  We use Tree-SPH simulations from the GalMer database by Chilingarian et al.
to characterize and quantify the non-circular motions induced by the presence
of bar-like structures on the observed rotation curve of barred galaxies
derived from empirical models of their line-of-sight velocity maps. The GalMer
database consists of SPH simulations of galaxies spanning a wide range of
morphological types and sizes. The aim is to compare the intrinsic velocities
and bar properties from the simulations with those derived from
pseudo-observations. This allows us to estimate the amount of non-circularity
and to test the various methods used to derive the bar properties and rotation
curves. The intrinsic velocities in the simulations are calculated from the
gravitational forces whereas the observed rotation velocities are derived by
applying the ROTCUR and DiskFit algorithms to well-resolved observations of
intermediate-inclination, strongly barred galaxies. Our results confirm that
the tilted ring method implemented in ROTCUR systematically
underestimates/overestimates the rotational velocities by up to 40 percent in
the inner part of the galaxy when the bar is aligned with one of the symmetry
axes for all the models. For the DiskFit analysis, we find that it produces
unrealistic values for all the models used in this work when the bar is within
$\sim$10 degrees of the major or minor axis.
