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    ABSTRACT: Correlation matching has been widely accepted as a rudimentary similarity measure to obtain dense 3D reconstruction from a stereo pair. In particular, given a large overlapping area between images with minimal scale differences, the correlation results followed by a geometrically constrained global optimisation delivers adequately dense and accurate reconstruction results. In order to achieve greater reliability, however, correlation matching should correctly account for the geometrical distortion introduced by the different viewing angles of the stereo or multi-view sensors. Conventional adaptive least squares correlation (ALSC) matching addresses this by modifying the shape of a matching window iteratively, assuming that the distortion can be approximated by an affine transform. Nevertheless, since an image captured from different viewing angle is often not practically identical due to scene occlusions, the matching confidence normally deteriorates. Subsequently, it affects the density of the reconstruction results from ALSC-based stereo region growing algorithms. To address this, we propose an advanced ALSC matching method that can progressively update matching weight for each pixel in an aggregating window using a relaxation labelling technique. The experimental results show that the proposed method can improve matching performance, which consequently enhances the quality of stereo reconstruction. Also, the results demonstrate its ability to refine a scale invariant conjugate point pair to an affine and scale invariant point pair.
    No preview · Article · Oct 2012 · Pattern Recognition
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    ABSTRACT: Commission V, WG V/4 ABSTRACT: GOTCHA is a well-tried and tested stereo region growing algorithm, which iteratively applies Adaptive Least Square Correlation (ALSC) matching to the adjacent neighbours of a seed point in order to achieve a dense reconstruction with sub-pixel precision. It is, however, a computationally expensive algorithm as every seed point collected by the ALSC matching produces quadrants or octants of new matching candidates. Accordingly, the computational complexity increases exponentially as the stereo matching region grows. To expedite the matching process of a traditional GOTCHA, this paper proposes a parallelised stereo region growing algorithm called a MT-GOTCHA. To achieve data parallelism, the proposed method initially divides a stereo image from arbitrary distributed seed points, which are able to employ multiple GOTCHA's. In addition, since it estimates a cluster of neighbours using a non-linear diffusion equation and performs multiple ALSC processes in parallel to verify local matching candidates, more tiepoints are obtained within less processing time. Experimental results demonstrate the proposed method can reduce the processing time of a dense reconstruction at a reasonable cost of memory consumption.
    Preview · Article · May 2012
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    ABSTRACT: The giant planetary magnetospheres surrounding Jupiter and Saturn respond in quite different ways, compared to Earth, to changes in upstream solar wind conditions. Spacecraft have visited Jupiter and Saturn during both solar cycle minima and maxima. In this paper we explore the large-scale structure of the interplanetary magnetic field (IMF) upstream of Saturn and Jupiter as a function of solar cycle, deduced from solar wind observations by spacecraft and from models. We show the distributions of solar wind dynamic pressure and IMF azimuthal and meridional angles over the changing solar cycle conditions, detailing how they compare to Parker predictions and to our general understanding of expected heliospheric structure at 5 and 9 AU. We explore how Jupiter’s and Saturn’s magnetospheric dynamics respond to varying solar wind driving over a solar cycle under varying Mach number regimes, and consider how changing dayside coupling can have a direct effect on the nightside magnetospheric response. We also address how solar UV flux variability over a solar cycle influences the plasma and neutral tori in the inner magnetospheres of Jupiter and Saturn, and estimate the solar cycle effects on internally driven magnetospheric dynamics. We conclude by commenting on the effects of the solar cycle in the release of heavy ion plasma into the heliosphere, ultimately derived from the moons of Jupiter and Saturn.
    No preview · Article · Dec 2011 · Solar Physics
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