  In this paper we present an efficient method for aggregating binary feature
descriptors to allow compact representation of 3D scene model in incremental
structure-from-motion and SLAM applications. All feature descriptors linked
with one 3D scene point or landmark are represented by a single low-dimensional
real-valued vector called a \emph{prototype}. The method allows significant
reduction of memory required to store and process feature descriptors in
large-scale structure-from-motion applications. An efficient approximate
nearest neighbours search methods suited for real-valued descriptors, such as
FLANN, can be used on the resulting prototypes to speed up matching processed
frames.
