2017.1321594 En ligne : https://doi.org/10.1080/01490419.2017.1321594 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=87142
in Marine geodesy > vol 40 n° 4 (July 2017) . - pp 224 - 238[article]
[article]
Titre : Les cartographes du désert Type de document : Article/Communication Auteurs : Paul Courbon, Auteur Année de publication : 2017 Article en page(s) : pp 62 - 70 Langues : Français (fre) Descripteur : [Vedettes matières IGN] Topographie ancienne
[Termes IGN] altimétrie
[Termes IGN] Arabie Saoudite
[Termes IGN] borne géodésique
[Termes IGN] canevas
[Termes IGN] carte thématique
[Termes IGN] enregistreur de profils aéroporté
[Termes IGN] gisement d'une direction
[Termes IGN] histoire de la cartographie
[Termes IGN] Jordanie
[Termes IGN] Mauritanie
[Termes IGN] mission de terrain
[Termes IGN] phosphate
[Termes IGN] photographie aérienne
[Termes IGN] rattachement APR
[Termes IGN] réseau de nivellement
[Termes IGN] Sahara, désert du
[Termes IGN] topographie locale
[Termes IGN] toponymie localeRésumé : (Auteur) Vers 1965, Robert Génot avait tourné pour l'IGN un film intitulé "La carte du désert". Ce film nous faisait revivre les diverses étapes d'une aventure extraordinaire qui s'est déroulée à une époque où le GPS était encore loin d'exister et où le Sahara n'était traversé que par de mauvaises pistes. Par l'intermédiaire de l'IGN, la France avait doté ses colonies d'une couverture cartographique exceptionnelle, inexistante dans les colonies voisines anglaises, ou italiennes. En retrouvant un cédérom de ce film que j'avais égaré, j'ai revécu cette aventure, avec d'autant plus d'émotions que j'y avais participé. J'ai eu alors envie de retracer cette participation qui m'a laissé des souvenirs exceptionnels. Mais à l'époque, la photographie numérique n'existait pas encore et on prenait infiniment moins de photos qu'aujourd'hui. De plus certaines des diapositives retrouvées avaient mal vieilli et étaient inutilisables. Lors de mes déménagements, je me suis allégé de nombreux documents anciens. Nous ferons avec. Numéro de notice : A2017-345 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85570
in XYZ > n° 151 (juin - août 2017) . - pp 62 - 70[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 112-2017021 RAB Revue Centre de documentation En réserve L003 Disponible Documents numériques
en open access
Les cartographes du désert - pdf éditeurAdobe Acrobat PDF A cyber-enabled spatial decision support system to inventory mangroves in Mozambique: coupling scientific workflows and cloud computing / Wenwu Tang in International journal of geographical information science IJGIS, vol 31 n° 5-6 (May-June 2017)
[article]
Titre : A cyber-enabled spatial decision support system to inventory mangroves in Mozambique: coupling scientific workflows and cloud computing Type de document : Article/Communication Auteurs : Wenwu Tang, Auteur ; Wenpeng Feng, Auteur ; Meijuan Jia, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 907 - 938 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] informatique en nuage
[Termes IGN] inventaire de la végétation
[Termes IGN] lever des détails
[Termes IGN] mangrove
[Termes IGN] modélisation
[Termes IGN] Mozambique
[Termes IGN] synergiciel
[Termes IGN] système d'aide à la décision
[Termes IGN] Zambèze (fleuve)
[Vedettes matières IGN] Inventaire forestierRésumé : (auteur) Mangroves are an important terrestrial carbon reservoir with numerous ecosystem services. Yet, it is difficult to inventory mangroves because of their low accessibility. A sampling approach that produces accurate assessment while maximizing logistical integrity of inventory operation is often required. Spatial decision support systems (SDSSs) provide support for integrating such a sampling design of fieldwork with operational considerations and evaluation of alternative scenarios. However, this fieldwork design driven by SDSS is often computationally intensive and repetitive. In this study, we develop a cyber-enabled SDSS framework to facilitate the computationally challenging fieldwork design that requires the efficacious selection of base camps and plots for the inventory of mangroves. Our study area is the Zambezi River Delta, Mozambique. Cyber-enabled capabilities, including scientific workflows and cloud computing, are integrated with the SDSS. Scientific workflows enable the automation of data and modeling tasks in the SDSS. Cloud computing offers on-demand computational support for interoperation among stakeholders for collaborative scenario evaluation for the fieldwork design of mangrove inventory. Further, this framework allows for harnessing high-performance computing capabilities for accelerating the fieldwork design. The cyber-enabled framework provides significant merits in terms of effective coordination among science and logistical teams, assurance of meeting inventory objectives, and an objective basis to collectively and efficaciously evaluate alternative scenarios. Numéro de notice : A2017-237 Affiliation des auteurs : non IGN Thématique : FORET/GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2016.1250900 En ligne : http://dx.doi.org/10.1080/13658816.2016.1250900 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85171
in International journal of geographical information science IJGIS > vol 31 n° 5-6 (May-June 2017) . - pp 907 - 938[article]Exemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 079-2017031 RAB Revue Centre de documentation En réserve L003 Disponible Frequency of extreme Sahelian storms tripled since 1982 in satellite observations / Christopher M. Taylor in Nature letters, vol 544 n° 7651 (27 April 2017)
[article]
Titre : Frequency of extreme Sahelian storms tripled since 1982 in satellite observations Type de document : Article/Communication Auteurs : Christopher M. Taylor, Auteur ; Danijel Belušić, Auteur ; Françoise Guichard, Auteur ; Douglas J. Parker, Auteur ; Théo Vischel, Auteur ; Olivier Bock , Auteur ; Phil P. Harris, Auteur ; Serge Janicot, Auteur ; Cornelia Klein, Auteur ; Gérémy Panthou, Auteur Année de publication : 2017 Projets : AMMA & AMMA-2 / Janicot, Serge Article en page(s) : pp 475 - 478 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse diachronique
[Termes IGN] changement climatique
[Termes IGN] convection
[Termes IGN] données météorologiques
[Termes IGN] pluie
[Termes IGN] Sahara, désert du
[Termes IGN] Sahel
[Termes IGN] température
[Termes IGN] tempêteRésumé : (auteur) The hydrological cycle is expected to intensify under global warming, with studies reporting more frequent extreme rain events in many regions of the world, and predicting increases in future flood frequency. Such early, predominantly mid-latitude observations are essential because of shortcomings within climate models in their depiction of convective rainfall. A globally important group of intense storms—mesoscale convective systems (MCSs)—poses a particular challenge, because they organize dynamically on spatial scales that cannot be resolved by conventional climate models. Here, we use 35 years of satellite observations from the West African Sahel to reveal a persistent increase in the frequency of the most intense MCSs. Sahelian storms are some of the most powerful on the planet, and rain gauges in this region have recorded a rise in ‘extreme’ daily rainfall totals. We find that intense MCS frequency is only weakly related to the multidecadal recovery of Sahel annual rainfall, but is highly correlated with global land temperatures. Analysis of trends across Africa reveals that MCS intensification is limited to a narrow band south of the Sahara desert. During this period, wet-season Sahelian temperatures have not risen, ruling out the possibility that rainfall has intensified in response to locally warmer conditions. On the other hand, the meridional temperature gradient spanning the Sahel has increased in recent decades, consistent with anthropogenic forcing driving enhanced Saharan warming. We argue that Saharan warming intensifies convection within Sahelian MCSs through increased wind shear and changes to the Saharan air layer. The meridional gradient is projected to strengthen throughout the twenty-first century, suggesting that the Sahel will experience particularly marked increases in extreme rain. The remarkably rapid intensification of Sahelian MCSs since the 1980s sheds new light on the response of organized tropical convection to global warming, and challenges conventional projections made by general circulation models. Numéro de notice : A2017-859 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1038/nature22069 Date de publication en ligne : 26/04/2017 En ligne : http://doi.org/10.1038/nature22069 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89838
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