  An improved method for estimating distances to open clusters is presented and
applied to Hipparcos data for the Pleiades and the Hyades. The method is
applied in the context of the historic Pleiades distance problem, with a
discussion of previous criticisms of Hipparcos parallaxes. This is followed by
an outlook for Gaia, where the improved method could be especially useful.
Based on maximum likelihood estimation, the method combines parallax, position,
apparent magnitude, colour, proper motion, and radial velocity information to
estimate the parameters describing an open cluster precisely and without bias.
We find the distance to the Pleiades to be $120.3 \pm 1.5$ pc, in accordance
with previously published work using the same dataset. We find that error
correlations cannot be responsible for the still present discrepancy between
Hipparcos and photometric methods. Additionally, the three-dimensional space
velocity and physical structure of Pleiades is parametrised, where we find
strong evidence of mass segregation. The distance to the Hyades is found to be
$46.35\pm 0.35$ pc, also in accordance with previous results. Through the use
of simulations, we confirm that the method is unbiased, so will be useful for
accurate open cluster parameter estimation with Gaia at distances up to several
thousand parsec.
