Qualitative representation of the effect of observational errors on the shape of the observed distribution of any sample of tracers. A perfectly spherical distribution, shown by the pink contours, is converted into an egg-shaped distribution (black contours) by the effect of the errors on the distances, which are always larger than the errors on the galactic coordinates. This would imply that a bar would be measured with a lower inclination angle with respect to the Sun-GC direction and a larger ellipticity.