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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Learning objects model and context for recognition and localisation / Apprentissage de modèles et contextes d'objets pour la reconnaissance et la localisation

Manfredi, Guido 18 September 2015 (has links)
Cette thèse traite des problèmes de modélisation, reconnaissance, localisation et utilisation du contexte pour la manipulation d'objets par un robot. Le processus de modélisation se divise en quatre composantes : le système réel, les données capteurs, les propriétés à reproduire et le modèle. En spécifiant chacune des ces composantes, il est possible de définir un processus de modélisation adapté au problème présent, la manipulation d'objets par un robot. Cette analyse mène à l'adoption des descripteurs de texture locaux pour la modélisation. La modélisation basée sur des descripteurs de texture locaux a été abordé dans de nombreux travaux traitant de structure par le mouvement (SfM) ou de cartographie et localisation simultanée (SLAM). Les méthodes existantes incluent Bundler, Roboearth et 123DCatch. Pourtant, aucune de ces méthodes n'a recueilli le consensus. En effet, l'implémentation d'une approche similaire montre que ces outils sont difficiles d'utilisation même pour des utilisateurs experts et qu'ils produisent des modèles d'une haute complexité. Cette complexité est utile pour fournir un modèle robuste aux variations de point de vue. Il existe deux façons pour un modèle d'être robuste : avec le paradigme des vues multiple ou celui des descripteurs forts. Dans le paradigme des vues multiples, le modèle est construit à partir d'un grand nombre de points de vue de l'objet. Le paradigme des descripteurs forts compte sur des descripteurs résistants aux changements de points de vue. Les expériences réalisées montrent que des descripteurs forts permettent d'utiliser un faible nombre de vues, ce qui résulte en un modèle simple. Ces modèles simples n'incluent pas tout les point de vus existants mais les angles morts peuvent être compensés par le fait que le robot est mobile et peut adopter plusieurs points de vue. En se basant sur des modèles simples, il est possible de définir des méthodes de modélisation basées sur des images seules, qui peuvent être récupérées depuis Internet. A titre d'illustration, à partir d'un nom de produit, il est possible de récupérer des manières totalement automatiques des images depuis des magasins en ligne et de modéliser puis localiser les objets désirés. Même avec une modélisation plus simple, dans des cas réel ou de nombreux objets doivent être pris en compte, il se pose des problèmes de stockage et traitement d'une telle masse de données. Cela se décompose en un problème de complexité, il faut traiter de nombreux modèles rapidement, et un problème d'ambiguïté, des modèles peuvent se ressembler. L'impact de ces deux problèmes peut être réduit en utilisant l'information contextuelle. Le contexte est toute information non issue des l'objet lui même et qui aide a la reconnaissance. Ici deux types de contexte sont abordés : le lieu et les objets environnants. Certains objets se trouvent dans certains endroits particuliers. En connaissant ces liens lieu/objet, il est possible de réduire la liste des objets candidats pouvant apparaître dans un lieu donné. Par ailleurs l'apprentissage du lien lieu/objet peut être fait automatiquement par un robot en modélisant puis explorant un environnement. L'information appris peut alors être fusionnée avec l'information visuelle courante pour améliorer la reconnaissance. Dans les cas des objets environnants, un objet peut souvent apparaître au cotés d'autres objets, par exemple une souris et un clavier. En connaissant la fréquence d'apparition d'un objet avec d'autres objets, il est possible de réduire la liste des candidats lors de la reconnaissance. L'utilisation d'un Réseau de Markov Logique est particulièrement adaptée à la fusion de ce type de données. Cette thèse montre la synergie de la robotique et du contexte pour la modélisation, reconnaissance et localisation d'objets. / This Thesis addresses the modeling, recognition, localization and use of context for objects manipulation by a robot. We start by presenting the modeling process and its components: the real system, the sensors' data, the properties to reproduce and the model. We show how, by specifying each of them, one can define a modeling process adapted to the problem at hand, namely object manipulation by a robot. This analysis leads us to the adoption of local textured descriptors for object modeling. Modeling with local textured descriptors is not a new concept, it is the subject of many Structure from Motion (SfM) or Simultaneous Localization and Mapping (SLAM) works. Existing methods include bundler, roboearth modeler and 123DCatch. Still, no method has gained widespread adoption. By implementing a similar approach, we show that they are hard to use even for expert users and produce highly complex models. Such complex techniques are necessary to guaranty the robustness of the model to view point change. There are two ways to handle the problem: the multiple views paradigm and the robust features paradigm. The multiple views paradigm advocate in favor of using a large number of views of the object. The robust feature paradigm relies on robust features able to resist large view point changes. We present a set of experiments to provide an insight into the right balance between both. By varying the number of views and using different features we show that small and fast models can provide robustness to view point changes up to bounded blind spots which can be handled by robotic means. We propose four different methods to build simple models from images only, with as little a priori information as possible. The first one applies to planar or piecewise planar objects and relies on homographies for localization. The second approach is applicable to objects with simple geometry, such as cylinders or spheres, but requires many measures on the object. The third method requires the use of a calibrated 3D sensor but no additional information. The fourth technique doesn't need a priori information at all. We apply this last method to autonomous grocery objects modeling. From images automatically retrieved from a grocery store website, we build a model which allows recognition and localization for tracking. Even using light models, real situations ask for numerous object models to be stored and processed. This poses the problems of complexity, processing multiple models quickly, and ambiguity, distinguishing similar objects. We propose to solve both problems by using contextual information. Contextual information is any information helping the recognition which is not directly provided by sensors. We focus on two contextual cues: the place and the surrounding objects. Some objects are mainly found in some particular places. By knowing the current place, one can restrict the number of possible identities for a given object. We propose a method to autonomously explore a previously labeled environment and establish a correspondence between objects and places. Then this information can be used in a cascade combining simple visual descriptors and context. This experiment shows that, for some objects, recognition can be achieved with as few as two simple features and the location as context. The objects surrounding a given object can also be used as context. Objects like a keyboard, a mouse and a monitor are often close together. We use qualitative spatial descriptors to describe the position of objects with respect to their neighbors. Using a Markov Logic Network, we learn patterns in objects disposition. This information can then be used to recognize an object when surrounding objects are already identified. This Thesis stresses the good match between robotics, context and objects recognition.
102

Using Structure-from-Motion Technology to Compare Coral Coverage on Restored vs. Unrestored Reefs

Rosing, Trina 17 June 2021 (has links)
No description available.
103

Mobilní aplikace pro 3D rekonstrukci / Mobile application for 3D reconstruction

Krátký, Martin January 2021 (has links)
The aim of this master thesis is to create mobile application for spatial reconstruction. Thesis describes image processing methods suitable for solving this problem. Available platforms for creating mobile application are described. The parameters of the measured scenes are defined. A mobile application containing the described methods is created. The application is tested by reconstruction of objects in different conditions.
104

Approches 2D/2D pour le SFM à partir d'un réseau de caméras asynchrones / 2D/2D approaches for SFM using an asynchronous multi-camera network

Mhiri, Rawia 14 December 2015 (has links)
Les systèmes d'aide à la conduite et les travaux concernant le véhicule autonome ont atteint une certaine maturité durant ces dernières aimées grâce à l'utilisation de technologies avancées. Une étape fondamentale pour ces systèmes porte sur l'estimation du mouvement et de la structure de l'environnement (Structure From Motion) pour accomplir plusieurs tâches, notamment la détection d'obstacles et de marquage routier, la localisation et la cartographie. Pour estimer leurs mouvements, de tels systèmes utilisent des capteurs relativement chers. Pour être commercialisés à grande échelle, il est alors nécessaire de développer des applications avec des dispositifs bas coûts. Dans cette optique, les systèmes de vision se révèlent une bonne alternative. Une nouvelle méthode basée sur des approches 2D/2D à partir d'un réseau de caméras asynchrones est présentée afin d'obtenir le déplacement et la structure 3D à l'échelle absolue en prenant soin d'estimer les facteurs d'échelle. La méthode proposée, appelée méthode des triangles, se base sur l'utilisation de trois images formant un triangle : deux images provenant de la même caméra et une image provenant d'une caméra voisine. L'algorithme admet trois hypothèses: les caméras partagent des champs de vue communs (deux à deux), la trajectoire entre deux images consécutives provenant d'une même caméra est approximée par un segment linéaire et les caméras sont calibrées. La connaissance de la calibration extrinsèque entre deux caméras combinée avec l'hypothèse de mouvement rectiligne du système, permet d'estimer les facteurs d'échelle absolue. La méthode proposée est précise et robuste pour les trajectoires rectilignes et présente des résultats satisfaisants pour les virages. Pour affiner l'estimation initiale, certaines erreurs dues aux imprécisions dans l'estimation des facteurs d'échelle sont améliorées par une méthode d'optimisation : un ajustement de faisceaux local appliqué uniquement sur les facteurs d'échelle absolue et sur les points 3D. L'approche présentée est validée sur des séquences de scènes routières réelles et évaluée par rapport à la vérité terrain obtenue par un GPS différentiel. Une application fondamentale dans les domaines d'aide à la conduite et de la conduite automatisée est la détection de la route et d'obstacles. Pour un système asynchrone, une première approche pour traiter cette application est présentée en se basant sur des cartes de disparité éparses. / Driver assistance systems and autonomous vehicles have reached a certain maturity in recent years through the use of advanced technologies. A fundamental step for these systems is the motion and the structure estimation (Structure From Motion) that accomplish several tasks, including the detection of obstacles and road marking, localisation and mapping. To estimate their movements, such systems use relatively expensive sensors. In order to market such systems on a large scale, it is necessary to develop applications with low cost devices. In this context, vision systems is a good alternative. A new method based on 2D/2D approaches from an asynchronous multi-camera network is presented to obtain the motion and the 3D structure at the absolute scale, focusing on estimating the scale factors. The proposed method, called Triangle Method, is based on the use of three images forming a. triangle shape: two images from the same camera and an image from a neighboring camera. The algorithrn has three assumptions: the cameras share common fields of view (two by two), the path between two consecutive images from a single camera is approximated by a line segment, and the cameras are calibrated. The extrinsic calibration between two cameras combined with the assumption of rectilinear motion of the system allows to estimate the absolute scale factors. The proposed method is accurate and robust for straight trajectories and present satisfactory results for curve trajectories. To refine the initial estimation, some en-ors due to the inaccuracies of the scale estimation are improved by an optimization method: a local bundle adjustment applied only on the absolute scale factors and the 3D points. The presented approach is validated on sequences of real road scenes, and evaluated with respect to the ground truth obtained through a differential GPS. Finally, another fundamental application in the fields of driver assistance and automated driving is road and obstacles detection. A method is presented for an asynchronous system based on sparse disparity maps
105

SfM-3DULC: Desarrollo y validación de un procedimiento fotogramétrico para el escaneo, medición, clasificación tisular y seguimiento clínico de úlceras cutáneas

Sánchez Jiménez, David 21 March 2022 (has links)
[ES] La Fotogrametría es una ciencia y tecnología que tiene utilidad médica creciente. Una aplicación médica destacable de la Fotogrametría es la medición de las úlceras de la piel. Las úlceras de la piel constituyen un problema médico y social importante: por su elevado coste económico, afectación de la salud y calidad de vida, frecuente cronicidad y complicaciones. La medición de la úlcera es necesaria y útil para el seguimiento clínico. La disminución de variables de tamaño de la úlcera indica su progresión hacia la cicatrización. Los procedimientos tradicionales de medición unidimensional y bidimensional, como la regla graduada y la planimetría con acetato, se siguen utilizando por su sencillez y comodidad de uso. Sin embargo, son invasivos y tienen inconvenientes técnicos, como inexactitud e imprecisión. Otros procedimientos de medición tridimensional (3D), como la inyección de líquido y los moldes de pasta, pueden tener, además, efectos adversos, como dolor, irritación o reacción alérgica. Algunos procedimientos sin contacto que utilizan técnicas de escaneo con luz estructurada o láser: 1/ necesitan dispositivos de escaneo específicos; 2/ no se ha demostrado su utilidad en la práctica clínica; 3/ tienen un coste elevado. Por otra parte, no hay un procedimiento de referencia (patrón oro) para la medición del volumen de las úlceras cutáneas. Una optimización de las técnicas utilizadas para la valoración objetiva de la evolución de las úlceras de la piel ayudaría a comparar la eficacia de los distintos tratamientos y seleccionar los más adecuados, así como predecir el tiempo de curación. Por todo lo anterior, se justifica el desarrollo de un procedimiento de medición de úlceras basado en una técnica fotogramétrica sin contacto, como la estereofotogrametría. El objetivo general de esta tesis es desarrollar un procedimiento fotogramétrico para el escaneo, medición, clasificación tisular y seguimiento clínico de úlceras cutáneas; y validar dicho procedimiento en un estudio clínico con pacientes, evaluando su fiabilidad y exactitud. El procedimiento SfM-3DULC está basado en las técnicas estereofotogramétricas SfM (Structure from Motion) y MVS (Multi View Stereo) y utiliza como software de escaneo Agisoft PhotoScan y como software de medición del modelo 3D el programa 3DULC, creado por los autores. Este procedimiento escanea y reconstruye un modelo digital 3D de la úlcera utilizando una cámara digital, con la que se adquieren una serie de fotografías desde varias localizaciones y orientaciones. Para la validación del procedimiento SfM-3DULC, se realizó un estudio piloto en el que se evaluó su fiabilidad y exactitud. También se propuso una nueva variante del procedimiento ImageJ, en la que se utiliza una ortofotografía (Ortho-ImageJ), para medir el área proyectada. Por último, se compararon las mediciones realizadas por un grupo de dermatólogos y otro grupo de no expertos. Todas las variables medidas por dermatólogos usando SfM-3DULC mostraron excelentes puntuaciones de fiabilidad intra-evaluador (ICC > 0.99) e inter-evaluador (ICC > 0.98). En conclusión, el software 3DULC desarrollado, en su versión 1.0: 1/ Interviene en la fase de medición de la úlcera cutánea, tras su escaneo. 2/ Es autónomo respecto al procedimiento de escaneo, y podría utilizarse junto a cualquier otra técnica que obtenga una nube de puntos de la úlcera cutánea. 3/ Detecta el contorno de la úlcera de forma asistida basándose en su respuesta espectral. 4/ Clasifica las zonas de la úlcera cutánea según su tipo de tejido utilizando un árbol de decisión. 5/ Mide las siguientes variables morfométricas de la úlcera cutánea: coeficiente de circularidad, coeficiente de lisura, longitud máxima, perímetro, profundidad máxima, área proyectada, área de la superficie excavada, área de la superficie de referencia y volumen. 6/ Presenta los resultados con un informe HTML que facilita la interpretación por personal sanitario. / [CA] La Fotogrametria és una ciència i tecnologia que té utilitat mèdica creixent. Una aplicació mèdica destacable de la Fotogrametria és el mesurament de les úlceres de la pell. Les úlceres de la pell constitueixen un problema mèdic i social important: pel seu elevat cost econòmic, afectació de la salut i qualitat de vida, freqüent cronicitat i complicacions. El mesurament de l'úlcera és necessària i útil per al seguiment clínic. La disminució de variables de mida de l'úlcera indica la seva progressió cap a la cicatrització. Els procediments tradicionals de mesurament unidimensional i bidimensional, com el regle graduat i la planimetria amb acetat, es continuen utilitzant per la seva senzillesa i comoditat d'ús. No obstant això, són invasius i tenen inconvenients tècnics, com inexactitud i imprecisió. Altres procediments de mesurament tridimensional (3D), com la injecció de líquid i els motles de pasta, poden tenir, a més, efectes adversos, com dolor, irritació o reaccions al·lèrgiques. Alguns procediments sense contacte que utilitzen tècniques d'escaneig amb llum estructurada o làser: 1 / necessiten dispositius d'escaneig específics; 2 / no s'ha demostrat la seva utilitat en la pràctica clínica; 3 / tenen un cost elevat. D'altra banda, no hi ha un procediment de referència (patró or) per al mesurament del volum de les úlceres cutànies. Una optimització de les tècniques utilitzades per a la valoració objectiva de l'evolució de les úlceres de la pell ajudaria a comparar l'eficàcia dels diferents tractaments i seleccionar els més adequats, així com predir el temps de curació. Per tot l'anterior, es justifica el desenvolupament d'un procediment de mesurament de úlceres basat en una tècnica fotogramètrica sense contacte, com la estereofotogrametría. L'objectiu general d'aquesta tesi és desenvolupar un procediment fotogramètric per a l'escaneig, mesurament, classificació tissular i seguiment clínic d'úlceres cutànies; i validar aquest procediment en un estudi clínic amb pacients, avaluant la seva fiabilitat i exactitud. El procediment SFM-3DULC està basat en les tècniques estereofotogramétricas SFM (Structure from Motion) i MVS (Multi View Stereo) i utilitza com a programari d'escaneig Agisoft PhotoScan i com a programari de mesurament de el model 3D el programa 3DULC, creat pels autors. Aquest procediment escaneja i reconstrueix un model digital 3D de l'úlcera utilitzant una càmera digital, amb la qual s'adquireixen una sèrie de fotografies des de diverses localitzacions i orientacions. Per a la validació de l'procediment SFM-3DULC, es va realitzar un estudi pilot en el qual es va avaluar la seva fiabilitat i exactitud. També es va proposar una nova variant del procediment ImageJ, en què s'utilitza una ortofotografia (Ortho-ImageJ), per mesurar l'àrea projectada. Finalment, es van comparar les mesures realitzades per un grup de dermatòlegs i un altre grup de no experts. Totes les variables mesures per dermatòlegs usant SFM-3DULC van mostrar excel·lents puntuacions de fiabilitat intra-avaluador (ICC> 0.99) i inter-avaluador (ICC> 0.98). En conclusió, el programari 3DULC desenvolupat, en la seva versió 1.0: 1 / Intervé en la fase de mesurament de l'úlcera cutània, després de la seva exploració. 2 / És autònom respecte a l'procediment d'escaneig, i podria utilitzar-costat de qualsevol altra tècnica que obtingui un núvol de punts de l'úlcera cutània. 3 / Detecta el contorn de l'úlcera de forma assistida basant-se en la seva resposta espectral. 4 / Classifica les zones de l'úlcera cutània segons el seu tipus de teixit utilitzant un arbre de decisió. 5 / Mesura les variables morfomètriques de l'úlcera cutània: coeficient de circularitat, coeficient de llisor, longitud màxima, perímetre, profunditat màxima, àrea projectada, àrea de la superfície excavada, àrea de la superfície de referència i volum. 6 / Presenta els resultats amb un informe HTML que facilita la interpretació per personal sanitari. / [EN] Photogrammetry is a science and technology of increasing medical utility. A notable medical application of photogrammetry is the measurement of skin ulcers. Skin ulcers are a major medical and social problem: due to their high economic cost, impact on health and quality of life, frequent chronicity and complications. Ulcer measurement is necessary and useful for the clinical follow-up. Decreasing ulcer size variables indicate progression towards healing. Traditional one- and two-dimensional measurement procedures, such as the graduated ruler and acetate planimetry, are still used because of their simplicity and ease of use. However, they are invasive and have technical drawbacks, such as inaccuracy and imprecision. Other three-dimensional (3D) measurement procedures, such as liquid injection and paste moulds, may also have adverse effects, such as pain, irritation or allergic reaction. Some non-contact procedures that use structured light or laser scanning techniques: 1/ require specific scanning devices; 2/ have not been demonstrated to be useful in clinical practice; 3/ are expensive. Moreover, there is no reference procedure (gold standard) for the measurement of skin ulcer volume. Optimisation of the techniques used for the objective assessment of the evolution of skin ulcers would help to compare the efficacy of different treatments and to select the most appropriate ones, as well as to predict healing time. Therefore, the development of an ulcer measurement procedure based on a non-contact photogrammetric technique, such as stereophotogrammetry, is justified. The main objective of this thesis is to develop a photogrammetric procedure for the scanning, measurement, tissue classification and clinical follow-up of skin ulcers; and to validate this procedure in a clinical study with patients, evaluating its reliability and accuracy. The SfM-3DULC procedure is based on the stereophotogrammetric techniques SfM (Structure from Motion) and MVS (Multi View Stereo) and uses Agisoft PhotoScan as scanning software and 3DULC as 3D model measurement software. This procedure scans and reconstructs a 3D digital model of the ulcer using a digital camera, which acquires photographs from various locations and orientations. In order to validate the SfM-3DULC procedure, a pilot study was conducted to assess its reliability and accuracy. A new variant of the ImageJ procedure was also proposed, in which an orthophotography (Ortho-ImageJ) is used to measure the projected area. Finally, measurements made by a group of dermatologists and a group of non-experts were compared. All the variables measured by dermatologists using SfM-3DULC showed excellent scores of intra-rater reliability (ICC > 0.99) and inter-rater reliability (ICC > 0.98). In conclusion, the 3DULC software developed, in its version 1.0: 1/ Is used to measure the skin ulcer, after its scan. 2/ Is autonomous with respect to the scanning procedure, and could be used with any other technique that obtains a point cloud of the skin ulcer. 3/ Outlines the edge of the ulcer semi-automatically, based on its spectral response. 4/ Classifies skin ulcer areas according to their tissue type, using a decision tree. 5/ Measures the following morphometric variables of the skin ulcer: circularity coefficient, evenness coefficient, maximum length, perimeter, maximum depth, projected area, surface area, reference surface area and volume. 6/ Presents the results with an HTML report that facilitates its interpretation by healthcare personnel. / Esta tesis doctoral fue financiada con una beca predoctoral de la Generalitat Valenciana – Consellería de Educación, Investigación, Cultura y Deporte, y el Fondo Social Europeo (ACIF/2018/160). / Sánchez Jiménez, D. (2022). SfM-3DULC: Desarrollo y validación de un procedimiento fotogramétrico para el escaneo, medición, clasificación tisular y seguimiento clínico de úlceras cutáneas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181691 / TESIS
106

Comparing Structure from Motion Photogrammetry and Computer Vision for Low-Cost 3D Cave Mapping: Tipton-Haynes Cave, Tennessee

Elmore, Clinton 01 August 2019 (has links)
Natural caves represent one of the most difficult environments to map with modern 3D technologies. In this study I tested two relatively new methods for 3D mapping in Tipton-Haynes Cave near Johnson City, Tennessee: Structure from Motion Photogrammetry and Computer Vision using Tango, an RGB-D (Red Green Blue and Depth) technology. Many different aspects of these two methods were analyzed with respect to the needs of average cave explorers. Major considerations were cost, time, accuracy, durability, simplicity, lighting setup, and drift. The 3D maps were compared to a conventional cave map drafted with measurements from a modern digital survey instrument called the DistoX2, a clinometer, and a measuring tape. Both 3D mapping methods worked, but photogrammetry proved to be too time consuming and laborious for capturing more than a few meters of passage. RGB-D was faster, more accurate, and showed promise for the future of low-cost 3D cave mapping.
107

Potentialities of Unmanned Aerial Vehicles in Hydraulic Modelling : Drone remote sensing through photogrammetry for 1D flow numerical modelling

Reali, Andrea January 2018 (has links)
In civil and environmental engineering numerous are the applications that require prior collection of data on the ground. When it comes to hydraulic modelling, valuable topographic and morphology features of the region are one of the most useful of them, yet often unavailable, expensive or difficult to obtain. In the last few years UAVs entered the scene of remote sensing tools used to deliver such information and their applications connected to various photo-analysis techniques have been tested in specific engineering fields, with promising results. The content of this thesis aims contribute to the growing literature on the topic, assessing the potentialities of UAV and SfM photogrammetry analysis in developing terrain elevation models to be used as input data for numerical flood modelling. This thesis covered all phases of the engineering process, from the survey to the implementation of a 1D hydraulic model based on the photogrammetry derived topography The area chosen for the study was the Limpopo river. The challenging environment of the Mozambican inland showed the great advantages of this technology, which allowed a precise and fast survey easily overcoming risks and difficulties. The test on the field was also useful to expose the current limits of the drone tool in its high susceptibility to weather conditions, wind and temperatures and the restricted battery capacity which did not allow flight longer than 20 minutes. The subsequent photogrammetry analysis showed a high degree of dependency on a number of ground control points and the need of laborious post-processing manipulations in order to obtain a reliable DEM and avoid the insurgence of dooming effects. It revealed, this way, the importance of understanding the drone and the photogrammetry software as a single instrument to deliver a quality DEM and consequently the importance of planning a survey photogrammetry-oriented by the adoption of specific precautions. Nevertheless, the DEM we produced presented a degree of spatial resolution comparable to the one high precision topography sources. Finally, considering four different topography sources (SRTM DEM 30 m, lidar DEM 1 m, drone DEM 0.6 m, total station&RTK bathymetric cross sections o.5 m) the relationship between spatial accuracy and water depth estimation was tested through 1D, steady flow models on HECRAS. The performances of each model were expressed in terms of mean absolute error (MAE) in water depth estimations of the considered model compared to the one based on the bathymetric cross-sections. The result confirmed the potentialities of the drone for hydraulic engineering applications, with MAE differences between lidar, bathymetry and drone included within 1 m. The calibration of SRTM, Lidar and Drone based models to the bathymetry one demonstrated the relationship between geometry detail and roughness of the cross-sections, with a global improvement in the MAE, but more pronounced for the coarse geometry of SRTM.
108

Registration and Localization of Unknown Moving Objects in Markerless Monocular SLAM

Troutman, Blake 05 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Simultaneous localization and mapping (SLAM) is a general device localization technique that uses realtime sensor measurements to develop a virtualization of the sensor's environment while also using this growing virtualization to determine the position and orientation of the sensor. This is useful for augmented reality (AR), in which a user looks through a head-mounted display (HMD) or viewfinder to see virtual components integrated into the real world. Visual SLAM (i.e., SLAM in which the sensor is an optical camera) is used in AR to determine the exact device/headset movement so that the virtual components can be accurately redrawn to the screen, matching the perceived motion of the world around the user as the user moves the device/headset. However, many potential AR applications may need access to more than device localization data in order to be useful; they may need to leverage environment data as well. Additionally, most SLAM solutions make the naive assumption that the environment surrounding the system is completely static (non-moving). Given these circumstances, it is clear that AR may benefit substantially from utilizing a SLAM solution that detects objects that move in the scene and ultimately provides localization data for each of these objects. This problem is known as the dynamic SLAM problem. Current attempts to address the dynamic SLAM problem often use machine learning to develop models that identify the parts of the camera image that belong to one of many classes of potentially-moving objects. The limitation with these approaches is that it is impractical to train models to identify every possible object that moves; additionally, some potentially-moving objects may be static in the scene, which these approaches often do not account for. Some other attempts to address the dynamic SLAM problem also localize the moving objects they detect, but these systems almost always rely on depth sensors or stereo camera configurations, which have significant limitations in real-world use cases. This dissertation presents a novel approach for registering and localizing unknown moving objects in the context of markerless, monocular, keyframe-based SLAM with no required prior information about object structure, appearance, or existence. This work also details a novel deep learning solution for determining SLAM map initialization suitability in structure-from-motion-based initialization approaches. This dissertation goes on to validate these approaches by implementing them in a markerless, monocular SLAM system called LUMO-SLAM, which is built from the ground up to demonstrate this approach to unknown moving object registration and localization. Results are collected for the LUMO-SLAM system, which address the accuracy of its camera localization estimates, the accuracy of its moving object localization estimates, and the consistency with which it registers moving objects in the scene. These results show that this solution to the dynamic SLAM problem, though it does not act as a practical solution for all use cases, has an ability to accurately register and localize unknown moving objects in such a way that makes it useful for some applications of AR without thwarting the system's ability to also perform accurate camera localization.
109

Structure from Motion with Unstructured RGBD Data

Svensson, Niclas January 2021 (has links)
This thesis covers the topic of depth- assisted Structure from Motion (SfM). When performing classic SfM, the goal is to reconstruct a 3D scene using only a set of unstructured RGB images. What is attempted to be achieved in this thesis is adding the depth dimension to the problem formulation, and consequently create a system that can receive a set of RGBD images. The problem has been addressed by modifying an already existing SfM pipeline and in particular, its Bundle Adjustment (BA) process. Comparisons between the modified framework and the baseline framework resulted in conclusions regarding the impact of the modifications. The results show mainly two things. First of all, the accuracy of the framework is increased in most situations. The difference is the most significant when the captured scene only is covered from a small sector. However, noisy data can cause the modified pipeline to decrease in performance. Secondly, the run time of the framework is significantly reduced. A discussion of how to modify other parts of the pipeline is covered in the conclusion of the report. / Följande examensarbete behandlar ämnet djupassisterad Struktur genom Rörelse (eng. SfM). Vid klassisk SfM är målet att återskapa en 3D scen, endast med hjälp av en sekvens av oordnade RGB bilder. I djupassiterad SfM adderas djupinformationen till problemformulering och följaktligen har ett system som kan motta RGBD bilder skapats. Problemet har lösts genom att modifiera en befintlig SfM- mjukvara och mer specifikt dess Buntjustering (eng. BA). Resultatet från den modifierade mjukvaran jämförs med resultatet av originalutgåvan för att dra slutsatser rådande modifikationens påverkan på prestandan. Resultaten visar huvudsakligen två saker. Först och främst, den modifierade mjukvaran producerar resultat med högre noggrannhet i de allra flesta fall. Skillnaden är som allra störst när bilderna är tagna från endast en liten sektor som omringar scenen. Data med brus kan dock försämra systemets prestanda aningen jämfört med orginalsystemet. För det andra, så minskar exekutionstiden betydligt. Slutligen diskuteras hur mjukvaran kan vidareutvecklas för att ytterligare förbättra resultaten.
110

Modeling Smooth Time-Trajectories for Camera and Deformable Shape in Structure from Motion with Occlusion

Gotardo, Paulo Fabiano Urnau 28 September 2010 (has links)
No description available.

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