I am trying to use NDSolve`FEM`ElementMeshInterpolation on a triangular structured grid constructed from a Delaunay triangulation with zero area triangles dropped. My question is regarding the kind of spline interpolation being used. I would like at least C^1 accuracy, but none of the options shown seem to have any effect.

{ {"ExtrapolationHandler" -> Automatic}, {InterpolationOrder -> Automatic}, {Method -> Automatic}, {PeriodicInterpolation -> False} }

Anyone who knows how this works or where this is documented? Niels