  We present an improved method to measure the rotation curves for disks with
non-axisymmetric brightness profiles initially published in Teague et al.
(2018a). Application of this method to the well studied AS$~$209 system shows
substantial deviations from Keplerian rotation of up to $\pm 5\%$. These
deviations are most likely due to perturbations in the gas pressure profile,
including a perturbation located at $\approx 250~$au and spanning up to
$\approx 50~$au which is only detected kinematically. Modelling the required
temperature and density profiles required to recover the observed rotation
curve we demonstrate that the rings observed in $\mu$m scattered light are
coincident with the pressure maxima, and are radially offset from the rings
observed in mm continuum emission. This suggests that if rings in the NIR are
due to sub-$\mu$m grains trapped in pressure maxima that there is a vertical
dependence on the radius of the pressure minima.
