“…A very large number of ATR algorithms have been proposed in recent decades [ 3 , 4 , 6 , 7 ]. Some have been based primarily on the computation of certain types of features, such as PCA [ 8 ], edge and corner descriptors [ 9 ], wavelets [ 10 ] or deformable templates [ 11 ], while others have been driven more by a particular classification scheme, e.g., neural networks [ 12 ], support vector machines (SVM) [ 13 ] or sparse representations [ 14 ]. In the closely-related fields of computer vision and visual tracking, there have been significant developments in object detection and recognition based on visual features, including the histogram of oriented gradients (HOG) [ 15 , 16 ], the scale-invariant feature transform (SIFT) [ 17 ], spin images [ 18 ], patch features [ 19 ], shape contexts [ 20 ], optical flow [ 21 ] and local binary patterns [ 22 ].…”