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Factorization with Uncertainty
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Factorization with Uncertainty
Michal Irani4 and P. Anandan5
| (4) |
Department of Computer Science and Applied Mathematics, The Weizmann Institute of Science, Rehovot, 76100, Israel |
| (5) |
Microsoft Corporation, One Microsoft Way, Redmond, WA 98052, USA |
Abstract
Factorization using Singular Value Decomposition (SVD) is often used for recovering 3D shape and motion from feature correspondences
across multiple views. SVD is powerful at finding the global solution to the associated least-square-error minimization problem.
However, this is the correct error to minimize only when the x and y positional errors in the features are uncorrelated and identically distributed. But this is rarely the case in real data.
Uncertainty in feature position depends on the underlying spatial intensity structure in the image, which has strong directionality
to it. Hence, the proper measure to minimize is covariance-weighted squared-error (or the Mahalanobis distance). In this paper, we describe a new approach to covariance-weighted factorization, which can factor noisy feature correspondences
with high degree of directional uncertainty into structure and motion. Our approach is based on transforming the raw-data
into a covariance-weighted data space, where the components of noise in the different directions are uncorrelated and identically
distributed. Applying SVD to the transformed data now minimizes a meaningful objective function. We empirically show that
our new algorithm gives good results for varying degrees of directional uncertainty. In particular, we show that unlike other
SVD-based factorization algorithms, our method does not degrade with increase in directionality of uncertainty, even in the
extreme when only normal-flow data is available. It thus provides a unified approach for treating corner-like points together
with points along linear structures in the image.
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