Methods to account for interstellar extinction

A detailed knowledge of the galactic extinction is mandatory to obtain the time variation of the astrophysical/kinematical parameters outside the solar neighborhood. One may hope that the GAIA photometry itself will contribute color excesses for most of the studied objects, otherwise the extinction must be deduced from the external sources. 3-D galactic models where the dust distribution is an integral part seems to be a viable solution. Some statistical information may be obtained even from a color vs. distance diagrams.