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Hu, Ronghai. "Estimation cohérente de l'indice de surface foliaire en utilisant des données terrestres et aéroportées." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD021/document.
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L’indice de surface foliaire (Leaf Area Index, LAI), défini comme la moitié de la surface foliaire par unité de surface de sol, est un paramètre clé du cycle écologique de la Terre, et sa précision d'acquisition a toujours la nécessité et la possibilité d'amélioration. La technologie du scanner laser actif offre une possibilité d'obtention cohérente du LAI à plusieurs échelles, car le scanner laser terrestre et le scanner laser aéroporté fonctionnent sur le même mécanisme physique. Cependant, les informations tridimensionnelles du scanner laser ne sont pas complètement explorées dans les méthodes actuelles et les théories traditionnelles ont besoin d'adaptation. Dans cette thèse, le modèle de distribution de longueur de trajet est introduit pour corriger l'effet d’agrégation, et il est appliqué aux données du scanner laser terrestre et du scanner laser aéroporté. La méthode d'obtention de la distribution de longueur de trajet de différentes plates-formes est étudiée et le modèle de récupération cohérent est établi. Cette méthode permet d’améliorer la mesure du LAI des arbres individuels dans les zones urbaines et la cartographie LAI dans les forêts naturelles, et ses résultats sont cohérents à différentes échelles. Le modèle devrait faciliter la détermination cohérente de l'indice de surface foliaire des forêts à l'aide de données au sol et aéroportéesLeaf Area Index (LAI), defined as one half of the total leaf area per unit ground surface area, is a key parameter of vegetation structure for modeling Earth's ecological cycle and its acquisition accuracy always has the need and opportunity for improvement. Active laser scanning provides an opportunity for consistent LAI retrieval at multiple scales because terrestrial laser scanning (TLS) and airborne laser scanning (ALS) have the similar physical mechanism. However, the three-dimensional information of laser scanning is not fully explored in current methods and the traditional theories require adaptation. In this thesis, the path length distribution model is proposed to model the clumping effect, and it is applied to the TLS and ALS data. The method of obtaining the path length distribution of different platforms is studied, and the consistent retrieval model is established. This method is found to improve the individual tree measurement in urban areas and LAI mapping in natural forest, and its results at consistent at different scales. The model is expected to facilitate the consistent retrieval of the forest leaf area index using ground and airborne data
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Béland, Martin. "Estimation de paramètres structuraux des arbres dans une savane à partir de mesures LiDAR terrestre et d'imagerie à très haute résolution spatiale." Thèse, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/2849.
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This thesis takes its place in a context where information on the biophysical state of forest ecosystems at spatial scales only remote sensing can retrieve is in demand more than ever. In order to provide reliable information using validated approaches, the remote sensing research community recognises the need for new and innovative methods, especially in heterogeneous environments like savannas. The recent emergence of terrestrial LiDAR scanners (TLS) and the increase in the computational capability of computers which allow running ray tracing model simulations with a high level of realism hold great potential to improve our understanding of the processes influencing the radiance measured by satellite sensors. This thesis makes use of these two cutting edge technologies for estimating the spatial distribution of tree leaf area, a key element of modeling radiative transfer processes. The first part of the thesis concerns the development of methods for estimating tridimensional leaf area distribution in a savanna environment from TLS measurements. The methods presented address certain issues related to TLs measures affecting the application of classical theories (the probability of light transmission and the contact frequency) to the estimation of leaf area through indirect means. These issues pertain to the cross-section of laser pulses emitted by a TLS and the occlusion effects caused by the interception of laser pulses by material inside the crown. The developed methods also exploit additional information provided by the active nature of the TLS sensor that is not available to passive sensors like hemispherical photography, i.e. the intensity of a pulse return offers the possibility to distinguish between energy interception by wood and foliage. A simplified approach of this method is presented to promote its use by other research groups. This approach consists of a series of parameterisations and represents a significant gain in terms of the required resources to produce the leaf area, estimates. The second part of the thesis explores the combination of the tree representations generated in the first part with a ray tracing model to simulate the interactions of light with tree crowns. This approach is highly innovative and our study showed its potential to improve our understanding of the factors influencing the radiative environment in a savanna. The methods presented offer a solution to map leaf area at the individual tree scale over large areas from very high spatial resolution imagery.
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Soma, Maxime. "Estimation de la distribution spatiale de surface et de biomasse foliaires de couverts forestiers méditerranéens à partir de nuages de points acquis par un LIDAR terrestre." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0111.
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Pour mieux comprendre le fonctionnement des écosystèmes forestiers à échelle fine, les modèles écophysiologiques cherchent à intégrer les flux d’énergie et de matière. Ces échanges dépendent de la distribution de la végétation. Leur modélisation nécessite donc une description de la structure de la végétation en trois dimensions (3D) à un niveau de détail que seule la télédétection peut produire à haut débit. Les LiDAR terrestre (Light Detection And Ranging) possèdent un fort potentiel pour caractériser en 3D la végétation au sein des canopées. De précédents travaux qui relient la densité de points à la quantité de végétation ont montré des résultats prometteurs. Cette thèse développe ces approches en explorant les diverses sources d’erreurs. Les biais systématiques sont corrigés à l’échelle de la branche, de l’arbre et de la placette. Ce travail s’appuie à la fois sur des travaux théoriques et expérimentaux. Nous avons d’abord évalué des estimateurs théoriques sur des branches. Sur cette végétation réelle, les estimateurs se sont révélés sensibles à la taille de voxel utilisée et à la distance de mesure. Les corrections apportées sont demeurées robustes sur des arbres entiers. Cependant, l’échantillonnage au LiDAR terrestre est limité par l’occlusion végétale. Un travail spécifique a été conduit pour optimiser les estimations en tirant avantage des corrélations spatiales présentes dans la végétation. Cette approche permet de limiter les sous-estimations systématiques liées à l’occlusion. L’ensemble des outils présentés offrent la possibilité de dresser des cartes de végétation à l’échelle de la placette en fournissant des estimateurs non biaisés de la surface foliaireTo better understand functioning of forest ecosystems at fine scale, ecophysiological model attempt to include energy and material fluxes. Such exchanges depend on the distribution of vegetation. Hence, these models require a tridimensional (3D) description of vegetation structure, at a level of detail which can only be retrieve with remote sensing at large scale. Terrestrial LiDAR (Light Detection And Ranging) have a great potential to provide 3D description of vegetation elements in canopy. Previous studies established promising relations between the point density and quantity of vegetation. This work develop these statistical methods, focusing on source of errors. Systematic biases are corrected at branch, tree and plot scales. This study relies on both numerical simulations and field experiments. First, we test estimators on branches in laboratory conditions. On this natural vegetation, estimators are sensitive to voxel size and distance from instrument with phase-shift LiDAR. Developed corrections from this branch experiment are valid at tree scale. However, difficulties arising from sampling limitations due to occlusion and instrument sampling pattern cause negative biases in dense areas. Specific investigations are conducted to identify source of errors and to optimize multiscan estimations. A statistical method called LAD-kriging, based on spatial correlation within vegetation, improves local accuracy of estimations and limits underestimations due to occlusion. The tools produced in this work allow to map vegetation at plot scale by providing unbiased estimator of leaf area. Some of these tools are currently implemented within open access Computree software
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Soontornchainaksaeng, Puangpaka. "Mise en place de la surface foliaire, accumulation et répartition de la matière sèche de sorgho (Sorghum bicolor (L. ) Moench) : effet de la température." Toulouse, INPT, 1995. http://www.theses.fr/1995INPT050G.
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Les objectifs de cette étude sont de tester l'action (gamme de 15 à 31°C) sur la mise en place de la surface foliaire pendant la phase végétative, chez deux sorghos sucriers (Keller et Lorall), un sorgho fibre et un mai͏̈s. Les expériences ont été réalisées en chambres climatisées, en concition hydriques et azotées optimales et sous un éclairement constant. Cette étude consiste en un suivi et une analyse du rythme d'apparition des feuilles, de l'allongement foliaire et de la taille finale des feuilles, ce qui a permis de déterminer un phyllochrone et une température de base, une vitesse d'élongation et un profil de surface finale de feuilles. Le nombre et la taille des cellules sont aussi suivis pour cerner le mécanisme d'action de la température sur la division et l'élongation cellulaire. Afin de préciser les relations entre la mise en place de la surface foliaire et les aspects trophique et hydrique, la répartition de la matière sèche entre les feuilles, tiges et racines est précisée ainsi que la photosynthèse, la respiration obscure et la transpiration. Les apports de ce travail sont l'acquisition de connaissances en écophysiologie et sur les variations génotypiques, en relation avec la sélection des plantes ; la modélisation des différentes fonctions et de l'interaction plantes-milieux permet de tester différents scénarios agronomiques afin de rechercher une productivité mmaximale en conditions naturelles.
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Claverie, Martin. "Estimation spatialisée de la biomasse et des besoins en eau des cultures à l'aide de données satellitales à hautes résolutions spatiale et temporelle : application aux agrosystèmes du sud-ouest de la France." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1789/.
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Il existe un lien étroit entre les agrosystèmes et les cycles du carbone (processus de séquestration du carbone dans les sols) et de l'eau (systèmes de production par irrigation). Cette thèse contribue à l'analyse et la validation des méthodes de quantification, sur de grandes surfaces, de la biomasse (cycle du carbone) et des besoins en eau (cycle de l'eau) des agrosystèmes. Pour répondre à cet objectif, des données de télédétection sont assimilées dans un modèle de cultures, SAFY (Simple Algorithm For Yield Estimate), au travers d'une variable biophysique clés, le GAI (Green area index). Des méthodes d'estimation in situ (par proxy-détection) et spatialisées (par inversion de modèles de transfert radiatif) du GAI sont, tout d'abord, étudiées et validées. Les séries temporelles de GAI déterminées à partir des données de télédétection sont ensuite utilisées pour étalonner le modèle SAFY, conduisant à des estimations spatialisées de biomasse et des besoins en eau des cultures. Ces estimations sont validées par confrontation à un dispositif expérimental mis en place entre 2006 et 2010 et situé dans le sud-ouest de la France. Les cultures étudiées sont des cultures d'été non irriguées (tournesol) et irriguées (maïs, soja). Les données de télédétection utilisées pour estimer les séries temporelles de GAI sont issues du capteur Formosat-2. Ces données sont particulièrement pertinentes car elles combinent une haute résolution spatiale (8 m) et une haute fréquence temporelle (1 jour), indispensables pour le suivi des surfaces agricolesThere is a close relationship between agrosystems (or agroecosystems) and carbon (soil carbon sequestration process) and water (irrigation management systems) cycles. This PhD thesis contributes to the analysis and the validation of methods for quantification of agrosystems biomass (carbon cycle) and water needs (water cycle) over large land surfaces. To this end, remote sensing data are assimilated within a crop model, SAFY (Simple Algorithm For Yield Estimate), through a key biophysical variable, the GAI (Green area index). GAI in situ (proxy-detection) and spatialized (inversion of radiative transfer models) estimation methods are first assessed. Secondly, remote sensed time series of GAI are used for the calibration of the SAFY crop model in order to deliver spatial estimates of crop biomass and water needs. These estimations are validated, through direct comparison with an experimental system which is located in the southwest of France and run from 2006 to 2010. Studied crops are maize and soybean, which are irrigated, and also sunflower, which is non-irrigated. Remote sensing data used to estimate the time series of GAI are taken from Formosat-2 sensors. Such data are particularly relevant for the crop monitoring because they combine high spatial resolution (8 m) and high temporal frequency (1 day)
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Mohammadi, Vahid. "Design, Development and Evaluation of a System for the Detection of Aerial Parts and Measurement of Growth Indices of Bell Pepper Plant Based on Stereo and Multispectral Imaging." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2022. http://www.theses.fr/2022UBFCK109.
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Au cours de la croissance des plantes, leur suivi apporte beaucoup d'avantages aux producteurs. Cette surveillance comprend la mesure des propriétés physiques, le comptage des feuilles des plantes, la détection des plantes et leur séparation des mauvaises herbes. Toutes ces techniques peuvent être réalisées de différentes manières, cependant, les techniques favorables sont non destructives car la plante est une créature très sensible que toute manipulation peut perturber sa croissance ou entraîner la perte de feuilles ou de branches. Les techniques d'imagerie sont les meilleures solutions pour le suivi de la croissance des plantes et les mesures géométriques. À cet égard, dans ce projet, l'utilisation de l'imagerie stéréo et des données multispectrales a été étudiée. L'imagerie stéréo active et passive a été utilisée pour l'estimation des propriétés physiques et le comptage des feuilles et des données multispectrales ont été utilisées pour la séparation des cultures et des mauvaises herbes. La plante de poivron a été utilisée pour des mesures d'imagerie pendant une période de 30 jours et pour la séparation culture/mauvaise herbe, les réponses spectrales du poivron et de cinq mauvaises herbes ont été mesurées. Neuf propriétés physiques des feuilles de poivre (c. Le système stéréo était composé de deux caméras LogiTech et d'un vidéoprojecteur. Tout d'abord, le système stéréo a été calibré à l'aide d'images d'échantillons d'un damier standard dans différentes positions et angles. Le système a été contrôlé à l'aide de l'ordinateur pour allumer une ligne lumineuse, enregistrer des vidéos des deux caméras pendant que la lumière est balayée sur la plante, puis arrêter la lumière. Les cadres ont été extraits et traités. L'algorithme de traitement a d'abord filtré les images pour supprimer le bruit, puis a seuillé les pixels indésirables de l'environnement. Ensuite, en utilisant la méthode de détection de pic du centre de masse, la partie principale et centrale de la ligne lumineuse a été extraite. Ensuite, les images ont été rectifiées en utilisant les informations d'étalonnage. Ensuite, les pixels correspondants ont été détectés et utilisés pour le développement du modèle 3D. Le nuage de points obtenu a été transformé en une surface maillée et utilisé pour la mesure des propriétés physiques. Pour les réponses spectrales des plantes, celles-ci ont été fraîchement déplacées au laboratoire, les feuilles ont été détachées des plantes et placées sur un fond sombre flou. Des lumières de type A ont été utilisées pour l'éclairage et les mesures spectrales ont été effectuées à l'aide d'un spectroradiomètre de 380 nm à 1000 nm. Pour réduire la dimensionnalité des données, l'ACP et la transformée en ondelettes ont été utilisées. Les résultats de cette étude ont montré que l'utilisation de l'imagerie stéréo peut proposer un outil bon marché et non destructif pour l'agriculture. Un avantage important de l'imagerie stéréo active est qu'elle est indépendante de la lumière et peut être utilisée pendant la nuit. Cependant, l'utilisation de la stéréo active pour le stade primaire de croissance fournit des résultats acceptables, mais après ce stade, le système sera incapable de détecter et de reconstruire toutes les feuilles et les parties de la plante. En utilisant l'ASI, les valeurs R2 de 0,978 et 0,967 ont été obtenues pour l'estimation de la surface foliaire et du périmètre, respectivement. Les résultats de la séparation des cultures et des mauvaises herbes à l'aide de données spectrales étaient très prometteurs et le classificateur, qui était basé sur un apprentissage en profondeur, pouvait complètement séparer le poivre des cinq autres mauvaises herbesDuring the growth of plants, monitoring them brings much benefits to the producers. This monitoring includes the measurement of physical properties, counting plants leaves, detection of plants and separation of them from weeds. All these can be done different techniques, however, the techniques are favorable that are non-destructive because plant is a very sensitive creature that any manipulation can put disorder in its growth or lead to losing leaves or branches. Imaging techniques are of the best solutions for plants growth monitoring and geometric measurements. In this regard, in this project the use of stereo imaging and multispectral data was studied. Active and passive stereo imaging were employed for the estimation of physical properties and counting leaves and multispectral data was utilized for the separation of crop and weed. Bell pepper plant was used for imaging measurements for a period of 30 days and for crop/weed separation, the spectral responses of bell pepper and five weeds were measured. Nine physical properties of pepper leaves (i.e. main leaf diameters, leaf area, leaf perimeter etc.) were measured using a scanner and was used as a database and also for comparing the estimated values to the actual values. The stereo system consisted of two LogiTech cameras and a video projector. First the stereo system was calibrated using sample images of a standard checkerboard in different position and angles. The system was controlled using the computer for turning a light line on, recording videos of both cameras while light is being swept on the plant and then stopping the light. The frames were extracted and processed. The processing algorithm first filtered the images for removing noise and then thresholded the unwanted pixels of environment. Then, using the peak detection method of Center of Mass the main and central part of the light line was extracted. After, the images were rectified by using the calibration information. Then the correspondent pixels were detected and used for the 3D model development. The obtained point cloud was transformed to a meshed surface and used for physical properties measurement. Passive stereo imaging was used for leaf detection and counting. For passive stereo matching six different matching algorithms and three cost functions were used and compared. For spectral responses of plants, they were freshly moved to the laboratory, leaves were detached from the plants and placed on a blur dark background. Type A lights were used for illumination and the spectral measurements were carried out using a spectroradiometer from 380 nm to 1000 nm. To reduce the dimensionality of the data, PCA and wavelet transform were used. Results of this study showed that the use of stereo imaging can propose a cheap and non-destructive tool for agriculture. An important advantage of active stereo imaging is that it is light-independent and can be used during the night. However, the use of active stereo for the primary stage of growth provides acceptable results but after that stage, the system will be unable to detect and reconstruct all leaves and plant's parts. Using ASI the R2 values of 0.978 and 0.967 were obtained for the estimation leaf area and perimeter, respectively. The results of separation of crop and weeds using spectral data were very promising and the classifier—which was based on deep learning—could completely separate pepper from other five weeds
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Wang, Wei-Min. "Estimation of component temperatures of vegetative canopy with Vis/NIR and TIR multiple-angular data through inversion of vegetative canopy radiative transfer model." Strasbourg, 2009. http://www.theses.fr/2009STRA6027.
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Les mesures de la température de brillance des couverts végétaux s’appliquent à de très nombreux domaines comme la climatologie, l’hydrologie, l’agronomie, écologie. Son intérêt principal est de permettre d’accéder à l’estimation du bilan énergétique de la surface. Les mauvaises performances des modèles actuels en terme de restitution de la température de surface sont attribuées, en grande partie, à l'hétérogénéité des surfaces continentales. Les modèles actuels sont inaptes à rendre compte correctement des flux dans ces conditions (même éventuellement avec une correction de type kB-1). Les espoirs portent sur les modèles à deux sources qui traitent de façon différente les flux surface/atmosphère pour les sols et pour la végétation. Ce travail a permis de montrer que les paramètres structurels de la végétation comprenant l'indice de superficie foliaire, la distribution d'angle foliaire et l’indice de groupement exercent de grands effets sur la simulation du transfert radiatif dans le couvert végétal, et également sur la séparation des températures composantes du couvert végétal à partir des données multidirectionnelles dans les domaines visible et infrarouge thermique. Ce travail a aussi montré qu’il était possible d’amélioration la séparation des températures composantes du couvert végétal en utilisant la distribution d'angle foliaire et l’indice de groupement obtenus de données satellitaires. Un modèle analytique en tenant compte de la structure de la végétation a été développé et l'architecture optimale du réseau neuronal a été étudiée et proposée pour extraire les températures composantes du couvert végétal à partir des données multidirectionnelles dans les domaines visible et infrarouge thermiqueThe separation of component temperature is the basic step for the application of two-source algorithm. Multi-angular thermal infrared measurements provide a chance for the estimation of component temperatures (namely, soil and vegetation temperatures) with remotely-sensed data. The objective of this study is to explore the factors that affect the estimation of component temperatures and propose new algorithm for inverting the canopy radiative transfer models to compute component temperatures. The objectives of this dissertation include: (1) finding an appropriate candidate leaf angle distribution functions for modeling and inversion, (2) evaluating the scaling behavior of Beer's law and its effect on the estimation of component temperatures, (3) proposing an analytical model for directional brightness temperature at top of canopy, (4) retrieving component temperatures with neural network and simplex algorithms. The effects of leaf angle distribution function on extinction coefficient, which is a key parameter for simulating the radiative transfer through vegetative canopy, is explored to improve the radiative transfer modeling. These contributions will enhance our understanding of the basic problems existing in thermal IR remote sensing and improve the simulation of land surface energy balance. Further work can be conducted to continue the enhancement and application of proposed algorithm to remote sensing images
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Abd, el Rahman Nabil. "Essai d'établissement de diagnostics physiologiques précoces appliqués à diverses variétés de maïs." Paris 11, 1989. http://www.theses.fr/1989PA112097.
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La recherche de diagnostics physiologiques de la précocité chez 8 génotypes de Maïs nous a permis de mener une étude portant sur les premiers stades de la croissance à partir de la germination : passage de l'hétérotrophie à l'autotrophie, croissance des parties aériennes et racinaires, décroissance du poids des réserves de la graine, échanges gazeux (CO2 et O2) et incorporation de 14CO2. Alors que les mesures effectuées au champ, en salle conditionnée et en serre nous permettent d'en tirer certains critères de précocité de diagnostic rapide, celles effectuées au laboratoire -échanges gazeux (CO2 et CO2) et incorporation de 14CO2- renforcent ces résultats et permettent de réduire encore le temps de réponse (5 jours) sous réserve de plus amples résultats au lieu de 45 jours au champ, de 30 jours en serre et de 12 jours en salle conditionnée.
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Dejean, Sébastien. "Comparaison de procédures d'estimation dans le cadre des modèles non linéaires à paramètres aléatoires : application à la modélisation de l'évolution temporelle de l'indice de surface foliaire de cultures observées par télédétection spatiale." Toulouse 3, 2002. http://www.theses.fr/2002TOU30062.
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Dans le cadre de la télédétection spatiale pour l'agriculture, nous nous intéressons à l'estimation d'un modèle d'évolution de l'indice de surface foliaire d'une culture à partir d'images à haute résolution temporelle ; l'enjeu étant d'améliorer la prévision de rendement sur une région agricole. Les acquisitions d'images sont assimilables à des données longitudinales sur une population de pixels. Nous proposons une modélisation par paramètres aléatoires pour exprimer la variabilité inter-pixels et traiter l'ensemble des pixels simultanément. Nous présentons les expressions paramétriques et non paramétriques de la variabilité inter-pixels. Nous nous attachons au modèle paramétrique pour lequel nous passons en revue les méthodes d'estimation basées soit sur des régressions non linéaires par pixel soit sur la maximisation d'une approximation de la vraisemblance globale. .In the spatial remote sensing for agriculture framework, we deal with the estimation of a crop leaf area index evolution model from high temporal resolution images ; the scope of the work is the improvement of yield prediction over a large area. Regular measurements can be considered as longitudinal data of a population of pixels. We propose a random parameter modelling to express between-pixels variability and to deal with the whole pixels simultaneously. We present parametric and non parametric expressions of the between-pixels variability. We focus on the parametric model for which we review estimation methods based either on a per-pixel approach or on the maximization of an approximated global likelihood. .
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Van, Aarde John Benjamin. "Stereological estimation of surface area in MRI." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531787.
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Herrick, David Richard Mark. "Wavelet methods for curve and surface estimation." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310601.
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Viggh, Herbert E. M. "Surface Prior Information Reflectance Estimation (SPIRE) algorithms." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/17564.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 393-396).
In this thesis we address the problem of estimating changes in surface reflectance in hyperspectral image cubes, under unknown multiplicative and additive illumination noise. Rather than using the Empirical Line Method (ELM) or physics-based approaches, we assumed the presence of a prior reflectance image cube and ensembles of typical multiplicative and additive illumination noise vectors, and developed algorithms which estimate reflectance using this prior information. These algorithms were developed under the additional assumptions that the illumination effects were band limited to lower spatial frequencies and that the differences in the surface reflectance from the prior were small in area relative to the scene, and have defined edges. These new algorithms were named Surface Prior Information Reflectance Estimation (SPIRE) algorithms. Spatial SPIRE algorithms that employ spatial processing were developed for six cases defined by the presence or absence of the additive noise, and by whether or not the noise signals are spatially uniform or varying. These algorithms use high-pass spatial filtering to remove the noise effects. Spectral SPIRE algorithms that employ spectral processing were developed and use zero-padded Principal Components (PC) filtering to remove the illumination noise. Combined SPIRE algorithms that use both spatial and spectral processing were also developed. A Selective SPIRE technique that chooses between Combined and Spectral SPIRE reflectance estimates was developed; it maximizes estimation performance on both modified and unmodified pixels. The different SPIRE algorithms were tested on HYDICE airborne sensor hyperspectral data, and their reflectance estimates were compared to those from the physics-based ATmospheric REMoval (ATREM) and the Empirical Line Method atmospheric compensation algorithms. SPIRE algorithm performance was found to be nearly identical to the ELM ground-truth based results. SPIRE algorithms performed better than ATREM overall, and significantly better under high clouds and haze. Minimum-distance classification experiments demonstrated SPIRE's superior performance over both ATREM and ELM in cross-image supervised classification applications. The taxonomy of SPIRE algorithms was presented and suggestions were made concerning which SPIRE algorithm is recommended for various applications.
by Herbert Erik Mattias Viggh.
Ph.D.
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Shahnaz, Sabina. "Gas flux estimation from surface gas concentrations." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55073.
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A gradient-independent model of gas fluxes was formulated and tested. The
model is built on the relationship between gas flux and the time history of surface gas
concentration, known as half-order derivative (HOD), when the transport of the gas in the
boundary layer is described by a diffusion equation. The eddy-diffusivity of gas is
parameterized based on the similarity theory of boundary layer turbulence combined with
the MEP model of surface heat fluxes. Test of the new model using in-situ data of CO2
concentration and fluxes at several locations with diverse vegetation cover, geographic
and climatic conditions confirms its usefulness and potential for monitoring and
modeling greenhouse gases. The proposed model may also be used for estimating other
GHGS fluxes such as methane (CH4) and Water vapor flux. This proof-of-concept study
justifies the proposed model as a practical solution for monitoring and modeling global
GHGS budget over remote areas and oceans where ground observations of GHGS fluxes
are limited or non-existent. One focus of the on-going research is to investigate its
application to producing regional and global distributions of carbon fluxes for identifying
sinks and sources of carbon and re-evaluating the regional and global carbon budget at
monthly and annual time scales.
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KHOUJA, NABIL. "Contribution a l'etude de la mise en place de la surface foliaire du mais en relation avec la temperature." Paris 11, 1990. http://www.theses.fr/1990PA112379.
Full textAbstract:
Cette etude confirme certains resultats, comme par exemple: 1) la vitesse d'allongement est tres dependante de la temperature (1 a 4 mm/h soit 2,5 a 10 cm/jour) entre 14 et 22#oc; 2) la region meristematique est le site de perception de la temperature; 3) il existe des segments a allongement privilegie a l'interieur de la zone d'elongation. A temperature meristematique constante et basse (14#oc), l'analyse des variations residuelles de vitesse d'allongement montre que la vitesse d'allongement nocturne est d'autant plus faible que le numero d'ordre de la feuille est faible. Pour les feuilles d'ordre 10, il n'existe plus de differences jour/nuit. Ceci peut s'expliquer par une augmentation de l'offre en carbone liee a l'augmentation des surfaces foliaires qui permet de lever la limitation qui existe pour les premieres feuilles a basse temperature. L'analyse de la taille finale des limbes doit integrer les deux parametres explicatifs suivants: la duree et la vitesse d'allongement. Les longueurs finales sont egales en moyenne a 16 et 22#oc, sauf pour les 3 premieres feuilles. La duree d'allongement est une somme de temperatures fixe pour chaque numero de feuille. L'assimilation nette est peu affectee par les variations de temperature, alors que la vitesse d'allongement est fortement influencee par les fluctuations thermiques. L'offre en carbone, sauf dans des cas limites (basse temperature, premieres feuilles preformees) ne constitue pas un facteur limitant de la croissance: c'est generalement la demande foliaire, c'est-a-dire l'allongement, qui est limitant
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Estrada, Francisco J. "Estimation of surface orientation from a single image." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58772.pdf.
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Liu, Miaomiao, and 刘苗苗. "Pose estimation from reflections for specular surface recovery." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47246376.
Full textAbstract:
This thesis introduces novel methods for estimating the poses of a reference plane from its reflections for specular surface recovery. Traditional methods for specular surface recovery usually introduce a second camera and an auxiliary calibration pattern to calibrate the poses of the reference plane with respect to the camera. The calibration procedures are comparatively tedious. Auto-estimating the poses of the reference plane is therefore an appealing problem.
In the first part of this thesis, two novel and practical methods are proposed to recover the poses of a moving reference plane from its reflections produced on the specular surface given its initial position. As for the first approach, the reference plane is constrained to undergo an unknown pure translation. By observing the reflections of the moving reference plane produced on the specular surface, a closed form solution is derived for recovering the unknown translation. Degenerate cases in which the proposed method fails are studied. As for the second approach, the constraint on the motion of the reference plane is removed, and the reference plane can move freely. Again, a closed form solution is derived for the unknown motion defined by a rotation matrix and a translation vector, and the degenerate cases are also presented. The thesis finally considers the problem for auto-calibrating the reference plane against the camera for specular surface recovery without prior knowledge of the reference plane’s initial position. By only observing its reflections produced on the specular surface, the poses of the reference planes can be recovered in two steps. First, by applying a collinearity constraint to the specular correspondences, a simple closed form solution is derived for recovering the poses of the reference plane relative to its initial pose. Second, by applying a ray incidence constraint to the incident rays formed by the specular correspondences and the visual rays cast from the image, a closed form solution is derived for recovering the poses of the reference plane relative to the camera. The shape of the specular surface then follows.published_or_final_version
Computer Science
Doctoral
Doctor of Philosophy
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Bradley, Cecil D. "A statistical analysis of Surface Escort cost estimation/." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23407.
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This study investigates the relationship of the component weights of US Navy Surface Escort Ships and their corresponding costs of construction. The procedures of various US Navy agencies who conduct Surface Ship Costing are described, with emphasis upon the method followed by COMNAVSEASYSCOM, Washington D.C.. A statistical analysis is provided which focuses upon multiple linear regression techniques applied to the weight/cost relationship. Additionally, the research includes the investigation of non-weight explanatory variable contribution to the various regression models. The analysis concludes that linear relationships do exist between the variables. The statistical evidence provided suggests that linear regression provides equivalent results to non-linear logarithmic transformation of the dependent cost variable. Further, the analysis indicates that the inclusion of non-weight dummy variables, such as contract type for vessel construction, enhance models with strictly weight explanatory variables. The models developed herein lack the precision demanded of budgetary cost estimating. However, the equations will generate point estimates that may add credence to existing methods, especially within concept formulation or tradeoff studies. Keywords: Cost estimation, Surface ship cost estimation, Statistical analysis of ship costing, Theses. (SDW)
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Ekström, Marcus. "Road Surface Preview Estimation Using a Monocular Camera." Thesis, Linköpings universitet, Datorseende, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-151873.
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Recently, sensors such as radars and cameras have been widely used in automotives, especially in Advanced Driver-Assistance Systems (ADAS), to collect information about the vehicle's surroundings. Stereo cameras are very popular as they could be used passively to construct a 3D representation of the scene in front of the car. This allowed the development of several ADAS algorithms that need 3D information to perform their tasks. One interesting application is Road Surface Preview (RSP) where the task is to estimate the road height along the future path of the vehicle. An active suspension control unit can then use this information to regulate the suspension, improving driving comfort, extending the durabilitiy of the vehicle and warning the driver about potential risks on the road surface. Stereo cameras have been successfully used in RSP and have demonstrated very good performance. However, the main disadvantages of stereo cameras are their high production cost and high power consumption. This limits installing several ADAS features in economy-class vehicles. A less expensive alternative are monocular cameras which have a significantly lower cost and power consumption. Therefore, this thesis investigates the possibility of solving the Road Surface Preview task using a monocular camera. We try two different approaches: structure-from-motion and Convolutional Neural Networks.The proposed methods are evaluated against the stereo-based system. Experiments show that both structure-from-motion and CNNs have a good potential for solving the problem, but they are not yet reliable enough to be a complete solution to the RSP task and be used in an active suspension control unit.
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Osgood, Elizabeth. "Nonlinear surface approximation using photogammetry." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3314.
Full textAbstract:
Many satellite applications require a model that represents a surface as it deforms
over time. Yet, space applications demand a precise, low-weight, low-volume, and easy
to implement solution. A metrology sensing system is presented in this thesis, consisting
of a series of cameras and laser dot projectors positioned along the length of the antenna.
This system accurately models the geometry of the surface to meet the demands of a
space based radar. Each laser dot projector casts a matrix of points onto the antenna
surface. The points are then imaged simultaneously by a pair of cameras, each having a
different, but overlapping, viewpoint. Given the two overlapping images, a Gaussian
nonlinear least squares algorithm solves the stereo-triangulation problem which provides
the coordinates of the projected points and thereby maps the surface.
There are three different strategies discussed in this thesis. The first strategy
assumes the positions and orientations of the cameras are absolutely known. This
produces an extremely accurate result; yet it is unrealistic to assume absolute knowledge
of cameras locations and orientations for the application. The next strategy assumes the
positions and orientations of the cameras are completely unknown in addition to the
unknown surface. This program produces a less accurate, but more realistic, result
considering the dynamic nature of rigid structures in space. To increase the accuracy and
improve the robustness of these results, the third method employs a global metrology
sensing system to reduce the uncertainty in the location and orientation of the outboard
cameras relative to the center camera. This approach estimates the surface extremely accurately and, although more complex, offers advantages and addresses the desire for a
family of designs wherein higher accuracy is achievable by further optimization.
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Bateni, Sayed Mohyeddin. "Estimation of turbulent surface heat fluxes using sequences of remotely sensed land surface temperature." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66850.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 330-366).
Fluxes of heat and moisture at the land-surface play a significant role in the climate system. These fluxes interact with the overlying atmosphere and influence the characteristics of the planetary boundary layer (e.g. temperature and water vapor content), ultimately influencing the presence and growth of low level clouds and precipitation. Nevertheless, there is currently no network of in situ sensors that can map these fluxes globally. Recently a number of studies have focused on the estimation of surface energy flux components based on the assimilation of land surface temperature (LST) within a variational data assimilation (VDA) framework. This study provides the theoretical basis for why sequences of LST contain the necessary information to estimate surface fluxes with minimal reliance on ancillary data and empirical parameterizations. Furthermore this study addresses one of the main drawbacks of the existing VDA models. They use the simple force-restore equation for soil heat diffusion as a physical constraint. The force-restore equation provides a simplified description of the LST dynamics. Also, its performance is highly affected by the specification of a deep ground temperature. These shortcomings cause significant errors in the diurnal dynamics of heat diffusion in the soil and ultimately the retrieval of components of surface energy balance. This study advances the VDA scheme by using the full heat diffusion equation as a constraint in lieu of the forcerestore approximation. The new VDA scheme is tested over several experimental field sites. The results show that inclusion of the heat diffusion equation decreases the phase error associated with the ground heat flux diurnal cycle, and improves surface heat flux estimation. The VDA scheme is further advanced by incorporating model uncertainty in order to account for measurement and model errors. Tests indicate that the VDA scheme with model uncertainty captures measurement errors as well as structural model errors. In order to provide coupled estimates of surface heat fluxes and vegetation dynamics, remotely sensed LST and fraction of photosynthetically active radiation are assimilated into a surface energy balance and a vegetation dynamics model. The application of the assimilation over West Africa shows that the scheme provides reliable estimates of important vegetation dynamics parameters that are required for understanding the role of plant phenology on surface energy balance and vice-versa.
by Sayed Mohyeddin Bateni.
Ph.D.
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Ben, Khadhra Kais. "Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements." Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200801439.
Full textAbstract:
To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introducedAktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert
22
Mathur, Shailendra. "Edge localization in surface reconstruction using optimal estimation theory." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23750.
Full textAbstract:
In this thesis the problem of localizing discontinuities while smoothing noisy data is solved for the surface reconstruction method known as Curvature Consistency. In this algorithm, noisy initial estimates of surface patches are refined according to a continuity model, using a relaxation process. The interaction between neighbouring pixels in local neighbourhoods during relaxation is shown to be equivalent to a multiple measurement fusion process, where each pixel acts as a measurement source. Using optimal estimation theory as a basis, an adaptive weighting technique is developed to estimate interpolant surface patch parameters from neighbouring pixels. By applying the weighting process iteratively within local neighbourhoods, discontinuities are localized and a piecewise-continuous surface description is achieved. The resulting discontinuity localization algorithm is adaptive over different signal to noise ratios, robust over discontinuities of different scales and independent of user set parameters.
23
Laufenberg, Derek Paul. "Surface effectiveness estimation for control reconfiguration of impaired aircraft." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/39024.
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Miller, James Henry 1957. "Estimation of sea surface wave spectra using acoustic tomography." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/44595.
Full textAbstract:
Thesis (Sc. D.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 1987.Bibliography: p. 164-171.
Vita.
by James Henry Miller.
Sc.D.
25
Ben, Khadhra Kais. "Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements." Doctoral thesis, Deutsches Zentrum für Luft- und Raumfahrt e.V. in der Helmholtz-Gemeinschaft, 2007. https://monarch.qucosa.de/id/qucosa%3A18987.
Full textAbstract:
To date only very few bistatic measurements (airborne or in controlled laboratories) have been reported. Therefore most of the current remote sensing methods are still focused on monostatic (backscatter) measurements. These methods, based on theoretical, empirical or semi-empirical models, enable the estimation of soil roughness and the soil humidity (dielectric constant). For the bistatic case only theoretical methods have been developed and tested with monostatic data. Hence, there still remains a vital need to gain of experience and knowledge about bistatic methods and data. The main purpose of this thesis is to estimate the soil moisture and the soil roughness by using full polarimetric bistatic measurements. In the experimental part, bistatic X-band measurements, which have been recorded in the Bistatic Measurement Facility (BMF) at the DLR Oberpfaffenhofen, Microwaves and Radar Institute, will be presented. The bistatic measurement sets are composed of soils with different statistical roughness and different moistures controlled by a TDR (Time Domain Reflectivity) system. The BMF has been calibrated using the Isolated Antenna Calibration Technique (IACT). The validation of the calibration was achieved by measuring the reflectivity of fresh water. In the second part, bistatic surface scattering analyses of the calibrated data set were discussed. Then, the specular algorithm was used to estimate the soil moisture of two surface roughnesses (rough and smooth) has been reported. A new technique using the coherent term of the Integral Equation Method (IEM) to estimate the soil roughness was presented. Also, the sensitivity of phase and reflectivity with regard to moisture variation in the specular direction was evaluated. Finally, the first results and validations of bistatic radar polarimetry for the specular case of surface scattering have been introduced.Aktuell sind nur sehr wenige Messungen mit bistatischem Radar durchgeführt worden, sei es von Flugzeuggetragenen Systemen oder durch spezielle Aufbauten im Labor. Deshalb basieren die meisten der bekannten Methoden zur Fernerkundung mit Radar auf monostatis-chen Messungen der Rückstreuung des Radarsignals. Diese Methoden, die auf theoretischen, empirischen oder halb-empirischen Modellen basieren, ermöglichen die Schätzung der Oberfächenrauhigkeit und die Bodenfeuchtigkeit (Dielektrizitätskonstante). Im bistatischen Fall wurden bisher nur theoretische Modelle entworfen, die mittels monostatischer Messungen getestet wurden. Aus diesem Grund ist es von großer Bedeutung, Erfahrung und Wissen über die physikalischen Effekte in bistatischen Konfigurationen zu sammeln. Das Hauptziel der vorliegenden Dissertation ist es, anhand vollpolarimetrischer, bistatischer Radarmessungen die Oberfächenrauhigkeit und Bodenfeuchtigkeit zu bestimmen. Im experimentellen Teil der Arbeit werden die Ergebnisse bistatischer Messungen präsentiert, die in der Bistatic Measurement Facility (BMF) des DLR Oberpfaffenhofen aufgenommen wurden. Die Datensätze umfassen Messungen von Böden unterschiedlicher statistischer Rauhigkeit und Feuchtigkeit, die mittels eines Time Domain Reflectivity (TDR) Systems bestimmt werden. Zur Kalibration des BMF wurde die Isolated Antenna Calibration Technique (IACT) verwendet und anhand der Messung der Reflektivität von Wasser überprüft. Im zweiten Teil der vorliegenden Arbeit wird anhand der kalibrierten Daten eine Analyse der Oberflächenstreuung in bistatischen Konfigurationen vorgenommen. Im Anschluss daran wird mittels des Specular Algorithm eine Schätzung der Bodenfeuchte zweier Proben unter- schiedlicher Rauhigkeit (rau und fein) durchgeführt. Ein neues Verfahren zur Schätzung der Oberfächenrauhigkeit, das auf dem kohärenten Term der Integral Equation Method (IEM) basiert, wurde eingeführt. Daneben wird die Empfindlichkeit der Phase sowie der Reflektivität des vorwärtsgestreuten Signals gegenüber Veränderungen der Bodenfeuchtigkeit analysiert. Schließlich werden erste Ergebnisse und Validierungen bistatischer Radarpolarimetrie für den Fall der Vorwärtsstreuung präsentiert.
26
Bi, Yuyun. "Estimation of land surface evapotranspiration from remotely sensed data." Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/BI_Yuyun_2010.pdf.
Full textAbstract:
L’évapotranspiration (ET) joue un rôle important en hydrologie, météorologie et en agriculture et l’estimation précise de l’ET régionale à différentes échelles temporelles et spatiales est essentielle pour ces disciplines. La télédétection est identifiée comme le seul moyen rationnel de cartographier l’ET de la surface terrestre à l’échelle régionale de façon globale, cohérente et économiquement raisonnable. Cette thèse porte donc sur l’élaboration et la mise au point de méthodes permettant de déterminer l’ET régionale des surfaces terrestres à partir des données de l’instrument MODIS à bord des satellites polaires Terra et Aqua. Le travail de cette thèse a permis de montrer les atouts de la méthode de triangle Ts-VI par rapport aux autres méthodes traditionnellement utilisées pour la détermination de l’ET régionale et de proposer des méthodes permettant de calculer la température de surface et l’émissivité de surface à partir des luminances mesurées par les satellites. Cette thèse a montré également qu’il était possible d’estimer l’ET sur des régions arides et semi-arides à partir uniquement de données satellitaires et ce avec une précision acceptable. Elle ouvre des perspectives intéressantes. Dans la restitution de l’ET régionale, l'exactitude de cette restitution dépend principalement de l'exactitude de la détermination quantitative des limites sèche et humide dans le triangle Ts-VI et de la performance du modèle d'interpolation impliqué dans l'évaluation de la fraction évaporative. Les performances du modèle et du nouvel algorithme développé dans cette étude devront donc être évaluées de façon précise et avec attentionEvapotranspiration (ET) plays an important role in hydrology, meteorology, and agriculture. Accurate estimates of regional ET at different temporal and spatial scales are essential in these disciplines. Remote sensing technology is recognized as the only viable means to map regional- and meso-scale patterns of ET at the earth’s surface in a globally consistent and economically feasible manner and surface temperature helps to establish the direct link between surface radiances and the components of surface energy balance. This thesis thus concerns the methodological development permitting to determine the regional land surface ET from the MODIS data onboard the polar satellites Terra and Aqua. The work of this thesis showed the advantage of the Ts-VI triangle method compared to the other methods traditionally employed for the determination of the regional ET and proposed methods to calculate land surface temperature and emissivity from the radiances measured by the satellites. This thesis showed also that it was possible to estimate ET in arid and semi-arid areas only from the satellite data with an acceptable precision. This work opens interesting prospects. In the restitution of regional ET, the exactitude of this restitution depends mainly on the exactitude of the dry and wet edges determination in the Ts-VI triangle and on the performance of the interpolation model involved in the evaluation of the evaporative fraction in the ET estimation model. The performances of the model and the new algorithm developed in this study have to be evaluated in the future in a precise and attentive way
27
Riggins, Jamie N. "Location Estimation of Obstacles for an Autonomous Surface Vehicle." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33227.
Full textAbstract:
As the mission field for autonomous vehicles expands into a larger variety of territories, the development of autonomous surface vehicles (ASVs) becomes increasingly important. ASVs have the potential to travel for long periods of time in areas that cannot be reached by aerial, ground, or underwater autonomous vehicles. ASVs are useful for a variety of missions, including bathymetric mapping, communication with other autonomous vehicles, military reconnaissance and surveillance, and environmental data collecting.
Critical to an ASV's ability to maneuver without human intervention is its ability to detect obstacles, including the shoreline. Prior topological knowledge of the environment is not always available or, in dynamic environments, reliable. While many existing obstacle detection systems can only detect 3D obstacles at close range via a laser or radar signal, vision systems have the potential to detect obstacles both near and far, including "flat" obstacles such as the shoreline. The challenge lies in processing the images acquired by the vision system and extracting useful information. While this thesis does not address the issue of processing the images to locate the pixel positions of the obstacles, we assume that we have these processed images available. We present an algorithm that takes these processed images and, by incorporating the kinematic model of the ASV, maps the pixel locations of the obstacles into a global coordinate system. An Extended Kalman Filter is used to localize the ASV and the surrounding obstacles.Master of Science
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Bachalany, Yara. "Estimation du mouvement 3D d’une sphère de surface réfléchissante." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10142/document.
Full textAbstract:
Dans le cadre de cette thèse, nous proposons une solution au problème de l'estimation du mouvement 3D d'objets dont la surface est réfléchissante, lequel est très complexe quand leurs caractéristiques géométriques à elles seules ne permettent pas de définir des indices caractéristiques d'un mouvement. Nous avons focalisé notre étude sur le cas particulier de la sphère, dont la parfaite symétrie complique au maximum le problème d'estimation du mouvement.En effet, lorsqu'une sphère est affectée d'un mouvement de rotation pure autour d'un de ses axes, ses contours extérieurs apparaissent statiques. Ces derniersn'apportent donc pas d'information utilisable par le système pour estimer le mouvement. Nous proposons donc une approche se basant sur la texture dans un schéma de mise en correspondance 3D/2D modifié. Ici, cette information est exploitée différemment si elle provient d'une composante spéculaire ou diffuse.Enfin, nous démontrons que la propriété réfléchissante de la surface n'est plus considérée comme un obstacle mais que au contraire, cette propriété procure une information supplémentaire sur le mouvement recherchéRecovering 3D motion of reflective objects in image sequences is still a cumbersome problem for computer vision. One common approach is to track geometric features of the object such as contours and edges since they are rather insensitive to light reflections. However, such basic features fail to recover the actual 3D motion in some cases. For example, the external contour of a sphere rotating about one of its axes remains static in the image. In thisthesis, we propose a new approach to 3D motion recovery of a reflective sphere visible in an image sequence.Instead of tracking only geometric features, our technique makes use of texture information in a slightly modified image alignment method. Unlike in classical image alignment methods, texture information is processed differently whether it comes from a diffuse or a specular light component.Using this technique, we show that motion estimation is not only possible when dealing with reflective objects, but also that specular components can offer information about the 3D motion. Finally, we present some results obtained from the analysis of image sequences
29
Khadhra, Kais Ben. "Surface Parameter Estimation using Bistatic Polarimetric X-band Measurements." Oberpfaffenhofen [u.a.] : DLR, 2008. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016969697&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Kim, Hye-Yun. "Estimation of land surface radiation budget from MODIS data." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8577.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Geography. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
31
Love, Robert Charles. "Surface reflection model estimation from naturally illuminated image sequences." Thesis, University of Leeds, 1997. http://etheses.whiterose.ac.uk/1276/.
Full textAbstract:
This thesis addresses the problem of estimating the surface reflection model of objects observed in a terrestrial scene, illuminated by natural illumination; that is, a scene which is illuminated by sun and sky light alone. This is a departure from the traditional analysis of laboratory scenes, which are illuminated by idealised light sources with positions and radiance distributions that are precisely controlled. Natural illumination presents a complex hemispherical light source which changes in both spatial and spectral distribution with time, terrestrial location, and atmospheric conditions. An image-based approach to the measurement of surface reflection is presented. The use of a sequence of images, taken over a period of time, allows the varying reflection from the scene due to the changing natural illumination to be measured. It is shown that the temporal change in image pixel values is suitable for the parameters of a reflection model to be estimated. These parameters are estimated using regression techniques. Two such regression methods are considered: a traditional non-linear method and the probabilistic approach of simulated annealing. It is shown that simulated annealing provides consistent performance in this application. This work focuses on the use of physically-based models of illumination, surface reflection and camera response. Using such models allows the system to produce quantitative, as opposed to qualitative, results and allows radiometric measurements to be made from image pixel values. The use of accurate models of daylight illumination allows scenes illuminated by skies of varying atmospheric conditions to be considered. The results obtained by the presented methods may be used for a variety of tasks ranging from object recognition to the automated generation of virtual environments. Results are presented which show that the proposed method is suitable for the wide variety of camera positions, surface orientations and sky conditions that may be experienced. The method is also shown to be tolerant of image noise and may be used on single or multiple pixels within each image. These results are based on the analysis of synthetic image sequences generated using a validated lighting simulation system. Results are also presented for real data recorded using a camera.
32
De, Chiara Giovanna. "Satellite remote sensing for surface soil water content estimation." Doctoral thesis, Universita degli studi di Salerno, 2010. http://hdl.handle.net/10556/125.
Full textAbstract:
2008 - 2009Satellite remote sensing is a useful source of observations of land surface hydrologic variables and processes and could be a practical substitution of conventional in-situ monitoring. Most of hydrological dynamic processes change not only throughout the years but also within weeks or months and their monitoring requires frequent observations. The most prominent advantage of the remote sensing technologies is that they offer a synoptic view of the dynamics and spatial distribution of phenomena and parameters, often difficult to monitor with traditional ground survey, with a frequent temporal coverage. Many of the variables in the land surface water balance can now be observed with satellite techniques thanks to an extensive development over the last decades. Often the problem connected to the use of remotely sensed data is their accuracy that, according to the sensor used and to the application considered, can ranges from moderate to excellent. The objective of this thesis has been to evaluate the use of satellite remote sensing techniques for the monitoring of two variables useful for hydrology applications: water body extension and soil moisture monitoring. The capability to map water surface is important in many hydrological applications, in particular accurate information on the extent of water boundary is essential for flood monitoring and water reservoir management. Often, this information is difficult to retrieve using traditional survey techniques because water boundaries can be fast moving as in floods or may be inaccessible. In this PhD thesis, an artificial basin for which in-situ information about the water extension are available is used as case study. The area extension recorded daily by the dam owner is compared to the one retrieved by using satellite images acquired from SAR and TM/ETM+ sensors. The outcomes of the analysis show that satellite images are able to map water body surfaces with a good accuracy. The analysis also highlighted the factor to be taken into account while using types of sensors. Soil moisture is recognized as a key variable in different hydrological and ecological processes as it controls the exchange of water and heat energy between land surface and the atmosphere. Despite the high spatial variability of this parameter it has been demonstrated that many satellite sensors are able to retrieve soil moisture information of the surface layer at catchment scale. Among other sensors, the Scatterometer is very useful for climatic studies and modelling analysis thanks, respectively, to the temporal frequency, global coverage and to the long time series availability. Even though the ERS Scatterometer has been designed to measure the wind over the ocean surface, in recent years it has been pointed out that backscattering measurements have high potentiality for soil moisture retrieval. The second task of this PhD thesis, concerning the use of satellite data for soil moisture monitoring, has been developed at Serco S.p.A. in the framework of the Advanced Scatterometer Processing System (ASPS) project developed by ESA (European Space Agency) to reprocess the entire ERS Scatterometer mission. Since the beginning of the ERS-1 Scatterometer mission in 1991 a long dataset of C-band backscattering signal from the Earth surface is available for studies and researches. This is a very consistent dataset, but in particular for climatology studies it is important to have high quality and homogeneous long term observation as also stated in the key guidelines included in the Global Climate Observing System (GCOS) from the World Meteorological Organization (WMO). The main goal of this task has been the generation of the new Scatterometer ASPS products with improved data quality and spatial resolution. This achievement required a long preparation activity but represents an important contribution to the C-band Scatterometer dataset available to the scientific community. In order to evaluate the usage of the re-processed Scatterometer data for soil moisture estimation, the backscattering measurements derived in the new ASPS products have been then compared to in-situ volumetric soil moisture data and the relationship between radar backscattering and soil moisture measurements has been investigated under different conditions: angle of incidence, angle of azimuth, data measurements resolution, season of the year. Analysis results show that a relationship between the C-band backscattering coefficient and the in-situ volumetric soil moisture exists and takes into account the incidence and azimuth angles and the vegetation cover. [edited by author]
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Mukasa, Tomoyuki. "Mesoscopic Surface Characterization for Skeletal Kinematics Estimation from 3D Video." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202742.
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Gibson, David Riviere. "Model building and design augmentation for improved response surface estimation." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/32948.
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Dupigny-Giroux, Lesley-Ann. "Techniques for rainfall estimation and surface characterization over northern Brazil." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40345.
Full textAbstract:
The sertao of northeast Brazil is a semiarid region characterized by recurring droughts. The vastness of the area (650,000 km$ sp2)$ poses a challenge to the effective monitoring of the impacts of drought at a scale that would be useful to the inhabitants of the sertao. Remote sensing data provide a viable way of assessing the extent and nature of drought across the landscape.The work present a more effective algorithm to estimate rainfall from both the cold and warm cloud types present. Using a decision-tree methodology, the analysis yields rainfall estimates over the 0-21 mm range. Because seasonal variations in rainfall produce differences in vegetation, soils and hydrologic responses, Principal Components Analysis was used to examine these land surface responses. Individual components and component pairings were useful in identifying variations in vegetation density, geobotanical differences and drainage characteristics. The presence of cloud cover was found to dampen the land surface information that could be extracted. Landsat Thematic Mapper (TM) imagery was then used to produce a moisture index which characterizes surface wetness in relation to other features present in a scene. The multispectral combination of TM bands 1, 4 and 6 allowed for the separation of the surface types present, in locational space. This space was defined by an open-ended triange made up of a vertical "water line", a horizontal line of equal vegetation density; and a negatively-slopping iso-moisture line. The stability of the moisture index was influenced by varying scale and seasonal conditions.
In the drought conditions that prevailed in 1991-1992, these methods provide important additions to existing drought monitoring approaches in the Brazilian northeast. Further calibration is required in order to extend their applicability to other geographical regions and time frames.
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Park, ShinJu. "Water vapor estimation using near-surface radar refractivity during IHOP_2002." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81424.
Full textAbstract:
A ground-based radar refractivity mapping technique is used to measure water vapor near the surface during the International H2O Project in May and June, 2002 (IHOP_2002). Radar-measured refractivity is compared with refractivity estimated from surface station observations during this field experiment. Bias in radar and station refractivity is found to occur often when humidity is high. Possible reasons for this difference between radar and station observations are discussed. Most of the biases were associated either with inaccurate humidity observations by stations or with the small height difference of the two measurements. With confirming this last observation further during these wet ground conditions, radar refractivity shows much better agreement with radiosonde sounding refractivity just above the surface than with station refractivity.In addition, columnar water vapor is computed using the mixing ratios retrieved from radar and station refractivity and using the observed height of the convective boundary layer from a FM-CW radar. Surface moisture fluxes are computed as a residual of the columnar water vapor and compared with observations from flux-towers, which compute this using the eddy-covariance technique. Although the results show that the radar-based measurements may have some skill over longer time periods, the technique completely fails to reproduce observations over scales smaller than 1 hour.
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Walker, Don Gregory Jr. "Estimation of Unsteady Nonuniform Heating Rates from Surface Temperature Measurements." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/40387.
Full textAbstract:
Shock wave interactions such as those that occur during atmospheric
re-entry, can produce extreme thermal loads on aerospace structures.
These interactions are reproduced experimentally in hypersonic wind
tunnels to study how the flow structures relate to the deleterious
heat fluxes. In these studies, localized fluid jets created by shock
interactions impinge on a test cylinder, where the temperature due to
the heat flux is measured. These measurements are used to estimate the
heat flux on the surface as a result of the shock interactions. The
nature of the incident flux usually involves dynamic transients and
severe nonuniformities. Finding this boundary flux from discrete
unsteady temperature measurements is characterized by instabilities in
the solution. The purpose of this work is to evaluate existing
methodologies for the determination of the unsteady heat flux and to
introduce a new approach based on an inverse technique. The
performance of these methods was measured first in terms of accuracy
and their ability to handle inherently ``unstable'' or highly dynamic
data such as step fluxes and high frequency oscillating fluxes. Then
the method was expanded to estimate unsteady and nonuniform heat
fluxes. The inverse methods proved to be the most accurate
and stable of the methods examined, with the proposed method being
preferable.Ph. D.
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Malladi, Subrahmanya Sastry Venkata. "Modeling and Algorithm Performance For Seismic Surface Wave Velocity Estimation." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1194630399.
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Mukherjee, Nandini. "3-D deormable contour surface reconstruction an optimized estimation method /." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1078255615.
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Cooper, Daniel Ira. "Estimation of sensible heat flux from remotely sensed surface temperatures." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185151.
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A series of energy-balance experiments were performed over a winter wheat field in Southern Arizona. A Bowen ratio energy-balance system (BREB), anemometer, and thermal infrared thermometer (IRT) were placed in the center of the field on day 15 of 1988 shortly after germination. The BREB system generated 12-minute averages of net radiation, soil heat flux, latent energy, and sensible heat flux (H) throughout the season, terminating on day 152, just before harvest. On day 134, an eddy-correlation system was placed adjacent to the BREB system, where it collected H-data concurrently for 17 successive days. The data from the BREB and eddy-correlation systems were regressed against each other to quantify their field performance. The regression standard error (SE) between the two systems was ±40 W/m². BREB H-data was used as a "standard" to evaluate three different sensible heat flux models that are suitable for remote sensing applications. The three models require thermal canopy temperature, air temperature, and wind speed as input. Two of the three models use aerodynamic resistance theory, one of which is stability corrected, and the third remote-sensing model employs Monin-Obukhov turbulent transfer theory. The regression analysis between the BREB H-values and the three remote-sensing models shows that the stability corrected aerodynamic resistance model and the Monin-Obukhov model are capable of estimating H-values over a wide range of surface and atmospheric conditions.
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Wang, Wei. "Signal processing methods to improve ocean surface wave estimation from a high frequency surface wave radar." Thesis, University of Sheffield, 2011. http://etheses.whiterose.ac.uk/1996/.
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High frequency surface wave radars are operated as a remote sensor to measure ocean surface parameters to ranges exceeding 200-300 km from the coastline. The Bragg peaks in the power spectrum of backscattered radar electromagnetic signals from ocean waves reveal the Bragg resonant effect and the second order continuum reflect a hydrodynamic and electromagnetic modulation on the radio waves from the ocean waves. The power spectrum is thus utilized to invert the ocean wave directional spectrum by a non-linear integral equation. Further integrations of the ocean wave directional spectrum yield the estimates of wave parameters: significant waveheight, mean wave period, mean direction, directional spread, etc. Beside sea echoes, non-sea echoes or interferences (collectively termed ‘clutter'), are also received by radar antenna receivers and included in the power spectrum. Clutters which occupy the second order continuum are treated as sea echoes in the inverse algorithm and cause inaccurate estimation of the ocean wave directional spectrum. Thus clutter mitigation is the main purpose of this thesis and is intensively investigated. A three-step image processing approach is proposed in this thesis which could mitigate visible clutters, e.g. radio frequency interferences and ionospheric interferences, and also invisible clutters. The kernel implements a decomposition of the mixture space and then a projection of the mixture space into a desired subspace. In addition to this main approach, various signal processing methods are also investigated for improving the wave estimates, e.g. wavelet analysis, AR modeling, adaptive filtering algorithm. The clutter mitigation scheme is validated by operational use on a whole month of Pisces data and exhibits some improvements in the accuracy of wave estimates. To aid the operational use, a statistical pattern recognition method is also developed. Finally, the best schemes are chained together for a sequential operational use in terms of providing better wave estimation.
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Clerget, Benoît. "Le rôle du photopériodisme dans l'élaboration du rendement de trois variétés de sorgho cultivées en Afrique de l'Ouest." Phd thesis, INAPG (AgroParisTech), 2004. http://pastel.archives-ouvertes.fr/pastel-00001186.
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Résumé Le rôle du photopériodisme dans l'élaboration du rendement de trois variétés de sorgho cultivées en Afrique de l'Ouest Les sorghos d'Afrique de l'Ouest sont très photopériodiques parce que ce caractère leur confère un important avantage évolutif en raison du climat continental de la zone, caractérisé par de fortes variations inter-annuelles du régime pluviométrique. Cette adaptation doit être maintenue dans les variétés améliorées pour la région. Mais en dehors de la variation de la durée du cycle de la phase végétative, les réponses physiologiques à la photopériode ont été peu quantifiées chez les céréales chez lesquelles ce caractère a été contre-selectionné jusqu'à présent. Une étude écophysiologique a été conduite sur 3 variétés de sorgho représentatives du matériel cultivé en Afrique de l'Ouest afin de quantifier la physiologie du photopériodisme. Les expérimentations ont été réalisées en conditions naturelles à Samanko, Mali, pendant 2 années et demi. Plusieurs conclusions originales sur le développement et la croissance des sorghos photopériodiques ont pu être tirées, grâce en particulier aux réponses très marquées de la variété de race guinea, originaire de la région, dont les principales sont : - Le déclenchement de l'initiation paniculaire est sous la double dépendance de la photopériode et du sens de variation de la durée du jour ou de ses composantes, les heures de lever et de coucher du soleil. - Le rythme de production des feuilles par l'apex varie en relation avec la photopériode et ses variations quotidiennes au moment de la levée, durée ou heures de l'aurore et du crépuscule. Il conserve ensuite la valeur initialement acquise jusqu'à un brusque ralentissement aux environs de la date de production de la 23ème feuille, lorsque débute la montaison spontanée en l'absence d'initiation paniculaire. - Le déclenchement de l'élongation des entre-nœuds à cette date est probablement la conséquence de la rapide augmentation du LAI et par conséquent de la biosynthèse. Tous les autres rythmes de développement et de croissance ralentissent simultanément en raison de la concurrence trophique et des relations de coordination entre phytomères qui organisent la cohésion architecturale de la plante. - Lorsque plus de 23 feuilles sont produites la concurrence trophique entre organes est minimale et la répartition de la biomasse est pilotée par la demande potentielle de chacun d'eux. En revanche, en dessous de 23 feuilles la panicule est en concurrence avec la tige pendant son développement et une part de sa croissance. - La taille de la panicule est peu variable en raison de l'évolution antagoniste de la durée et de la vitesse de son développement sur lesquels la photopériode exerce une influence inverse. Un modèle de croissance synthétisant ces connaissances et hypothèses a été calibré et testé pour chacune des variétés. Son utilisation couplée aux connaissances physiologiques acquises permet de conclure à destination des équipes de sélection que le tallage et la réduction de taille ne sont probablement pas de bonnes voies vers l'amélioration du potentiel de rendement des sorghos photopériodiques. L'effort doit essentiellement porter sur la décorrélation de la relation qui lie actuellement la taille potentielle de la panicule à la date de floraison de la variété.
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Seiler, Santiago. "Surface XRF mapping for intraparticle heterogeneity assessment and particle grade estimation." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63812.
Full textAbstract:
Sensor-based sorting is perceived as a feasible solution for some of the most critical aspects of mineral processing. There are two basic classes of sensors, 1. those that measure a property characteristic of the bulk of a particle; and 2. those that measure a property of the surface of a particle. For the second class, the surface measurement is then correlated to the bulk property of interest. The correlation does not only depend on how well the sensors can analyze the surface, but also on how well the surface correlates to the volume of the rock. The correlation is even more complex since only part of the rock surface is scanned by an actual sorter. Thus, the heterogeneity within each particle, defined as intraparticle heterogeneity, is an important variable to be characterized.
The main objective of this work was to design and develop a method for rock surface mapping to assess intraparticle heterogeneity and to evaluate the correlation between surface grade and bulk grade for run of the mine or primary crushed rocks. The XRF mapping technique developed, and the procedure selected to analyze the mapping data, were described and applied to two porphyry copper ore samples.
According to an univariate statistical analysis, for the samples analyzed, copper and iron data distributions did not follow either normal or lognormal distribution. Median and median absolute deviation were proposed as the best parameters to summarize the surface grade and the intraparticle heterogeneity, respectively. The median value of the surface grade data showed the best correlation to the bulk grade of the rock for both elements.
For the copper ore used in this work, with mainly vein type mineralization, the one-dimensional heterogeneity assessment showed a high degree of intraparticle heterogeneity. This characteristic of the ore might generate poor reproducibility in the results of an XRF sorter when sensing only one face of each rock. The variogram was evaluated as a measure of heterogeneity in two dimensions. Two-color mapping method was selected to display the data collected in the XRF mapping for both samples analyzed.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
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Park, Shinju. "On the estimation of near-surface atmospheric refraction uing scanning radar." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94913.
Full textAbstract:
Near-surface atmospheric refraction, often characterized by the quantity refractivity, affects the propagation of the radar beam, yet it is poorly measured due to its complex pattern. The aim of this thesis is to characterize the structure of near-surface refractivity and its errors. The refractivity retrieval in the horizontal is obtained from the radar phase measurements that can be affected systematically by the variability of ground target heights over complex terrain coupled with propagation conditions. This study characterizes such factors statistically and reproduces the expected uncertainty (noisiness) by simulating phase for the assessment of the radar refractivity retrieval. However, the noisiness of simulated phase is much smaller compared with that of observations suggesting that such factors are incapable of characterizing moving ground targets and thus insufficient to fully explain the phase noisiness. The vertical structure of refractivity is, on the other hand, characterized in order to inform about low-level propagation conditions. The coverage of radar ground echo observed at low elevation angles is affected by the path of the radar beam determined with the vertical gradient of refractivity. Hence, this study simulates the coverage of ground targets with given vertical gradient of refractivity and compares it with the observed one. The best match between the simulation and observation is used to determine the radar estimate of refractivity changes in the vertical. The results are validated with the estimates from several sounding instruments. Although the identification of ground targets is required for better performance, this novel technique shows certain skill in extracting additional low-level atmospheric information out of radar measurements from ground targets. In both studies, the characterization of ground targets observed by radar plays a critical role: on one hand, it allows us to extract the structure of the near-ground refractivityPrès de la surface terrestre, la réfraction atmosphérique affecte la propagation des ondes radars. Cette caractéristique de l'atmosphère, qu'on nomme la réfractivité, est spatialement complexe et mal connue. Dans cette thèse, la structure de la réfractivité ainsi que ses erreurs sont caractérisés. La réfractivité est mesurée à partir du déphasage des échos radars provenant de cibles terrestres. Ce déphasage est une fonction de la complexité du terrain ainsi que des conditions de propagations. Ces deux facteurs sont analysés statistiquement afin de simuler l'incertitude attendue (le bruit) de la phase des échos radars affectant les mesures de réfractivité. Les simulations ainsi conduites possèdent un niveau de bruit sur la phase beaucoup plus petit que celui des mesures instrumentales. Cette observation suggère que le bruit sur la phase causé par le terrain et les conditions de propagation a un impact limité sur les mesures de réfractivité comparé au bruit provenant d'autres sources tel que les cibles mobiles. Dans un deuxième temps, la structure verticale de la réfractivité est étudiée afin de déduire les conditions de propagation en basse altitude. L'étendue des échos de sol observés à faibles élévations est affectée par la trajectoire des ondes radars qui à son tour est affectée par le gradient vertical de la réfractivité. Cette étude simule l'étendue des échos de sols en supposant différents gradients de réfractivité. Les gradients qui mènent à la meilleure ressemblance entre l'étendue des échos simulée et observée sont utilisés pour estimer les gradients réels de l'atmosphère. La validation des résultats est ensuite faite par comparaison avec d'autres instruments. Malgré le fait que les échos de sols doivent être identifiés pour une performance optimale, cette nouvelle technique démontre la possibilité d'inférer de nouvelles informations sur l'atmosphère en basse altitude à partir d'éch
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Lahlou, Mouncef. "Color-Based Surface Reflectance Separation for Scene Illumination Estimation and Rendering." FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/381.
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Given the importance of color processing in computer vision and computer graphics, estimating and rendering illumination spectral reflectance of image scenes is important to advance the capability of a large class of applications such as scene reconstruction, rendering, surface segmentation, object recognition, and reflectance estimation. Consequently, this dissertation proposes effective methods for reflection components separation and rendering in single scene images. Based on the dichromatic reflectance model, a novel decomposition technique, named the Mean-Shift Decomposition (MSD) method, is introduced to separate the specular from diffuse reflectance components. This technique provides a direct access to surface shape information through diffuse shading pixel isolation. More importantly, this process does not require any local color segmentation process, which differs from the traditional methods that operate by aggregating color information along each image plane.
Exploiting the merits of the MSD method, a scene illumination rendering technique is designed to estimate the relative contributing specular reflectance attributes of a scene image. The image feature subset targeted provides a direct access to the surface illumination information, while a newly introduced efficient rendering method reshapes the dynamic range distribution of the specular reflectance components over each image color channel. This image enhancement technique renders the scene illumination reflection effectively without altering the scene’s surface diffuse attributes contributing to realistic rendering effects.
As an ancillary contribution, an effective color constancy algorithm based on the dichromatic reflectance model was also developed. This algorithm selects image highlights in order to extract the prominent surface reflectance that reproduces the exact illumination chromaticity. This evaluation is presented using a novel voting scheme technique based on histogram analysis.
In each of the three main contributions, empirical evaluations were performed on synthetic and real-world image scenes taken from three different color image datasets. The experimental results show over 90% accuracy in illumination estimation contributing to near real world illumination rendering effects.
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Awadallah, Mahmoud Sobhy Tawfeek. "Image Analysis Techniques for LiDAR Point Cloud Segmentation and Surface Estimation." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73055.
Full textAbstract:
Light Detection And Ranging (LiDAR), as well as many other applications and sensors,
involve segmenting sparse sets of points (point clouds) for which point density is the only
discriminating feature. The segmentation of these point clouds is challenging for several
reasons, including the fact that the points are not associated with a regular grid. Moreover,
the presence of noise, particularly impulsive noise with varying density, can make it difficult
to obtain a good segmentation using traditional techniques, including the algorithms that
had been developed to process LiDAR data.
This dissertation introduces novel algorithms and frameworks based on statistical techniques
and image analysis in order to segment and extract surfaces from sparse noisy point clouds.
We introduce an adaptive method for mapping point clouds onto an image grid followed
by a contour detection approach that is based on an enhanced version of region-based Active Contours Without Edges (ACWE). We also proposed a noise reduction method using
Bayesian approach and incorporated it, along with other noise reduction approaches, into
a joint framework that produces robust results. We combined the aforementioned techniques with a statistical surface refinement method to introduce a novel framework to detect
ground and canopy surfaces in micropulse photon-counting LiDAR data. The algorithm is
fully automatic and uses no prior elevation or geographic information to extract surfaces.
Moreover, we propose a novel segmentation framework for noisy point clouds in the plane
based on a Markov random field (MRF) optimization that we call Point Cloud Densitybased Segmentation (PCDS). We also developed a large synthetic dataset of in plane point
clouds that includes either a set of randomly placed, sized and oriented primitive objects
(circle, rectangle and triangle) or an arbitrary shape that forms a simple approximation for
the LiDAR point clouds. The experiment performed on a large number of real LiDAR and
synthetic point clouds showed that our proposed frameworks and algorithms outperforms
the state-of-the-art algorithms in terms of segmentation accuracy and surface RMSE.Ph. D.
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Gedafa, Daba Shabara. "Estimation of remaining service life of flexible pavements from surface deflections." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/1026.
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KHOSRO, ANJOM FARBOD. "S-wave and P-wave velocity model estimation from surface waves." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2912984.
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Ozturk, Emre. "Estimation Of The Height Of Surface Breaking Cracks Using Ultrasonic Timing Methods." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607176/index.pdf.
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In this thesis, two ultrasonic timing methods are used in order to investigate the accuracy and reliability of measurements for surface breaking cracks having different orientations and heights. Also the best applicable measurement technique is searched by comparing the received test results. These methods are the Time of Flight Diffraction (TOFD) Method using diffraction of longitudinal waves and another method using the reflection of shear waves from the crack tips. In order to simulate and measure the height of surface breaking cracks three sets of test blocks from steel, and two sets of wedges from plexiglas material are manufactured. Also several probes having frequencies of 2Mhz, 4Mhz, 5Mhz and angles of 45o and 70o are used.
Some test procedures are created to make realistic comparisons between the test results and the ones found by previous studies in literature. The results are compared according to the standard deviations of errors in crack height
measurements and it is found that the depth, orientation of defects and the frequency of probes have considerable affect on the results. With wider probe angles and higher frequencies of probes to some extent the errors are observed
to be running low and the height of cracks could be measured closer to the original size. The amount of the errors is increased in measurements with the increasing angle of cracks. The results of both methods are found to be very
satisfactory. A range of ±0.5 mm for means of error from the original vertical crack heights is determined. The results agree with the previous studies.
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Li, Guilong. "Accurate estimation of standard errors in the global averaging of surface temperatures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60454.pdf.
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