Approximation algorithms for computing the earth mover's distance under transformations

  • Authors:
  • Oliver Klein;Remco C. Veltkamp

  • Affiliations:
  • Department of Computer Science, FU Berlin;Department of Computer Science, Universiteit Utrecht

  • Venue:
  • ISAAC'05 Proceedings of the 16th international conference on Algorithms and Computation
  • Year:
  • 2005

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Abstract

The Earth Mover's Distance (EMD) on weighted point sets is a distance measure with many applications. Since there are no known exact algorithms to compute the minimum EMD under transformations, it is useful to estimate the minimum EMD under various classes of transformations. For weighted point sets in the plane, we will show a 2-approximation algorithm for translations, a 4-approximation algorithm for rigid motions and an 8-approximation algorithm for similarity transformations. The runtime for translations is O(TEMD(n,m)), the runtime of the latter two algorithms is O(nmTEMD(n,m)), where TEMD(n,m) is the time to compute the EMD between two fixed weighted point sets with n and m points, respectively. All these algorithms are based on a more general structure, namely on reference points. This leads to elegant generalizations to higher dimensions. We give a comprehensive discussion of reference points for weighted point sets with respect to the EMD.