  We introduce a corrective function to compensate errors in contact area
computations coming from mesh discretization. The correction is based on
geometrical arguments and requires only one additional quantity to be computed:
the length of contact/non-contact interfaces. The new technique enables us to
evaluate accurately the true contact area using a coarse mesh for which the
shortest wavelength in the surface spectrum reaches the grid size. The validity
of the approach is demonstrated for surfaces with different fractal dimensions
and different spectral content using a properly designed mesh convergence test.
In addition, we use a topology preserving smoothing technique to adjust the
morphology of contact clusters obtained with a coarse grid.
