1,721,041 research outputs found
Study of the complementarity and the fusion of the images that will be provided by the future satellite sensors OLCI/Sentinel-3 and FCI/Meteosat Third Generation
No full textL’objectif de cette thèse était de proposer, valider et comparer des méthodes de fusion d’images provenant d’un capteur héliosynchrone multispectral et d’un capteur géostationnaire multispectral, pour produire des cartes de composition de l’eau détaillées spatialement et les mieux rafraîchies possibles. Notre méthodologie a été appliquée au capteur héliosynchrone OLCI sur Sentinel-3 et au capteur géostationnaire FCI sur Météosat Troisième Génération. Dans un premier temps, la sensibilité des deux capteurs à la couleur de l’eau a été analysée. Les images des capteurs OLCI et FCI n’étant pas encore disponibles, ont donc été simulées sur le Golfe du Lion, grâce à des cartes d’hydrosols (chlorophylle, matières en suspension et matières organiques dissoutes) et à des modèles de transfert radiatifs (Hydrolight et Modtran). Deux méthodes de fusion ont ensuite été adaptées puis testées à partir des images simulées : la méthode SSTF (Spatial, Spectral, Temporal Fusion) inspirée de la fusion de (Vanhellemont et al., 2014) et la méthode STARFM (Spatial Temporal Adaptative Reflectance Fusion Model) de (Gao et al., 2006). Les résultats de fusion ont alors été validés avec des images de référence simulées et les cartes d’hydrosols estimées à partir de ces images ont été comparées aux cartes utilisées en entrée des simulations. Pour améliorer le SNR des images FCI, un filtrage temporel a été proposé. Enfin, comme le but est d’obtenir des indicateurs de qualité de l’eau, nous avons testé les méthodes de fusion sur les cartes d’hydrosols estimées à partir des images FCI et OLCI simulées.The objective of this thesis was to propose, validate and compare fusion methods of images provided by a Low Earth Orbit multispectral sensor and a geostationary multispectral sensor in order to obtain water composition maps with spatial details and high temporal resolution. Our methodology was applied to OLCI Low Earth Orbit sensor on Sentinel-3 and FCI Geostationary Earth Orbit (GEO) sensor on Meteosat Third Generation. Firstly, the sensor sensivity, regarding the water color, was analyzed. As the images from both sensors were not available, they were simulated on the Golf of Lion, thanks to hydrosol maps (chl, SPM and CDOM) and radiative transfer models (Hydrolight and Modtran). Two fusion methods were then adapted and tested with the simulated images: the SSTF (Spatial, Spectral, Temporal Fusion) method inspired from the method developed by (Vanhellemont et al., 2014)) and the STARFM (Spatial Temporal Adaptative Reflectance Fusion Model) method from (Gao et al., 2006)). The fusion results were then validated with the simulated reference images and by estimating the hydrosol maps from the fusion images and comparing them with the input maps of the simulation process. To improve FCI SNR, a temporal filtering was proposed. Finally, as the aim is to obtain a water quality indicator, the fusion methods were adapted and tested on the hydrosol maps estimated with the FCI and OLCI simulated images
Fusion of images from different satellite sensors for monitoring water quality in coastal areas
No full textLe suivi des zones côtières nécessite à la fois une bonne résolution spatiale, une bonne résolution spectraleassociée à un bon rapport signal sur bruit et enfin une bonne résolution temporelle pour visualiser deschangements rapides de couleur de l’eau.Les capteurs disponibles actuellement, et même ceux prévus prochainement, n’apportent pas à la fois unebonne résolution spatiale, spectrale ET temporelle. Dans cette étude, nous nous intéressons à la fusion de 2futurs capteurs qui s’inscrivent tous deux dans le programme Copernicus de l’agence spatiale européenne:MSI sur Sentinel-2 et OLCI sur Sentinel-3.Comme les capteurs MSI et OLCI ne fournissent pas encore d’images, il a fallu les simuler. Pour cela nousavons eu recours aux images hyperspectrales du capteur HICO. Nous avons alors proposé 3 méthodes : uneadaptation de la méthode ARSIS à la fusion d’images multispectrales (ARSIS), une méthode de fusion baséesur la factorisation de tenseurs non-négatifs (Tenseur) et une méthode de fusion basée sur l’inversion dematrices (Inversion)Ces 3 méthodes ont tout d’abord été évaluées à l’aide de paramètres statistiques entre les images obtenuespar fusion et l’image « parfaite » ainsi que sur les résultats d’estimation de paramètres biophysiques obtenuspar minimisation du modèle de transfert radiatif dans l’eau.Monitoring coastal areas requires both a good spatial resolution, good spectral resolution associated with agood signal to noise ratio and finally a good temporal resolution to visualize rapid changes in water color.Available now, and even those planed soon, sensors do not provide both a good spatial, spectral ANDtemporal resolution. In this study, we are interested in the image fusion of two future sensors which are bothpart of the Copernicus program of the European Space Agency: MSI on Sentinel-2 and OLCI on Sentinel-3.Such as MSI and OLCI do not provide image yet, it was necessary to simulate them. We then used thehyperspectral imager HICO and we then proposed three methods: an adaptation of the method ARSIS fusionof multispectral images (ARSIS), a fusion method based on the non-negative factorization tensors (Tensor)and a fusion method based on the inversion de matrices (Inversion).These three methods were first evaluated using statistical parameters between images obtained by fusionand the "perfect" image as well as the estimation results of biophysical parameters obtained by minimizingthe radiative transfer model in water
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Image simulation of future geostationnary multispectral sensor dedicated to water color : Assessment of solar and sensor angles influence on measured radiance and chlorophyll estimation error
No full textLes progrès effectués dans le domaine des instruments optiques permettent d’envisager désormais de placer des capteurs à moyenne résolution spatiale et haute résolution spectrale sur des orbites géostationnaires ce qui permettrait d’observer la Terre à la fois avec une moyenne résolution spatiale, une bonne résolution spectrale et une haute résolution temporelle, ce que ne permettent pas les satellites héliosynchrones. L'objectif de cette thèse est donc de simuler les images en luminance qui seraient acquises par un capteur géostationnaire hypothétique dédié à l'observation de la couleur de l'océan, afin de caractériser les images qui seraient acquises, de spécifier les futurs instruments et de valider des algorithmes de traitement sur des images réalistes. Pour parvenir à simuler les luminances spectrales qui seraient mesurées par le capteur, nous avons combiné les modèles de transfert radiatif directs de l'eau (Hydrolight) et de l'atmosphère (MODTRAN). Les données d’entrée d’Hydrolight ont été déduites des données provenant des cartes climatologiques de GlobColour (chlorophylle, matières minérales et organiques en suspension) pour simuler des images de couverture globale (Global Area Coverage) d'un capteur géostationnaire à basse résolution spatiale, moyenne résolution spectrale et haute résolution temporelle. L'analyse de ces images permet de déterminer la gamme de luminances pour chaque bande spectrale et pour différentes acquisitions au cours de la journée. Les résultats indiquent aussi les limites angulaires pour éviter le phénomène du sunglint et pour assurer un niveau minimum de luminance provenant de l'eau, contenu dans le signal mesuré. Les images en luminance ainsi simulées ont permis d’évaluer aussi la performance d’un algorithme d'estimation de concentration en chlorophylle de rapport de bandes dans les eaux au large. Les résultats montrent que l'erreur d'estimation est moyennement sensible aux angles d'observation et d’éclairement, importants dans les images géostationnaires.Improvements of optical sensors now make it possible to launch medium spatial and high spectral resolution sensors on the Geostationary Earth Orbit (GEO). The GEO allows sensors to observe the Earth with high temporal resolution, unlike Low Earth Orbit (LEO) satellites. The objective of this thesis is to simulate radiance images that would be provided by a theoretical ocean color sensor, on a geostationary orbit, in order to characterize the images to be acquired, to specify the future instruments and to validate the image processing algorithms. For this purpose, we have combined a radiative transfer model for ocean waters (Hydrolight) and a radiative transfer model for the atmosphere (MODTRAN) to obtain simulated radiance images at the sea surface level and at the Top-Of-Atmosphere (TOA) level. The inputs of Hydrolight have been deduced from GlobColour Project data (chlorophyll, mineral suspended matter and organic matter) to simulate the Global Area Coverage (GAC) images of a geostationary sensor with low spatial resolution, medium spectral resolution and high temporal resolution. The analysis of these images enables to determine the radiance dynamic range for each spectral band over the day. The results indicate the angular limits to avoid the sunglint phenomenon and to ensure a minimum proportion of water leaving radiance in the measured TOA radiance. The simulated radiance images allow to evaluate the performance of an ocean color algorithm for chlorophyll concentration estimation in open waters. The results show that the error of chlorophyll estimation is moderately sensitive to observation and lighting angles, which are so important in geostationary images
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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