HMI now routinely produces vector magnetic field synoptic charts. This Nugget describes the data reduction procedures and the method chosen to resolve the 180-degree ambiguity in azimuth.
The HMI team has developed several Python codes that can be used to conveniently analyze its many magnetic field data products. Check it out!
The effect of the spatial resolution of the boundary data on nonlinear force-free extrapolations is systematically explored for a solar case.