  The geometry of a light wavefront, evolving from a initial flat wavefront in
the 3-space associated with a post-Newtonian relativistic spacetime, is studied
numerically by means of the ray tracing method. For a discretization of the
bidimensional light wavefront, a surface fitting technique is used to determine
the curvature of this surface. The relationship between the intrinsic curvature
of the wavefront and the change of the arrival time at different points on the
Earth is also numerically discussed.
