Example of a rebinned and noisified profile such as described in Sect. 3.2. The template spectrum was the THINGS observation of NGC 3184. The template data have been rebinned by a factor of 4 to give a channel width of 10.35 km s^-1; noise has then been added to bring the S/N to a figure of 2.0 in peak-to-rms terms, which for this galaxy is equivalent to about 3.9 according to the ALFALFA formula, as described in Sect. 3.2.3.