We propose a new model of topographic mapping organization based on nerve fields which allow traveling excitatory waves. The behavior of the model is understood from the viewpoint of phase-locking between excitation patterns in two nerve fields. Computer simulations have shown the model to be able to refine faintly topological mappings into almost complete ones. The model is different from any previous ones of this kind in that the organization depends on the spatio-temporal structure of the excitation patterns on the presynaptic nerve field.