  The relevance of the Tremaine-Weinberg (TW) method is tested to measure the
bar, spiral and inner structure pattern speeds using a gaseous velocity field.
The TW method is applied to various simulated barred galaxies in order to
demonstrate its validity in seven different configurations, including star
formation or/and dark matter halo. The reliability of the different physical
processes involved and of the various observational parameters are also tested.
The simulations show that the TW method could be applied to the gaseous
velocity fields to get a good estimate of the bar pattern speed, under the
condition that regions of shocks are avoided and measurements are confined to
regions where the gaseous bar is well formed. We successfully apply the TW
method to the \ha velocity field of the Virgo Cluster Galaxy M100 (NGC 4321)
and derive pattern speeds of 55+/-5 km/s/kpc for the nuclear structure, 30+/-2
km/s/kpc for the bar and 20+/-1 km/s/kpc for the spiral pattern, in full
agreement with published determinations using the same method or alternative
ones.
