  In a recent experimental breakthrough, Hersen et al. [1] demonstrated that by
changing the agitating medium from air to water, one can obtain, on laboratory
scale, dunes that are downsized copies of desert dunes, thereby overcoming a
major obstacle for their systematic study. Here we argue in two steps (i),(ii)
that an alternative data analysis leads to some conclusions that are
qualitatively and quantitatively different from Hersen et al.'s but justify
their similarity hypothesis on different grounds.
  [1] P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89 (2002) 264301
