  Precise stellar parameters are crucial for several reasons, amongst which are
the precise characterization of orbiting exoplanets and the correct
determination of galactic chemical evolution. The atmospheric parameters are
extremely important because all the other stellar parameters depend on them.
Using our standard equivalent-width method on high-resolution spectroscopy,
good precision can be obtained for the derived effective temperature and
metallicity. The surface gravity, however, is usually not well constrained with
spectroscopy. We use two different samples of FGK dwarfs to study the effect of
the stellar surface gravity on the precise spectroscopic determination of the
other atmospheric parameters. Furthermore, we present a straightforward formula
for correcting the spectroscopic surface gravities derived by our method and
with our linelists. Our spectroscopic analysis is based on Kurucz models in
LTE, performed with the MOOG code to derive the atmospheric parameters. The
surface gravity was either left free or fixed to a predetermined value. The
latter is either obtained through a photometric transit light curve or derived
using asteroseismology. We find first that, despite some minor trends, the
effective temperatures and metallicities for FGK dwarfs derived with the
described method and linelists are, in most cases, only affected within the
errorbars by using different values for the surface gravity, even for very
large differences in surface gravity, so they can be trusted. The temperatures
derived with a fixed surface gravity continue to be compatible within 1 sigma
with the accurate results of the InfraRed Flux Method (IRFM), as is the case
for the unconstrained temperatures. Secondly, we find that the spectroscopic
surface gravity can easily be corrected to a more accurate value using a linear
function with the effective temperature.
