L1 rotation averaging using the Weiszfeld algorithm

  • Authors:
  • R. Hartley;K. Aftab;J. Trumpf

  • Affiliations:
  • Australian Nat. Univ., Canberra, ACT, Australia;Australian Nat. Univ., Canberra, ACT, Australia;Australian Nat. Univ., Canberra, ACT, Australia

  • Venue:
  • CVPR '11 Proceedings of the 2011 IEEE Conference on Computer Vision and Pattern Recognition
  • Year:
  • 2011

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Abstract

We consider the problem of rotation averaging under the L_1 norm. This problem is related to the classic Fermat-Weber problem for finding the geometric median of a set of points in IR^n. We apply the classical Weiszfeld algorithm to this problem, adapting it iteratively in tangent spaces of SO(3) to obtain a provably convergent algorithm for finding the L_1 mean. This results in an extremely simple and rapid averaging algorithm, without the need for line search. The choice of L_1 mean (also called geometric median) is motivated by its greater robustness compared with rotation averaging under the L_2 norm (the usual averaging process). We apply this problem to both single-rotation averaging (under which the algorithm provably finds the global L_1 optimum) and multiple rotation averaging (for which no such proof exists). The algorithm is demonstrated to give markedly improved results, compared with L_2 averaging. We achieve a median rotation error of 0.82 degrees on the 595 images of the Notre Dame image set.