  The coherent photoproduction of $\rm{J/\psi}$ and $\rm{\psi'}$ mesons was
measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy
$\sqrt{s_{\mathrm{NN}}}~=~5.02$ TeV with the ALICE detector. Charmonia are
detected in the central rapidity region for events where the hadronic
interactions are strongly suppressed. The $\rm{J/\psi}$ is reconstructed using
the dilepton ($l^{+} l^{-}$) and proton-antiproton decay channels, while for
the $\rm{\psi'}$, the dilepton and the $l^{+} l^{-} \pi^{+} \pi^{-}$ decay
channels are studied. The analysis is based on an event sample corresponding to
an integrated luminosity of about 233 ${\mu b}^{-1}$. The results are compared
with theoretical models for coherent $\rm{J/\psi}$ and $\rm{\psi'}$
photoproduction. The coherent cross section is found to be in a good agreement
with models incorporating moderate nuclear gluon shadowing of about 0.65 at a
Bjorken-$x$ of around $6\times 10^{-4}$, such as the EPS09 parametrization,
however none of the models is able to fully describe the rapidity dependence of
the coherent $\rm{J/\psi}$ cross section including ALICE measurements at
forward rapidity. The ratio of $\rm{\psi'}$ to $\rm{J/\psi}$ coherent
photoproduction cross sections was also measured and found to be consistent
with the one for photoproduction off protons.
