  To use libraries of observed stellar spectra, one needs to know the
atmospheric parameters of the stars associated to those spectra. It is,
however, hard to know what are the real levels of precision and accuracy of
these parameters. To overcome this very same problem in a stellar survey, the
Gaia-ESO Survey implements a comprehensive calibration effort together with the
use of multiple parallel analysis methodologies. Here, we discuss the multiple
analyses approach and the effort to understand the accuracy and precision of
the provided stellar atmospheric parameters.
