  Considering a singularly perturbed convection-diffusion problem, we present
an analysis for a superconvergence result using pointwise interpolation of
Gau{\ss}-Lobatto type for higher-order streamline diffusion FEM.
  We show a useful connection between two different types of interpolation,
namely a vertex-edge-cell interpolant and a pointwise interpolant. Moreover,
different postprocessing operators are analysed and applied to model problems.
