We study the kinematics of the barred spiral galaxy NGC 6946 by investigating the velocity field from H \alpha Fabry-Perot observations , determined the pattern speed of the bar by using the Tremaine-Weinberg method , and find a main pattern speed of 21.7 ( +4.0 , -0.8 ) km/s/kpc .
Our data clearly suggest the presence of an additional pattern with a pattern speed more than twice that of the large pattern in this galaxy .
We use the epicycle approximation to deduce the location of the resonance radii and subsequently determine the pattern speed between the radii , and find that inside the Inner Inner Lindblad Resonance radius , a bar-like system has evolved .