“…Real-valued, local feature descriptors, such as Scale-Invariant Feature Transform (SIFT) [24] and Speeded Up Robust Features (SURF) [5] have already found their place in many computer vision applications, e.g., recognition [14], localisation [11,12], tracking [8,34], simultaneous localisation and mapping [17], or retrieval [6,15]. However, there is a need for the development of more ef icient techniques, in terms of computation time, storage requirements, or robustness [6,10,12,13,25,27].…”