  We present updated magnetic field maps of the chemically peculiar B9p star
$\alpha^2$ CVn created using a series of time resolved observations obtained
using the high resolution spectropolarimeters ESPaDOnS and Narval. We compare
these new magnetic field maps with the original magnetic Doppler imaging maps
based on spectra recorded with the MuSiCoS spectropolarimeter and taken a
decade earlier. These new maps are inferred from line profiles in all four
Stokes parameters using the magnetic Doppler imaging code INVERS10. With the
addition of new lines exhibiting Stokes $IQUV$ signatures we have a unique
insight into how the derived magnetic surface structure may be affected by the
atomic lines chosen for inversion. We report new magnetic maps of $\alpha^2$
CVn created using strong iron lines (directly comparable to the published
MuSiCoS maps), weak iron lines and chromium lines, all of which yield a
magnetic field structure roughly consistent with that obtained previously.
  We then derive an updated magnetic structure map for $\alpha^2$ CVn based on
the complete sample of Fe and Cr lines, which we believe to produce a more
representative model of the magnetic topology of $\alpha^2$ CVn. In agreement
with the previous mapping, this new updated magnetic map shows a dipolar-like
field which has complex sub-structure which cannot be explained by a simple low
order multipolar geometry. Our new maps show that regardless of the atomic line
or species choice, the reconstructed magnetic field is consistent with that
published previously, suggesting that the reconstructed field is a realistic
representation of the magnetic field of $\alpha^2$ CVn. $\alpha^2$ CVn is the
first Ap star for which multiple, high resolution magnetic maps have been
derived, providing important observational evidence for the stability of both
the large and small-scale magnetic field.
