“…As regards appearance‐based vision methods, the whole information in the scenes is used. Several alternatives can be used to describe images, such as the principal components of the image [30, 31], Haar wavelet coefficients [32, 33], Fourier components [34, 35], image histograms [36] or image frequency filtering [37]. To complete the information provided by vision systems, it is possible to take also into account the wheel odometry, GPS information or visual odometry and to set up a probabilistic context with all this information.…”