  The Moir\'{e} structure of epitaxial graphene mono layer grown on
6H-SiC(0001) has been investigated recently by grazing incidence fast atom
diffraction, and the results were compared with the calculation of the
structure \textit{ab initio} and exact diffraction codes. We review these
results and present a complementary approach using the Hard Wall Model to
extract information without any \textit{a priori}. Reversely, taking advantage
of previous exact calculations we evaluate quantitatively the performance of
this simplified approach by comparing predictions using the same potential
energy surface.
