  We report on a comparison of spectroscopic analyses for hydrogen (DA) and
helium atmosphere (DB) white dwarfs with Gaia Data Release 2 (DR2) parallaxes
and photometry. We assume a reddening law and a mass-radius relation to connect
the effective temperatures (Teff) and surface gravities (log g) to masses and
radii. This allows the comparison of two largely independent sets of
fundamental parameters for 7039 DA and 521 DB stars with high-quality
observations. This subset of the Gaia white dwarf sample is large enough to
detect systematic trends in the derived parameters. We find that spectroscopic
and photometric parameters generally agree within uncertainties when the
expectation of a single star is verified. Gaia allows the identification of a
small systematic offset in the temperature scale between the two techniques, as
well as confirming a small residual high-mass bump in the DA mass distribution
around 11,000-13,000 K. This assessment of the accuracy of white dwarf
fundamental parameters derived from Gaia is a first step in understanding
systematic effects in related astrophysical applications such as the derivation
of the local stellar formation history, initial-to-final mass relation, and
statistics of evolved planetary systems.
