This paper investigates ordinal image description for
invariant feature correspondence. Ordinal description is
a meta-technique which considers image measurements in
terms of their ranks in a sorted array, instead of the measurement
values themselves. Rank-ordering normalizes descriptors
in a manner invariant under monotonic deformations
of the underlying image measurements, and therefore
serves as a simple, non-parametric substitute for ad hoc
scaling and thresholding techniques currently used. Ordinal
description is particularly well-suited for invariant features,
as the high dimensionality of state-of-the-art descriptors
permits a large number of unique rank-orderings, and
the computationally complex step of sorting is only required
once after geometrical normalization. Correspondence trials
based on a benchmark data set show that in general,
rank-ordered SIFT (SIFT-Rank) descriptors outperform
other state-of-the-art descriptors in terms of precisionrecall,
includin...
Matthew Toews, William M. Wells III