  We discretize a tangential tensor field equation using a surface-finite
element approach with a penalization term to ensure almost tangentiality. It is
natural to measure the quality of such a discretization intrinsically, i.e., to
examine the tangential convergence behavior in contrast to the normal behavior.
We show optimal order convergence with respect to the tangential quantities in
particular for an isogeometric penalization term that is based only on the
geometric information of the discrete surface.
