1,524 research outputs found

    Calibration Wizard: A Guidance System for Camera Calibration Based on Modelling Geometric and Corner Uncertainty

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    It is well known that the accuracy of a calibration depends strongly on the choice of camera poses from which images of a calibration object are acquired. We present a system -- Calibration Wizard -- that interactively guides a user towards taking optimal calibration images. For each new image to be taken, the system computes, from all previously acquired images, the pose that leads to the globally maximum reduction of expected uncertainty on intrinsic parameters and then guides the user towards that pose. We also show how to incorporate uncertainty in corner point position in a novel principled manner, for both, calibration and computation of the next best pose. Synthetic and real-world experiments are performed to demonstrate the effectiveness of Calibration Wizard.Comment: Oral presentation at ICCV 201

    Is the minimum value of an option on variance generated by local volatility?

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    We discuss the possibility of obtaining model-free bounds on volatility derivatives, given present market data in the form of a calibrated local volatility model. A counter-example to a wide-spread conjecture is given

    Linear extensions and order-preserving poset partitions

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    We examine the lattice of all order congruences of a finite poset from the viewpoint of combinatorial algebraic topology. We will prove that the order complex of the lattice of all nontrivial order congruences (or order-preserving partitions) of a finite nn-element poset PP with n≄3n\geq 3 is homotopy equivalent to a wedge of spheres of dimension n−3n-3. If PP is connected, then the number of spheres is equal to the number of linear extensions of PP. In general, the number of spheres is equal to the number of cyclic extensions of PP

    Zum Stellenwert von Raumwissen und Wissensraum im Rahmen einer archÀologischen Analyse alltÀglichen Handelns

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    Dieser Beitrag hat zum Ziel, die Tauglichkeit der Begriffe Raumwissen und Wissensraum als analytische Kategorien der historisch-archĂ€ologischen Forschung zu ĂŒberprĂŒfen. Vor dem Hintergrund einer praxistheoretischen Perspektive wird diskutiert, wie sich Raumwissen und Wissensraum in die archĂ€ologische Analyse alltĂ€glichen Handelns einbetten lassen. Den Ausgangspunkt bildet Pierre Bourdieus Konzept des Habitus. Um dessen vergleichsweise statischen Charakter zu dynamisieren, wird das Eigensinn- Konzept des Alltagshistorikers Alf LĂŒdtke herangezogen. Durch die Eingliederung von Eigensinn in den Habitus entsteht eine theoretische Konzeption, die fĂŒr die archĂ€ologische Untersuchung alltĂ€glicher Praxis gut geeignet ist. Dazu wird ein methodischer Zugang illustriert. Schließlich wird geklĂ€rt, welcher Stellenwert Raumwissen und Wissensraum in diesem Rahmen zukommenkann

    Productivity impacts of infrastructure investment in the Netherlands 1853-1913

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    The paper considers a (static) portfolio system that satisfies adding-up contraints and the gross substitution theorem. The paper shows the relationship of the two conditions to the weak dominant diagonal property of the matrix of interest rate elasticities. This enables to investigate the impact of simultaneous changes in interest rates on the asset demands.

    International Comparison of the Sources of Productivity Slowdown 1973 1982

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    This paper uses an integrated model of aggregate supply to analyze the post-1973 slowdown in productivity growth in the seven major OECD economies. Factor substitution, unexpected demand changes, profitability, and inventory disequilibrium all contribute to the explanation, which is based on a three-factor nested aggregate production function, including energy, and postulating Harrod-neutral disembodied technical progress. The model is first applied separately to the seven countries assuming constant (though country-specific) rates of technical progress. This model provides empirical evidence that this rate of progress has in fact slowed down for several of the faster-growing countries, even after adjusting for factor substitution and cyclical factors. The model is therefore re-estimated, and the sources of productivity decline recalculated, on the hypothesis that rates of efficiency growth in other countries are converging to those in the United States.

    Output responses to infrastructure investment in the Netherlands, 1850-1913

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    This paper combines a new historical data set regarding capital formation in infrastructure in the Netherlands in the nineteenth century with data-oriented econometric techniques aimed at testing the causal relationship between these infrastructural investments and economic growth. The resulting vector autoregression (VAR) model is analysed further with impulse response analysis. The results show that the time series characteristics of both capital formation and GDP are trend stationary, which is a fundamental difference with their twentieth century counterparts. The paper finds strong evidence of both a long term and medium term or short term impact. In the short run positive expenditure effects are partly offset bu negative transitional dynamics. To fine tune the analysis we have exploited the possibility to disaggregate the data set in basic and complementary infrastructure investment. Whereas the effect on output is significantly positive for basic infrastructure investment, it is absent for complementary infrastructure investment.

    A Minimalist Approach to Type-Agnostic Detection of Quadrics in Point Clouds

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    This paper proposes a segmentation-free, automatic and efficient procedure to detect general geometric quadric forms in point clouds, where clutter and occlusions are inevitable. Our everyday world is dominated by man-made objects which are designed using 3D primitives (such as planes, cones, spheres, cylinders, etc.). These objects are also omnipresent in industrial environments. This gives rise to the possibility of abstracting 3D scenes through primitives, thereby positions these geometric forms as an integral part of perception and high level 3D scene understanding. As opposed to state-of-the-art, where a tailored algorithm treats each primitive type separately, we propose to encapsulate all types in a single robust detection procedure. At the center of our approach lies a closed form 3D quadric fit, operating in both primal & dual spaces and requiring as low as 4 oriented-points. Around this fit, we design a novel, local null-space voting strategy to reduce the 4-point case to 3. Voting is coupled with the famous RANSAC and makes our algorithm orders of magnitude faster than its conventional counterparts. This is the first method capable of performing a generic cross-type multi-object primitive detection in difficult scenes. Results on synthetic and real datasets support the validity of our method.Comment: Accepted for publication at CVPR 201

    Calculating indices for urban sprawl

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    Urban sprawl is a complex concept, that is generally associated with auto-oriented, low-density development. It is the subject of a wide range of research efforts, aiming at understanding and characterizing the underlying driving factors. This report follows an effort by Burchfield et al. who proposed in [burchfield06] a simple measure for urban sprawl, a so-called sprawl index. It proposes variants of this index and describes their implementation using the R statistical computation environment, the Geospatial Data Abstraction Library and the Quantum GIS (Geographic Information System).L'étalement urbain est un concept complexe qui est généralement associé à un développement de faible densité et basé sur l'automobile. Il fait l'objet de beaucoup de recherches ayant pour but la compréhension et la caractérisation des facteurs sous-jacents. Ce rapport suit un travail par Burchfield et al. qui ont proposé, dans [burchfield06], une mesure simple pour l'étalement urbain, appelé indexe d'étalement. Nous proposons des variantes pour cet indexe et décrivons leur implémentation utilisant l'environnement de calcul statistique R, la Geospatial Data Abstraction Library et le SIG (SystÚme d'Information Géographique) Quantum

    Methods and Geometry for Plane-Based Self-Calibration

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    International audienceWe consider the problem of camera self-calibration from images of a planar object with unknown Euclidean structure. The general case of possibly varying focal length is addressed. This problem is nonlinear in general. One of our contributions is a nonlinear approach that makes abstraction of the (possibly varying) focal length, resulting in a computationally efficient algorithm. In addition, it does not require a good initial estimate of the focal length, unlike previous approaches. As for the initialization of other parameters, we propose a practical approach that simply requires taking one image in roughly fronto-parallel position. Closed-form solutions for various configurations of unknown intrinsic parameters are provided. Our methods are evaluated and compared to previous approaches using simulated and real images. Besides our practical contributions, we also provide a detailed geometrical interpretation of the principles underlying our approach
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