Ratio between the standard deviations of the RVs of each spectral line measured using one wavelength solution and using a wavelength solution every night. As we can see, on the edges of the HARPS CCD, which corresponds to pixels smaller than 1000 and larger than 3000, our new RV extraction procedure using only one wavelength solution give RVs for which the standard deviation is smaller than when deriving the RVs using a wavelength solution every night.