8,917 research outputs found
Binary Adaptive Semi-Global Matching Based on Image Edges
Image-based modeling and rendering is currently one of the most challenging topics in Computer Vision and Photogrammetry. The key issue here is building a set of dense correspondence points between two images, namely dense matching or stereo matching. Among all dense matching algorithms, Semi-Global Matching (SGM) is arguably one of the most promising algorithms for real-time stereo vision. Compared with global matching algorithms, SGM aggregates matching cost from several (eight or sixteen) directions rather than only the epipolar line using Dynamic Programming (DP). Thus, SGM eliminates the classical “streaking problem” and greatly improves its accuracy and efficiency. In this paper, we aim at further improvement of SGM accuracy without increasing the computational cost. We propose setting the penalty parameters adaptively according to image edges extracted by edge detectors. We have carried out experiments on the standard Middlebury stereo dataset and evaluated the performance of our modified method with the ground truth. The results have shown a noticeable accuracy improvement compared with the results using fixed penalty parameters while the runtime computational cost was not increased
Nonlinear force-free coronal magnetic stereoscopy
Getting insights into the 3D structure of the solar coronal magnetic field
have been done in the past by two completely different approaches: (1.)
Nonlinear force-free field (NLFFF) extrapolations, which use photospheric
vector magnetograms as boundary condition. (2.) Stereoscopy of coronal magnetic
loops observed in EUV coronal images from different vantage points. Both
approaches have their strength and weaknesses. Extrapolation methods are
sensitive to noise and inconsistencies in the boundary data and the accuracy of
stereoscopy is affected by the ability of identifying the same structure in
different images and by the separation angle between the view directions. As a
consequence, for the same observational data, the computed 3D coronal magnetic
field with the two methods do not necessarily coincide. In an earlier work
(Paper I) we extended our NLFFF optimization code by the inclusion of
stereoscopic constrains. The method was successfully tested with synthetic data
and within this work we apply the newly developed code to a combined data-set
from SDO/HMI, SDO/AIA and the two STEREO spacecraft. The extended method
(called S-NLFFF) contains an additional term that monitors and minimizes the
angle between the local magnetic field direction and the orientation of the 3D
coronal loops reconstructed by stereoscopy. We find that prescribing the shape
of the 3D stereoscopically reconstructed loops the S-NLFFF method leads to a
much better agreement between the modeled field and the stereoscopically
reconstructed loops. We also find an appreciable decrease by a factor of two in
the angle between the current and the magnetic field which indicates the
improved quality of the force-free solution obtained by S-NLFFF.Comment: 9 pages, 7 figure
Computational intelligence approaches to robotics, automation, and control [Volume guest editors]
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