57 research outputs found

    Integrating Vision and Physical Interaction for Discovery, Segmentation and Grasping of Unknown Objects

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    In dieser Arbeit werden Verfahren der Bildverarbeitung und die FĂ€higkeit humanoider Roboter, mit ihrer Umgebung physisch zu interagieren, in engem Zusammenspiel eingesetzt, um unbekannte Objekte zu identifizieren, sie vom Hintergrund und anderen Objekten zu trennen, und letztendlich zu greifen. Im Verlauf dieser interaktiven Exploration werden außerdem Eigenschaften des Objektes wie etwa sein Aussehen und seine Form ermittelt

    3D Multi-Field Multi-Scale Features From Range Data In Spacecraft Proximity Operations

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    A fundamental problem in spacecraft proximity operations is the determination of the 6 degree of freedom relative navigation solution between the observer reference frame and a reference frame tied to a proximal body. For the most unconstrained case, the proximal body may be uncontrolled, and the observer spacecraft has no a priori information on the body. A spacecraft in this scenario must simultaneously map the generally poorly known body being observed, and safely navigate relative to it. Simultaneous localization and mapping(SLAM)is a difficult problem which has been the focus of research in recent years. The most promising approaches extract local features in 2D or 3D measurements and track them in subsequent observations by means of matching a descriptor. These methods exist for both active sensors such as Light Detection and Ranging(LIDAR) or laser RADAR(LADAR), and passive sensors such as CCD and CMOS camera systems. This dissertation presents a method for fusing time of flight(ToF) range data inherent to scanning LIDAR systems with the passive light field measurements of optical systems, extracting features which exploit information from each sensor, and solving the unique SLAM problem inherent to spacecraft proximity operations. Scale Space analysis is extended to unstructured 3D point clouds by means of an approximation to the Laplace Beltrami operator which computes the scale space on a manifold embedded in 3D object space using Gaussian convolutions based on a geodesic distance weighting. The construction of the scale space is shown to be equivalent to both the application of the diffusion equation to the surface data, as well as the surface evolution process which results from mean curvature flow. Geometric features are localized in regions of high spatial curvature or large diffusion displacements at multiple scales. The extracted interest points are associated with a local multi-field descriptor constructed from measured data in the object space. Defining features in object space instead of image space is shown to bean important step making the simultaneous consideration of co-registered texture and the associated geometry possible. These descriptors known as Multi-Field Diffusion Flow Signatures encode the shape, and multi-texture information of local neighborhoods in textured range data. Multi-Field Diffusion Flow Signatures display utility in difficult space scenarios including high contrast and saturating lighting conditions, bland and repeating textures, as well as non-Lambertian surfaces. The effectiveness and utility of Multi-Field Multi-Scale(MFMS) Features described by Multi-Field Diffusion Flow Signatures is evaluated using real data from proximity operation experiments performed at the Land Air and Space Robotics(LASR) Laboratory at Texas A&M University

    Single and multiple stereo view navigation for planetary rovers

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    © Cranfield UniversityThis thesis deals with the challenge of autonomous navigation of the ExoMars rover. The absence of global positioning systems (GPS) in space, added to the limitations of wheel odometry makes autonomous navigation based on these two techniques - as done in the literature - an inviable solution and necessitates the use of other approaches. That, among other reasons, motivates this work to use solely visual data to solve the robot’s Egomotion problem. The homogeneity of Mars’ terrain makes the robustness of the low level image processing technique a critical requirement. In the first part of the thesis, novel solutions are presented to tackle this specific problem. Detection of robust features against illumination changes and unique matching and association of features is a sought after capability. A solution for robustness of features against illumination variation is proposed combining Harris corner detection together with moment image representation. Whereas the first provides a technique for efficient feature detection, the moment images add the necessary brightness invariance. Moreover, a bucketing strategy is used to guarantee that features are homogeneously distributed within the images. Then, the addition of local feature descriptors guarantees the unique identification of image cues. In the second part, reliable and precise motion estimation for the Mars’s robot is studied. A number of successful approaches are thoroughly analysed. Visual Simultaneous Localisation And Mapping (VSLAM) is investigated, proposing enhancements and integrating it with the robust feature methodology. Then, linear and nonlinear optimisation techniques are explored. Alternative photogrammetry reprojection concepts are tested. Lastly, data fusion techniques are proposed to deal with the integration of multiple stereo view data. Our robust visual scheme allows good feature repeatability. Because of this, dimensionality reduction of the feature data can be used without compromising the overall performance of the proposed solutions for motion estimation. Also, the developed Egomotion techniques have been extensively validated using both simulated and real data collected at ESA-ESTEC facilities. Multiple stereo view solutions for robot motion estimation are introduced, presenting interesting benefits. The obtained results prove the innovative methods presented here to be accurate and reliable approaches capable to solve the Egomotion problem in a Mars environment

    Removing Parallax-Induced False Changes in Change Detection

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    Accurate change detection (CD) results in urban environments is of interest to a diverse set of applications including military surveillance, environmental monitoring, and urban development. This work presents a hyperspectral CD (HSCD) framework. The framework uncovers the need for HSCD methods that resolve false change caused by image parallax. A Generalized Likelihood Ratio Test (GLRT) statistic for HSCD is developed that accommodates unknown mis-registration between imagery described by a prior probability density function for the spatial mis-registration. The potential of the derived method to incorporate more complex signal proccessing functions is demonstrated by the incorporation of a parallax error mitigation component. Results demonstrate that parallax mitigation reduces false alarms

    Study and Development of Techniques for 3D Dental Identification

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    Ph.DDOCTOR OF PHILOSOPH

    ModĂ©lisation tridimensionnelle prĂ©cise de l'environnement Ă  l’aide des systĂšmes de photogrammĂ©trie embarquĂ©s sur drones

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    Abstract : Images acquired from unmanned aerial vehicles (UAVs) can provide data with unprecedented spatial and temporal resolution for three-dimensional (3D) modeling. Solutions developed for this purpose are mainly operating based on photogrammetry concepts, namely UAV-Photogrammetry Systems (UAV-PS). Such systems are used in applications where both geospatial and visual information of the environment is required. These applications include, but are not limited to, natural resource management such as precision agriculture, military and police-related services such as traffic-law enforcement, precision engineering such as infrastructure inspection, and health services such as epidemic emergency management. UAV-photogrammetry systems can be differentiated based on their spatial characteristics in terms of accuracy and resolution. That is some applications, such as precision engineering, require high-resolution and high-accuracy information of the environment (e.g. 3D modeling with less than one centimeter accuracy and resolution). In other applications, lower levels of accuracy might be sufficient, (e.g. wildlife management needing few decimeters of resolution). However, even in those applications, the specific characteristics of UAV-PSs should be well considered in the steps of both system development and application in order to yield satisfying results. In this regard, this thesis presents a comprehensive review of the applications of unmanned aerial imagery, where the objective was to determine the challenges that remote-sensing applications of UAV systems currently face. This review also allowed recognizing the specific characteristics and requirements of UAV-PSs, which are mostly ignored or not thoroughly assessed in recent studies. Accordingly, the focus of the first part of this thesis is on exploring the methodological and experimental aspects of implementing a UAV-PS. The developed system was extensively evaluated for precise modeling of an open-pit gravel mine and performing volumetric-change measurements. This application was selected for two main reasons. Firstly, this case study provided a challenging environment for 3D modeling, in terms of scale changes, terrain relief variations as well as structure and texture diversities. Secondly, open-pit-mine monitoring demands high levels of accuracy, which justifies our efforts to improve the developed UAV-PS to its maximum capacities. The hardware of the system consisted of an electric-powered helicopter, a high-resolution digital camera, and an inertial navigation system. The software of the system included the in-house programs specifically designed for camera calibration, platform calibration, system integration, onboard data acquisition, flight planning and ground control point (GCP) detection. The detailed features of the system are discussed in the thesis, and solutions are proposed in order to enhance the system and its photogrammetric outputs. The accuracy of the results was evaluated under various mapping conditions, including direct georeferencing and indirect georeferencing with different numbers, distributions and types of ground control points. Additionally, the effects of imaging configuration and network stability on modeling accuracy were assessed. The second part of this thesis concentrates on improving the techniques of sparse and dense reconstruction. The proposed solutions are alternatives to traditional aerial photogrammetry techniques, properly adapted to specific characteristics of unmanned, low-altitude imagery. Firstly, a method was developed for robust sparse matching and epipolar-geometry estimation. The main achievement of this method was its capacity to handle a very high percentage of outliers (errors among corresponding points) with remarkable computational efficiency (compared to the state-of-the-art techniques). Secondly, a block bundle adjustment (BBA) strategy was proposed based on the integration of intrinsic camera calibration parameters as pseudo-observations to Gauss-Helmert model. The principal advantage of this strategy was controlling the adverse effect of unstable imaging networks and noisy image observations on the accuracy of self-calibration. The sparse implementation of this strategy was also performed, which allowed its application to data sets containing a lot of tie points. Finally, the concepts of intrinsic curves were revisited for dense stereo matching. The proposed technique could achieve a high level of accuracy and efficiency by searching only through a small fraction of the whole disparity search space as well as internally handling occlusions and matching ambiguities. These photogrammetric solutions were extensively tested using synthetic data, close-range images and the images acquired from the gravel-pit mine. Achieving absolute 3D mapping accuracy of 11±7 mm illustrated the success of this system for high-precision modeling of the environment.RĂ©sumĂ© : Les images acquises Ă  l’aide d’aĂ©ronefs sans pilote (ASP) permettent de produire des donnĂ©es de rĂ©solutions spatiales et temporelles uniques pour la modĂ©lisation tridimensionnelle (3D). Les solutions dĂ©veloppĂ©es pour ce secteur d’activitĂ© sont principalement basĂ©es sur des concepts de photogrammĂ©trie et peuvent ĂȘtre identifiĂ©es comme des systĂšmes photogrammĂ©triques embarquĂ©s sur aĂ©ronefs sans pilote (SP-ASP). Ils sont utilisĂ©s dans plusieurs applications environnementales oĂč l’information gĂ©ospatiale et visuelle est essentielle. Ces applications incluent notamment la gestion des ressources naturelles (ex. : agriculture de prĂ©cision), la sĂ©curitĂ© publique et militaire (ex. : gestion du trafic), les services d’ingĂ©nierie (ex. : inspection de bĂątiments) et les services de santĂ© publique (ex. : Ă©pidĂ©miologie et gestion des risques). Les SP-ASP peuvent ĂȘtre subdivisĂ©s en catĂ©gories selon les besoins en termes de prĂ©cision et de rĂ©solution. En effet, dans certains cas, tel qu’en ingĂ©nierie, l’information sur l’environnement doit ĂȘtre de haute prĂ©cision et de haute rĂ©solution (ex. : modĂ©lisation 3D avec une prĂ©cision et une rĂ©solution infĂ©rieure Ă  un centimĂštre). Pour d’autres applications, tel qu’en gestion de la faune sauvage, des niveaux de prĂ©cision et de rĂ©solution moindres peut ĂȘtre suffisants (ex. : rĂ©solution de l’ordre de quelques dĂ©cimĂštres). Cependant, mĂȘme dans ce type d’applications les caractĂ©ristiques des SP-ASP devraient ĂȘtre prises en considĂ©ration dans le dĂ©veloppement des systĂšmes et dans leur utilisation, et ce, pour atteindre les rĂ©sultats visĂ©s. À cet Ă©gard, cette thĂšse prĂ©sente une revue exhaustive des applications de l’imagerie aĂ©rienne acquise par ASP et de dĂ©terminer les challenges les plus courants. Cette Ă©tude a Ă©galement permis d’établir les caractĂ©ristiques et exigences spĂ©cifiques des SP-ASP qui sont gĂ©nĂ©ralement ignorĂ©es ou partiellement discutĂ©es dans les Ă©tudes rĂ©centes. En consĂ©quence, la premiĂšre partie de cette thĂšse traite des aspects mĂ©thodologiques et d’expĂ©rimentation de la mise en place d’un SP-ASP. Le systĂšme dĂ©veloppĂ© a Ă©tĂ© Ă©valuĂ© pour la modĂ©lisation prĂ©cise d’une graviĂšre et utilisĂ© pour rĂ©aliser des mesures de changement volumĂ©trique. Cette application a Ă©tĂ© retenue pour deux raisons principales. PremiĂšrement, ce type de milieu fournit un environnement difficile pour la modĂ©lisation, et ce, en termes de changement d’échelle, de changement de relief du terrain ainsi que la grande diversitĂ© de structures et de textures. DeuxiĂšment, le suivi de mines Ă  ciel ouvert exige un niveau de prĂ©cision Ă©levĂ©, ce qui justifie les efforts dĂ©ployĂ©s pour mettre au point un SP-ASP de haute prĂ©cision. Les composantes matĂ©rielles du systĂšme consistent en un ASP Ă  propulsion Ă©lectrique de type hĂ©licoptĂšre, d’une camĂ©ra numĂ©rique Ă  haute rĂ©solution ainsi qu’une station inertielle. La composante logicielle est composĂ©e de plusieurs programmes dĂ©veloppĂ©s particuliĂšrement pour calibrer la camĂ©ra et la plateforme, intĂ©grer les systĂšmes, enregistrer les donnĂ©es, planifier les paramĂštres de vol et dĂ©tecter automatiquement les points de contrĂŽle au sol. Les dĂ©tails complets du systĂšme sont abordĂ©s dans la thĂšse et des solutions sont proposĂ©es afin d’amĂ©liorer le systĂšme et la qualitĂ© des donnĂ©es photogrammĂ©triques produites. La prĂ©cision des rĂ©sultats a Ă©tĂ© Ă©valuĂ©e sous diverses conditions de cartographie, incluant le gĂ©orĂ©fĂ©rencement direct et indirect avec un nombre, une rĂ©partition et des types de points de contrĂŽle variĂ©s. De plus, les effets de la configuration des images et la stabilitĂ© du rĂ©seau sur la prĂ©cision de la modĂ©lisation ont Ă©tĂ© Ă©valuĂ©s. La deuxiĂšme partie de la thĂšse porte sur l’amĂ©lioration des techniques de reconstruction Ă©parse et dense. Les solutions proposĂ©es sont des alternatives aux techniques de photogrammĂ©trie aĂ©rienne traditionnelle et adaptĂ©e aux caractĂ©ristiques particuliĂšres de l’imagerie acquise Ă  basse altitude par ASP. Tout d’abord, une mĂ©thode robuste de correspondance Ă©parse et d’estimation de la gĂ©omĂ©trie Ă©pipolaire a Ă©tĂ© dĂ©veloppĂ©e. L’élĂ©ment clĂ© de cette mĂ©thode est sa capacitĂ© Ă  gĂ©rer le pourcentage trĂšs Ă©levĂ© des valeurs aberrantes (erreurs entre les points correspondants) avec une efficacitĂ© de calcul remarquable en comparaison avec les techniques usuelles. Ensuite, une stratĂ©gie d’ajustement de bloc basĂ©e sur l’intĂ©gration de pseudoobservations du modĂšle Gauss-Helmert a Ă©tĂ© proposĂ©e. Le principal avantage de cette stratĂ©gie consistait Ă  contrĂŽler les effets nĂ©gatifs du rĂ©seau d’images instable et des images bruitĂ©es sur la prĂ©cision de l’autocalibration. Une implĂ©mentation Ă©parse de cette stratĂ©gie a aussi Ă©tĂ© rĂ©alisĂ©e, ce qui a permis de traiter des jeux de donnĂ©es contenant des millions de points de liaison. Finalement, les concepts de courbes intrinsĂšques ont Ă©tĂ© revisitĂ©s pour l’appariement stĂ©rĂ©o dense. La technique proposĂ©e pourrait atteindre un haut niveau de prĂ©cision et d’efficacitĂ© en recherchant uniquement dans une petite portion de l’espace de recherche des disparitĂ©s ainsi qu’en traitant les occlusions et les ambigĂŒitĂ©s d’appariement. Ces solutions photogrammĂ©triques ont Ă©tĂ© largement testĂ©es Ă  l’aide de donnĂ©es synthĂ©tiques, d’images Ă  courte portĂ©e ainsi que celles acquises sur le site de la graviĂšre. Le systĂšme a dĂ©montrĂ© sa capacitĂ© a modĂ©lisation dense de l’environnement avec une trĂšs haute exactitude en atteignant une prĂ©cision 3D absolue de l’ordre de 11±7 mm

    Automatic Reconstruction of Urban Objects from Mobile Laser Scanner Data

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    Aktuelle 3D-Stadtmodelle werden immer wichtiger in verschiedenen stĂ€dtischen Anwendungsbereichen. Im Moment dienen sie als Grundlage bei der Stadtplanung, virtuellem Tourismus und Navigationssystemen. Mittlerweile ist der Bedarf an 3D-GebĂ€udemodellen dramatisch gestiegen. Der Grund dafĂŒr sind hauptsĂ€chlich Navigationssysteme und Onlinedienste wie Google Earth. Die Mehrheit der Untersuchungen zur Rekonstruktion von GebĂ€udemodellen von Luftaufnahmen konzentriert sich ausschließlich auf Dachmodellierung. Jedoch treiben Anwendungen wie Virtuelle RealitĂ€t und Navigationssysteme die Nachfrage nach detaillieren GebĂ€udemodellen, die nicht nur die geometrischen Aspekte sondern auch semantische Informationen beinhalten, stark an. Urbanisierung und Industrialisierung beeinflussen das Wachstum von urbaner Vegetation drastisch, welche als ein wesentlicher Teil des Lebensraums angesehen wird. Aus diesem Grund werden Aufgaben wie der ÖkosystemĂŒberwachung, der Verbesserung der Planung und des Managements von urbanen Regionen immer mehr Aufmerksamkeit geschenkt. Gleichermaßen hat die Erkennung und Modellierung von BĂ€umen im Stadtgebiet sowie die kontinuierliche ÜberprĂŒfung ihrer Inventurparameter an Bedeutung gewonnen. Die steigende Nachfrage nach 3D-GebĂ€udemodellen, welche durch Fassadeninformation ergĂ€nzt wurden, und Informationen ĂŒber einzelne BĂ€ume im stĂ€dtischen Raum erfordern effiziente Extraktions- und Rekonstruktionstechniken, die hochgradig automatisiert sind. In diesem Zusammenhang ist das Wissen ĂŒber die geometrische Form jedes Objektteils ein wichtiger Aspekt. Heutzutage, wird das Mobile Laser Scanning (MLS) vermehrt eingesetzt um Objekte im stĂ€dtischen Umfeld zu erfassen und es entwickelt sich zur Hauptquelle von Daten fĂŒr die Modellierung von urbanen Objekten. Eine Vielzahl von Objekten wurde schon mit Daten von MLS rekonstruiert. Außerdem wurden bereits viele Methoden fĂŒr die Verarbeitung von MLS-Daten mit dem Ziel urbane Objekte zu erkennen und zu rekonstruieren vorgeschlagen. Die 3D-Punkwolke einer stĂ€dtischen Szene stellt eine große Menge von Messungen dar, die viele Objekte von verschiedener GrĂ¶ĂŸe umfasst, komplexe und unvollstĂ€ndige Strukturen sowie Löcher (Rauschen und DatenlĂŒcken) enthĂ€lt und eine inhomogene Punktverteilung aufweist. Aus diesem Grund ist die Verarbeitung von MLS-Punktwolken im Hinblick auf die Extrahierung und Modellierung von wesentlichen und charakteristischen Fassadenstrukturen sowie BĂ€umen von großer Bedeutung. In der Arbeit werden zwei neue Methoden fĂŒr die Rekonstruktion von GebĂ€udefassaden und die Extraktion von BĂ€umen aus MLS-Punktwolken vorgestellt, sowie ihre Anwendbarkeit in der stĂ€dtischen Umgebung analysiert. Die erste Methode zielt auf die Rekonstruktion von GebĂ€udefassaden mit expliziter semantischer Information, wie beispielsweise Fenster, TĂŒren, und Balkone. Die Rekonstruktion lĂ€uft vollautomatisch ab. Zu diesem Zweck werden einige Algorithmen vorgestellt, die auf dem Vorwissen ĂŒber die geometrische Form und das Arrangement von Fassadenmerkmalen beruhen. Die initiale Klassifikation, mit welcher die Punkte in Objektpunkte und Bodenpunkte unterschieden werden, wird ĂŒber eine lokale Höhenhistogrammanalyse zusammen mit einer planaren Region-Growing-Methode erzielt. Die Punkte, die als zugehörig zu Objekten klassifiziert werden, werden anschließend in Ebenen segmentiert, welche als Basiselemente der Merkmalserkennung angesehen werden können. Information ĂŒber die GebĂ€udestruktur kann in Form von Regeln und Bedingungen erfasst werden, welche die wesentlichen Steuerelemente bei der Erkennung der Fassadenmerkmale und der Rekonstruktion des geometrischen Modells darstellen. Um Merkmale wie Fenster oder TĂŒren zu erkennen, die sich an der GebĂ€udewand befinden, wurde eine löcherbasierte Methode implementiert. Einige Löcher, die durch Verdeckungen entstanden sind, können anschließend durch einen neuen regelbasierten Algorithmus eliminiert werden. Außenlinien der MerkmalsrĂ€nder werden durch ein Polygon verbunden, welches das geometrische Modell reprĂ€sentiert, indem eine Methode angewendet wird, die auf geometrischen Primitiven basiert. Dabei werden die topologischen Relationen unter Beachtung des Vorwissens ĂŒber die primitiven Formen analysiert. Mögliche Außenlinien können von den Kantenpunkten bestimmt werden, welche mit einer winkelbasierten Methode detektiert werden können. Wiederkehrende Muster und Ähnlichkeiten werden ausgenutzt um geometrische und topologische Ungenauigkeiten des rekonstruierten Modells zu korrigieren. Neben der Entwicklung des Schemas zur Rekonstruktion des 3D-Fassadenmodells, sind die Segmentierung einzelner BĂ€ume und die Ableitung von Attributen der stĂ€dtischen BĂ€ume im Fokus der Untersuchung. Die zweite Methode zielt auf die Extraktion von individuellen BĂ€umen aus den Restpunktwolken. Vorwissen ĂŒber BĂ€ume, welches speziell auf urbane Regionen zugeschnitten ist, wird im Extraktionsprozess verwendet. Der formbasierte Ansatz zur Extraktion von EinzelbĂ€umen besteht aus einer Reihe von Schritten. In jedem Schritt werden Objekte in AbhĂ€ngigkeit ihrer geometrischen Merkmale gefunden. StĂ€mme werden unter Ausnutzung der Hauptrichtung der Punktverteilung identifiziert. DafĂŒr werden Punktsegmente gesucht, die einen Teil des Baumstamms reprĂ€sentieren. Das Ergebnis des Algorithmus sind segmentierte BĂ€ume, welche genutzt werden können um genaue Informationen ĂŒber die GrĂ¶ĂŸe und Position jedes einzelnen Baumes abzuleiten. Einige Beispiele der Ergebnisse werden in der Arbeit angefĂŒhrt. Die ZuverlĂ€ssigkeit der Algorithmen und der Methoden im Allgemeinen wurden unter Verwendung von drei DatensĂ€tzen, die mit verschiedenen Laserscannersystemen aufgenommen wurden, verifiziert. Die Untersuchung zeigt auch das Potential sowie die EinschrĂ€nkungen der entwickelten Methoden wenn sie auf verschiedenen DatensĂ€tzen angewendet werden. Die Ergebnisse beider Methoden wurden quantitativ bewertet unter Verwendung einer Menge von Maßen, die die QualitĂ€t der Fassadenrekonstruktion und Baumextraktion betreffen wie VollstĂ€ndigkeit und Genauigkeit. Die Genauigkeit der Fassadenrekonstruktion, der Baumstammdetektion, der Erfassung von Baumkronen, sowie ihre EinschrĂ€nkungen werden diskutiert. Die Ergebnisse zeigen, dass MLS-Punktwolken geeignet sind um stĂ€dtische Objekte detailreich zu dokumentieren und dass mit automatischen Rekonstruktionsmethoden genaue Messungen der wichtigsten Attribute der Objekte, wie Fensterhöhe und -breite, FlĂ€chen, Stammdurchmesser, Baumhöhe und KronenflĂ€che, erzielt werden können. Der gesamte Ansatz ist geeignet fĂŒr die Rekonstruktion von GebĂ€udefassaden und fĂŒr die korrekte Extraktion von BĂ€umen sowie ihre Unterscheidung zu anderen urbanen Objekten wie zum Beispiel Straßenschilder oder Leitpfosten. Aus diesem Grund sind die beiden Methoden angemessen um Daten von heterogener QualitĂ€t zu verarbeiten. Des Weiteren bieten sie flexible Frameworks fĂŒr das viele Erweiterungen vorstellbar sind.Up-to-date 3D urban models are becoming increasingly important in various urban application areas, such as urban planning, virtual tourism, and navigation systems. Many of these applications often demand the modelling of 3D buildings, enriched with façade information, and also single trees among other urban objects. Nowadays, Mobile Laser Scanning (MLS) technique is being progressively used to capture objects in urban settings, thus becoming a leading data source for the modelling of these two urban objects. The 3D point clouds of urban scenes consist of large amounts of data representing numerous objects with significant size variability, complex and incomplete structures, and holes (noise and data gaps) or variable point densities. For this reason, novel strategies on processing of mobile laser scanning point clouds, in terms of the extraction and modelling of salient façade structures and trees, are of vital importance. The present study proposes two new methods for the reconstruction of building façades and the extraction of trees from MLS point clouds. The first method aims at the reconstruction of building façades with explicit semantic information such as windows, doors and balconies. It runs automatically during all processing steps. For this purpose, several algorithms are introduced based on the general knowledge on the geometric shape and structural arrangement of façade features. The initial classification has been performed using a local height histogram analysis together with a planar growing method, which allows for classifying points as object and ground points. The point cloud that has been labelled as object points is segmented into planar surfaces that could be regarded as the main entity in the feature recognition process. Knowledge of the building structure is used to define rules and constraints, which provide essential guidance for recognizing façade features and reconstructing their geometric models. In order to recognise features on a wall such as windows and doors, a hole-based method is implemented. Some holes that resulted from occlusion could subsequently be eliminated by means of a new rule-based algorithm. Boundary segments of a feature are connected into a polygon representing the geometric model by introducing a primitive shape based method, in which topological relations are analysed taking into account the prior knowledge about the primitive shapes. Possible outlines are determined from the edge points detected from the angle-based method. The repetitive patterns and similarities are exploited to rectify geometrical and topological inaccuracies of the reconstructed models. Apart from developing the 3D façade model reconstruction scheme, the research focuses on individual tree segmentation and derivation of attributes of urban trees. The second method aims at extracting individual trees from the remaining point clouds. Knowledge about trees specially pertaining to urban areas is used in the process of tree extraction. An innovative shape based approach is developed to transfer this knowledge to machine language. The usage of principal direction for identifying stems is introduced, which consists of searching point segments representing a tree stem. The output of the algorithm is, segmented individual trees that can be used to derive accurate information about the size and locations of each individual tree. The reliability of the two methods is verified against three different data sets obtained from different laser scanner systems. The results of both methods are quantitatively evaluated using a set of measures pertaining to the quality of the façade reconstruction and tree extraction. The performance of the developed algorithms referring to the façade reconstruction, tree stem detection and the delineation of individual tree crowns as well as their limitations are discussed. The results show that MLS point clouds are suited to document urban objects rich in details. From the obtained results, accurate measurements of the most important attributes relevant to the both objects (building façades and trees), such as window height and width, area, stem diameter, tree height, and crown area are obtained acceptably. The entire approach is suitable for the reconstruction of building façades and for the extracting trees correctly from other various urban objects, especially pole-like objects. Therefore, both methods are feasible to cope with data of heterogeneous quality. In addition, they provide flexible frameworks, from which many extensions can be envisioned

    Image Registration Workshop Proceedings

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    Automatic image registration has often been considered as a preliminary step for higher-level processing, such as object recognition or data fusion. But with the unprecedented amounts of data which are being and will continue to be generated by newly developed sensors, the very topic of automatic image registration has become and important research topic. This workshop presents a collection of very high quality work which has been grouped in four main areas: (1) theoretical aspects of image registration; (2) applications to satellite imagery; (3) applications to medical imagery; and (4) image registration for computer vision research

    Raum-Zeit Interpolationstechniken

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    The photo-realistic modeling and animation of complex scenes in 3D requires a lot of work and skill of artists even with modern acquisition techniques. This is especially true if the rendering should additionally be performed in real-time. In this thesis we follow another direction in computer graphics to generate photo-realistic results based on recorded video sequences of one or multiple cameras. We propose several methods to handle scenes showing natural phenomena and also multi-view footage of general complex 3D scenes. In contrast to other approaches, we make use of relaxed geometric constraints and focus especially on image properties important to create perceptually plausible in-between images. The results are novel photo-realistic video sequences rendered in real-time allowing for interactive manipulation or to interactively explore novel view and time points.Das Modellieren und die Animation von 3D Szenen in fotorealistischer QualitĂ€t ist sehr arbeitsaufwĂ€ndig, auch wenn moderne Verfahren benutzt werden. Wenn die Bilder in Echtzeit berechnet werden sollen ist diese Aufgabe um so schwieriger zu lösen. In dieser Dissertation verfolgen wir einen alternativen Ansatz der Computergrafik, um neue photorealistische Ergebnisse aus einer oder mehreren aufgenommenen Videosequenzen zu gewinnen. Es werden mehrere Methoden entwickelt die fĂŒr natĂŒrlicher PhĂ€nomene und fĂŒr generelle Szenen einsetzbar sind. Im Unterschied zu anderen Verfahren nutzen wir abgeschwĂ€chte geometrische EinschrĂ€nkungen und berechnen eine genaue Lösung nur dort wo sie wichtig fĂŒr die menschliche Wahrnehmung ist. Die Ergebnisse sind neue fotorealistische Videosequenzen, die in Echtzeit berechnet und interaktiv manipuliert, oder in denen neue Blick- und Zeitpunkte der Szenen frei erkundet werden können

    Recent Advances in Indoor Localization Systems and Technologies

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    Despite the enormous technical progress seen in the past few years, the maturity of indoor localization technologies has not yet reached the level of GNSS solutions. The 23 selected papers in this book present the recent advances and new developments in indoor localization systems and technologies, propose novel or improved methods with increased performance, provide insight into various aspects of quality control, and also introduce some unorthodox positioning methods
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